FIELD OF THE INVENTION

The invention relates to an arrangement for storing energy as disclosed in the preamble of claim 1. In this application, the arrangement according to the invention will hereafter also be referred to as "the solution according to the invention". The solution utilizes a discarded or otherwise useless combustion power plant or the like, a boiler and an infrastructure asso- dated therewith, as well as a grid connection.

BACKGROUND OF THE INVENTION AND PRIOR ART PROBLEMS

The low price and availability of energy have enabled our cur rent way of life and standard of living but the energy solutions have always suffered from the problem of abuse and pollution of nature to a varying extent. Oil has been drilled from the sea bed increasingly in order to find new oil deposits while the previous ones are running dry. Drilling oil from the sea bed is expensive, and, in addition, the process involves a high risk of an environmental disaster. Disadvantages of fossil en ergy sources include the restricted availability thereof, en vironmental destruction and air pollution. Therefore, it is natural to search for novel, less polluting and renewable en ergy production solutions. As known, these less polluting and renewable solutions include wind and solar power, for example. However, they both suffer from the problem of being dependent on the weather conditions and susceptible to huge variations in the amount of energy produced. The electricity produced by wind mills has been made competitive with other energy produc- tion methods by introducing new large wind mills. Therefore, the portion of wind energy will, assumingly, increase in many countries, which, in turn, results in a need of load following.

Coal is extracted from the earth in vast mines, with a detri mental effect on the environment. Burning coal causes consid erable carbon dioxide emissions which clearly are largely to blame for the climate change. Therefore, many countries are shutting down a large number of their coal power plants. Coal power plants and boiler power plants usually have a major in frastructure associated therewith, which possibly is economi cally profitable, by means the present invention, also after the shutdown of the plant.

There is a high variation in the production of wind power, causing its price to vary as well, partly because the number of noteworthy electricity reserves in use still remains low. As the energy production is increasingly moving towards renew able solar, wave and wind power, even higher variations in the price of electricity can be expected. The solution according to the invention allows electrical energy to be stored in the form of thermal energy, when the production of electricity exceeds the consumption of energy, and allows the stored elec tricity to be discharged when the consumption of electricity is high. The introduction of the solutions according to the invention have a balancing effect on the price of electricity by allowing any extra production to be stored more efficiently and to be consumed when the demand is high.

The solutions according to US 2016024973 A1 and JP 2000274979 for storing energy are examples of the known prior art. How ever, these solutions, unlike the solution according the in vention, do not utilize a discarded boiler for storing energy. OBJECTIVE OF THE INVENTION

This invention aims at providing an arrangement that makes it possible to level a difference between the production of elec tricity and the consumption of electricity. This invention al- lows energy to be stored during low consumption and to dis charge it, in the form of electricity, during low consumption.

The solution according to the invention repurposes a coal power plant, or some other power plant comprising a boiler, from an energy-producing power plant to a power plant storing thermal energy, to a load-following power plant.

The arrangement according to the invention is characterized in what is set forth in the preamble of claim 1. Other embodiments of the invention are characterized in what is set forth in the rest of the claims.

BRIEF DESCRIPTION OF THE INVENTION

The arrangement according to the invention stores and releases energy from a thermal energy storage (TES) converted from a boiler of a discarded power plant, by utilizing an existing boiler and infrastructure of the power plant, including, inter alia, an energy production equipment with a heat-transfer chan neling, turbine and electrical generator. The discarded boiler is converted to a thermal energy storage by filling it with an appropriate material capable of storing a sufficient amount of energy in the form of heat.

ADVANTAGES OF THE INVENTION

An advantage of the solution according to the invention is that it is inexpensive, simple and allows a boiler of a discarded power plant, and the power plant, to be quickly converted and repurposed to a thermal energy storage (TES) and to a load- following power plant, respectively. The invention allows for the utilization of the infrastructure of the discarded power plant, making it unnecessary to disassemble the power plant or the infrastructure thereof once it has been discarded. Another advantage is that the solution according to the invention al lows recycled concrete or the like to be used as the filling material of the boiler, for storing heat. This solution ac cording to the invention utilizes, where applicable and neces sary, an existing heat-transfer channeling of the boiler, thus avoiding to construct a new heat-transfer channeling, that is, a medium-circulating pipework, for the new thermal energy stor age. The filling material supports and seals the heat-transfer channeling of the boiler, which possibly is at the end of its service life, thus allowing it to be used longer. Another ad- vantage is that the heat-charging mass of the thermal energy storage can be charged, when there is an oversupply in the production of electricity, by heating a medium that heats up the mass, by means of electricity. Another advantage is that the electrical energy for heating up the chargeable mass can be produced by renewable energy sources, such as wind, solar or wave energy, or by hydropower as well.

LIST OF FIGURES

In the following, the invention will be explained in detail by means of two exemplifying embodiments, with reference to the accompanying drawings where

Figure 1 is a schematic view of an operation state of the arrangement according to the invention, while the thermal energy storage is being charged,

Figure 2 is a schematic view of a second operation state of the arrangement according to the invention, while the thermal energy storage is being charged, Figure 3 is a schematic view of a third operation state of the arrangement according to the invention, while the thermal energy storage is being discharged, and Figure 4 is a schematic view of another alternative embodiment of the arrangement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a schematic and simplified view of an operation state of the arrangement according to the invention in a load following power plant 1, converted from a discarded power plant, such as a coal power plant. The load-following power plant 1 according to the invention comprises a thermal energy storage 2, a heat-transfer channeling 3, which preferably is a pipework forming a closed circulation circuit, a thermal energy charging, i.e. storing mass 4, a feeder pump 10 and a heating member 11, such as a heating resistor. A boiler of a discarded combustion power plant, at least partly, preferably almost en- tirely filled with a thermal energy charging mass 4, preferably constituted by recycled concrete, for example, is used as the thermal energy storage 2. Preferably, the charging mass 4 is provided at least on the heat-transfer surfaces of the dis carded boiler.

In the situation shown in Figure 1, the thermal energy storage 2 is charged, by means of a medium, with electrical energy from a renewable energy source 9. In this exemplifying embodiment, the energy source 9 is a wind mill. In this exemplifying em- bodiment, the energy source 9, that is the wind mill, is con nected to the load-following power plant 1 by a grid connection 7. In this step of charging the thermal energy storage 2, the feeder pump 10 is adapted to feed a medium, which, in this case, is water, to the heating member 11. The heating member 11 is adapted to heat the medium and the heated medium is adapted to be partly led to the heat-transfer channeling 3 within the thermal energy storage 2 for heating up the mass 4 provided inside the thermal energy storage 2. The effect of the heating member 11 is adapted to be adjustable.

At this stage of the charging, the water is vaporized by the heating member 11 and the vapor is transferred, along the heat- transfer channeling 3, to the thermal energy storage 2, in the direction denoted by the arrow A. The vapor releases thermal energy to the heat-charging mass 4, via the heat-transfer sur faces of the heat-transfer channeling 3, causing the mass 4 to heat up, and the temperature of the vapor to drop with the result that is condenses back into water. Thereafter, the con densed water is adapted to be pumped to the heating member 11 by the feeder pump 10. The above-mentioned process is repeated until the mass 4 is so hot that the temperature difference between the mass 4 and the vapor is not high enough to cause a phase change in the vapor, resulting in that the vapor no longer condenses into water. At this stage, the charging pro cess proceeds to the next step.

Figure 2 shows the next step of charging the thermal energy storage 2. The thermal energy storage 2 is still being charged, by means of the medium, with electrical energy from the renew able energy source 9. The load-following power plant 1 com prises, in addition to the components shown in Figure 1, a turbine 5 and an electrical apparatus 6, which in the case shown in Figure 2, acts as an electric motor.

In this step of charging the thermal energy storage 2, the turbine 5 is adapted to supply the medium, which at this stage is vapor, to the heating member 11. The heating member 11 is adapted to heat the medium and the heated medium is adapted to be partly led into the heat-transfer channeling 3 within the thermal energy storage 2 for heating up the mass 4 provided inside the thermal energy storage 2.

At this stage of the charging, the heating member 11 is adapted to heat the vapor which is adapted to be transferred, along the heat-transfer channeling 3, to the thermal energy storage 2, in the direction denoted by the arrow A. The vapor releases thermal energy to the heat-charging mass 4, via the heat- transfer surfaces of the heat-transfer channeling 3, causing the mass 4 to heat up and the temperature of the vapor to drop. Thereafter, the vapor is adapted to be re-directed to the heating member 11 by means of the turbine 5 driven by the electrical apparatus acting as an electrical motor. The above- mentioned process is repeated until the capacity of the system is reached. This refers, for example, to that the temperature of the vapor no longer heats up the chargeable mass 4.

Figure 3 shows a step of discharging the thermal energy storage 2. The thermal energy storage 2 is discharged by means of a medium in order to produce electricity for an electrical grid 8. The load-following power plant 1 comprises, in addition to the components shown in Figures 1 and 2, a feeder pump 14 and an electrical apparatus 6 acting as an electrical generator. The feeder pump 14 is adapted to feed the medium to the heat- transfer channeling 3 partly provided within the thermal energy storage 2, in the direction denoted by the arrow A. In this exemplifying embodiment, the medium is water. The energy stored in the mass 4 heats up and vaporizes the water which releases the energy received from the mass 4 in the turbine 5, in the form of a rotational movement. The electrical generator coupled to the shaft of the turbine 5 is adapted to convert the rota tional movement into electricity and to supply the electricity that is has produced, through the grid connection 7, to the electrical grid 8.

The heat-transfer channeling 3, the turbine 5 and the electri cal generator form part of the infrastructure of a discarded combustion power plant.

Figure 4 shows another embodiment of the arrangement according to the invention. In this exemplifying embodiment, the heating member 11 is at least partly provided within the heat-charging mass 4 and the heating member 11 is at least partly in contact with the heat-transfer channeling 3. Thus, the mass 4 is adapted to be charged directly, without a medium, by means of heating resistors 11.

The thermal energy of the mass 4 is adapted to the discharged, at a desired time, as electrical energy, into the electrical grid 8, by means of the medium, turbine 5 and electrical gen erator. The discharging is adapted to be carried out in the substantially same manner as explained in the description of Figure 3.

It will be appreciated by a person skilled in the art that the invention is not solely restricted to the above-described ex amples but may vary within the scope of the accompanying claims. Thus, some of the structural solutions may differ from the ones disclosed above, and the mass may comprise some other material than concrete. Preferably, it can be any material having a high heat-charging capacity and easily depositable into the boiler and on the heat-transfer surfaces thereof, by casting or in some other way. It will also be appreciated by the person skilled in the art that the arrangement may include, in addition to those dis closed above, other parts, such as condenser, which, at the stage of discharging thermal energy, is adapted to cool the medium, if necessary. Further, the arrangement may include, for instance, means of adjusting the medium when necessary.

It will also be appreciated by the person skilled in the art that the electrical motor driving the turbine and the electri- cal generator can be constituted by a single electrical appa ratus, or, alternatively, they can be separate apparatuses.

It will also be appreciated by the person skilled in the art that the thermal energy storage can be charged with electricity from some other energy source than a wind mill, such as with solar or wave energy, or with hydropower as well.

It will also be appreciated by the person skilled in the art that the medium heated by means of the thermal energy storage can be adapted to be led to a district heating grid where the medium is adapted to release its energy for heating buildings, for example, or the vapor heated by means of the thermal energy storage can be adapted to be delivered for process use.