THERMOELECTRIC DEVICE FOR STORAGE OR CONVERSION OF ENERGY

Abstract

The invention relates to a device for thermoelectric storage or energy conversion, reducing the complexity, the thermodynamic irreversibilities and the costs of previous solutions.

The device consists of main pressurized tanks (1THERMO) (1TRANSIT), containing the hydraulic fluid (3), the propellant fluid (2), liquid communications (7), equipped with hydroelectric conversion assemblies for pumping (6) or turbining (5) and including heat exchange systems (8COND) (8EVAP).

The device may include mobile physical separations (11) between fluids, hot (15), or cold (16) thermal reserves, secondary tanks (13) equipped with pipes (14).

The device is intended for energy storage, in particular intermittent renewable energies, economical production of Cold and Hot, and net electricity generation exploiting weak thermal sources.

Claims

1. The device is constituted – by at least two main pressurized tanks, abbreviated MPT, called MPT of Thermodynamic Work (1THERMO) for one, called MPT of Hydraulic Transit (1TRANSIT) for one other, each containing at least one propellant fluid (2), not deemed to be lost, and sharing at least one hydraulic fluid (3) moving between them in an opposite manner via at least one liquid communication (7) equipped with at least one hydroelectric conversion machine such as a pumping assembly (6) or a turbining assembly (5), – by a heat exchange system exchanging with the propellant fluids (2) comprising at least one evaporator (8EVAP) and at least one condenser (8COND), characterized in – that the thermodynamic sequence consisting of an expansion and then a contraction of each of the propellant fluids (2) is carried out slowly, discontinuously, and quantitatively bounded in mass, by the variation of the volume which contains them in the large MPT (1THERMO) (1TRANSIT), – that the propellant fluids (2) either work by alternating state changes of at least two states among the three liquid, gaseous, supercritical states, or work in the exclusively supercritical state by large alternating variations in their supercritical density, – and that the pressure of the propellant fluid (2) within the MPT of Hydraulic Transit (1TRANSIT) is quasi-constant and close to the minimum value encountered in the range of pressures covered by the propellant fluid (2) within the MPT of Thermodynamic Work (1THERMO).

2. Device according to claim 1 characterized in that the device incorporates at least one cold thermal reserve (16) or at least one hot thermal reserve (15) of thermal energy storage via one or more masses of liquid or solid matter, including the possibility of thermocline tanks or areas of the Earth’s soil, and in that, at the heat exchange systems (8EVAP) (8COND) (8CIRC), the major amount of extractions of heat or inputs of heat to propellant fluids (2) are carried-out through inputs and extractions of heat from these thermal reserves (15) (16).

3. Device according to claim 1 characterized in that; at the heat exchange systems (8EVAP) (8COND) (8CIRC), the major amount of extractions of heat or inputs of heat to propellant fluids (2) are carried-out by hot or cold thermal sources external to the main device, for example in the form of solar thermal energy, or availability of ice, cold water or cold air, or availability of steam, hot water or hot air, or natural or artificial geothermal energy, or wasted heat energy of third party processes, etc.

4. Device according to claim 2 or claim 3 characterized in that a conjunction of different means of heat exchanges including condensers (8CCOND), evaporators (8EVAP), recirculation exchangers (8CIRC) and physical transfers of propellant fluids (2) via exchangers intercalated between two MPTs, allows inputs of heat or extractions of heats to these propellant fluids (2) in all segments of the thermodynamic cycles, including in those segments carrying out the movements of hydraulic fluid (3).

5. Device according to any preceding claim characterized in that masses of heat transfer fluids, or masses of hydraulic fluid (3), having exchanged heat with propellant fluids (2) are temporarily stored according to their cooler or hotter temperatures in several differentiated compartments (9).

6. Device according to claim 2 or claim 5 characterized in that all or part of the compartments differentiated for temporary storage of fluids according to their temperatures (9) or all or part of the thermal reserves (15) (16) uses Phase Change Materials, including the possibility of salt water ice, or uses an aqueous mixture slurry under the Liquid-Solid states.

7. Device according to any preceding claim characterized in that the propellant fluids (2) benefit from the addition of one or more dedicated secondary pressurized tank(s) (13), communicating with the MPT (1THERMO) (1TRANSIT) by one or more pipes (14) equipped with valves, and also possibly equipped with forced convection mechanisms, between the secondary pressurized tank(s) (13) and these MPT (1THERMO) (1TRANSIT).

8. Device according to any preceding claim characterized in that the upper portion of all or part of the pressurized tank(s) (1THERMO) (1TRANSIT) (13) is equipped with systems for spraying and dropping by gravity droplets (10) of propellant fluid (2) or hydraulic fluid (3) or with other physical techniques for improving heat transfer such as trays or packings.

9. Device according to any preceding claim characterized in that the propellant fluid (2) are chemical substances or mixtures of chemical molecules selected to have, at the maximum temperatures encountered in the pressurized tank (1THERMO) (1TRANSIT) (13), saturated vapor pressures lower than the maximum pressures allowed by these pressurized tanks (1THERMO) (1TRANSIT) (13), such as carbon dioxide, ethane or such as mixtures of carbon dioxide with hydrocarbons, with nitrogen compounds or with alcohols.

10. Device according to any preceding claim characterized in that all or part of the propellant fluids (2) is heated or cooled by a heat input or heat extraction taking benefits of the high or low temperatures of fluids from a different portion of the thermodynamic cycle or of their plurality, for example by a counter-current heating-cooling exchanger between two different masses of propellant fluid (2), or from hot or cold fluids stored in previous operations, or exploiting an external thermal source or the ambient environment.

11. Device according to any one of the preceding claims characterized in that is provided means for reducing dissolutions between propellant fluids (2) and hydraulic fluid (3) such as mobile physical separations (11) between these fluids, or increases in chemical pH or such as the use of additives.

12. Device according to claim 1 characterized in that part of the heat accumulated by the hydraulic fluid (3) because of the inevitable energy losses by friction during the operations of the pumping assembly (6) or of the turbining assembly (5) is recovered, under the form of heat supplied to the propellant fluid (2).

13. Device according to claim 7 characterized in that one or more secondary pressurized tank(s) (13) are used to perform the sequestration and physical storage of excess amounts of carbon dioxide (CO2), which in gaseous form is a greenhouse gas, including optionally heating or cooling portions of this excess CO2 by advance, in order to physically substitute them for equivalent masses of regular CO2 used as propellant fluid (2), at optimal times of operations.

14. Device according to claim 1 or claim 7 characterized in that at least one of the pressurized tanks (1THERMO) (1TRANSIT) (13) consists of a natural or artificial underground cavern or consists of an underwater tank.

15. Device according to claim 1 or claim 2 characterized in that at least one hydraulic transit MPT (1TRANSIT) or at least one thermal reserve (15) (16) consists of a basin, of a river or of a natural body of water.

16. Set comprising a plurality of devices according to any one of the preceding claims wherein the components of the devices such as MPT (1THERMO) (1TRANSIT), secondary pressurized tanks (13), hydraulic fluids (3), propellant fluids (2), heat exchange systems (8COND) (8EVAP) (8CIRC), compartments differentiated storage of fluids according to their temperatures (9), liquid communications (7), pipes (14) of propellant fluid (2), pumping assemblies (6), turbining assemblies (5), cold thermal reserves (16), hot thermal reserves (15), receiving basins (4) are connected to each others by pipes equipped with valves.

17. Use of a device according to any one of claims 1 to 15, or of a set according to claim 16, to store energy or to convert energy.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0047] The accompanying drawings illustrate the invention.

FIG. 1

[0048] [FIG. 1] represents in section, the device of the invention in a configuration where the pressurized tanks are placed above the ground.

FIG. 2

[0049] [FIG. 2] represents in section, a variant of this device in a configuration where the pressurized tanks are constituted by artificial underground caverns.

FIG. 3

[0050] [FIG. 3] represents in section, the detail of a Thermodynamic Work MPT equipped with an external heat exchange system including an optional mechanism of recirculation of the propellant fluid through the MPT and where the condenser and evaporator of the MPT are not shown.

FIG. 4

[0051] [FIG. 4] represents on an Enthalpy-Pressure diagram an illustration of one of the possible thermodynamic operating modes of the device, here in a 3-state mode Liquid-Gaseous-Supercritical, and in the particular case where the propellant fluid is carbon dioxide (CO2). The horizontal x-axis indicates the enthalpy variations of the carbon dioxide in kJ/kg and the vertical y-axis indicates the pressure to which this fluid is subjected, in MPa.

FIG. 5

[0052] [FIG. 5] represents on an Enthalpy-Pressure diagram an illustration of a possible thermodynamic operation of the device in a Heat Pump function, here in the particular case where the propellant fluid is carbon dioxide (CO2). The horizontal x-axis indicates the enthalpy variations of the carbon dioxide in kJ/kg and the vertical y-axis indicates the pressure to which this fluid is subjected, in hecto kiloPascal.

FIG. 6

[0053] [FIG. 6] represents on an Enthalpy-Pressure diagram an illustration of a possible thermodynamic operation of the device in a function of Heat Engine, here again in the particular case where the propellant fluid is carbon dioxide (CO2). The horizontal x-axis indicates the enthalpy variations of the carbon dioxide in kJ/kg and the vertical y-axis indicates the pressure to which this fluid is subjected, in hecto kiloPascal.

DESCRIPTION OF REALIZATION MODES

[0054] With reference to the first 3 drawings FIG. 1, FIG. 2 and FIG. 3, the device comprises at least one Thermodynamic Working MPT (1THERMO) and a Hydraulic Transit MPT (1TRANSIT), each containing at least one hydraulic fluid (3), and at least one propellant fluid (2), comprises at least one liquid communication (7) equipped by at least one hydroelectric conversion machine (5) (6) and comprises at least two heat exchange systems (8COND) (8EVAP) in contact with the propellant fluid (2).

[0055] With reference to these drawings, the device may also comprise, a reception basin (4) of the hydraulic fluid (3) replacing the MPT of Hydraulic Transit in the event of a significant difference in level between the basin and the MPT of Thermodynamic Work, may also comprise external heat recirculation exchangers (8CIRC) of the propellant fluid (2) through the MPT of Thermodynamic Work (1THERMO), several differentiated compartments (9) to store, according to their colder and warmer temperatures, the possible heat transfer fluid(s) circulating in contact with heat exchange systems (8COND) (8EVAP) (8CIRC). The device generally includes hot thermal reserves (15) or cold thermal reserves (16), in particular to carry out thermoelectric storage, and concerning cold thermal reserves (16), to achieve the low pressure stability of the MPT of Hydraulic Transit (1TRANSIT). The device may include pressurized secondary tanks (13) dedicated to propellant fluids (2), necessarily connected to MPTs by means of pipes (14). The device may also include, in the upper portion of the tanks (1THERMO) (1TRANSIT) (13) systems for spraying and dropping droplets by gravity (10) of propellant fluid (2) or of hydraulic fluid (3). The device may also include one or more mobile physical separations (11) between the hydraulic fluid (3) and the propellant fluid(s) (2). The closure of the pressurized tanks (1THERMO) (1TRANSIT) (13) of the device can be carried out by means of an airlock (12).

[0056] With reference to the first drawing using here the Enthalpy-Pressure diagram of carbon dioxide, named FIG. 4, one generates in this example similar to conventional operation of a Heat Pump function consuming electrical energy, a strong expansion (17) to reach the temperature of the Cold that one wishes to recover, then one carries out an evaporation at almost constant temperature and pressure (18) to produce the Cold to be stored. Subsequently, since it is often desirable to also produce heat at high temperature at a later time, the dry gas is preheated (19) by adding heat from the ambient environment, or from an external heat source, or from the residual heat of the previous operations (22). In a subsequent step, one will cause a strong compression (20) of the propellant fluid (2) up to the pressure which will set the maximum temperature of the desired Hot, then one will carry out in supercritical state a significant extraction of heat at almost constant pressure which will cause an extreme contraction of volume (21) of the propellant fluid (2). At the end of the contraction, the heat extraction recovers only low-temperature heat (22), nevertheless interesting to be store temporarily to achieve the preheating (19) of the propellant fluid (2) of the next operation. It is remarkable to note on this diagram the possible superposition of the discontinuous working periods of the propellant fluid (2) of the device with the visualization of the recirculation steps of the working fluids of conventional heat pumps and conventional refrigeration machines. A thermodynamic cycle rotating in the opposite direction would be the cycle of a Heat Engine function, depleting for example the cold (16) and hot (15) thermal reserves to return electricity.

[0057] With reference to the second drawing using here the Enthalpy-Pressure diagram of the carbon dioxide, named FIG. 5, in this example of counterclockwise operation corresponding to the function of Heat Pump to store electrical energy in thermal form, the FP13 plot reproduces the states of the propellant fluid (2) in secondary pressurized tanks (13), the FP1THERMO plot reproduces the states of the propellant fluid (2) in the MPT of Thermodynamic Work (1THERMO) and the VIS1TRANSIT plot allows to visualize the transfers of the hydraulic fluid (3) between the 2 MPT (1THERMO) (1TRANSIT), without reproducing the states of the propellant fluid (2) in the MPT of Hydraulic Transit (1TRANSIT), these states being quasi-constant, at low temperature and at low pressure. Note that in the isochoric branch of highest value (on the right side), it is advisable to heat the cold and gaseous propellant fluid (2) located in the MPT of Hydraulic Transit (1TRANSIT), now devoid of hydraulic fluid (3) as a result of the hydraulic pumping of the previous cycle, by using the desirable cooling of the dense propellant fluid (2) located, hot in quasi-isochore, in the secondary pressurized tanks (13) of the MPT of Thermodynamic Work (1THERMO). For this purpose, during section AB an additional counter-current warming-cooling heat exchanger, not shown in the figures, is used between these two masses of propellant fluid (2). To succeed in this essential thermal operation, the entire mass of gaseous and cold propellant fluid (2) is transferred entirely via this additional exchanger, thanks to a mechanical transfer of hydraulic fluid (3) by a low-power pump and hydraulic line, between the MPT of Hydraulic Transit (1TRANSIT) and the MPT of Thermodynamic Work (1THERMO), originally completely filled with hydraulic fluid (3) as a result of the hydraulic pumping of the previous cycle. Without this sequential transfer, this mutual heat exchange would be impossible under conditions of quasi-reversibility. The BC section illustrates a partial isentropic compression. The CD section illustrates an interesting and unusual extraction of heat at maximum temperature during diabatic compression. The DE section illustrates a classic production of Hot by isobaric heat extraction in the supercritical phase thanks to the use of the condenser (8COND), located at high pressure. The EF section illustrates cooling to the dense (or liquid) state of the propellant fluid (2). Section FG illustrates the cooling of propellant fluid (2) in secondary pressurized tanks (13). The GH section illustrates a classic isenthalpic expansion to lower the temperature of the propellant fluid (2) to its minimum. The HA section illustrates an isobaric evaporation for the production of cold thanks to the evaporator (8EVAP), located at low pressure. It is important to note that a second voluntary permutation of the two MPTs (1THERMO) (1TRANSIT) must necessarily be performed between point F and point A.

[0058] With reference to the third and last drawing using here again the Enthalpy-Pressure diagram of the carbon dioxide, named FIG. 6, in this example of clockwise operation corresponding to the function of Heat Engine restituting electrical energy, the FP13 plot reproduces the states of the propellant fluid (2) in the secondary pressurized tanks (13), the FP1THERMO plot reproduces the states of the propellant fluid (2) in the Thermodynamic Work MPT and the VIS1TRANSIT plot allows to visualize the hydraulic fluid transfers (3) between the 2 MPT (1THERMO) (1TRANSIT), without reproducing the states of the propellant fluid (2) in the MPT of Hydraulic Transit (1TRANSIT), these states being most often constant, at low temperature and at low pressure. Note that in the isochoric branch of highest value (on the right side), it is advisable to cool the hot and gaseous propellant fluid (2) located in the MPT of Thermodynamic Work (1THERMO), devoid of hydraulic fluid (3) as a result of hydraulic turbining, from the desirable reheating of the dense propellant fluid (2), cold in quasi-isochore, contained in secondary pressurized tanks (13). For this purpose, during section MN the counter-current warming-cooling heat exchanger, mentioned in the previous paragraph, is used between these two masses of propellant fluid (2). To succeed in this essential thermal operation, the gaseous and hot propellant fluid (2) is completely transferred via this additional exchanger, thanks to a mechanical transfer of hydraulic fluid (3) by a low-power pump and additional hydraulic lines, between the MPT of Thermodynamic Work (1THERMO) and the MPT of Hydraulic Transit (1TRANSIT), originally completely filled with hydraulic fluid (3) as a result of the hydraulic turbining of the previous cycle. Section IJ illustrates this reheating of the propellant fluid (2) in the secondary pressurized tanks (13). The JK section illustrates a supercritical reheating. The KL section illustrates a supercritical isobaric heating and expansion of the propellant fluid (2), thanks to the evaporator (8EVAP) located at high pressure and thanks to heat consumption from, for example, the hot thermal reserve (15). The LM section illustrates a diabatic expansion, interesting and unusual, because not classically isentropic, to provide more work thanks to an additional supply of heat. The MN section illustrates the isochoric cooling on the right side mentioned above. The Nl section illustrates a contraction of the propellant fluid (2) through a heat extraction at the condenser (8COND) located at low pressure, extraction which will cause a consumption of the cold thermal reserve (16). It is important to note that a second voluntary permutation of the two MPTs (1THERMO) (1TRANSIT) must necessarily be performed between point N and point J.

EXAMPLES

[0059] A first example of operation concerns, according to FIG. 2, and for the mode of the two Liquid-Gaseous states, the thermal storage of electrical energy. The device carries out a main period of pumping of hydraulic fluid (3), a period driven by several valves not shown in the figures. The pumping assembly (6) driven by the external energy to be stored pushes the hydraulic fluid (3) at low pressure from the MPT of Hydraulic Transit (1TRANSIT) to the MPT of Thermodynamic Work (1THERMO) via liquid communication ducts (7), thus decreasing in the MPT of Thermodynamic Work (1THERMO) the volume occupied by its propellant fluid (2). The latter, simultaneously subjected to intense heat extraction thanks to heat exchange systems (8COND) (8ClRC) intended for the production of heat, starts to condense at its saturated vapor pressure, increases in overall density, then will change into the liquid phase occupying a reduced volume, triggering at this moment the end of the pumping period. In the alternative where, working at higher high pressure, the propellant fluid (2) would have reached its supercritical state, it would increase sharply in density during the extraction of its heat, would occupy a reduced volume, and as in the subcritical alternative, would let the hydraulic fluid move-in (3). The sequence of thermodynamic cycles includes isochoric heat exchanges and two successive permutations of the 2 MPT (1THERMO1) (1TRANSIT), allowing the production of Cold as explained in FIG. 5 and its description.

[0060] A second example of operation concerns, according to the same FIG. 2, and for the mode of the two Liquid-Gaseous states, the electrical restitution of stored thermal energy. During the turbining period, a period driven by several valves not shown in the figure, the propellant fluid (2) of the MPT of Thermodynamic Work (1THERMO), simultaneously subjected to an intense heat input from the hot thermal reserve (16) thanks to heat exchange systems (8EVAP) (8CIRC) will change from the liquid state to the gaseous state, and will thus expel at its saturated vapor pressure to the MPT of Hydraulic Transit (1TRANSIT) the hydraulic fluid (3) from this MPT of Thermodynamic Work (1THERMO)via the liquid communication ducts (7) and via the turbining assembly (5) which thus recovers the stored energy. In the alternative where, working at higher high pressure, the propellant fluid (2) would have reached its supercritical state, it would decrease sharply in density during the heat input, occupy a much larger volume, and as in the subcritical alternative, expel-out the hydraulic fluid (3). The sequence of thermodynamic cycles includes isochoric heat exchanges and two successive permutations of the 2 MPT (1THERMO) (1TRANSIT) and causes a consumption of the cold thermal reserve (16) as explained in FIG. 6 and its description.

[0061] An observation which confirms that we are in the presence of propellant fluids (2) working quantitatively bounded in mass, and not in the presence of a heat pump with continuous recirculation circuit, is that, in the absence of physical permutation of equipment, the production of Cold and Hot will not be able to persist beyond the complete change of state of the propellant fluids (2) (or beyond the maximum variation in density of the propellant fluid, in the case of operation in supercritical state).

[0062] It is specified that to achieve the restitution of stored electricity, it is necessary to equip the device with a cold thermal reserve (16) integrated into the device (storage by sensible heat, or by latent heat or thermochemical storage). The Cold produced during the periods of expansion of the propellant fluid (2) after compression is therefore stored in the cold thermal reserves (16) of this thermoelectric storage. This storage requires the use of one or more masses of liquid or solid matter, including salt water in the liquid or solid state, preferably organized according to differentiated temperatures, possibly including thermocline tanks or different depth of the Earth’s soil. The amount of Cold produced is, in the case of CO2 used as propellant fluid, about 5 times greater than the amount of electrical energy stored.

[0063] Similarly, to benefit of the thermal dipole of electrical restitution, it is necessary to equip the device with a hot thermal reserve (15) integrated into the device (storage by sensible heat, or by latent heat or thermochemical storage). The produced Hot is therefore thermally stored in the hot thermal reserves (15) of this thermoelectric storage, during periods of compression of the propellant fluid. This storage requires the use of one or more masses of liquid or solid matter, preferably organized according to differentiated temperatures, possibly including thermocline tanks or different depth of the Earth’s soil. The amount of heat produced is, in the case of CO2 used as propellant fluid, about 5 times greater than the amount of electrical energy available.

[0064] As a third example of operation, it is notable that in the situations already described by which external cold or hot sources become available, the device can achieve a net production of mechanical energy over a complete round trip sequence of contraction and expansion of the propellant. For example, in the case of pure CO2 used as propellant fluid (2) in both the 2 MPT (1THERMO) (1TRANSlT), thanks only to the arrangement of the environment and thanks to a cold source at zero degrees Celsius, which would be applied to the condenser (8Cond) of the MPT of Hydraulic Transit (1TRANSIT), the pressure of the hydraulic fluid (3) will be about 40 Bar only, while the pressure of energy restitution at the turbining of the MPT of Thermodynamic Work (1THERMO) is about 55 Bar, which is the saturated vapour pressure of CO2 heated by the evaporator (8EVAP) by ambient air or water, assuming an ambient temperature of 20° C. Even in this example of a modest temperature difference, a net production of mechanical energy is generated by this pressure differential equal to 15 bar.

INDUSTRIAL APPLICATIONS

[0065] The device according to the invention is intended for storage and energy conversion to store, produce or move electrical or thermal energy.

[0066] Its first industrial application is to provide an economical solution to the intermittency of intermittent renewable energies (solar and wind) feeding local and national electricity grids in increasing quantities, as part of the mitigation of greenhouse gas emissions produced by the many power plants running on fossil fuels.

[0067] A second industrial application is to provide an economical solution to the necessary decarbonization of the cooling needs and heating needs of industries and residential and tertiary buildings. In 2020, the consumption of Cold and Hot, major consumers of fossil energy, represented 40% of greenhouse gas emissions.

[0068] A third industrial application is the net generation of electricity, from the availability of a hot source or a cold source, including in situations of low temperature difference (low temperature geothermal energy, warm effluents, thermal energy from the seas) in which conventional heat engines, economically requiring deviations greater than 25° C., can not operate.

PATENTS DOCUMENTS

[0069] WO 2010/128222 A2 entitled in French « Procédé et équipements de stockage d′énergie mécanique par compression et détente quasi-isotherme d′un gaz » (“Method and equipment for storing mechanical energy by compression and quasi-isothermal expansion of a gas”)

NON-PATENT LITERATURE

[0070] 10.1016/j.energy.2012.09.057 A2 « Transcritical CO2 cycles with TES (thermal energy storage) for electricity storage ».