SYSTEM AND METHOD TO STORE AND GENERATE ENERGY WHERE A PRESSURE IS RELEASED INTO A LIQUID CIRCUIT WHICH IN TURN MOVES A LIQUID TURBINE TO GENERATE POWER

Abstract

A pressure of a working compressed fluid is released into a liquid circuit to drive a turbine for energy generation, comprising a compressor and a primary tank of high pressure, a first main tank of liquid and a second main tank of liquid, an auxiliary tank of liquid, a turbine of liquid located between the first and the second main tanks, and at a lower level than that of the bottom of the main and second and auxiliary tank, to ensure that the pressure inside the tanks forces the liquid in the proper direction through the turbine, a network of pipelines with their respective valves, such as inlet valves, outlet valves, control valves or pressure-regulating valves, as well as ventilation valves; where the operation is performed in short cycles and at a constant pressure by means of a control system that acts on at least one pressure-regulating valve.

Claims

1. A system for storing and generating energy, where a pressure generated by a working fluid is released into a liquid circuit which in turn moves a liquid turbine to generate energy, the system comprising: a first main tank (10); a second main tank (20); an auxiliary tank (30), wherein said first main tank, second main tank and said auxiliary tank comprise a driving liquid; a turbine (40) located between the first main tank (10) and said second main tank (20), and at a lower level than the bottom of the first (10) and second (20) main tanks and the auxiliary tank (30), to ensure that the pressure inside said main tank and said second main tank forces said driving liquid through said turbine (40) and not in the opposite direction; and a network of pipelines with their respective valves, including inlet valves, outlet valves, control valves as well as ventilation valves, wherein the operation is performed in short cycles and at a constant working pressure by means of a control system acting on at least one pressure regulating valve, which provides the working pressure of the system.

2. The system for storing and generating energy according to claim 1, wherein the pressure inside the tanks is generated by compressed air.

3. The system to store and generate energy according to claim 2, further comprises a compressor (60) and a high-pressure primary tank (50) for the production of the compressed air.

4. The system to store and generate energy according to claim 2, wherein the compressed air is provided by compressed-air remnants from external sources.

5. The system to store and generate energy according to claim 1, wherein the pressure inside the tanks is generated by a cryogenic liquid which, when injected into the tanks, heats-up and expands, generating pressure.

6. The system to store and generate energy according to claim 1, wherein said respective valves of said pipeline network are opened or closed to allow the movement of liquid flow between said first main tank and said second main tank (20) through said turbine (40).

7. The system to store and generate energy according to claim 1, wherein said auxiliary tank (30) only works while the system is changing from operating in one direction or in the opposite direction, for the transfer of liquid between said first main tank (10) and said second main tank (20).

8. The system to store and generate energy according to claim 1, wherein said first main tank (10) and said auxiliary tank (30) must be filled with a predetermined amount of liquid, while the second main tank (20) is left without liquid.

9. The system for storing and generating energy according to claim 1, wherein said driving liquid comprises any liquid that is not mixable with the working fluid that provides the pressure.

10. The system to store and generate energy according to claim 9, wherein said driving liquid is water and said working fluid is gaseous air.

11. The system to store and generate energy according to claim 9, wherein said driving liquid is water and said working fluid is gaseous nitrogen.

12. The system to store and generate energy according to claim 1, wherein said control system acts on the inlet valves, outlet valves, control valves and ventilation valves.

13. A method to store and generate energy, where a pressure generated by a fluid is released into a liquid circuit which in turn moves a liquid turbine to generate energy, comprising the steps of: a) providing a system that comprises a first main tank (10) of liquid with a predetermined level of liquid inside and a second main tank (20) of liquid without liquid inside, an auxiliary tank (30) of liquid with a predetermined level of liquid inside it, a turbine (40) of liquid located between the first (10) and second (20) main tanks, and at a lower level than the bottom level of the first (10) and second (20) main tanks and the auxiliary tank (30), to ensure that the working fluid forces the liquid through the turbine (40) and not in the opposite sense, a network of pipes with their respective valves, including inlet valves, outlet valves, control valves as well as ventilation valves, wherein the operation is performed in short cycles and at a constant pressure by means of a control system that acts on at least one pressure regulating valve; b) pressurizing the first main tank (10), the auxiliary tank (30) and the piping network to an operating pressure; c) opening the first main tank to turbine outlet valve (VS10-40), the second main tank inlet valve (VE20) and the second main tank ventilation valve (VS20At) so that the liquid moves from the first tank main tank (10), through the first main tank to turbine outlet valve (VS10-40), up to the turbine (40) and then, through the second main tank inlet valve (VE20) it is discharged into the second main tank (20), while the second main tank ventilation valve (VS20At) allows that the second main tank (20) is filled up without increasing the pressure; d) controlling the pressure of the first main tank (10) through a first main tank control valve (VC10) that controls the pressure as the liquid level decreases, thus ensuring a stable working pressure; e) closing the first main tank to turbine outlet valve (VS10-40), the second main tank inlet valve (VE20) and the second main tank ventilation valve (VS20At) and open the auxiliary tank to turbine outlet valve (VS30-40) to allow the auxiliary tank (30) to feed the turbine (40), during the transition from one discharge mode to another, while a new operating cycle is initiated; f) opening the first main tank ventilation valve (VS10At) and pressurize the second main tank (20) to the operating pressure by means of a second main tank control valve (VC20); g) opening the first main tank inlet valve (VE10) so that the flow can be discharged into the first main tank (10) that is already vented or is already at atmospheric pressure; h) opening the auxiliary tank ventilation valve (VS30At) to ventilate the pressure from the emptied auxiliary tank (30) and close the auxiliary tank to turbine outlet valve (VS30-40); i) opening the second main tank to turbine outlet valve (VS20-40) to feed the turbine (40) from the liquid coming from the discharge of the second main tank (20); j) closing the first main tank to auxiliary tank outlet valve (VS10-30) when the auxiliary tank (30) is at the predetermined liquid level of stage a), where this condition occurs when the liquid level in the first main tank (10) has reached the necessary level to allow that the water enters into the auxiliary tank (30) by gravity; k) controlling the pressure of the second main tank (20) through the second main tank control valve (VC20) which controls the pressure as the liquid level lowers, thus ensuring a stable working pressure; and l) closing all opened valves and start the stages from stage d) to stage l).

14. The method for storing and generating energy according to claim 13, further comprises pressurizing a primary tank (50) of high pressure by means of a compressor (60), or to store a gas or gas mixture at cryogenic temperature, before said step (b) of pressurizing said first main tank (10).

15. The method to store and generate energy according to claim 13, further comprises filling said auxiliary tank to its predetermined level in stage a), according to stage j), is done when the liquid level of the first main tank (10) has reached the necessary level to allow that the water enters in the auxiliary tank (30), by gravity.

16. The method for storing and generating energy according to claim 13, further comprises configuring said control system to execute steps b) to l).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a general schematic representation of a system of the present invention.

[0033] FIG. 2 shows a schematic representation of the functioning of a system of the invention, where the system is ready to start generating energy.

[0034] FIG. 3 shows a schematic representation of a system of the present invention where the first main tank has been emptied, the auxiliary tank has to maintain the power generation while the first main tank and the second main tank are prepared to reverse the flow.

[0035] FIG. 4 shows a schematic representation of a system of the present invention where the auxiliary tank has been emptied and the second main tank has been filled.

[0036] FIG. 5 shows an intermediate operation stage where once the level of liquid in the first main tank is high enough, the liquid will fill the auxiliary tank. When this stage has been finished, the system will be in the startup configuration shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention has two main interacting parts. On one hand, a working fluid under pressure, for example, a gas, and on the other, a liquid. Therefore, the present invention is a system and method that uses a pressurized-working fluid, such as a compressed gas (for example air), to pressurize tanks with liquid (for example water) which in turn actuates a liquid turbine to produce electric energy. However, the most relevant issue for the efficient production of energy is the capability to maintain a constant pressure. The pressure is monitored with pressure sensors and if more pressure is needed in the system as the liquid is discharged, the control system can react and maintain the desired working conditions by actuating on at least one pressure-regulating valve that provides the working pressure to the system.

[0038] The tanks that contain liquid are small. This means that for prolonged functioning time periods the system can work in cycles.

[0039] As shown in FIG. 1, the system comprises two liquid tanks or liquid reservoirs, a first main tank 10 and a second main tank 20 and, in addition, at least one auxiliary tank 30 of liquid that functions between cycles to give the system time to restart the cycle without loss of energy generation. An alternative system configuration is with three main tanks or liquid reservoirs, thus eliminating the auxiliary tank.

[0040] The system can also comprise a primary tank 50, which corresponds to a high-pressure vessel with a pressure that ranges between 30 bar and 300 bar. This main tank 50 feeds a primary pressure line that is operating at a lower pressure, e.g. 8 bar. This pressure does not exclude other working pressures, neither higher nor lower.

[0041] Taking 8 bar as the reference pressure and water as the reference liquid, the pressure is optionally supplied by a compressor 60. If there is a pressure derived from other processes, this pressure can be used to generate electricity, thus the shown compressor would not be necessary.

[0042] This pressure of 8 bar is connected, via piping and at least one pressure-regulating valve to the first 10 and second 20 main tanks with a first main tank control valve VC10 and a second main tank control valve VC20, and also to the auxiliary tank 30 via an auxiliary tank control valve VC30. Both liquid inputs and liquid outlets between the first 10 and second 20 main tanks, the auxiliary tank 30 and a turbine 40 have their own valves, which are controlled by an electronic system (not shown).

[0043] All the liquid tanks 10, 20, 30 are connected at their bottom part by pipes to the turbine 40. This ensures that the pressurized working fluid will force the liquid through the turbine 40 and not in the opposite sense.

[0044] There is a second pipe after the turbine 40 to allow that the flow goes from the first main tank 10, through the opening of an first tank inlet valve VE10, to the second main tank 20 through the opening of a second main tank inlet valve VE20 or in reverse order.

[0045] Each of the liquid tanks 10, 20, 30 has a ventilation valve VS10At, VS20At, VS30At that connects the inside with the outside, thus establishing an atmospheric pressure. Said valves are also controlled by an electronic system (not shown).

[0046] The auxiliary tank 30 is small compared to the first main tank 10 and the second main tank 20. The purpose of the auxiliary tank 30 is to operate intermittently, e.g. for 20 to 40 seconds, while the system is changing its operating direction in one direction or in the opposite direction. The auxiliary tank 30 can only be omitted if there is an alternative way to manage the downtime in the switching operation. One alternative way would be to operate the system with 3 main tanks, without an auxiliary tank.

[0047] The size of the first 10 and second 20 main tanks determines the cycle time. If you wish to operate the first main tank 10 or the second main tank 20 for 3 minutes, then the main tanks have a given size. If it is more suitable for this time to be of 6 minutes, then the main tanks have to be resized to that capacity.

[0048] The total operating time is set by the pressure and the size of the high-pressure primary tank 50 or by the pressure and the flow of the working fluid under pressure. According to one modality, it is estimated that this system can produce 1 MW for 4 hours using only 200 m.sup.2 of terrain. The use of terrain can be reduced if the tanks are made taller.

[0049] According to one modality, the high-pressure primary tank 50 is pressurized by means of a compressor 60 through solar energy, or low-cost energy from the grid, or any other convenient way. It can also be pressurized by non-conventional compressors. In accordance with another modality, the primary tank 50 has primary tank pressure-regulating valve VC50 to control the working pressure that said tank delivers to the entire system.

[0050] The first main tank 10 is filled with liquid as is the auxiliary tank 30, while the pressure is set at, for example, 8 bar through one or more pressure regulating valves. The first main tank to turbine outlet valve VS10-40 is opened and the second main tank inlet valve VE20 is also opened, which passes through the turbine 40, where the second main tank 20 operates as a discharge tank. The second main tank ventilation valve VS20At is opened, thus having an atmospheric pressure in the second main tank 20.

[0051] For the duration of the discharge, the only working elements are the pressure control in the first main tank 10, maintaining a constant working pressure.

[0052] When the first main tank 10 approaches its lower limit, the first main tank to turbine outlet valve VS10-40 is closed and the auxiliary tank 30 takes over, where the auxiliary tank to turbine outlet valve VS30-40 opens. This creates a time window, and energy is still being generated. During this window, the first main tank 10 is ventilated at atmospheric pressure, opening the first main tank ventilation valve VS10At, while the second main tank 20 is pressurized to, for example, 8 bar.

[0053] When the auxiliary tank 30 reaches its lowest level, the second main tank to turbine outlet valve VS20-40 and first main tank inlet valve VE10 are opened so that the flow from the second main tank 20 passes through the turbine 40 and is discharged into the first main tank 10. Along with that, the auxiliary tank to turbine outlet valve VS30-40 is closed so that the auxiliary tank 30 is also recharged with liquid and pressure, for the next cyclical event.

[0054] To reduce losses during the transition from one discharge mode to another, the auxiliary tank 30 can be adjusted to a slightly higher pressure. This compensates for the possible losses generated by the switching. According to one modality, the auxiliary tank 30 is forced to discharge liquid into the first main tank 10 that is lowering the pressure, but that has not yet reached atmospheric pressure.

[0055] FIG. 2 shows the status of the system when it is ready to start generating energy. The first main tank 10 and the auxiliary tank 30 are full of liquid, for example, water. Both are at a working pressure. The pressure is provided through the connection of pipes that reach the top of each tank, while the first main tank to turbine outlet valve VS10-40, the second main tank inlet valve VE20 that passes through the turbine 40 and the second main tank ventilation valve VS20At are open. All other valves are closed. The liquid goes from the first main tank 10, through the first main tank to turbine outlet valve VS10-40, to the turbine 40. Then, through the second main tank inlet valve VE20 it is discharged into the second main tank 20. The second main tank ventilation valve VS20At remains open. This allows the second main tank 20 to be filled without increasing the pressure. The first main tank 10 has a control valve VC10 that controls the pressure as the liquid level decreases, thus ensuring a stable working pressure. The path taken by the liquid is shown in FIG. 2 by means of a thicker layout of the pipes connecting the various components.

[0056] As shown in FIG. 3, the system of the present invention has emptied the first main tank 10. Now the auxiliary tank 30 has to take over the energy generation while the first main tank 10 and the second main tank 20 are prepared to reverse the flow. All the valves are closed. The first main tank ventilation valve VS10At is open to allow that the pressure in the first main tank 10 equalizes atmospheric pressure, the auxiliary tank to turbine output valve VS30-40 is open to allow that the auxiliary tank 30 feeds the turbine 40. The first main tank inlet valve VE10 is opened so that the flow can be discharged into the first main tank 10 which is already in the ventilation process. The second main tank control valve VC20 is opened to increase the pressure in the second main tank 20. The liquid path is shown in FIG. 3 by a thicker pipe layout that connects the various components.

[0057] In FIG. 4, the auxiliary tank 30 has been emptied, and the liquid has already been deposited in the first main tank 10. The first main tank ventilation valve VS10At remains open to allow the liquid to be discharged from the second main tank 20 without generating pressure inside the first main tank 10. The first main tank to auxiliary tank outlet valve VS10-30 is open to ventilate the pressure from the auxiliary tank 30, this remains open to fill the auxiliary tank 30 with liquid when the liquid level in the first main tank 10 has reached the level necessary to allow that the liquid enters the auxiliary tank 30, in this example by gravity. The second main tank turbine outlet valve VS20-40 is open to feed the turbine 40, the first main tank inlet valve VE10 remains open to allow that the flow is discharged into the first main tank 10. The second main tank control valve VC20 provides the necessary pressure to the second main tank 20 as the liquid level decreases. This allows that the second main tank 20 has a stable pressure condition. The liquid path is shown in FIG. 4 by a thicker pipe layout connecting the various components. If an overpressure is detected in the auxiliary tank 30, the auxiliary tank ventilation valve VS30At can be opened to discharge this overpressure.

[0058] FIG. 5 shows the partial filling of the first main tank 10 and the filling of auxiliary tank 30. The intermediate step shown in FIG. 5 is the fact that once the liquid level in the first main tank 10 is high enough, the liquid fills the auxiliary tank 30. The auxiliary tank ventilation valve VS30At is opened to allow filling of the auxiliary tank 30. When this stage is finished, the system is in the initial configuration shown in FIG. 2. The liquid path is shown in FIG. 5 by a thicker layout of the pipes connecting the various components.

[0059] Additional improvements can be made to retain some of the pressure discharge being vented into the atmosphere. This energy loss represents 9 to 15% depending on the working pressure at which the system of the present invention is operating.

Application Example

[0060] If one wishes to generate energy with a Francis turbine that produces 1.2 MW, with a water column of 60 m, a flow rate of 1.24 m.sup.3/s (cubic meter per second), with first and second main tanks of liquid, in this case water, containing 350 m.sup.3 each, with an auxiliary tank of 25 m.sup.3, with a duration of 4 hours, then a working pressure of 8 bar is needed, the discharge time from the first main tank 10 to the second main tank 20 is approximately 4.5 minutes. The auxiliary tank 30 provides a 20 second window to make the switch over. Approximately 54 cycles are required to operate for 4 hours.

[0061] To store the pressure at 100 bar, a high-pressure primary tank 50 of approximately 1000 m.sup.3 is required. If the pressure is stored at 200 bar, a high-pressure primary tank 50 of approximately 535 [m3] is required. The high-pressure primary tank 50 preferably has a cylindrical shape of approximately 10 meters high and a radius of 4 meters.

[0062] The present invention can be used to store energy and produce electricity under demand. In addition, an objective for land and power usage have been presented.

LIST OF REFERENCES

[0063] 10 First main tank [0064] 20 Second main tank [0065] 30 Auxiliary Tank [0066] 40 Turbine [0067] 50 Primary Tank [0068] 60 Compressor [0069] VS10At First main tank ventilation valve [0070] VS20At Second main tank ventilation valve [0071] VS30At Auxiliary tank ventilation valve [0072] VC10 First main tank control valve [0073] VC20 Second main tank control valve [0074] VC30 Auxiliary tank control valve [0075] VC50 Primary tank pressure-regulating valve [0076] VS10-30 First main tank to auxiliary tank outlet valve [0077] VS10-40 First main tank to turbine outlet valve [0078] VS20-40 Second main tank to turbine outlet valve [0079] VS30-40 Auxiliary tank to turbine outlet valve [0080] VE10 First main tank inlet valve [0081] VE20 Second main tank inlet valve