A heat pump is a device that can provide heating, cooling and hot water for residential, commercial and industrial applications. Heat pumps transform energy from the air, ground and water to useful heat.

A heat pump typically has an outdoor heat source and an indoor outlet. Outdoor sources can be, for example, ambient air, exhaust air, groundrock, groundwater, or water. Indoor outlets can be, for example, a heating system for a house (e.g. air blower, floor heating or radiators).

In a ground source heat pump, for example, fluid in underground pipes absorbs the heat from the ground. The energy from these sources is renewable. This energy typically makes up about 75% of the energy that is used to drive the heat pump.

An outdoor heat exchanger, the evaporator, uses the thermal energy from the outdoor source to boil refrigerant (the liquid in the heat pump) and turns it into a gaseous state. The ground has a stable temperature of around 10-12°C throughout the year. This source temperature is enough to boil the refrigerant because the refrigerant circuit is designed around this boiling point.

Then the refrigerant arrives at a compressor. The compressor compresses the refrigerant - which is in a gaseous state - to a higher pressure, which leads to a rise in temperature. To drive the compressor, additional energy is needed: from electricity, gas or thermal energy. This typically makes up about 25% of the total energy needed to run the heat pump. If green electricity is used - e.g. by means of photovoltaics - then a heat pump is using 100% renewables and therefore CO ₂ neutral.

On the discharge side of the compressor the now hot and highly pressurised vapor passes through a second heat exchanger, called a condenser. This heat exchanger allows the refrigerant to release the heat to the indoor outlet. As a result the refrigerant then condenses, i.e. the refrigerant moves from gaseous into liquid state.

The indoor outlet can be an air system (as the typical air conditioner units) or a hydronic (water-based) system, where the heat pump is connected to a floor-heating system or radiators. For the provision of sanitary hot water, the indoor outlet can include a hot water storage tank. i The condensed refrigerant then passes through a pressure-lowering device, the expansion valve. The now low-pressure liquid refrigerant then enters the evaporator and the cycle starts again.

The present invention seeks to provide improvements in or relating to heat pumps.

An aspect of the present invention provides a heat pump operable between an energy source and a heating load, the pump comprises a heat exchanger for recovering heat from the energy source and transferring it to refrigerant in a refrigerant circuit, in which the pump comprises a thermal battery integrated into the refrigerant circuit for storing heat received from the refrigerant and/or delivering heat to the heating load.

The heat pump may comprise a pressure-lowering means, such as a thermal expansion valve. The pressure-lowering means may be positioned between in the refrigeration circuit between the thermal battery and the evaporator.

The heat pump may comprise a compressor, for example a variable speed or fixed speed compressor.

The thermal battery may comprise phase change material. Phase change materials are substances that absorb and release heat energy when they change phase (known as latent heat). When a material melts, it changes from a solid phase to a liquid phase. During the phase transition, many materials are able to absorb a significant amount of heat energy. The opposite is true when the material freezes and solidifies: the material will give out the heat that it absorbed when it melted. Different materials will melt and solidify at different temperatures and are able to absorb different amounts of heat energy.

The thermal battery may comprise two heat exchangers: a charge exchanger; and a demand exchanger.

The system may comprise means for measuring charge level in the or each thermal store.

Thermistors may, for example, be supplied with the PCM in order to measure charge levels. They can show a low charge level to an acceptable level of accuracy (although not very repeatable). Temperature measurement of energy levels in PCM is intrinsically a poor method due to very little temperature variation during phase change.

More accurate measurement of stored energy levels may be provided in order for performance gains from load shifting to be optimized. This would maximise cost savings on off-peak charging, for example.

Different sensors to measure stored energy (such as heat flux) may be provided and then their readings can be mapped to temperature sensors on the PCMs.

The heat pump may comprise two or more thermal batteries. In some embodiments the heat pump consists of (only) two thermal batteries.

In some embodiments the thermal batteries are arranged in series.

In some embodiments the thermal batteries are arranged in parallel.

The thermal batteries may comprise phase change material having different melt temperatures to each other. This would allow, for example, a first battery having a higher melt temperature to be arranged to receive heat from a compressor first and then a second battery having a lower melt temperature to receive (the then lower temperature) heat from the first battery.

The energy source may be selected from: air; ground; water.

The present invention also provides a heat pump system comprising a heat pump as described herein.

The heat pump system may have multiple thermal batteries and/or multiple heating loads.

In systems with multiple thermal stores it may be possible for one store to charge another (without using a compressor, for example).

In systems with multiple thermal stores it may be possible to use one store to pre-heat heating load (e.g. direct hot water) before going into another store (which could be “hotter” for example). The heat pump system may comprise loops to draw/return energy from/to individual batteries, thereby enabling a heating load to be supplied by multiple batteries, or separate heating loads to be supplied concurrently. The system may also allow for heat exchange between the batteries.

The present invention also provides a heat pump including a refrigeration circuit, in which a phase change material heat battery is integrated into the refrigeration circuit.

The present invention also provides a combined ground source heat pump and phase change material (PCM) energy store.

The present invention also provides a domestic ground source heat pump system comprising a heat pump including a refrigeration circuit comprising two phase change material thermal batteries, the batteries having different charging characteristics, the system comprising separate loops to draw the energy from the individual batteries, enabling a single heating load to be supplied by both batteries for higher flow rates, or two separate heating loads to be supplied concurrently.

The system may be configured to be able to supply both heating and direct hot water concurrently.

Load shifting may, for example, be possible in some embodiments.

Some embodiments allow for decoupling of the supply of heat from electrical demand.

In some embodiments a heat pump system supplies heating and hot water; the heat for either/both of these loads could, for example, be drawn from one or more refrigeration circuit heat stores.

The present invention also provides a dwelling having a system as described herein.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings.

Example embodiments are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

The terminology used herein to describe embodiments is not intended to limit the scope. The articles “a,” “an,” and “the” are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, items, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

Figure 1 - What is a Heat Pump? When the compressor (Comp) is operating, heat is provided from the Energy Source to the Heating Load via the refrigeration circuit (Blue arrows inside Heat Pump). The Condenser and Evaporator are both Heat Exchangers within the refrigerant circuit inside the Heat Pump.

Energy from the ground heats the fluid entering the ground array. This heats the refrigerant in the evaporator, which is then compressed (which heats it even more), this heat is then exchanged into the heaters or immersion tank via the condenser. The refrigerant then expands through the thermal expansion valve (TEV) which cools it down lower than ground temperature to begin the cycle again.

The two heat exchangers allow the transfer of energy through the system via the refrigeration circuit.

The Heating Load is sourced from a combination of the energy taken from the Heat Source plus electrical energy used to run the compressor.

When the compressor is off heat cannot be transferred to the heating load, hence the use of immersion tanks to store Direct Hot Water (DHW).

Figure 2 - Heat Pump with Integrated PCM Heat Battery (Single)

In this embodiments of the present invention the Condenser is exchanged for a PCM Heat Battery in the refrigeration circuit.

The PCM can either deliver heat straight to the Heating Load or store the energy when there is no load, or a combination of both. Note that there is now no need for an immersion tank in the Heating Load as the PCM is storing the energy directly from the refrigeration circuit.

Heating Load can be provided when the compressor is off - load shifting the electricity demand in all instances.

This system is significantly more compact when compared with an orthodox heat pump with an immersion tank.

Figure 3 - Phase Change Material When a solid material is warmed up, its temperature increases and it stores a portion of the energy used to heat it.

When heating a material through the Change of Phase from solid to liquid, the energy is still being stored, however the temperature of the material does not rise.

This is like a thermal battery and is a very efficient way of storing energy. They can also be significantly smaller than the size of an equivalent immersion tank. This saves a lot of space in an airing cupboard, for example.

The present invention can provide an innovative way of charging phase change material energy units.

The use of phase change material in the refrigeration circuit of a heat pump stabilises the temperature of the refrigerant because the temperature of the material does not rise through the phase change. This in turn maintains the refrigerant at a lower average temperature which has a positive effect on compressor efficiencies.

Figure 4 - Heat Pump Integrated PCM (Multi Store & Multi Load)

In this embodiment two thermal stores are provided in the refrigeration circuit. One of the thermal stores supplies a first heating load and the other of the thermal stores supplies a second heating load. Closed or open loops may, for example, operate between each store and its respective load.

Figure 5 - Heat Pump Integrated PCM (Multi PCM Single Load e.g. DHW)

This embodiment retains the architecture of the Multiple PCM Refrigeration Circuit. Adds separate loops to draw the energy from the individual PCM Batteries. This enables a single heating load (e.g. Direct Hot Water) to be supplied by both PCM batteries for higher flow rates. In a further embodiment two (or more) separate heating loads can be supplied concurrently by one (or more) thermal stores.

Examples of the way systems of this type formed in accordance with the present invention could run include: PCM Heat Battery 1 could form part of a loop to Heating Load 1 .

PCM Heat Battery 2 could form part of a loop to Heating Load 2.

Both Heat Batteries could serve one Heating Load.

Both Heat Batteries could serve both Heating Loads.

Testing has shown this system to be more efficient than an orthodox heat pump.

This configuration gives a performance benefit to the charging efficiency as the individual PCMs will have slightly different charging characteristics. It will also be able to supply both heating and DHW concurrently. It can also supply DHW at higher flow rates when the water is channelled through both PCMs. It can store heat with lower losses than an immersion tank.

Figure 6 - Heat Pump Integrated PCM (Multi PCM Single Load e.g. Heating).

Figure 7 - Heat Pump with Multiple Integrated PCM Stores. This embodiment allows for multiple different heat store I heat load transfer loops. Either store could release heat to either or both heating loads, separately or together with the other store. Heat can be transferred between the two stores.

One Heat Battery could charge another Heat Battery (without using the compressor).

Figure 8 - Heat Pump Integrated PCM (Multi PCM Battery Balance).

The heat batteries can transfer heat between themselves.

Figure 9 - Orthodox PCM Battery Heat Exchanger Configuration

1 heat exchanger to transfer energy into the PCM material

1 heat exchanger to extract energy from the PCM material

If the heat in needs to be extracted immediately then the heat must travel through the PCM Material. The PCM Material has a thermal conductivity rating that differs according to its physical state, i.e. Solid PCM transfers heat more efficiently than liquid PCM.

Figure 10 - Direct Contact PCM Heat Exchangers

This embodiment has a direct path between the Heat in and heat out heat exchangers, i.e. the heat does not flow through the PCM in order to travel through the device.

This removes the sensitivity to PCM phase change state.

Improves heat exchange efficiency at higher states of charge i.e. liquid phase.

Figure 11 - Controls Decision Matrix

GSM controls the ground pump, compressor and load pump.

Figure 12 - Controls Electrical Configuration

Key:

PCB=Printed Circuit Board

PCM=Phase Change Material

Although illustrative embodiments of the invention have been disclosed in detail herein, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention.