The present invention relates generally to a thermal energy storage for selectively storing and selectively receiving thermal energy from one or more heating sources and/or selectively transfer thermal energy to one or more cooling sources; an energy system comprising a thermal energy storage; and a method of constructing a thermal energy storage and/or an energy system.

Background

Many types of energy storage systems exist today. Typical goals in relation to energy systems include providing energy to the storage as efficiently as possible (i.e. obtaining a high energy conversion ratio and/or high energy efficiency when adding energy to the storage) and storing energy as efficiently as possible (i.e. minimizing losses of energy during a given storage period).

A class or type of energy storages relate to the storage of thermal energy. Some thermal energy storages are aimed at relatively long term storage of thermal energy, e.g. over one or more months.

A thermal energy storage generally allows storage (and transfer to and from) of heat energy (or alternatively energy from 'cold' sources like ice, cold air or water, or other cold fluids or liquids) in one or more suitable media, e.g. water for some uses. A challenge, especially in relation to certain 'green' or renewable energy sources, is e.g. efficient and valuable storing of energy generated at 'off-peak' times, i.e. when a current demand for energy in some form is less than a current supply for the energy. Examples e.g. includes production of electricity from wind turbines and/or photovoltaic solar panels under favourable (wind and/or solar) conditions and/or at off-peak times (e.g. at night-time) where such electricity then is sold and distributed at a very low price, or even at a negative price, i.e. it costs money to 'sell' or distribute the generated electricity, due to excess supply and no readily available efficient storage means. It is not appropriate or valuable only to store energy but the energy should be able to be efficiently released or transferred from the storage again as well at a suitable time, i.e. valuable storing. This issue increases with the proportion of energy/electricity that is covered by such sources like wind turbines since the greater the total of such production, the greater absolute amount of energy/electricity is wasted or sold at very low prices increasing the overall cost of such energy production. Without available storage capacity, and available efficient storage capacity, it is not efficient to cover a greater and greater part of a city's or a country's need for energy by renewable energy sources like wind power, solar based energy sources, etc.

A demand for heat energy e.g. for a district heating facility will depend on the number of recipients of heat of course, but also depend on a geographical location due to local conditions like typical weather (windy or not, sunny or less sunny, etc.), typical seasonal temperatures of e.g. air and e.g. water, etc. The demand for heat for a district heating facility will typically fluctuate over the year. Figure 3 illustrates one example of a yearly demand for heat for a district heating facility supplying heat to a regional part of a city. This particular example is for a regional part of Copenhagen in Denmark and has a higher demand during autumn and winter and a lesser demand during spring and summer. It is to be understood that a demand may differ for other locations due to other conditions but a similar situation is the case for cities located in similar weather conditions. A demand for cooling for

Copenhagen would have a higher demand during summer and lower demand during winter. A district heating facility generally needs to be designed to be able to cope with potential worst case demand situations even though the demand will not always (or even often) be at that level.

Furthermore, many current district heating facilities still depend on burning of fossil and/or non-fossil fuels, such as coal, oil, biomass, etc., at least to an extent, especially in situations of unexpected or non-planned high demand, e.g. if the temperature is colder than normally for the time of year. It would be an advantage to eliminate, or at least reduce, the need for burning of fossil fuels. Additionally, it would be an advantage to eliminate, or at least reduce, the need for burning of any fuels (fossil or non-fossil) as burning such will create air pollution.

An issue with smaller thermal energy storages is that the loss is relatively large. Therefore it would be a benefit to provide a thermal energy storage having a large scale capacity of thermal energy, e.g. at least in the gigawatt hour range. Such a large scale is needed to have a significant impact or benefit e.g. in relation to supporting district heating facilities. Current large scale thermal energy storages are often costly to construct and therefore it would be an advantage to be able to provide relatively low-cost and/or cost-efficient construction of such large scale gigawatt hour thermal energy storages.

Even though progress have been made in connection with providing batteries for storage of electricity e.g. from renewable sources, the production costs of those are still such that it is generally expensive even when assessed over a long time, e.g. about 20 years. Especially compared to the value or price of the electricity they may store. One type of renewable energy source is e.g. the use of wind turbines and increasingly the use of offshore wind turbines. However, the cost of installing offshore wind turbines is still very high. Additionally, service and maintenance costs for offshore wind turbines are also relatively high compared to service and maintenance costs for onshore wind turbines. Summary

It is an object to provide a thermal energy storage that alleviates, at least to an extent, one or more of the above mentioned drawbacks.

Additionally, an objective is to provide an efficient large scale or large capacity thermal energy storage. An aspect of the invention is defined in claim 1.

Accordingly, in one aspect, one or more of these objects is/are achieved at least to an extent by a thermal energy storage for selectively storing and receiving and/or transferring thermal energy, wherein the thermal energy storage is adapted to receive a liquid energy storage medium during use and wherein the thermal energy storage comprises - a barrier structure adapted to contain the liquid energy storage medium when

present in the thermal energy storage,

- a cover where the cover and the barrier structure is adapted to insulate the liquid energy storage medium when present in the thermal energy storage,

- at least one outlet adapted to selectively receive an outgoing flow of at least a part of the liquid energy storage medium, and

- at least one return inlet adapted to selectively return at least a part of the outgoing flow back to the thermal energy storage, wherein

- the thermal energy storage is adapted to

o selectively receive thermal energy from one or more heating sources

configured to selectively heat at least a part of the liquid energy storage medium thereby increasing the thermal energy of the thermal energy storage, wherein the one or more heating sources are adapted to receive energy from one or more energy sources to increase the thermal energy, and/or o to selectively transfer thermal energy to one or more cooling sources configured to selectively cool at least a part of the liquid energy storage medium thereby decreasing the thermal energy of the thermal energy storage, wherein the one or more cooling sources are adapted to receive energy from one or more energy sources to decrease the thermal energy,

- the thermal energy storage is configured for selectively transferring thermal energy by transferring heat to at least one external heat receiving unit and/or by receiving thermal energy by cooling at least one external cooling unit by providing the outgoing flow of the liquid energy storage medium in the at least one outlet and receiving at least a part of the outgoing flow via the at least one return inlet back to the thermal energy storage, and

- the thermal energy storage is an offshore thermal energy storage.

Applying heat to the energy storage medium of the thermal energy storage from an external source will effectively transfer thermal energy from the external source to the energy storage medium of the thermal energy storage thereby increasing the internal energy of the thermal energy storage by increasing the temperature of the contained energy storage medium, i.e. 'storing heat' for later heating of something.

Removing heat from the energy storage medium of the thermal energy storage to an external source will effectively transfer thermal energy from the energy storage medium of the thermal energy storage to the external source thereby decreasing the internal energy of the thermal energy storage by decreasing the temperature of the contained energy storage medium, i.e. 'storing cold' for later cooling of something.

In this way, a thermal energy storage is provided that readily enables efficient large capacity seasonal storing of thermal energy (heat and/or cold). An efficient seasonal thermal storage allows storage of thermal energy (heat and/or cold) from when it is available or produced to subsequent later times of a greater demand of (heat and/or cold) thermal energy.

Furthermore, the thermal energy storage enables efficient storage of (heat and/or cold) energy from one or more energy sources. The one or more energy sources (or one or some of them) may be external to thermal energy storage, be internal to the thermal energy storage, be integrated with the thermal energy storage, and/or combinations thereof. If one or more energy sources produces electricity (and in particular electricity based on renewable energy sources), e.g. wind turbines, electricity generating solar panels, etc., and the one or more heating sources produces heat (and/or cold) in the energy storage medium using that electricity, it becomes possible to effectively 'store electricity in the energy storage medium (as heat and/or cold)' for a long period of time whereby the electricity is valuable at all or most times (day and night and throughout the whole year) as opposed to being sold at very low (or even negative) rates due to supply being greater than demand. Cheaper energy overall is provided due to the electricity becoming valuable more often. Efficient storage in this manner also enables over- or worst-case production of electricity - giving higher security of supply of electricity from variable energy sources such as many renewable energy sources - since surplus variable electricity production valuably can be stored rather than being wasted or having much less value when current demand is less than current production. Traditionally, backup capacity is provided by old fossil based infrastructure to cope with worst-case or low production that must be maintained and kept operational for the periods of time where renewable energy production cannot keep up with current demand.

Additionally, the thermal energy storage does not require any substantial modifications of an energy providing and/or distributing facility, such as a district heating facility, being connected for transfer of thermal energy to the thermal energy storage (cooling) and/or from the thermal energy storage (heating). Furthermore, such infrastructure is typically already in place to a large extent in many countries.

The term "offshore" as used herein includes near-shore and next-to-the-shore. The thermal energy storage may e.g. be located in connection with a coastline or similar (e.g. becoming an extension thereof) or be located fully offshore in a body of water. In some situations where the surrounding body of water is used to an effect (e.g. to heat or transfer thermal energy to the liquid energy storage medium), there may e.g. be advantages in having an offshore thermal energy storage since terrain differences (being more significant closer to the shore) can lead to colder groundwater currents reducing the temperature of the surrounding body of water. Further away from the shore, the cooling of groundwater currents due to terrain differences will have less or no practical impact on the temperature of the surrounding body of water.

In some embodiments, the thermal energy storage may form or be part of a coastal protection facility or measure, sluice system, flooding protection facility, dike facility, etc. offering protection for increased or rising water or sea levels. The thermal energy storage may have a shape and structural integrity so that it may double in function as a coastal protection facility or measure, etc. The thermal energy storage - given its intended large scale volume - is well suited for this and has, at least in some embodiments, additional advantages as disclosed herein when being located or constructed in a naturally occurring and/or already existing body of water.

Such a thermal energy storage being suitable for coastal protection may e.g. be located at a near-shore or next-to-the-shore location and shield the shore, be located at a narrow part of a fjord, bay, etc.

At least some barrier structures as disclosed herein, e.g. comprising an inner wall and an outer wall with one or more materials (e.g. (reinforced) concrete, sand, dirt, mud, and/or the like) in-between is well suited for a thermal energy storage doubling in function as a coastal protection facility or measure. In some embodiments, the barrier structure forming or being a part of a coastal protection facility or measure, a flooding protection facility, etc. may have a height that is about 3 to about 4 metres above a normal or average water height. Such barrier structures may be a part of other flooding measures like sluices, (e.g. moveable) dikes, etc.

If seawater is used as the energy storage medium, as in certain embodiments disclosed herein, the offshore location of the thermal energy storage enables the use of readily available very large volumes of an efficient energy storage medium. Using seawater also avoid the need for using water that otherwise could be used as drinking water (which may be a scarce resource) as a source for thermal energy storage as otherwise often is done.

In some embodiments and e.g. as disclosed herein, the thermal energy storage only comprises one or more heating sources with the aim to efficiently store thermal energy to be used for heating (by transferring heat from the thermal energy storage). In such

embodiments is provided, a thermal energy storage for selectively storing and receiving thermal energy, wherein the thermal energy storage is adapted to receive a liquid energy storage medium during use and wherein the thermal energy storage comprises - a barrier structure adapted to contain the liquid energy storage medium when present in the thermal energy storage,

- a cover where the cover and the barrier structure is adapted to insulate the liquid energy storage medium when present in the thermal energy storage,

- at least one outlet adapted to selectively receive an outgoing flow of at least a part of the liquid energy storage medium, and

- at least one return inlet adapted to selectively return at least a part of the outgoing flow back to the thermal energy storage, wherein

- the thermal energy storage is adapted to

o selectively receive thermal energy from one or more heating sources

configured to selectively heat at least a part of the liquid energy storage medium thereby increasing the thermal energy of the thermal energy storage, wherein the one or more heating sources are adapted to receive energy from one or more energy sources to increase the thermal energy,

- the thermal energy storage is configured for selectively transferring thermal energy by transferring heat to at least one external heat receiving unit by providing the outgoing flow of the liquid energy storage medium in the at least one outlet and receiving at least a part of the outgoing flow via the at least one return inlet back to the thermal energy storage, and

- the thermal energy storage is an offshore thermal energy storage.

In some embodiments and e.g. as disclosed herein, the thermal energy storage only comprises one or more cooling sources with the aim to efficiently store thermal energy to be used for cooling (by transferring heat to the thermal energy storage). In such embodiments is provided, a thermal energy storage for selectively storing and transferring thermal energy, wherein the thermal energy storage is adapted to receive a liquid energy storage medium during use and wherein the thermal energy storage comprises - a barrier structure adapted to contain the liquid energy storage medium when

present in the thermal energy storage,

- a cover where the cover and the barrier structure is adapted to insulate the liquid energy storage medium when present in the thermal energy storage,

- at least one outlet adapted to selectively receive an outgoing flow of at least a part of the liquid energy storage medium, and

- at least one return inlet adapted to selectively return at least a part of the outgoing flow back to the thermal energy storage, wherein

- the thermal energy storage is adapted to

o to selectively transfer thermal energy to one or more cooling sources

configured to selectively cool at least a part of the liquid energy storage medium thereby decreasing the thermal energy of the thermal energy storage, wherein the one or more cooling sources are adapted to receive energy from one or more energy sources to decrease the thermal energy,

- the thermal energy storage is configured for selectively transferring thermal energy by receiving thermal energy by cooling at least one external cooling unit by providing the outgoing flow of the liquid energy storage medium in the at least one outlet and receiving at least a part of the outgoing flow via the at least one return inlet back to the thermal energy storage, and

- the thermal energy storage is an offshore thermal energy storage.

However, in some embodiments and e.g. as disclosed herein, the thermal energy storage comprises both one or more heating sources and one or more cooling sources as will be described further in the following thereby fulfilling both a heating need and a cooling need. In cases with both heating and cooling, the thermal energy storage may comprise a number of respective outlets and return inlets, e.g. being separate for the respective heating and cooling part of the thermal energy storage. The one or more energy sources, supplying energy to the heating and/or cooling source(s), is or includes in some embodiments renewable, clean, green, etc. energy sources such as one or more of wind turbines, electricity generating solar panels, heat pumps, etc. e.g. as disclosed herein and/or combinations thereof. The thermal energy storage readily provides an efficient storage of thermal energy from or based on such sources, e.g. generated during off-peak demand times, under especially favourable conditions (e.g. strong wind, sunny weather, etc.), etc. Further, this may e.g. contribute to a reduction of emissions of carbon dioxide and other unwanted particles from power plants burning fossil and/or non-fossil fuels as the reliance on such energy sources is reduced even at relatively higher (seasonal) demand, which will increase the quality of the air e.g. in a city, etc. An advantage of an offshore thermal energy storage is also a possibility of being located near and/or for simple connection with energy sources in the form of offshore wind turbines.

The liquid energy storage medium is preferably a liquid medium suitable for efficiently storing thermal energy by application of heat and/or cooling to the energy storage medium.

Alternatively, the thermal energy storage comprises a mix of a plurality of energy storage media. In some embodiments, the energy storage medium is (or comprises) water and in some further embodiments, the energy storage medium is (or comprises) seawater. In some other embodiments, the liquid energy storage medium is a medium allowing storage of thermal energy in liquid form above temperatures of 100° Celsius. In some other embodiments, the liquid energy storage medium is a medium allowing storage of thermal energy in liquid form below temperatures of 0° Celsius. For embodiments of a thermal energy storage comprising both a heat storage part and a cold storage part, the liquid energy storage medium/media may be the same or alternatively different for heat storage part and the cold storage part. The liquid energy storage medium is throughout this description sometimes referred to simply as energy storage medium.

The cover that (also) insulates the liquid energy storage may e.g. be one single cover or consist of a plurality of cover segments. The cover may be a floatable cover capable of floating on the energy storage medium of the thermal energy storage when the cover and the energy storage medium are in place. Alternatively, the cover may also be supported in another way, e.g. by the barrier structure. The cover may e.g. be collapsible, foldable, and/or removable. In some embodiments, the cover is free-floating, i.e. floating and located on the surface of the energy storage medium when contained in the thermal energy storage, e.g. with gaps between the 'side' of the cover and adjacent barrier structure. In some embodiments, the cover is secured or moored to the barrier structure and/or the thermal energy storage. In preferred embodiments, the cover is on top of the energy storage medium with clear spacing above (but in some further embodiments e.g. comprising structures, such as solar devices etc. as disclosed herein).

Preferably, the cover and the barrier structure are insulating thereby reducing a loss of thermal energy from the thermal energy storage. In some embodiments, the liquid energy storage medium is water or seawater.

In some embodiments, the thermal energy storage is located, fully or partly, in a naturally occurring and/or already existing body of water. In some embodiments, the thermal energy storage is located offshore in a sea. In some alternative embodiments, the thermal energy storage is located offshore in a natural lake, an artificial lake, a natural or artificial reservoir, a sufficiently larger river, etc. The artificial reservoirs or lakes may e.g. be a result from excavations, stone works, or other mining, etc. This is especially advantageous if the body of water is also used as the liquid energy storage medium.

In some embodiments, the barrier structure

- extends at a first end (e.g. upper end) above a level of the naturally occurring and/or already existing body of water, and/or

- extends at a second end (e.g. lower end) into a bed of the naturally occurring and/or already existing body of water. In some embodiments, the barrier structure comprises a wall structure driven into a bed of the naturally occurring and/or already existing body of water wherein the wall structure separates the liquid energy storage medium from the naturally occurring and/or already existing body of water (which may be the same as the body of water the thermal energy storage is located in (for such embodiments) or different).

In some embodiments, the barrier structure is a rigid structure.

In some embodiments, the barrier structure fully encapsulates the liquid storage medium about a vertical axis.

In some embodiments, the wall structure is or comprises a sheet pile wall structure. Such sheet pile wall structures are relatively low cost and easy and low-cost to install in water depths up to at least 20 - 30 meters. Using such structures greatly reduces the cost associated with constructing a thermal energy storage as disclosed herein.

In some embodiments, the wall structure comprises a double wall structure comprising an inner wall and an outer wall having one or more materials in-between the inner and outer wall. The outer wall at least partly, e.g. fully or substantially fully, encompasses the inner wall. The one or more materials may be any materials suitable for a given need or design. Preferably, the material(s) are insulating with respect to heat and/or cold in order to reduce losses from the thermal energy storage. The material(s) may e.g. be (e.g. reinforced) concrete, sand, dirt, mud, and/or the like. The sand, dirt, mud, etc. may e.g. be obtained directly from the bed of the (naturally occurring and/or already existing) body of water that the thermal energy storage is or may be located in e.g. as part of increasing the volume of the thermal energy storage by digging into the bed after the inner and outer wall have been put in place. Concrete may e.g. be used, if the double wall needs to support something relatively heavy, e.g. one or more wind turbines as disclosed herein; however a wind turbine foundation may also be used in a wall comprising sand, dirt, mud, etc. to support one or more wind turbines as also disclosed herein.

In some embodiments, the inner wall and the outer wall each is a sheet pile wall structure.

In some embodiments, the thermal energy storage comprises a waterproof sealing, membrane, etc. at the side(s) of the barrier structure and/or the floor of the bed of the thermal energy storage.

In some embodiments, the barrier structure comprises one or more wind turbines foundations (and eventually after full construction wind turbines) and/or one or more wind turbines integrated with the barrier structure. The wind turbines may in some embodiments be located so that they obstruct or 'shadows' solar based energy sources of the thermal energy storage - if present - the least or to a lesser degree. For certain such embodiments with solar based energy sources generally located along an eastern-western direction, the wind turbines are located in or towards a northern direction of the thermal energy storage.

Using the barrier structure (e.g. the double wall structure) as a support for one or more wind turbines (integrated or located thereon) actually provides an onshore working environment for construction and/or installation of the one or more wind turbines, which will save costs. As an example, land based cranes (working from the barrier structure) may be used rather than floating cranes. Furthermore, in some embodiments, onshore wind turbine foundations may be used instead of offshore foundations (as the wind turbines is located on or integrated with the barrier structure). Additionally, standard onshore cabling may also be used at least at some locations instead of sea cables again saving costs. Basically, onshore wind turbines may be used rather than offshore wind turbines. Furthermore, performing later service operations will also be simplified and thereby involve less costs. The one or more wind turbines are in this way (at least for some embodiments) located offshore but onshore on the thermal energy storage.

In some embodiments, the one or more energy sources comprises one or more wind turbines adapted to selectively deliver electrical power to one or more of the one or more heating sources thereby selectively heating at least a part of the liquid energy storage medium and/or to selectively deliver electrical power to one or more of the one or more cooling sources thereby selectively cooling at least a part of the liquid energy storage medium.

In some embodiments, the one or more wind turbines are adapted to selectively - deliver electrical power to the one or more heating sources and/or the one or more cooling sources, or

- deliver electrical power to an electrical supply or distribution network in response to one or more predetermined criteria.

The one or more predetermined criteria may e.g. be comparing a current/real-time available market price pr. unit of electricity (sometimes also referred to as a spot-price for wind power electricity) with a predetermined threshold and distribute the electricity to the power grid, the electrical supply or distribution network, etc. when the available market price is above the predetermined threshold and distribute the electricity for use in heating up and/or cooling the energy storage medium when the available market price is below the predetermined threshold. The determination of where to distribute the electricity may e.g. be made automatically, semi-automatically, or even manually. In this way, it is possible to control delivery of generated electricity to where the benefit will be greatest. Additionally, it is possible to obtain a value (storage of heat for later valuable heat distribution) of otherwise low value electricity due to a current low market price.

In some embodiments, at least one of the heating sources is an electric boiler immersed in or in heat exchanging connection with the liquid energy storage medium. In some embodiments, at least one of the heating sources is a solar thermal collector providing a heated medium, e.g. water or seawater, in heat exchanging connection with the liquid energy storage medium, in general any solar based energy source that can deliver and/or remove thermal energy to/from the thermal energy storage.

In some embodiments, the thermal energy storage is adapted to receive heat, e.g. surplus heat or heat generated as a by-product or waste-product, from one or more land-based or offshore activities and/or facilities. This may e.g. be receiving (surplus) heat from incineration plants e.g. burning waste, etc.

In some embodiments, the thermal energy storage is adapted to receive cooling, e.g. surplus cooling or cooling generated as a by-product or waste-product, from land-based or offshore activities and/or facilities. In some embodiments, at least one of the cooling sources is a chiller, a heat pump, a compression refrigerator, or the like.

In some embodiments, the one or more energy sources comprises a number of electricity generating solar panels adapted to deliver energy to one or more of the one or more heating sources thereby selectively heating at least a part of the liquid energy storage medium and/or to deliver energy to one or more of the one or more cooling sources thereby selectively cooling at least a part of the liquid energy storage medium.

The electricity generating solar panels may e.g. be photovoltaic solar panels (also referred to simply as photovoltaic panels) providing electricity, hybrid photovoltaic (HPV) solar panels providing both electricity and a heated medium, or the like. At least some of the (photovoltaic and/or HPV) solar panels may e.g. be adapted to selectively deliver generated electricity to an (e.g. land-based) power grid, electrical supply or distribution network, etc. In some embodiments, the number of electricity generating solar panels is adapted to selectively

- deliver electrical power to the one or more heating sources and/or the one or more cooling sources, or

- deliver electrical power to an electrical supply or distribution network in response to one or more predetermined criteria.

The one or more predetermined criteria may e.g. be comparing a current/real-time available market price pr. unit of electricity (sometimes also referred to as a spot-price for wind power electricity) with a predetermined threshold as mentioned above. In some embodiments, at least a part of the number of solar panels (photovoltaic, HPV, and/or solar thermal collector), e.g. all, are located on the top of the cover. In this way, the area of the cover may be used for an additional purpose (in addition to help insulating the energy storage medium reducing losses) namely providing space for a (relatively large) number of external energy sources (photovoltaic, HPV) and/or heating sources (solar thermal collectors) located close-by simplifying the transfer of energy by requiring simpler connections, etc.

In some embodiments,

- the one or more heating sources comprises at least one water or seawater heat pump adapted to selectively supply heat to at least a part of the liquid energy storage medium, where the at least one water or seawater heat pump is connected to the liquid energy storage medium and to a naturally occurring and/or already existing body of water, and/or

- the one or more cooling sources comprises at least one water or seawater heat pump adapted to selectively remove heat from at least a part of the liquid energy storage medium, where the at least one water or seawater heat pump is connected to the liquid energy storage medium and to a naturally occurring and/or already existing body of water (e.g. the body of the water the thermal energy storage is located in or alternatively another body of water).

In some embodiments, the thermal energy storage comprises at least one additional barrier dividing the thermal energy storage into at least two separate parts, each part comprising a respective part of the liquid energy storage medium (or alternatively comprising different liquid energy storage media), i.e. dividing the thermal energy storage into at least two separate 'containers' or compartments for (a part of) the liquid energy storage medium. In some embodiments, one or some of the parts may be one or more heat storages while another or some of the other parts may be one or more cold storages. Having a plurality of separate parts each comprising a respective part of the liquid energy storage medium also enables that the thermal energy storage still can operate e.g. even when performning maintenance and repairs perhaps requiring temporarily emptying or draining a particular part.

Furthermore, splitting up the thermal energy storage into a plurality separate parts increases the overall efficiency of the thermal energy storage - even if all are used for a same single purpose like heating or cooling.

In some embodiments, the thermal energy storage comprises one or more pumps adapted to pump energy storage media from a first part to a second part of the at least two separate parts for containment and wherein the thermal energy storage further comprises one or more generators adapted to generate electricity in response to energy storage media being released from the second part into the first part. In this way, a hydrostatic application is added to the thermal energy storage. This may e.g. be useful if a need for generating electricity arises, e.g. unexpectedly.

In some embodiments, the at least one outlet is in heat transferring and/or heat removing connection with an energy providing and/or distributing system adapted to provide and/or distribute heating and/or cooling to one or more domestic, commercial, manufacturing, and/or production facilities, such as houses, apartments, companies, factories, shops, plants, etc. of various ages.

In some embodiments, the at least one outlet (for transferring heat from the thermal energy storage) is located for intake of the outgoing flow of the liquid energy storage medium at a location of the barrier structure in the vicinity of where the liquid energy storage medium is or is expected to be about sixty five to about ninety five degrees Celsius or be about eighty degrees Celsius.

In some respective embodiments, the thermal energy storage is adapted to contain a volume of about 0.1 - about 100 million cubic metres, about 10 - about 100 million cubic metres, about 50 - about 100 million cubic metres, about 10 - about 50 million cubic metres, about 0.1 - about 50 million cubic metres, about 0.1 - about 10 million cubic metres, at least about 0.1 million cubic metres, at least about 10 million cubic metres, at least about 50 million cubic metres, or respectively at least about 100 million cubic metres of liquid energy storage medium. The volume will however typically depend on a specific need or use of the thermal energy storage and may e.g. in some embodiment contain a volume being greater than about 100 million cubic metres.

Having a relatively large volume thermal energy storage enables that the loss of thermal energy (heat and/or cold) is minimised. In some embodiments, the thermal energy storage is at least a 4.5 gigawatt hour thermal energy storage. In some embodiments, the thermal energy storage is at least a 50 gigawatt hour thermal energy storage.

The thermal energy storage may in some embodiments have a cross section (perpendicular to a lengthwise direction, i.e. 'up/down') generally having a rectangular or square shape, a circular shape, an oval shape, and/or any suitable shape.

In some embodiments where the thermal energy storage is adapted for cooling (only or in addition to heating) as disclosed herein and the thermal energy storage is located, fully or partly, in a naturally occurring and/or already existing body of water, the thermal energy storage is adapted to selectively introduce outside water to the liquid energy storage medium (being used for cooling) when the temperature of the outside water is lower (e.g. by a predetermined margin) than the temperature of the liquid energy storage medium (being used for cooling). This may e.g. be done in colder months or during winter and will effectively decrease the thermal energy of the liquid energy storage medium (being used for cooling). This saves energy otherwise needed for cooling the liquid energy storage medium to the same temperature. Alternatively or in addition, where the thermal energy storage is adapted for heating (only or in addition to cooling) as disclosed herein, the thermal energy storage is adapted to selectively introduce outside water to the liquid energy storage medium (being used for heating) when the temperature of the outside water is higher (e.g. by a

predetermined margin) than the temperature of the liquid energy storage medium (being used for heating).

The thermal energy storage may e.g. be further adapted to selectively remove a part of the existing liquid energy storage medium (being used for cooling or heating, respectively) e.g. to make room in the thermal energy storage for the introduced colder or warmer outside water. In some embodiments, the liquid energy storage medium in the form of cold/colder water, or parts thereof e.g. in separate enclosures, may be used for aquaculture or aquafarming purposes. Other parts of the thermal energy storage may still be used for heating. Advantages include one or more of readily facilitating cleaning and recirculation of water used for aquaculture or aquafarming, temperature control (cooling) water (water in open sea cages typically gets too hot for optimal conditions due to heating by contained fish/animals, which together with less clean water increases the likelihood of diseases in the water), control of the oxygenation of the water for optimal levels, room for movement and/or suitable layout (e.g. circular) for making contained fish/animals naturally move more, which increases the quality of the meat of the contained fish/animals, better control of amount of consumed food (whereas in open sea cages an amount of the provided food very likely will flow outside the sea cage without knowledge of how much that precisely is), isolating the fish/animals ensuring that diseases from other produces does not spread into the enclosure, enabling ecological farming, control of the light intensity in the contained water using suitable lamps (which may influence e.g. the colour of salmon without using coloured food for the fish), and producing/using hydrogen gas e.g. for electricity generation, where the hydrogen gas is a 'waste' product of producing oxygen by hydrolosis e.g. used for oxygenation of the water. In some embodiments, the one or more energy sources comprises a number of electricity generating solar panels, such as photovoltaic/PV or HPV solar panels, and a panel mounting structure (also referred to as solar panel mounting structure or photovoltaic panel mounting structure) comprising the number of electricity generating solar panels and at least one enclosure comprising an enclosed gaseous medium wherein the at least one enclosure is located so that at least a part of solar energy being subjected to the one or more electricity generating solar panels is transferred to the enclosed gaseous medium as thermal energy, and wherein thermal energy storage comprises or is connected to an energy transfer unit, the energy transfer unit being configured for receiving at least a part of the enclosed gaseous medium and transferring thermal energy from a received part of the gaseous medium to a further medium.

Traditionally, only about 15% to about 20%, or in any event a relatively small part, of the solar energy being exposed to photovoltaic panels of a photovoltaic panel mounting structure is actually converted into electrical power by the photovoltaic panels. Typically about 35% to about 40% of the received solar energy is reflected leaving a remaining part of about 40 to about 50%. The remaining part of about 40% to about 50% would traditionally be exchanged with air surrounding the photovoltaic panels and 'disappear' or dissipate.

However, accord to this embodiment, a large proportion of the remaining 40 to about 50% energy is absorbed or captured by the enclosed gaseous medium as thermal energy, which then can be put to use instead of simply being 'wasted'. This increases the overall energy output, in the form of electrical power and thermal energy, of the photovoltaic panel mounting structure.

The energy transfer unit will transfer thermal energy from a received part of the enclosed gaseous medium to a further medium enabling the thermal energy to distributed or provided to where it may be put to use.

The specific percentages mentioned about may vary according to type of photovoltaic panels and/or e.g. other external factors but in any event, a relatively large proportion of the solar energy is available for being obtained and effectively captured as thermal energy by the enclosed gaseous medium, which then may be transferred further on for use. Preferably, the gaseous medium is atmospheric air, which is readily available and does not have any associated costs. In addition, atmospheric air has good and usable thermal energy absorbing and retaining capabilities.

In some embodiments, the further medium is the liquid energy storage medium (used for heating) or the further medium is in heat exchanging connection with the liquid energy storage medium (used for heating).

In some embodiments, the energy transfer unit is a gas to liquid energy transfer unit. This enables an efficient transfer of the thermal energy from the gaseous medium to a further liquid medium.

In some embodiments, the energy transfer unit is a heat pump or e.g. more specifically an air to water (or liquid) heat pump. Such air to water heat pumps are often very efficient and may have an SCOP (seasonal coefficient of performance) factor of about 5, signifying that they, on average, deliver about 5 times as much energy than the electrical energy needed to run them.

Air being heated as disclosed above and herein and being used by a heat pump has the further advantage that it will increase the SCOP factor of the heat pump compared to using Ordinary' ambient air (i.e. not heated as disclosed above and herein) as warmer air generally will increase the SCOP factor, so the efficiency of the heat pump is increased.

In some further embodiments, the energy transfer unit is powered by electricity generated by at least some of the one or more photovoltaic panels. A circuit including an inverter or the like may e.g. connect the photovoltaic panels, normally producing DC current, to the energy transfer unit. In some embodiments, the panel mounting structure comprises one or more support structures adapted to support the one or more photovoltaic panels (104) on a surface such as the cover of the thermal energy storage.

In some further embodiments, at least some of the one or more support structures comprise a first support part and a second support part where the first support part supports at least some of the one or more photovoltaic panels and the second support part supports the first support part. A first support part may e.g. be a frame or similar that one or more photovoltaic panels is attached to, on, or in. In some embodiments, a first support part may e.g. comprise a sheet, plate, etc. of steel or another suitable material located under the PV panels. A second support part may e.g. be support legs, struts, beams, rods, bars, etc. supporting one or more first support parts. A second support part may e.g. be made of or comprise a wooden, metallic, or other suitable material. In some embodiments, the first and the second support parts (or at least some of them) may be integrated with each other. In other embodiments, the first and the second support parts are distinct from each other but then secured, e.g. welded or fixed in another way, to each other. A first support pay may e.g. also simply rest on a second support part.

In some embodiments, the photovoltaic panel mounting structure comprises one or more insulation elements that reduces losses of thermal energy from the at least one enclosure. In some further embodiments, the one or more insulation elements defines, at least in part, the at least one enclosure. The one or more insulation elements may e.g. be integrated with or be a part of (e.g. some of) the one or more support structures. The one or more insulation elements may e.g. also be (e.g. some of) the one or more support structures.

In some embodiments, the one or more insulation elements defines the at least one enclosure together with at least a part of the one or more support structures and/or at least a part of a surface of the one or more photovoltaic panels.

In some embodiments, the circumference of photovoltaic panel mounting structure comprises one or more insulation elements e.g. for a photovoltaic panel mounting structure comprises PV panels arranged adjacent to each other such as in rows/columns. This simplifies the construction of the photovoltaic panel mounting structure. In general, any suitable insulation material as traditionally used in the construction industry may be used.

In some embodiments, at least some of the one or more photovoltaic panels are arranged so that they have cross-section (seen from a side of the photovoltaic panel mounting structure) generally being a consecutive shape of v-shapes, a consecutive shape of upside-down v- shapes, a saw-tooth shape, or similar; e.g. with gaps in-between.

In some embodiments, at least some of the one or more photovoltaic panels are arranged in a planar configuration (e.g. on or at least supported by the first support part) with a space or gap between the respective photovoltaic panels. This allows for thermal energy to be absorbed or obtained by the gaseous medium of the at least one enclosure more readily.

In some embodiments, the photovoltaic panel mounting structure comprises one or more controllable ventilation elements connecting at least one enclosure with external ambient air and wherein the one or more controllable ventilation elements is configured to open for external ambient air when a determined temperature of the gaseous medium is above a predetermined threshold and otherwise close for external ambient air. This may e.g. be an advantage if the temperature of the gaseous medium is too high since the effectiveness (i.e. the capability of converting solar energy into electrical power) of photovoltaic panels generally is diminished when being too warm. The same (diminished effectiveness when being too warm) may e.g. be the case for the energy transfer unit(s). Certain heat pumps, as an example, operate best with a gaseous medium having a maximum temperature of about 35° Celsius.

In some embodiments, the photovoltaic panel mounting structure comprises one or more controllable ventilation elements connecting at least one enclosure with external ambient air and wherein the one or more controllable ventilation elements is configured to open for external ambient air when a determined temperature of the gaseous medium is below a determined temperature of the external ambient air. This allows for drawing in warmer outside air into the at least one enclosure when the outside temperature is higher than the temperature of the enclosed gaseous medium thereby readily increasing the thermal energy of the gaseous medium.

The respective temperatures may e.g. be obtained by one or more appropriate temperature sensors.

In some embodiments, the photovoltaic panel mounting structure may also comprise one or more additional controllable ventilation elements located elsewhere e.g. located at or near the opposite end of the first support part (i.e. closer towards the surface). Generally, the one or more controllable ventilation elements may be used regardless of what type the one or more insulation elements are and/or how the enclosure is established. One or more of the ventilation elements, e.g. the one(s) located closest to the surface, may be passive ventilation elements such as passive air intakes that may draw air in when the one or more additional controllable ventilation elements are opened.

In some embodiments, e.g. in combination with embodiments comprising one or more controllable ventilation elements, the photovoltaic panel mounting structure further comprises circulation elements configured for circulating the enclosed gaseous medium, e.g.

distributing hotter air otherwise generally located towards the top or 'roof to energy transfer unit e.g. located on the surface or 'floor'. The circulation elements may e.g. be powered by at least some of the one or more photovoltaic panels. In some embodiments, the panel mounting structure comprises a number of walls portioning the at least one enclosure into several separate enclosures where at least one energy transfer unit is located in each separate enclosure and being configured for receiving a gaseous medium from one enclosure and expel it into a neighbouring enclosure.

In some embodiments, the thermal energy storage is part of or may be constructed in connection with a residential and/or commercial area extending out in the water or sea having buildings such as one or more of apartments, high rise buildings, offices, hotels, etc.

A part of the barrier structure for embodiments of a giga thermal energy storage as disclosed herein may easily e.g. be about 1 kilometres times 70 metres providing ample room.

Recreational areas may also be provided e.g. outside open hot tub facilities with hot (or cold) water throughout the whole year enabled or provided by the thermal energy storage.

According to another aspect of the present invention, an energy system is provided, the energy system comprising at least one thermal energy storage, one or more heating sources, and/or one or more cooling sources as disclosed herein.

In some embodiments, the energy system further comprises one or more energy sources adapted to deliver energy to one or more of the one or more heating sources thereby selectively heating at least a part of the liquid energy storage medium and/or to one or more of the one or more cooling sources thereby selectively cooling at least a part of the liquid energy storage medium.

In some embodiments, the one or more heating sources is one or more selected from the group consisting of: - an electric boiler immersed in or in heat exchanging connection with the liquid energy storage medium and adapted to selectively supply heat to the liquid energy storage medium,

- solar thermal collector providing a heated medium (e.g. water or seawater) in heat exchanging connection with the liquid energy storage medium, and

- at least one water or seawater heat pump adapted to selectively supply heat to at least a part of the liquid energy storage medium, where the at least one water or seawater heat pump is connected to the liquid energy storage medium and to a naturally occurring and/or already existing body of water, e.g. comprising the at least one thermal energy storage, and/or wherein the one or more cooling sources is one or more selected from the group consisting of:

- a chiller or chilling unit,

- a compression refrigerator, and

- at least one water or seawater heat pump adapted to selectively remove heat from at least a part of the liquid energy storage medium, where the at least one water or seawater heat pump is connected to the liquid energy storage medium and to a naturally occurring and/or already existing body of water, e.g. comprising the at least one thermal energy storage, and/or the one or more energy sources is one or more selected from the group consisting of:

- one or more wind turbines, and

- a number of electricity generating solar panels such as a number of photovoltaic or hybrid photovoltaic solar panels.

According to another aspect of the present invention, an energy providing and/or distributing system is provided, the energy providing and/or distributing system being adapted to receive energy from and/or transfer energy to a thermal energy storage as disclosed herein.

In some embodiments, the method of constructing a thermal energy storage and/or an energy system further comprises the steps of:

- constructing a barrier structure in a naturally occurring and/or already existing body of water, the barrier structure enclosing a part of the naturally occurring and/or already existing body of water after construction, - constructing or installing one or more wind turbine foundations on or next to the barrier structure,

- constructing or installing one or more wind turbines on the one or more wind turbine foundations,

- installing a cover, where the cover and the barrier structure is adapted to

encapsulate and insulate a liquid energy storage medium when present, installing a number of solar panels on the cover.

In some embodiments, the method of constructing a thermal energy storage and/or an energy system further comprises installing a waterproof sealing, membrane, etc. at the side(s) of the barrier structure and/or the floor of the bed of the thermal energy storage.

In some embodiments, the enclosed part of the naturally occurring and/or already existing body of water is the liquid energy storage medium.

In some embodiments, the method of constructing a thermal energy storage and/or an energy system comprises the step of constructing at least one additional barrier separating or dividing the enclosed part of the naturally occurring and/or already existing body of water into further parts, and wherein the method comprises subsequently constructing or installing one or more additional wind turbine foundations on or next to the at least one additional barrier and subsequently constructing or installing one or more wind turbines on the additional wind turbine foundations. In some embodiments, the method of constructing a thermal energy storage and/or an energy system further comprises the steps of:

- emptying or draining the enclosed part of the naturally occurring and/or already existing body of water from the barrier structure prior to the step of constructing or installing one or more wind turbine foundations on or next to the barrier structure or prior to the step of constructing the at least one additional barrier (1 10), and

- filling the barrier structure with the liquid energy storage medium after the one or more wind turbines has or have been constructed or installed.

Emptying or draining the enclosed part will create an onshore environment with the advantages as mentioned above, even if the one or more wind turbines are located at or adjacent to (rather than on or integrated with) the barrier structure.

According to another aspect of the present invention, a method of distributing electricity generated by a number of wind turbines and/or a number of photovoltaic and/or hybrid photovoltaic solar panels is provided, wherein the method of distributing electricity generated by a number of wind turbines and/or a number of photovoltaic solar panels comprises the steps of:

- obtaining or providing a data value representing a current available market price pr. unit of electricity, and

- distributing electricity generated by the one or more wind turbines and/or by the number of photovoltaic solar panels to an electrical supply or distribution network if the data value is above the predetermined threshold and distributing electricity generated by the one or more wind turbines and/or by the number of photovoltaic solar panels to a thermal energy storage if the data value is below the

predetermined threshold.

In some embodiments of the method, the thermal energy storage is the thermal energy storage as disclosed herein.

According to another aspect is provided a thermal energy storage, wherein the thermal energy storage is constructed according to the method of constructing a thermal energy storage (and/or an energy system) as disclosed herein and in the accompanying claims.

Some further embodiments and advantages are mentioned throughout the present specification in relation to the Figures and are meant to be included here.

Definitions All headings and sub-headings are used herein for convenience only and should not be constructed as limiting the invention in any way.

The use of any and all examples, or exemplary language provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

This invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law.

Brief description of the drawings Figure 1 schematically illustrates a side view of a thermal energy storage according to an aspect of the present invention being connected to an energy providing and/or distributing facility;

Figures 2a - 2c schematically illustrate details of an embodiment of a barrier structure of a thermal energy storage e.g. as shown in Figures 1 , 4a-4b, 5a-5b, and 8 - 12;

Figure 3 schematically illustrates a graph of an exemplary need for thermal energy in the form of heat for a regional part of a city distributed over one year;

Figure 4a schematically illustrates a top view of a thermal energy storage (shown without a cover) according to some embodiments, e.g. such as the one shown in Figure 1 or 2; Figure 4b schematically illustrates the thermal energy storage of Figure 4a being connected to a number of external sources selectively providing energy to one or more heating sources providing thermal energy to the thermal energy storage or to one or more cooling sources removing thermal energy from the thermal energy storage;

Figures 5a and 5b schematically illustrate a top view and a side view, respectively, of an embodiment of a cover of a thermal energy storage including a number of alternative or additional energy providing external sources;

Figures 6a - 6d schematically shows graphs illustrating monthly energy production by a number of different external sources providing thermal energy to the thermal energy storage and the total monthly energy production according to some embodiments; Figure 7 schematically illustrates a graph illustrating respective exemplary monthly added, transferred, and current level of thermal energy of a thermal energy storage according to some embodiments as disclosed herein;

Figure 8 schematically illustrates a top view of a thermal energy storage (shown without a cover) according to alternative embodiments; Figure 9 schematically illustrates a top view of a thermal energy storage (shown without a cover) according to yet other alternative embodiments;

Figure 10 schematically illustrates a top view of a thermal energy storage being a variation of the thermal energy storage of Figure 9; Figure 1 1 schematically illustrates a top view of a thermal energy storage according to other embodiments;

Figure 12 schematically illustrates a side view of an embodiment of a thermal energy storage e.g. corresponding to one as shown in Figure 9 or 10; Figures 13a and 13b schematically illustrate a side and perspective view, respectively, of an embodiment of a cover of a thermal energy storage including a number of energy providing external sources and/or heating sources;

Figure 14 schematically illustrates a side view of a thermal energy storage being connected to an energy providing and/or distributing facility according to an alternative embodiment; Figure 15 schematically illustrates a side view of one or more heating sources providing thermal energy to a thermal energy storage;

Figure 16 schematically illustrates a side view of a thermal energy storage used in connection with an energy system adapted to provide both heating and cooling according to another aspect of the present invention; Figures 17a - 17j schematically illustrate steps of constructing a thermal energy storage, e.g. corresponding to the ones shown in Figures 9 and 10, according to another aspect of the present invention;

Figure 18 schematically illustrates a side view of an embodiment of a photovoltaic panel mounting structure as disclosed herein; Figure 19 schematically illustrates a side view of a further embodiment of a photovoltaic panel mounting structure as disclosed herein comprising one or more ventilation elements;

Figure 20 schematically illustrates a top view of a photovoltaic panel mounting structure together with an illustrated air flow according to an embodiment of a photovoltaic panel mounting structure as disclosed herein; and Figure 21 schematically illustrates one exemplary embodiment of a thermal energy storage as disclosed herein doubling in function as a coastal protection facility or measure.

Detailed description

Various aspects and embodiments of a thermal energy storage, a method of constructing a thermal energy storage, an energy system comprising at least one thermal energy storage, and an energy providing and/or distributing system adapted to receive energy from a thermal energy storage as disclosed herein will now be described with reference to the figures.

When/if relative expressions such as "upper" and "lower", "right" and "left", "horizontal" and "vertical", "clockwise" and "counter clockwise" or similar are used in the following terms, these typically refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes.

Some of the different components are only disclosed in relation to a single embodiment of the invention, but is meant to be included in the other embodiments without further explanation.

Figure 1 schematically illustrates a side view of a thermal energy storage according to an aspect of the present invention being connected to an energy providing and/or distributing facility. Schematically illustrated is one embodiment of a thermal energy storage 100 comprising a preferably liquid energy storage medium 101 , or alternatively a mix of a plurality of energy storage media. In the shown exemplary embodiment, the energy storage medium 101 is water and more particularly seawater.

Water or seawater is very suited for storing thermal energy even for prolonged times such as one or more months if the thermal energy storage containing the water or seawater is designed appropriately to reduce loss. Water or seawater is very efficient with respect to increasing or decreasing the thermal energy when being subjected to heat. Alternatively other liquid energy storage medium/media may be used e.g. as disclosed herein.

The thermal energy storage 100 comprises a barrier structure 106, such as an enclosing wall structure or similar (see e.g. also Figures 2a and 2b), where the barrier structure 106 is adapted to contain the energy storage medium 101 (when present in the thermal energy storage) and reduce loss of energy.

The thermal energy storage 100 also comprises a cover 104 where the cover 104 and the barrier structure 106 together encapsulate and insulate the energy storage medium 101 thereby reducing loss of thermal energy. Depending on specific design, the cover 104 may be supported by the barrier structure 106 (as shown here) or some other suitable structure. Alternatively, in some other embodiments, the cover 104 may float directly on the thermal energy storage 100 (see e.g. Figures 12 and 14). The cover 104 may be a single piece cover or a cover comprising a number of cover segments.

The cover 104 preferably comprises one or more insulating materials to reduce the loss of thermal energy from the thermal energy storage 100. See e.g. also Figure 13 and related description for details of an embodiment of a cover.

In some embodiments, the cover is free-floating, i.e. floating and located on the surface of the energy storage medium when contained in the thermal energy storage, e.g. with gaps between the 'side' of the cover and adjacent barrier structure. In some embodiments, the cover is secured or moored to the barrier structure and/or the thermal energy storage. In preferred embodiments, the cover is on top of the energy storage medium with clear spacing above (but in some further embodiments e.g. comprising structures, such as solar devices etc. as disclosed herein).

In some embodiments and as shown, the thermal energy storage 100 is an offshore, e.g. near-shore, thermal energy storage. In some embodiments, the thermal energy storage 100 is located at water depths of about 10 meters to about 20 meters.

In some embodiments and as shown, the thermal energy storage 100 is located in a naturally occurring and/or already existing body of water 103. The body of water 103 may e.g. be the sea. Alternatively, the body of water 103 may be a natural or artificial lake, a natural or artificial reservoir, a sufficiently larger river, etc. The artificial reservoirs or lakes may e.g. be a result from excavations, granite, limestone or other mining, etc.

In some embodiments and as shown, the barrier structure 106 of the thermal energy storage 100 extends into a bed 102 of the naturally occurring and/or already existing body of water 103 (as explained further e.g. in connection with Figure 2c). In this way, part of the bed 102 is actually used as a 'floor' of the thermal energy storage 100, which simplifies construction of the thermal energy storage 100 and the costs associated therewith. In some further or alternative embodiments and as shown, the barrier structure 106 extends above a level or surface 107 of the naturally occurring and/or already existing body of water 103. The barrier structure 106 should e.g. extend above the level or surface 107 sufficiently enough to accommodate for tides, rising sea levels, floods, storm surges, etc. In some embodiments, the thermal energy storage 100 comprises a waterproof sealing, membrane, etc. at the side(s) of the barrier structure 106 and/or the floor of the bed 102 of the thermal energy storage 100 instead of simply using the relevant part of the bed as the floor of the thermal energy storage 100. In some embodiments, the barrier structure is a rigid structure.

In some embodiments, the barrier structure fully encapsulates the liquid storage medium about a vertical axis.

As is explained more in detail herein, the thermal energy storage 100 is adapted to selectively receive thermal energy from one or more heating sources (or more generally from one or more thermal energy sources) (see e.g. 400 in Figure 4, 410 in Figure 15 and 16) being configured to selectively heat at least a part of the energy storage medium 101 in a suitable way and thereby increasing the thermal energy of the thermal energy storage 100 for later use. The heating sources may be internal or external to the thermal energy storage or a mix thereof with some being internal and others being external.

Alternatively, or in addition, the thermal energy storage 100 is adapted to selectively transfer thermal energy to one or more cooling sources (see e.g. 410 in Figures 15 and 16) configured to selectively cool at least a part of the liquid energy storage medium 101 thereby decreasing the thermal energy of the thermal energy storage 100, wherein the one or more cooling sources are adapted to receive energy from one or more energy sources to decrease the thermal energy of the thermal storage 100 for later use (for cooling). The cooling sources may be internal or external to the thermal energy storage or a mix thereof with some being internal and others being external.

If a thermal energy storage is to support both heating and cooling (e.g. as in Figure 16) the thermal energy storage may be divided into separate parts comprising a liquid energy medium 101 where one or more parts is used for heating while other one or more parts is used for cooling.

The one or more heating sources and/or one or more cooling sources is/are adapted to receive energy from one or more, preferably external (i.e. external or at least partly external to the energy storage medium 101 ), energy sources in order to supply the thermal energy. The external energy sources may comprise one or more input/output installations or the like in the energy storage medium 101 .

Examples of heating sources include (industrial grade/scale) electric boilers (see e.g. 400 in Figure 4b), (energy receiving side of) heat pumps (see e.g. 410 and 41 1 in Figure 15 and 410 in Figure 16), solar thermal collectors (see e.g. 300a in Figure 16), etc.

Examples of cooling sources include a chiller or chilling unit, a heat pump (see e.g. 410 and 41 1 in Figure 15 and 410 in Figure 16), a compression refrigerator etc. Examples of energy sources include wind turbines (see e.g. Figs. 4b, 12, 14, 16 and 17), solar based electricity generating sources like photovoltaic or HPV solar panels (see e.g. Figs. 5, 13, 14, 16 and 17), (energy providing side of) heat pumps or seawater heat pumps (see e.g. 410 and 412 in Figure 15), etc. In this way, thermal energy, and in particular thermal energy based on renewable energy sources, may be provided to and/or from the thermal energy storage 100.

Figure 6a illustrates an exemplary possible monthly solar based energy production according to some embodiments providing a total amount of energy of about 76,8 GWh over a year with highest contributions in the generally sunnier summer months (for the specific location). Figure 6b illustrates an exemplary possible monthly heat pump based energy production according to some embodiments providing a total amount of energy of about 20 GWh over a year. Figure 6c illustrates an exemplary possible monthly wind based energy production according to some embodiments providing a total amount of energy of about 45 GWh over a year with lowest contributions during summer due to less general wind (for the specific location).

Figure 6d shows the total energy production combined from Figures 6a - 6c. As readily can be seen, the amount of produced energy is significant (about 141 - 142 GWh) and enough to support a district heating facility distributing heat to about as many as about 9 - 10.000 households, apartments, etc. (including ones of older building date), preferably with thermal energy obtained from one or renewable energy sources, even assuming a loss from the thermal energy storage 100 of about 10% (providing about 127 - 128 GWh). The amount of thermal energy shown in Figures 6a - 6d are the amount of energy that is obtained by the thermal energy storage 100, i.e. after potential losses due to energy conversion, energy transportation, and the like In addition, the thermal energy storage 100 is configured for selectively releasing or transferring thermal energy by transferring heat to at least one external heat receiving unit. The external heat receiving unit(s) may e.g. be comprised by or be connected with an energy providing and/or distributing facility 200 such as a district heating facility supplying heating to a number of households, apartments, etc. 220. The external heat receiving unit(s) may also be one or more intermediate units located between the energy providing and/or distributing facility 200 and the thermal energy storage 100. In some embodiments, the at least one external heat receiving unit is a (closed loop) heat exchange system, as generally known, as this will separate the energy storage medium 101 from the water or medium used on the energy receiving side. When using seawater as the energy storage medium 101 , the heat exchange system, at least in the part receiving the energy storage medium 101 should be adapted to be impervious or at least little affected by the seawater (salt content, etc.). Similar or corresponding heat exchange systems may preferably also be employed in connection with any (sea) water heat pumps and/or other equipment as disclosed herein. Receiving heat for the purpose of cooling is somewhat similar.

In some embodiments, the thermal energy storage 100 comprises at least one outlet 105, such as pipe, conduits, etc., wherein the thermal energy storage is more specifically configured for selectively providing an outgoing flow of the energy storage medium 101 via the outlet(s) 105 e.g. to one or more energy transferring or energy converting devices, e.g. a heat exchange system, to transfer heat from the energy storage medium 101 to a heat receiving part of the energy transferring or energy converting devices or heat exchange system and/or to transfer heat to the energy storage medium 101 from a cooling part of the energy transferring or energy converting devices or heat exchange system. The heat exchange system(s) or other energy transferring or energy converting devices are then preferably connected, e.g. via other intermediate devices if preferred or required, to the energy providing and/or distributing facility 200.

In this way, thermal energy is efficiently transferred from and/or to the thermal energy storage 100 to and/or from, respectively, an energy providing and/or distributing facility 200 such as a district heating and/or cooling facility district in times of need. In some embodiments, the thermal energy storage is adapted to receive heat, e.g. surplus heat or heat generated as a by-product or waste-product, from land-based or offshore activities and/or facilities. This may e.g. be receiving (surplus) heat from incineration plants e.g. burning waste.

In some embodiments, the thermal energy storage is adapted to receive cooling, e.g. surplus cooling or cooling generated as a by-product or waste-product, from land-based or offshore activities and/or facilities.

Figure 7 schematically illustrates respective exemplary monthly added, transferred, and current level of thermal energy of a thermal energy storage according to some embodiments.

It is noted that even traditional heat exchange systems are especially efficient in transferring heat using water (or seawater).

In some further embodiments, the thermal energy storage 100 further comprises at least one return inlet 105 adapted to selectively return at least a part of the outgoing flow back to the thermal energy storage 100 after having transferred and/or received heat. In this way, a closed loop system is provided. This is also an advantage when the energy storage medium 101 is seawater as there is no special need for desalination, etc.

The flow of the energy storage medium 101 may be controlled and regulated by one or more pumps or similar devices e.g. located in the energy storage medium 101.

Generally and at least in some embodiments, the energy storage medium 101 in the thermal energy storage 100 will not actively be agitated (it may be agitated somewhat during use due to pumps pumping the medium through the outlet(s) and inlet(s)) and the energy storage medium 101 will be relatively or substantially still leading to a more or less steady state temperature distribution having a temperature gradient increasing from the bed 102 towards the surface 107.

In some embodiments relating to heating, the outlet(s) 105 is/are located substantially at or near where the temperature of the energy storage medium 101 substantially is about 60° Celsius or is expected to substantially be about 60° Celsius. This provides a temperature that is well suited for use with at least certain types of district heating facilities supplying generally older households, etc. In such embodiments, the inlet(s) 105 is preferably located lower than the outlet(s) 105. A district heating facility may also operate with supplying heat at different temperatures to different areas of the households, etc.

The temperature of the energy storage medium 101 for heating, especially when being water or seawater, may have a temperature of about 80° - about 100° Celsius or more specifically about 85 ° - about 95° Celsius near to the surface or top and may have a temperature of about 15° - about 45° Celsius or more specifically about 20° - about 40° Celsius near the bottom (i.e. at/near the bed 102), but the specific temperature and/or temperature distribution will typically be influenced to a relatively large extent by time of year, local ambient conditions, depth of the thermal energy storage 100, etc.

The temperature of the energy storage medium 101 for cooling, especially when being water or seawater, may have a temperature of about 10° - about 20° Celsius near to the surface or top and may have a temperature of about 2° - about 5° Celsius near the bottom (i.e. at/near the bed 102), but the specific temperature and/or temperature distribution will typically be influenced to a relatively large extent by time of year, local ambient conditions, depth of the thermal energy storage 100, etc. It is noted, that if another energy storage medium 101 than water or seawater is used, it is possible to have temperatures of the energy storage medium 101 exceeding 100° Celsius near the surface or top (for heating) or to have temperatures lower than 0° Celsius near the bottom (for cooling). The energy sources such as wind turbines, (photovoltaic or HPV) solar panels, etc. may additionally also provide electricity for the operation of the pumps, heat pumps, and other necessary equipment.

It is to be understood that the shape of the interior of the thermal energy storage 100 may be optimised in different ways. It is generally preferred that the surface area of the energy storage medium is relatively small compared to the overall (inner) volume of the thermal energy storage 100, but there may be other considerations to meet leading to different designs e.g. as also disclosed herein. A design, optimising the ratio of the surface area to the volume may e.g. be a design with a generally cylindrically shaped barrier structure 106 ending in a half-sphere at the bottom. Different designs for various embodiments of a thermal energy storage 100 is illustrated in Figs. 4a, 4b, 8 - 12, 14, 16 and 17 but a design may depend on an actual situation and/or need.

The thermal energy storage 100 may be constructed in many suitable ways as described further elsewhere, e.g. in connection with Fig. 17.

The shown exemplary embodiment of a thermal energy storage 100 is shown as being offshore, or more particularly near-shore, but it may also be constructed as an extension of an already existing shore, i.e. the barrier structure 106 would then only be partly surrounded by the naturally occurring and/or already existing body of water 103, whereby the thermal energy storage 100 shown in Figure 1 only would have a body of water 103 to the right in the Figure 1. In some embodiments, the thermal energy storage may form or be part of a coastal protection facility or measure, sluice system, flooding protection facility, dike facility, etc. as illustrated as an exemplary embodiment in Figure 21.

Figures 2a - 2c schematically illustrate details of an embodiment of a barrier structure of a thermal energy storage e.g. as shown in Figures 1 , 4a-4b, 5a-5b, and 8 - 12. Shown is one embodiment of a barrier structure 106 for a thermal energy storage 100 as disclosed herein, where the barrier structure 106 is a wall structure and more particularly a double wall 500 having or comprising an inner wall 501 and an outer wall 502 with one or more materials 503 in-between them. The term 'inner' and Outer' is used as the inner wall 501 is closer to the energy storage medium 101 than the outer wall 502. The outer wall 502 at least partly, e.g. fully or substantially fully, encompasses the inner wall 501.

Figure 2a illustrates a part of the double wall structure 500 from above (or below) and Figure 2b illustrates a cross section along line A-B in Figure 2a. Figure 2c illustrates further details and illustrates an embodiment of a thermal energy storage 100 comprising a double wall structure 500.

In some embodiments and as illustrated in Figures 2a and 2b, both the inner wall 501 and the outer wall 502 are each is a sheet pile wall structure or similar constructing using sheet pile segments as generally known. Using sheet pile wall structures has the advantage that they are relatively inexpensive, easy to install - even in water or seawater - lowering manufacturing costs for the thermal energy storage.

The one or more materials 503 may be any materials suitable for a given need or design. In some embodiments, the material(s) 503 are insulating with respect to heat and/or cold in order to reduce losses from the thermal energy storage. The material(s) 503 may e.g. be

(e.g. reinforced) concrete, sand, dirt, mud, and/or the like. The sand, dirt, mud, etc. may e.g. be obtained directly from the bed of the (naturally occurring and/or already existing) body of water that the thermal energy storage is or may be located in e.g. as part of increasing the volume of the thermal energy storage by digging into the bed after the inner and outer wall 501 , 502 have been put in place. Concrete may e.g. be used, if the double wall needs to support something relatively heavy, e.g. one or more wind turbines as explained further in connection with Figures 9 - 12, 14 and 15, however a wind turbine foundation may also be used in a wall comprising sand, dirt, mud, etc. to support one or more wind turbines.

In some embodiments of thermal energy storages, the width of the double wall (i.e. the distance between the inner and the outer wall at any given place) is about 10 - about 15 meters but can be more or less depending on use.

A barrier structure 106 comprising a double wall e.g. of sheet pile walls is suitable both for relatively circular and square or rectangular (as seen from above) designs.

In some alternative embodiments, the barrier structure 106 only comprises a single wall structure, e.g. a single sheet pile wall or other, but then offering less or basically no support.

Figure 2c illustrates an embodiment of a thermal energy storage 100 comprising a barrier structure 106 comprising a double wall structure 500, such as shown in Figures 2a and 2b, having an inner and an outer wall 501 , 502 with one or more materials 503 in-between them. In this embodiment, the thermal energy storage 100 is located in a naturally occurring and/or already existing body of water 103 and the barrier structure 106/the double wall 500 extends at a first (upper) end 510 above a level 107 of the body of water 103 and extends at a second (lower) end 51 1 into a bed 102 of the body of water 103. The barrier structure 106/the double wall 500 may simply be driven into the bed 102 of the body of water 103 wherein the barrier structure 106/the double wall 500 separates the energy storage medium 101 eventually contained in the thermal energy storage 100 from the body of water 103. As mentioned, the bed 102 within the walls 500 will in this way constitute the floor of the thermal energy storage 100 avoiding the need for manufacturing dedicated flooring saving costs and associated manufacturing time as well as necessarily specifically having to prepare the bed of the body of water. Alternatively, the thermal energy storage 100 comprises a waterproof sealing, membrane, etc. at the side(s) of the barrier structure 106/the double wall 500 and/or at the floor of the relevant part of the bed 102. The thermal energy storage 100 also comprises a suitable cover as disclosed herein.

Figure 3 schematically illustrates a graph of an exemplary need for thermal energy in the form of heat for a regional part of a city distributed over one year.

Shown is one typical example of a yearly demand for heat for a district heating facility supplying heat to a regional part of a city, e.g. with about 9 - 10.000 households, apartments, etc.

Figure 4a schematically illustrates a top view of a thermal energy storage (shown without a cover) according to some embodiments, e.g. such as the one shown in Figure 1 or 2.

Shown is a thermal energy storage 100 comprising a barrier structure 106 and an energy storage medium 101 as disclosed herein where the thermal energy storage 100 has a generally cylindrical shape and a generally circular cross section seen from the top. It may end in a more or less half-spherical shape (e.g. if the volume has been increased by digging into the bed of a body of water as disclosed herein) or simply end with the bed of a body of water more or less left as it were as also disclosed herein.

Such a general shape has the advantage that the surface area is minimised in comparison to the total volume of the energy storage medium 101 , which minimise losses of thermal energy.

Figure 4b schematically illustrates the thermal energy storage of Figure 4a being connected to a number of external sources selectively providing energy to one or more heating sources providing thermal energy to the thermal energy storage or to one or more cooling sources removing thermal energy from the thermal energy storage.

Shown, as an example is the thermal energy storage 100 of Figure 4a (but another thermal energy storage as disclosed herein could be applicable) shown here together with one or more heating sources or one or more cooling sources (or more generally one or more thermal energy sources) 400 that are connected with one or more external energy providing sources 230 via one or more suitable connections 205.

The heating or cooling source(s) 400 may be internal (to the thermal energy storage) as shown or alternatively be external or a mixture thereof. The heating or cooling source(s) 400 receives energy, such as electrical energy, from the external energy providing source(s) 230 and increases (heating) or decreases (cooling) the thermal energy of the thermal energy storage 100 by transferring heat to (heating) or from (cooling) the contained energy storage medium 101.

The heating sources 400 may e.g. be (industrial grade/scale) electric boilers or the like and the external energy providing sources 230 are offshore wind turbines although other types may be used as an alternative or in addition. Such electric boilers may have heating capabilities ranging from small to very large (50 megawatt or more). In some embodiments, only one electric boiler is used capable of delivering about 4.5 megawatt or alternatively 9 megawatt of heat depending on design and use. Cooling sources may e.g. be chiller or chilling units, heat pumps, or compression refrigerators and again the external energy providing sources 230 may be offshore wind turbines although other types may be used as an alternative or in addition.

The offshore wind turbines 230 may be connected via one or more sea cables 205 or the like to a transformer (e.g. located on or at the barrier structure 106) connected in turn to the heating source(s)/electric boiler(s) or cooling sources 400. Electricity from the wind turbines will power the electric boilers 400 increasing the thermal energy of the thermal energy storage 100 (or alternatively power the cooling sources to decrease the thermal energy of the thermal energy storage 100). The normal energy efficiency of such heaters is quite close to 100%, so little loss will be impaired when using the electricity from the wind turbines to heat the thermal energy storage medium.

In some embodiments, the offshore wind turbines 230 are also connected for delivering electricity to a regular power grid, an electrical supply or distribution network, etc. by one or more additional sea cables 215 as shown by the dotted line. In this way, the electricity provided to the heating or cooling sources, and thereby by extension the amount of thermal energy added or removed, may selectively be controlled. The provided electricity may e.g. be controlled to be provided for use in connection with the thermal energy store during off- peak times such as night time and/or during very favourable wind conditions, i.e. when the current supply of electricity exceeds a current demand for electricity. In this way, the electricity is used for storing or removing thermal energy that can be used right away or stored for (e.g. much) later use rather than having to sell it very cheaply or at a loss on an open marked (where current prices will be very low or even negative due to a current overproduction) or simply wasted.

According to one aspect and/or in some embodiments, the one or more wind turbines 230 are adapted (e.g. by a suitable controlling unit) to selectively deliver electrical power to the one or more heating or cooling sources 400 or deliver electrical power to the regular power grid, the electrical supply or distribution network, etc. in response to one or more predetermined criteria. The one or more predetermined criteria may e.g. be comparing a current/real-time available market price pr. unit of electricity (sometimes also referred to as a spot-price for wind power electricity) with a predetermined threshold and distribute the electricity to the power grid, the electrical supply or distribution network, etc. when the available market price is above the predetermined threshold and distribute the electricity for use in heating up and/or cooling the energy storage medium 101 when the available market price is below the predetermined threshold. The determination of where to distribute the electricity may e.g. be made automatically, semi-automatically, or even manually. In this way, it is possible to control delivery of generated electricity to where the benefit will be greatest. Additionally, it is possible to obtain a value (storage of heat for later valuable heat distribution and/or storage of cold for later valuable cooling distribution) of otherwise low or negative value electricity due to a current low market price.

The wind turbines 230 may be located relatively distant to the thermal energy storage 100, e.g. several kilometres or more, without any particular drawbacks. In some alternative embodiments, wind turbines are located on, at, or integrated with the barrier structure 106 as disclosed herein, e.g. in connection with Figures 9 - 12, 14 and 15.

Having one or more heating sources and/or cooling sources 400 and/or being connected to external offshore wind turbines 230 for electricity is independent of the design and shape of the thermal energy storage 100 and may equally be used with other designs, e.g. as shown in Figures 1 , 2c, 8 - 12, 14, and 15. Figures 5a and 5b schematically illustrate a top view and a side view, respectively, of an embodiment of a cover of a thermal energy storage including a number of alternative or additional energy providing external sources.

Shown is an embodiment of a cover 104 for a thermal energy storage as disclosed herein. This particular exemplary cover 104 is for a thermal energy storage having a circular cross section (as seen from the top).

According to the shown embodiment, the cover 104 comprises one or more external energy sources in the form of electricity generating solar based energy sources 300 like photovoltaic or HPV solar panels or similar providing electricity to power one or more heating and/or cooling sources - see e.g. 400 in Figure 4b - as disclosed herein to add/remove thermal energy to/from the thermal energy storage and/or one or more heating sources in the form of solar thermal collectors providing a heated medium, e.g. water or seawater, in heat exchanging connection with the liquid energy storage medium to add thermal energy to the thermal energy storage. The solar thermal collectors may in general be any solar based energy source that can deliver thermal energy to the thermal energy storage.

In this way, the area of the cover may be used for an additional purpose (in addition to help insulating the energy storage medium reducing losses) namely providing space for a (relatively large) number of external energy sources and/or heating sources. In addition, it is ensured that the distance between the external energy source and/or heating sources and the energy storage medium is relatively short, which may reduce losses and/or keep conduits of simpler (primarily when providing a heated medium rather than when providing electricity).

In at least some of the envisaged embodiments and uses, the surface area will be relatively large, e.g. about 3.500.000 - about 4.500.000 square metres (while an actual size will depend on specific use and design). For such sizes, e.g. for 4.000.000 square metres, it is feasible to have e.g. as many as about 12.000 solar panels with a combined active panel surface area of about 160.000 square meters on the cover 104 e.g. delivering about 75 - 80 GWh pr. year depending on actual whether conditions, efficiency, etc. (see also Figure 6a).

In some embodiments, the cover 104 may also support different external energy sources than solar panels.

For embodiments where the cover 104 comprises a number of external energy sources and/or heating sources the cover needs to be of a design being able to support the ensuing weight. As an example 12.000 solar panels of a particular type will together weigh about a little more than 3.000 tonnes. In some embodiments, the cover 104 is made of a rigid plastic material (e.g. polyethylene (including low-density and high-density), polypropylene, thermoplastic materials like polyvinylidene fluoride, etc.) e.g. having cavities comprising air, Styrofoam or other polystyrene foam(s), or other materials having good thermal insulating properties, and e.g. have a height of about 0.5 to about 1 metres. Some cover designs will be able to float directly on the energy storage medium (even with the added weight of external energy sources).

Alternatively, the cover 104 may also be made of (reinforced) concrete then typically being supported by the barrier structure, by supporting pillars, or by another structure. A cover 104 may also be comprises by a number of individual cover segments.

If the thermal energy storage is divided into at least two separate parts, as disclosed herein, a cover or cover segment may be used for each part.

In some embodiments, then typically without supporting a number of external energy sources and/or heating sources, the cover may e.g. be collapsible, foldable, removable, or the like.

Even though the cover of Figure 5a is shown to have a circular cross section is may generally have any suitable shape, e.g. square, rectangular, etc. fitting on thermal energy storages as shown in Figures 8, 9 - 10, 12, 14, and 15.

A more specific embodiment of a cover 104 comprising a number of external energy sources and/or heating sources 300 is e.g. shown and explained in connection with Figure 13.

Figures 6a - 6d schematically shows graphs illustrating monthly energy production by a number of different external sources providing thermal energy to the thermal energy storage and the total monthly energy production according to some embodiments.

Shown in Figure 6a is an exemplary possible monthly production of energy for a year by about 12.000 solar panels, e.g. of the type produced by Arcon-Sunmark each having a yearly production of about 75 - 80 GWh, of course depending on actual weather conditions (number of sun-hours, intensity, etc.). As disclosed herein, the solar panels may preferably be located on a top of a cover of a thermal energy storage according to various

embodiments. In this example, about 77 GWh of energy is produced for the year with highest contributions in the generally sunnier summer months (for the specific location). Shown in Figure 6b is an exemplary possible monthly production of energy for a year by about six seawater heat pumps, e.g. of the type Sabroe by Johnson Controls, providing a total amount of energy of about 20 GWh for a year again depending on actual conditions such as temperature of the surrounding seawater, current conditions, production and/or availability of electricity from external energy sources, such as wind turbines, as disclosed herein if such are used, etc. As disclosed herein, the seawater heat pumps may be located in a vicinity of a thermal energy storage, e.g. adjacent to the thermal energy storage, integrated into or located on top of the walls or barrier structure of the thermal energy storage (see e.g. Figure 15), internally in the thermal energy storage (i.e. in the energy storage medium), and/or combinations thereof. The seawater heat pumps are in some embodiments, and in this example, operated running on electricity supplied by one or more wind turbines.

As can be seen, the production of energy is greatest during the colder months (coinciding with the times for a greater/greatest need for heat energy) due to using electricity from a number of wind turbines that generally generate more electrical power during the more windy colder months.

Shown in Figure 6c is an exemplary possible monthly production of energy for a year by about three to four wind turbines providing a total amount of energy of about 45 GWh for the year with lowest contributions during summer due to less general wind (for the specific location). The produced electricity may be used to increase the thermal energy of a thermal energy storage as disclosed herein, e.g. using one or more electric boilers, etc., or alternatively only a part of the produced electricity is used in this way in response to a current available market price pr. unit of electricity as also disclosed herein.

Fig. 6d shows the total energy production combined from Figs. 6a - c. As readily can be seen, the amount of produced energy is significant (about 141 - 142 GWh) and enough to support or supplement a district heating facility distributing heat to about as many as 9 - 10.000 households, apartments, etc. (including ones of older building date), even assuming a loss from the thermal energy storage 100 of about 10%.

Figure 7 schematically illustrates a graph illustrating respective exemplary monthly added, transferred, and current level of thermal energy of a thermal energy storage according to some embodiments as disclosed herein.

Shown is a monthly addition of thermal energy that is stored in the thermal energy storage having, in this particular example, a storage capacity of about 2 million cubic metres of the energy storage medium. The monthly additions are the ones shown also in Figure 6d. It is noted that the thermal energy has a starting amount (i.e. at end of December the previous year) of thermal energy being about 39 GWh.

Also shown for each month is a transferred amount of thermal energy (including loss), i.e. the amount of thermal energy that is withdrawn from the thermal energy for use elsewhere. The transferred amount will depend on an actual need for thermal energy and will e.g.

correspond to (fluctuate with) a need such as indicated in Figure 3 if the thermal energy is to be used to supplement or support a district heating facility supplying heat to a regional part of a city.

The loss will depend on the specific embodiment of the thermal energy storage and e.g. ambient conditions like ambient temperature, weather conditions, etc. In this figure, a rather highly estimated loss of 10% is used.

Further shown for each month is the amount of thermal energy present (at the end of the respective month) that is present in the thermal energy storage given the added and transferred amounts of thermal energy. The stored thermal energy, preferably provided by renewable energy sources as disclosed herein, is stored when exceeding demand (i.e. in months May - September) and used in times where demand exceeds addition/production (January - April and October - December). In the times where demand exceed addition/production, the produced thermal energy would not be enough to cover the demand (at least to the same degree) and a district heating facility, etc. would need to rely on or more on other sources of energy, e.g. burning of fossil fuels, etc.

As can be seen, thermal energy is efficiently stored even for long periods of time between a time of production/addition and a time of use/demand. Furthermore, the monthly output of thermal energy (ranging from about 2 GWh to about 23) contributes significantly e.g. to a district heating facility supplying heat to a regional part of a city.

It is a significant advantage to be able to efficiently store thermal energy, especially from renewable sources and in particular on this scale, during times when production exceeds demand and be able to efficiently release the thermal energy at times of generally high(er) demand and/or when demand exceeds current production.

In the shown example, the stored thermal energy is close to not meeting the demand (for March and April) but still manages it. To mitigate this, additional thermal energy may be put into the storage initially and/or ongoingly to create a larger buffer e.g. for unexpected higher demand.

Figure 8 schematically illustrates a top view of a thermal energy storage (shown without a cover) according to alternative embodiments. Shown in Figure 8 is a thermal energy storage 100 corresponding to thermal energy storages as disclosed herein but where the thermal energy storage 100 has a generally rectangular cross section seen from the top. A generally rectangular shaped thermal energy storage 100 may e.g. be an advantage due to specific sea bed conditions, specific adjacent or nearby shipping traffic, facilitating one or more specific technical facilities, etc. A further advantage is e.g. if a number of wind turbines (see e.g. Figures 9 and 10) is to be located on or near the barrier structure of the thermal energy storage 100 as they more simply may be arranged in rows.

An exemplary size and capacity of such a thermal energy storage 100 is e.g. a length of about 4 kilometres, a width of about 500 metres and assuming an average water depth of about 10 metres will provide about 20.000.000 cubic metres of volume or capacity for the energy storage medium 101.

Figure 9 schematically illustrates a top view of a thermal energy storage (shown without a cover) according to yet other alternative embodiments.

Shown in Figure 9 is a thermal energy storage 100 corresponding to thermal energy storages as disclosed herein also having a generally rectangular cross section seen from the top but where the thermal energy storage 100 comprises an additional barrier 1 10 dividing or partitioning the thermal energy storage 100 into at least two separate parts (here precisely two parts) where each part comprises a respective part of the energy storage medium 101 . Dividing or partitioning the thermal energy storage 100 into several parts may e.g. be an advantage when providing both heating and cooling and/or in connection with greater maintenance tasks (as one part may be maintained while the other(s) still will be

operational). An advantage may e.g. also be that the different parts can contain the energy storage medium 101 at different temperatures - e.g. for supplying heat at different temperatures to different areas, regions, types of buildings, etc. (e.g. at least one high(er) temperature part and at least one low(er) temperature part), having at least one section comprising the energy storage medium 101 at a low or cold temperature for supplying cooling as disclosed herein, etc. Each part will have a cover or number of cover segments as disclosed herein. The additional barrier 1 10 may e.g. be corresponding to the barrier structure(s) or the wall structure(s) of a barrier structure as disclosed herein or by a different kind of structure. In some embodiments, the additional barrier 1 10 may e.g. be a dam structure, embankment, or the like made during manufacture of the thermal energy storage 100, e.g. as described in connection with Figure 17. The dam structure, embankment, or the like may e.g. be made from sand, dirt, mud, and/or the like e.g. obtained directly from the bed of the (naturally occurring and/or already existing) body of water that the thermal energy storage is e.g. as part of increasing the volume of the thermal energy storage by digging into the bed. The additional barrier 1 10 may e.g. be made from or comprise (reinforced) concrete. Further shown, is a number, here 24 as an example, of wind turbine foundations 210 that is built into, build in connection with, and/or integrated with the barrier structure 106. This readily provides an advantageous location for one or more external energy providing sources in the form of wind turbines (see e.g. 230 in Figures 12, 14 and 17) and do e.g. not require a connection to a remote grid of wind turbines (or require connection to less remotely located wind turbines)

The height of the wind turbines may be advantageously be different in some situations, e.g. as explained in connection with Figure 12.

The shown and corresponding shapes may of course also be used for thermal energy storages not comprising any wind turbine foundations 210. An exemplary size and capacity of such a thermal energy storage 100 is e.g. a length of about 4 kilometres, a width of about 1 kilometre and assuming an average water depth of about 10 metres will provide about 40.000.000 cubic metres of volume or capacity for the energy storage medium 101.

Figure 10 schematically illustrates a top view of a thermal energy storage being a variation of the thermal energy storage of Figure 9.

Shown is a thermal energy storage 100 as disclosed herein and in particular corresponding to the thermal energy storage of Figure 9 but where a further additional barrier 1 10 divides a part into two further smaller parts or reservoirs.

In some embodiments, the two further smaller parts or reservoirs may e.g. be used for hydrostatic applications, where the energy storage medium, in the form of water or seawater, 101 may be pumped from a first part or reservoir to a second part or reservoir e.g. using electricity (e.g. generated by wind turbines located on/in the barrier structure 106 if present, remotely located wind turbines, solar panels e.g. located on the top of a cover, or through other means, especially at off-peak situations). Thus potential energy is stored as generally known. In such embodiments, the thermal energy storage 100 comprises a number of water based turbines adapted to generate electricity where at least some of the water/seawater of the second part or reservoir selectively may be released to the first part or reservoir driving the water based turbines thereby generating electricity as generally known. An advantage of such an arrangement is e.g. that production of a relatively large amount of electrical energy at a steady state can be initiated virtually momentarily, if an increased need for electricity unexpectedly arises. The water based turbines is connected to a land-based electrical grid, facility, etc.

It is to be understood, that the designs according to Figures 9 and 10 and corresponding ones may also be used without any wind turbine foundations 210.

Figure 1 1 schematically illustrates a top view of a thermal energy storage according to other embodiments. Shown is a thermal energy storage 100 having a generally circular cross section seen from the top and corresponding e.g. to the thermal energy storage of Figures 1 , 2c, 4a, 4b, and 14 but where the barrier structure 106 also comprises a number, here 12 as an example, of wind turbine foundations 210 as disclosed herein.

Figure 12 schematically illustrates a side view of an embodiment of a thermal energy storage e.g. corresponding to one as shown in Figure 9 or 10.

Shown is an embodiment of a thermal energy storage 100 located in a naturally occurring and/or already existing body of water 103 and e.g. corresponding to the thermal energy stores of Figures 9 and 10, i.e. having a generally rectangular shape and having three (as an example) rows, a first, a second, and a third row, of wind turbine foundations 210 and wind turbines 230

The thermal energy storage 100 is preferably orientated (during manufacture) so that the rows face an expected or estimated general favourable wind direction as indicated by the arrow from left to right in the Figure.

As can be seen, the first row of wind turbines 230 is closest to the wind direction by the second row of wind turbines 230 and finally followed by the third row of wind turbines 230 being furthest away from the general wind direction. The wind turbines 230 of the first row has a smallest height, the wind turbines 230 of the second row has a middle height, and the wind turbines 230 of the third row has a highest height of the wind turbines.

In this way, the wind turbines do not block the wind for each other leading to increased efficiency. Figures 13a and 13b schematically illustrate a side and perspective view, respectively, of an embodiment of a cover of a thermal energy storage including a number of energy providing external sources and/or heating sources.

Shown is an expedient embodiment of a particular cover of a thermal energy storage as disclosed herein. The cover comprises a number of energy providing external sources and/or heating sources in the form of solar panels 300 (PV, hybrid, and/or solar thermal collector, or in principal any suitable type). A solar panel mounting structure (equally referred to as photovoltaic panel mounting structure when comprising photovoltaic panels) comprising separate solar panel modules or units e.g. arranged in suitable arrays, grids, layouts, etc. e.g. as illustrated by 300 or 1 104 in Figures 13, 14, and 18 - 20. According to an aspect of the present invention, the solar panel 300 comprises a number of generally V-shaped individual solar panel units, each unit comprising two individual solar panels in some embodiments angled at about 18° - 22°, e.g. 20°, in relation to the surface of the cover 104, where the two individual solar panels constitute the 'wings' of the V-shape. Such an angle and the V-shape has shown to be particularly efficient in relation to obtaining solar energy when generally located along an eastern-western direction whereby both respective panels will receive solar energy as opposed to the more traditional location of facing a southern direction (optimising production in relation to active solar panel surface area). There will be less efficiency (e.g. about 20% less or so) locating in the east-west direction compared to locating facing a southern direction but a solar panel facing a southern direction cannot efficiently make use of a double winged solar panel construction due to one of the panels then facing a generally northern direction. Here it makes most sense to use (a large number of) a single panel design. The double winged solar panel construction optimises the overall active solar panel surface area given a constrained amount of space to be located on (as the cover dictates). Therefore the double winged solar panel makes up for the loss of efficiency due to be located in a general direction being different from facing a southern direction. The direct length (as indicated by the shown double-arrow) from 'wing-tip' to 'wing-tip' of a unit may e.g. be about 4 metres. Each solar panel may have a length of about 1 .5 - 2 metres, e.g. about 1 .8 metres. Between and/or underneath the two wings of a solar panel unit is located one or more insulting elements 312, at least in some embodiments. This provides additional insulation (in addition to the cover) of the thermal energy storage 100 and furthermore fills the space beneath wings of the respective solar panels. The insulating element 312 may e.g. be made of Styrofoam or other polystyrene foam(s), or other materials having good thermal insulating properties.

Such solar panel units may be placed closely next to each other (both in x and y direction) and may provide, as seen in Figure 13b, a cover 104 that is densely packed with solar panels, thereby utilizing the surface area of a cover to a high degree. Further shown in Figure 13a are details of this embodiment of the cover 104. In this and similar embodiments, the cover 104 comprises a top layer 315 and a lower layer 316 with a number of cover insulating elements 320 in-between. The cover insulating elements 320 may e.g. be made of Styrofoam or other polystyrene foam(s), or other materials having good thermal insulating properties. The material of the cover insulating elements 320 and the material of the insulating element 312 need not be the same but can be. The top layer 315 and/or the lower layer 316 may e.g. be made of (reinforced) concrete or any other suitable material providing enough support for the weight of any energy providing external sources or solar panels to be located on the cover 104. The top layer 315 and/or the lower layer 316 may in some embodiments comprise a water resistant or water proof membrane e.g.

comprising high density polyethylen (HDPE) plastic material or other suitable material.

In the shown embodiment, the cover 104 comprises five times twenty times ten cover insulating elements 320 in the height, width, and length direction, respectively. A cover insulating element 320 may e.g. have a dimension (H x W x L) of about 0.220 metres x 1 meter x 2 metres. The number of used cover insulating elements 320 and their respective dimension(s) will typically vary a lot depending on specific use and/or design.

It is to be understood that other layouts (number of cover insulating elements 320 in respective directions) of the cover insulating elements 320 may be used depending on design and use.

Figure 13b illustrates a perspective view of the cover 104 comprising a densely packed number of energy providing external sources in the form of V-shaped solar panels 300. Such a cover may be used in connection with the embodiments of a thermal energy storage as disclosed herein. It is to be understood, the such a V-shaped solar panel as disclosed herein may be used in other connections than with a thermal energy storage, e.g. for traditional or other solar panel uses.

The cover 104 of Figures 13a and 13b could also have other general shapes, e.g. circular. Figure 14 schematically illustrates a side view of a thermal energy storage being connected to an energy providing and/or distributing facility according to an alternative embodiment.

The figure corresponds more or less to Figure 1 except as noted in the following.

Shown is a thermal energy storage 100 as disclosed herein being located in a naturally occurring and/or already existing body of water 103 and comprising an energy storage medium 101 being seawater or as otherwise disclosed herein. The thermal energy storage 100 comprises a barrier structure 106 wherein one or more external energy providing sources in the form of a number of wind turbines 230 is located. The wind turbines 230 are connected to deliver electricity via one or more suitable connections 205 to a technical facility 250. The technical facility is further connected to selectively receive the energy storage medium/seawater 101 via at least one outlet 105. The thermal energy storage 100 further comprises a cover 104 as disclosed herein upon which a number one or more external energy providing sources in the form of solar panels 300 are located delivering electricity or electricity and a heated medium depending on the type of solar panel. The cover 104 as shown comprises three separate cover segments. The technical facility 250 is connected via at least one supply and at least one return line or conduit 251 to an energy providing and/or distributing system 200 that in turn is connected to a heating distribution network 252 supplying to a number of households, etc. 220 as disclosed herein.

In some embodiments, the technical facility 250 is also connected to deliver electricity to a land-based electrical grid.

The thermal energy storage 100 may also be connected to one or more external energy providing sources in the form of seawater heat pumps (not shown) as disclosed herein.

Alternatively or in addition, the thermal energy storage 100 may also be adapted for cooling as disclosed herein. Figure 15 schematically illustrates a side view of one or more heating sources providing thermal energy to a thermal energy storage. Shown is a thermal energy storage 100 as disclosed herein comprising one or more heating sources here in the form of one or more heat pumps 410. In the shown embodiment, the heat pump(s) 410 are water, and more specifically seawater, heat pumps. The respective heat pump(s) 410 is/are adapted to selectively supply heat to the energy storage medium 101 of the thermal energy storage 100. In some embodiments, and as shown, the heat pump(s) 410 is connected to the energy storage medium 101 via one or more conduits 41 1 for intake and recirculation of the energy storage medium 101 and via one or more conduits 412 to a naturally occurring and/or already existing body of water 103, e.g. and as shown the body of water the thermal energy storage 100 is located in. Alternatively, the heat pump(s) 410 is connected via conduits 412 to another body of water. In some embodiments, the heat pump(s) 410 is - in addition or as an alternative - connected via conduits 412 to take in a volume of air.

The heat pump(s) 410 is/are connected with one or more external energy providing sources as disclosed herein, e.g. one or more wind turbines, one or more solar panels, etc., via one or more suitable connections 205.

As generally known, the heat pump(s) 410 is adapted to transfer heat from the water or air supplied (and returned) via the conduit(s) 412 to the energy storage medium 101 as supplied (and recirculated) via the conduit(s) 41 1. The heat pump(s) 410 may e.g. use natural coolants such as ammonia, water vapour or steam, carbon dioxide, hydrocarbons, etc. A coefficient of performance (COP) for the heat pump(s) 410 may e.g. be about 3 to about 3.5 or 4 as seen over a year.

It is advantageous if the heat supplying side of a heat pump 410, i.e. the conduit(s) 412, receives a medium with as high a temperature as possible.

Water and seawater heat pumps having a capacity of about 1 megawatt or more are generally known.

In the shown and corresponding embodiments, the heat pump(s) 410 are located on the top of a barrier structure 106 as disclosed herein. Alternatively, the heat pump(s) 410 may be integrated with the barrier structure 106, be located inside the thermal energy storage 100 in the energy storage medium 101 (where the conduit(s) 412 goes outside), or be located outside the thermal energy storage 100 e.g. in the body of water 103 (where the conduit(s) 41 1 goes inside the thermal energy storage 100). In some embodiments, the heat pump(s) 410 is/are adapted to selectable by-pass the thermal energy storage 100 and to heat a suitable medium transferring the transferred heat onshore to a suitable facility e.g. an energy providing and/or distributing facility (see e.g. 200 in Figures 1 and 14) such as a district heating facility. Alternatively or in addition, the heat pump(s) 410 may also be adapted for cooling as disclosed herein and e.g. as explained in connection with Figure 16.

Figure 16 schematically illustrates a side view of a thermal energy storage used in connection with an energy system adapted to provide both heating and cooling according to another aspect of the present invention. Shown is a thermal energy storage 100 as disclosed herein divided, in this particular example, into a heat storage (shown to the left in the Figure) and a cold storage (shown to the right in the Figure) by an additional barrier 110, both storages comprising a liquid energy storage medium (the same or alternatively different).

As disclosed herein, one or more energy providing sources in the form of wind turbines 230 (here integrated with a barrier structure 106 of the thermal energy storage 100) selectively supplies electricity, via one or more suitable connections 205, to operate one or more heating and cooling units here in the form of heat pumps 410 as disclosed herein, here as an example located on the additional barrier 1 10. In the shown embodiment, the one or more wind turbines 230 are also connected via the one or more suitable connections 205 to selectively provide electricity to an energy providing and/or distributing facility 200 such as a district heating facility or similar, distributing the provided electricity to a number of households, apartments, etc. 220.

Each part (i.e. the heat and the cold storage) comprises a cover 104 as disclosed herein, each cover comprising a number of energy sources in the form of solar based energy sources 300a, 300b as disclosed herein.

The solar based energy sources 300a associated with the heat storage part (and in this example located on the cover 104 of the heat storage part) are solar thermal collectors 300a that heats the liquid energy storage medium 101 being passed by the solar thermal collectors 300a, taking up heat along the way, from one or more outlets of the heat storage (shown with the leftmost 45° Celsius of the heat storage) and brought back into the heat store again via one or more inlets of the heat storage (shown with 95° Celsius). In this way, the thermal energy of the heat storage is increased by the solar thermal collectors 300a. The solar based energy sources 300b associated with the cold storage part (and in this example located on the cover 104 of the cold storage part) are photovoltaic solar panels 300b providing electricity to selectively operate the heat pumps 410 and/or to be selectively supplied to the energy providing and/or distributing facility 200 via the one or more connections 205.

The heat pump(s) 410 are connected with their energy removing side to the cold storage (as shown by the outlet and inlet designated 10° Celsius and 2° Celsius, respectively of the cold storage) and their energy receiving side to the heat storage (as shown by the outlet and inlet designated 45° Celsius and 90° Celsius, respectively of the heat storage). In this way, very efficient use is made of the heat pump(s) 410 both cooling the cold storage and heating the heat storage and running on renewable energy (from wind turbines 230 and/or from photovoltaic solar panels 300b).

The heat storage is connected, as disclosed herein, via one or more outlets 105 (located at an upper part of the heat storage having a generally higher temperature), for selectively providing an outgoing flow of the liquid energy storage medium 101 to the energy providing and/or distributing facility 200 supplying heating to the number of households, apartments, etc. 220, e.g. via one or more energy transferring or energy converting devices, such as a heat exchange system, to transfer heat from the energy storage medium 101 to the energy providing and/or distributing facility 200. After having transferred heat to the energy providing and/or distributing facility 200, the outgoing flow of the liquid energy storage medium is returned, now with a lower temperature, to the heat storage (at a lower part of the heat storage).

In the shown example, the number of households, apartments, etc. 220 comprises aging housing stock 220a and relatively newer housing stock 220b, and the energy providing and/or distributing facility 200 is adapted to provide the heat from the heat storage (then having a higher temperature) to the aging housing stock 220a first and subsequently to the newer housing stock 220b before returning the flow, via a suitable distribution network 252. This is a very efficient way to distribute heating involving both aging and newer housing stock. The cold storage is connected, as disclosed herein, via one or more outlets 105 (located at a lower part of the cold storage having a generally lower temperature), for selectively providing an outgoing flow of the liquid energy storage medium 101 to the energy providing and/or distributing facility 200 supplying cooling to the number of households, apartments, etc. 220, e.g. via one or more energy transferring or energy converting devices, such as a heat exchange system, to transfer cold from the energy storage medium 101 to the energy providing and/or distributing facility 200. After having transferred cold to the energy providing and/or distributing facility 200, the outgoing flow of the liquid energy storage medium is returned, now with a higher temperature, to the cold storage (at a higher part of the cold storage).

It should be noted, that the indicated temperature values of Figure 16 are only exemplary.

Figures 17a - 17j schematically illustrate steps of constructing a thermal energy storage, e.g. corresponding to the ones shown in Figures 9 and 10, according to another aspect of the present invention. Principally illustrated are steps of a method of constructing a thermal energy storage as disclosed herein.

Figure 17a illustrates an installation site before construction begins. Shown is a naturally occurring and/or already existing body of water 103 having a surface 107 and further shown is a bed 102 of the body of water 103. The body of water 103 may e.g. be the sea.

Alternatively, the body of water 103 may be a natural or artificial lake, a sufficiently larger river, etc. The construction site may e.g. be offshore or near-shore including right next to an existing shore. The depth of the body of water 103 may e.g. be about 8 - 15 metres but could be more or less.

Figure 17b illustrates a step where a barrier structure 106 is put in place according to a predetermined design, e.g. as disclosed herein, of the thermal energy storage to be constructed. The shown barrier structure 106 is, in the shown embodiment, a double wall having or comprising an inner wall 501 and an outer wall 502 as disclosed herein. The double wall is in this embodiment preferably constructed by constructing a sheet pile wall structure or similar for both the inner and the outer wall 501 , 502 constructed by driving sheet pile segments into the bed 102 of the body of water. This provides a very cost efficient way of constructing the barrier structure 106 and also a way that is suited for installation into water, including seawater. The length of the sheet pile walls will preferably be such that they extend above the level 107 of the body of water 103 after installation including a safety margin to prevent that water crosses the barrier structure on the cover of the thermal energy storage due to waves, etc.

In some embodiments, the distance between the inner and the outer wall 501 , 502 is about 15 metres. In some embodiments, the double wall will generally have a rectangular cross section as seen from the top (see e.g. Figures 9 and 10).

In some embodiments, the double wall will comprise one or more gates or similar at certain locations to allow construction equipment, such as barges, etc. to enter into area within the double wall.

In some embodiments, the double wall will comprise one or more gates, sluices, etc.

enabling filling of the interior of the double wall if emptied (as at the step of Figure 17d).

Figure 17c illustrates a next step where one or more materials 503 is/are filled in between the inner and outer wall. The one or more materials 503 may be any materials suitable for a given need or design as disclosed herein and be e.g. sand, dirt, mud, and/or the like obtained directly from the bed 102 of the body of water 103 e.g. as part of increasing the volume of the thermal energy storage by digging into the bed after installation of the inner and outer wall. This provides a suitable material 403 for use with the barrier structure 106 that is readily available on-site, i.e. no transportation costs, no material costs, and very little construction costs. Furthermore, using the material of the bed 102 will increase the resulting volume of the thermal energy storage and thereby its capacity of thermal energy. It is to be understood that the thermal energy storage may be increased beyond the capacity of the barrier structure. In such cases, the material of the bed is simple removed and handled appropriately. Alternatively concrete/reinforced concrete or other may be used as part of the one or more materials 503.

Filling the space between the inner and outer wall may e.g. be done by barges or similar having dredging equipment 'sucking' up material from the bed 102. If the wall is filled with material from the bed outside the double wall there is no need for gates or the like in the double wall (but the volume of the thermal energy storage will then not be increased, which however can be mitigated by increasing the circumference of the double wall).

If materials are simply removed from the bed 102 to fill the barrier structure for certain large/larger scale designs involving a relatively large surface area of the thermal energy storage, it will not overall significantly alter the shape of bed 102, i.e. not much construction work is actually needed reducing construction costs. Purposes of the one or more materials 503 include insulating the thermal energy storage thereby reducing (heat) losses and providing structural integrity to the barrier structure 106. Figure 17d illustrates a step where the body of water within the barrier structure 106 is pumped away e.g. using barges with pumping equipment and/or pumping equipment located on the barrier structure 106.

A reason to remove the water is to create an Onshore' working environment for subsequent construction (see the following), which will provide significant cost savings as offshore construction and/or installation, e.g. of wind turbine foundations, wind turbines, etc. is much more expensive. To obtain a same goal, e.g. for wind turbine construction and/or installation, it is not uncommon that achieving that goal offshore compared to achieving it onshore will be about four times or even more as costly. It will take time to pump away the water but the cost savings may very well be worth it.

In alternative embodiments, the water within the barrier structure 106 is not emptied (i.e. the method of constructing a thermal energy storage does not include the steps of Figure 17d) but just kept and used as the energy storage medium. This will reduce construction time (as there is no need to pump the water away) and costs associated therewith. This also readily provides the energy storage medium as the water/seawater then simply just is contained by constructing the barrier structure/the double wall whereby it is ready for use in this respect. This may be beneficial for embodiments that will not include one or more external energy providing sources in the form of wind turbines being located on or in connection with the barrier structure 106; the thermal energy storage may still be connected to a remotely array or grid of offshore wind turbines, e.g. as illustrated in Figure 4b).

Figure 17e illustrates a step where, e.g. after appropriate drying of the environment within the barrier structure has taken place, an additional barrier 1 10 is constructed that divides or partitions the thermal energy storage into at least two separate parts (here precisely two parts) where each part ultimately will comprises a respective part of the energy storage medium.

This step may be carried out only e.g. if a division or partition of the thermal energy storage is preferred, e.g. for adding an additional location for having one or more external energy providing sources in the form of wind turbines, and/or if a division into multiple parts is preferred, e.g. for hydrostatic uses as disclosed herein. Examples of such designs are e.g. shown in Figures 9, 10, and 12. For hydrostatic uses, at least two parts is constructed to have a height difference between them as disclosed herein.

The additional barrier 1 10 may be constructed in any suitable way. It may it e.g. be constructed using material(s) such as sand, dirt, mud, etc. e.g. obtained directly from the bed 102 as disclosed herein (increasing the volume of the thermal energy storage further e.g. by increasing a depth from about 10 to about 20 metres) e.g. simply covered by a plastic film or similar to keep the material from eroding, be corresponding to the barrier structure(s) and/or the (double) wall structure(s) as disclosed herein, or by a different kind of structure.

It is noted, that now construction is taking place in an onshore environment simplifying construction and/or reducing construction costs.

Figure 17f illustrates a step where a desired number of wind turbine foundations 210 is provided or built, e.g. as three separate generally parallel rows e.g. as shown in Figures 9, 10, and 12, along the additional barrier 1 10 and two sides of the barrier structure/the double wall being generally parallel to the additional barrier 1 10. The wind turbine foundations 210 may be onshore foundations, e.g. of the gravity type and e.g. be made of a material like concrete or the like.

Such foundations 210 are relatively cheap, especially compared to offshore wind turbine foundations. In this way, the thermal energy storage effectively enables use of onshore foundations for offshore wind turbines. Furthermore, as construction is carried out in an onshore environment instead of an offshore environment, installation costs for the wind turbines will be significantly less. A big proportion of the total costs for installation of offshore wind turbines is the offshore installation costs due to normally requiring specialised and expensive equipment such a floating cranes, etc.

The wind turbine foundations 210 may e.g. have a diameter of about 25 metres of causing depending on actually used type.

In the shown exemplary embodiment, the wind turbine foundations 210 placed on the additional barrier 1 10 is located on the top of the additional barrier 1 10 while the rest of the wind turbine foundations 210 are located adjacent to the barrier structure 106 inside the barrier structure, i.e. they rest on the bed 102 next to and inside the barrier structure 106 thereby effectively creating an onshore environment for the construction and/or installation of the wind turbine foundations 210 (and wind turbines) at least during the construction and/or installation process.

In alternative embodiments, the wind turbine foundations 210 is located on or integrated with the barrier structure 106/the double wall but this require a certain size and a sufficient structural integrity of the barrier structure 106/the double wall and may also put constraints on the type of foundation 210 that is usable. An advantage is that the that the body of water within the barrier structure does not necessarily needs to be drained away. Due to being installed on the additional barrier 1 10 and near or onto the barrier structure 106 an onshore environment is created for the wind turbines. This will also reduce later service and maintenance costs compared to real or fully offshore wind turbines.

Figure 17g illustrates a step where the construction of wind turbines 230 is completed by installing the wind turbines 230 on their respective foundations 210. Again the onshore environment will reduce the associated costs significantly.

In some embodiments, and as shown and explained further in connection with Figure 12, the height of the wind turbines 230 at respective rows or locations will be different.

Figure 17h illustrates a step where the interior of the barrier structure 106 is filled again (if it was drained at step 17d) with a suitable liquid energy storage medium 101. If the thermal energy storage is divided all parts are filled. The storage medium 101 may simply be seawater, and preferably is, and may be e.g. be filled into the barrier structure 106 using pumps, one or more gates or sluices (e.g. located in the barrier structure), or the like. An advantage of using seawater is that it readily is available while still having excellent thermal energy storage properties. If the step shown in Figure 17d is not carried out, this step is also not carried out.

Figure 17i illustrates a step, where an insulating cover or a number of insulating cover segments 104 as disclosed herein is installed, e.g. on top or in connection with the barrier structure 106 and additional barrier 1 10 or simply floating on the energy storage medium 101.

If wind turbines are present on the bed, the cover 104 needs to accommodate that in a suitable way.

Figure 17j illustrates a step, where one or more external energy sources in the form of solar based energy sources and/or heating sources 300 like solar panels or similar as disclosed herein is installed on the top of the cover or cover segments 104.

In addition to the steps shown and explained, the method of constructing a thermal energy storage may further comprise, dependent on specific embodiment, installation of other equipment or features, such as

- one or more heating sources or more generally one or more thermal energy sources (see e.g. 400 in Figure 4), e.g. (industrial grade/scale) electric boilers, (energy receiving side of) (seawater) heat pumps, etc.; - conduits, inlets, outlets, etc. (see e.g. 105, 251 in Figures 1 and 14) for providing thermal energy to a land-based energy providing and/or distributing facility (see e.g. 200 in Figures 1 and 14), e.g. a central district heating facility or other;

- a technical facility (see e.g. 250 in Figure 14);

- one or more suitable connections (see e.g. 205 in Figures 4b and 14) to one or more external energy providing sources (e.g. remote wind turbines either in addition or instead of wind turbines located on/at the barrier structure 106 of the thermal energy storage 100);

- one or more cooling sources (see e.g. 410 in Figures 15 and 16); and

- a waterproof sealing, membrane, etc. at the side(s) of the barrier structure and/or the floor of the bed of the thermal energy storage.

The construction method just described, does practically not differ for construction of thermal energy storages having a generally circular cross section seen from the top

In this way, a thermal energy storage 100 as disclosed herein is provided in an expedient manner, e.g. using onshore wind turbine foundations, and onshore installation and/or manufacturing, at least for some pars.

Thereby, thermal energy storages 100 may be constructed having volumes easily of at least about 40.000.000 cubic metres of energy storage medium (although it may be less for certain uses and/or designs) and up to as much as about 54.000.000 cubic metres of energy storage medium or even more. Consequently, a giga thermal energy storage 100 may be provided.

Figure 18 schematically illustrates a side view of an embodiment of a photovoltaic panel mounting structure as disclosed herein.

Illustrated is one or more external energy sources in the form of a number of electricity generating solar panels 1 104, e.g. as disclosed herein, adapted to deliver energy to one or more heating sources as disclosed herein thereby selectively heating at least a part of the liquid energy storage medium and/or to deliver energy to one or more of the one or more cooling sources as disclosed herein thereby selectively cooling at least a part of the liquid energy storage medium as disclosed herein. The electricity generating solar panels 1 104 is e.g. photovoltaic solar panels providing electricity or alternatively hybrid photovoltaic (HPV) solar panels providing both electricity and a heated medium, or the like. The one or more photovoltaic solar panels may e.g. be of the monocrystalline type, the polycrystalline type, thin film based solar cells, or any other suitable photovoltaic technology or combinations thereof.

Further illustrated in Figure 18 is a photovoltaic panel mounting structure 1 100 comprising a number, often quite a large number, of separate photovoltaic panel modules or units e.g. arranged in suitable arrays, grids, layouts, etc. e.g. as illustrated by 300 in Figures 5, 13, and 14. In this example, each module or unit comprises a number of the photovoltaic solar panels 1 104 and one or more support structures 1 102, 1 103 adapted to support the photovoltaic solar panels 1 104 on a surface such as a cover 104 of the thermal energy storage, both as disclosed herein.

The one or more support structures, in this example, comprises at least a first support part 1 103 and at least a second support part 1 102 where a first support part 1 103 supports respective photovoltaic solar panels 1 104 and a second support part 1 102 supports a first support part 1 103. The first support part 1 103 may e.g. be a frame or the like having a particular inclination optimising the received solar energy as generally known.

Even though the photovoltaic solar panels 1 104 are shown with some spacing, here between rows of panels, they may be located right next to each other as an aim often is to increase the active area of the photovoltaic solar panels 1 104 as much as possible in relation to the overall surface area, here the overall surface area of the first support part 1 103. The photovoltaic solar panel mounting structure 1 100 further comprises at least one enclosure 1 105, here one enclosure as an example, where the enclosure 1 105 contains an enclosed gaseous medium, preferably simply atmospheric air being present when constructing the photovoltaic solar panel mounting structure 1 100.

The at least one enclosure 1 105 is located so that at least a part of solar energy being subjected to the one or more photovoltaic solar panels 1 104 is transferred to the enclosed gaseous medium as thermal energy (i.e. heat).

Due to being enclosed, this thermal energy is effectively obtained and captured (even given losses) and can be put to other uses. Accordingly, it is possible to obtain more energy from the sun compared to standard photovoltaic solar panel mounting structures where the energy, now being captured, otherwise would simply 'disappear' or dissipate.

The photovoltaic solar panel mounting structure 1 100 further comprises one or more energy transfer units 1 1 1 1 that at least during operation ongoingly receives some of the enclosed gaseous medium - with obtained thermal energy - and transfers the thermal energy to another further medium, e.g. water. The further medium may e.g. be comprised by one or more conduits or pipes 1 1 12 in fluid communication with the one or more energy transfer units 1 1 1 1. Preferably, the energy transfer unit(s) 1 1 1 1 is/are heat pump(s), and more particularly air (or gas) to water (or liquid) heat pump(s), that may be supplied with electricity generated by at least some of the photovoltaic solar panels 1 104, e.g. supplied by an inverter and other electrical circuitry 1 1 13. It is not uncommon for such air to water heat pumps to have an SCOP (seasonal coefficient of performance) rating of about 5, signifying that they, on average, deliver about 5 times as much energy than the energy of the electricity needed to operate them. Alternatively, the energy transfer unit(s) 1 1 1 1 is/are gas to gas energy transfer unit(s).

The (heated) further medium is preferably the liquid energy storage medium, used for heating, of the thermal energy storage or is in heat exchanging connection with the liquid energy storage medium, used for heating, of the thermal energy storage.

In this way, thermal energy - that otherwise simply would 'disappear' or dissipate - is effectively captured and added to the thermal energy storage. In effect, more energy is harvested from the sun compared to standard photovoltaic panel mounting structures due to the gaseous medium of the enclosure 1 105 receiving and retaining (e.g. with minor losses) thermal energy. The overall energy output, in the form of electrical power and thermal energy, of the photovoltaic panel mounting structure is thereby increased.

During manufacture of the photovoltaic solar panel mounting structure 1 100, the enclosure 1 105 may be established or provided simply by closing off the volume (or a part thereof) between the photovoltaic solar panel mounting structure 1 100 and the surface/cover 104. In some embodiments, one or more insulation elements 1 1 10 as disclosed herein is/are used for this purpose thereby both providing the enclosure but also insulating the thermal energy of the enclosed gaseous medium from losses. The one or more insulation elements 1 1 10 may also be used to support the photovoltaic solar panel mounting structure 1 100 or parts thereof and/or are preferably, at least in some embodiments, waterproof or water resistant.

If the photovoltaic solar panel mounting structure 1 100 comprises a number of photovoltaic panel modules or units arranged in suitable arrays, grids, rows, layouts (e.g. as illustrated in Figures 5, 13, and 14) it is only the ends or circumference of the photovoltaic panel mounting structure 1 100 that needs to be sealed off by insulation elements 1 1 10 to form the enclosure 1 105 comprising the gaseous medium.

Figure 19 schematically illustrates a side view of a further embodiment of a photovoltaic solar panel mounting structure as disclosed herein comprising one or more ventilation elements.

The illustrated photovoltaic solar panel mounting structure 1 100 corresponds to the one of Figure 18 except as noted in the following. In Figure 19, the photovoltaic solar panel mounting structure 1 100 comprises one or more controllable ventilation elements 1 120 connecting the (at least one) enclosure 1 105 to external ambient air. The one or more controllable ventilation elements 1 120 is/are configured to open for external ambient air when a determined temperature of the gaseous medium is above a predetermined threshold and otherwise close for external ambient air.

In some embodiments, like the one shown in Figure 19 and corresponding or others, the photovoltaic solar panel mounting structure 1 100 may further comprise one or more additional controllable ventilation elements located elsewhere e.g. located at or near the opposite end of the first support part 1 103 (i.e. bottom left on the Figure). Generally, the one or more controllable ventilation elements may be used regardless of what type the one or more insulation elements 1 1 10 are and/or how the enclosure is established.

One or more of the ventilation elements, e.g. the one(s) located closest to the surface/cover 104, may be passive ventilation elements such as passive air intakes that may draw air in when the one or more additional controllable ventilation elements are opened.

In some embodiments, e.g. in combination with embodiments comprising one or more controllable ventilation elements, the photovoltaic panel mounting structure further comprises circulation elements configured for circulating the enclosed gaseous medium, e.g.

distributing hotter air otherwise generally located towards the top or 'roof to energy transfer unit e.g. located on the surface or 'floor'. The circulation elements may e.g. be powered by at least some of the one or more photovoltaic panels.

In this particular shown exemplary embodiment, the one or more conduits or pipes 1 1 12 comprising the further medium is run through the cover 104 and within the barrier structure holding the liquid energy storage medium. The photovoltaic solar panel mounting structure 1 100 further comprises, as an example, a number of braces or similar 1 130 for mounting the one or more photovoltaic solar panels 1 104 on respective first support parts 1 103.

The photovoltaic solar panel mounting structure 1 100 comprises one or more bars, struts, rods, or other type of rigid connection elements 1 1 15 connecting and stabilising one or more first support parts 1 103, e.g. as shown, by connecting it/them to one or more second support parts 1 102.

Figure 20 schematically illustrates a top view of a photovoltaic panel mounting structure together with an illustrated air flow according to an embodiment of a photovoltaic panel mounting structure as disclosed herein.

The illustrated photovoltaic panel mounting structure 1 100 corresponds to ones explained in connection with the previous figures except as noted in the following. The illustrated photovoltaic panel mounting structure 1 100 comprises a number of walls, partitions, or the like 1 125 (at the illustrative dashed lines) partitioning an enclosure into several separate enclosures 1 105. Please note, in the Figure an enclosure is the area between walls 1 125 whereas the smaller squares illustrates respective electricity generating solar panels 1 104. According to this and corresponding embodiments, an energy transfer unit 1 1 1 1 is located in a wall, partition, or the like 1 125 and is configured to receive a gaseous medium from one enclosure and expel it into a neighbouring enclosure as indicated by the arrows 1 135.

Alternatively, the energy transfer units may be located on either side of a wall, partition, or the like with suitable conduits transferring the gaseous medium through the wall, partition, or the like into a neighbouring enclosure.

The gaseous medium passing through an energy transfer unit 1 1 1 1 will be cooled (due to transfer of energy) and then heated again (as indicated by the colour gradient of the arrows 1 135) in the next enclosure by solar energy subjected to the one or more photovoltaic panels/the photovoltaic panel mounting structure and so on. It is more efficient, to draw out thermal energy in this way, instead of having a number of energy transfer units being located in a single large enclosure. Furthermore, having a closed system in this manner reduces waste of thermal energy since the cooled gaseous medium having passed through an energy transfer unit 1 1 1 1 will often still be warmer than an outside temperature.

An energy transfer unit may be located at the circumference or outer ends of the photovoltaic panel mounting structure 1 100 to expel the gaseous medium to a next row (if present) of enclosures and e.g. directing the flow of the gaseous medium in the opposite direction. The overall flow of gaseous medium may be closed across all the enclosures. Figure 21 schematically illustrates one exemplary embodiment of a thermal energy storage as disclosed herein doubling in function as a coastal protection facility or measure.

Illustrated is a thermal energy storage 100 as disclosed herein located near a shore 150, e.g. near a city, in a naturally occurring and/or already existing body of water 103 such as the sea, a lake, a fjord, etc.

The thermal energy storage 100 comprises a barrier structure 106, at least one cover 104, and a liquid energy storage medium 101 as respectively disclosed herein.

The thermal energy storage 100, or more specifically a part of its barrier structure 106, is connected to the shore 150 and the thermal energy storage 100 has a shape and structural integrity so that it doubles in function as a coastal protection facility or measure or the like. Further illustrated, is a barrier structure 145, such as a pier, etc. that together with at least a part of the thermal energy storage 100 defines an open inlet allowing passage of seagoing vessels. The inlet could alternatively be or comprise a sluice system.

In this particular example, the thermal energy storage 100 is divided into a number (here as an example eight) of separate parts, each part comprising a respective part of the liquid energy storage medium 101 and each part comprising a cover 104.

The covers 104 may each comprise a number of solar based energy sources (see e.g. 300 and/or 1104 elsewhere) as disclosed herein.

In addition or alternatively, the thermal energy storage 100 may comprise one or more external energy providing sources (see e.g. 230 elsewhere) as disclosed herein, e.g. in the form of one or more wind turbines, e.g. located on the barrier structure 106.

It should be noted, that while some of the Figures illustrates respective photovoltaic panel mounting structures comprising a single enclosure they could equally comprise a number of separate or connected enclosures e.g. by partitioning one enclosure into several smaller enclosures or constructing the enclosures separately.

Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject matter defined in the following claims.

In the claims enumerating several features, some or all of these features may be embodied by one and the same element, component or item. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, elements, steps or components but does not preclude the presence or addition of one or more other features, elements, steps, components or groups thereof.