NL2007346C2 - METHOD AND DEVICE FOR STORING AND GENERATING ELECTRICITY. - Google Patents

Description

METHOD AND DEVICE FOR STORING AND GENERATING ELECTRICITY

The invention relates to a device for generating electricity and storing electrical energy in the form of high-pressure gas, comprising a gas reservoir, a piston engine and an electric generator / engine, the piston engine comprising at least one piston device, which comprises at least one opening with a valve 10 connected to a high-pressure gas line and which comprises at least one opening with a valve connected to a low-pressure gas line and which piston device comprises at least one supply of fuel, the device being adapted to expansion cycles generate electricity by burning fuel in the piston device and / or allowing high-pressure gas from a gas reservoir to flow through the piston device such that the generator / engine is driven, the device being further adapted to generate electrical energy in compression cycles by driving the piston device by means of the electric generator / engine such that gas is pumped into the gas reservoir

Such a device is described in US 4,281,256.

25 Under normal circumstances, the power plants are well able to meet the large energy demand during the day, but the demand for electricity falls sharply in the evenings and at night. This while the power stations have little or no ability to adjust production, since coal or 30 nuclear power plants, for example, have too long a start-up time to keep up with the day-and-night rhythm. In the evening and at night there is also a surplus electricity, which despite the internationalization of the energy market, 2 cannot all be sold abroad. This surplus therefore results in lower prices for electricity than during the day.

In the known device a generator is present which can both generate electricity when it is driven by a piston engine, and can also drive the piston engine by using electricity, the generator acting as an electric motor.

10

For example, at times with a surplus of electricity, when the electricity is therefore cheap, energy is withdrawn from the grid and this energy is used to drive the electric motor that drives the shaft of a piston engine. This piston engine works in this way as a compressor, which can store gas under high pressure in a reservoir. The energy that is withdrawn from the electricity grid is, as it were, stored in the reservoir in the form of high-pressure gas.

When the electricity prices go up, for example during the day, the process can be reversed / the gas stored under high pressure is led in combination with fuel through the piston engine, which now acts as a combustion engine. The electric motor, which now functions as a generator, is connected to the axis of the piston engine and generates electricity.

To realize this switch into operation, the mass flow is reversed by the piston device. To change the flow through the high and low pressure lines from direction 30 and pressure, opening and closing (large) valves in a certain order is necessary; this has a duration of several revolutions and is greater than that for the valve times of the piston devices.

3

If the valve times do not match the pipe running, a problem arises: unwanted and dangerous pressures and / or flows in the pipes (for example shock waves and excessive pressures). In the known device it is not well possible to switch from generation to energy storage and vice versa while the device is in operation.

The object of the present invention is a reliable, more efficient, cheaper and / or simpler device for generating and storing electricity that is able to switch in operation from generating to storing energy.

To this end, the piston device comprises at least two valves, at least one of which is connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line, and becomes neutral during the change from an output cycle to a target cycle. cycle in which the second valve remains closed. By keeping one of the valves closed, the mass flow is interrupted by the piston device. The valve that remains closed during the neutral cycle is preferably connected to the high-pressure pipe.

The piston device preferably comprises at least three valves, of which at least two first valves are each connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line, and during the change from an output cycle to a target cycle a neutral cycle is set in which the two first valves 30 are open one after the other and closed one after the other for at least one revolution. Preferably, a first valve opens on TDC (Top Dead Center or top dead center) and closes the other first valve on TDC. By opening and closing the valves connected to the same pipe one after the other in one revolution, the piston can move freely without the piston being hindered by extremely high or low pressures in the piston device.

For the storage of electrical energy the energetic efficiency of the conversion is of great importance, so that the transport through pipes and ports preferably leads to minimal flow losses; the compression should likewise preferably be multi-stage, cooled in-between, with a minimum of harmful space in the cylinder and at a low temperature. The volume above the piston, if it is in the upper dead center, is then preferably as small as possible; valves that open inwards should be substantially closed when the piston is in the vicinity of the TDC to avoid any contact with the piston. After the compression in the piston device, the opening time for the outflow is more importantly shorter than the opening time used for a four-stroke duty cycle.

In a two-stroke piston engine with pump, as described, for example, in international patent application WO 2006/025743, during normal operation, compression takes place in a separate part (the pump) and, in addition to combustion, expansion takes place in the cylinders (expansors) place with 25 minimal harmful spaces.

The reservoir can consist of a collection of very long cooled tubes; this promotes isothermal compression / expansion in the reservoir; examples are underground tubes or tubes in an enclosing jacket with coolant. The reservoir has a fixed volume and during filling the pressure can increase from, for example, 15 to 100 bar.

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Preferably, during the neutral cycle, one of the first valves is set for the target cycle and the other first valve remains set for the exit cycle. This is attractive, since with an unchanged opening time only the opening time is changed.

Preferably, during the transition from the last exit cycle to the first neutral cycle, one of the first valves at least one revolution is closed and is set for the target cycle in a subsequent revolution. And preferably, during the transition from the neutral cycle to the target cycle, the valve set for the exit cycle is closed for at least one revolution and is set for the target cycle in a subsequent revolution. In this way a valve is switched off during at least one revolution of the shaft, so that a valve does not have to be opened twice in quick succession in order to switch to another cycle.

The piston engine preferably comprises at least one compressor to increase the pressure of the gas in the high-pressure line to at least a minimum operating pressure level. Preferably, the minimum operating pressure level is at least 10 bar, preferably at least 50 bar, and more preferably at least 70 bar. As a result, even when the gas reservoir is in danger of being hit, efficient expansion takes place in the piston engine by the supply of gas under high pressure.

The piston engine preferably comprises at least two piston devices and the piston devices comprise at least three valves, at least two of which are first valves connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line.

6

The piston engine preferably comprises at least a first piston device, at least a second piston device and a closable connecting line between the high-pressure line and the low-pressure line, wherein the gas flow in the pressure lines can be adjusted by means of valves such that gas via the connecting line after compression in the first piston device, is passed through the second piston device for further compression to at least the minimum operating pressure level. Such a series connection of at least two piston devices makes it possible to do the compression of the gas in two phases, wherein the piston devices can be adapted to the operating pressure of the gas. In this way a more efficient compression takes place.

15

Preferably, the connecting conduit comprises a heat exchanger for extracting heat from the gas produced during the first phase compression as described above.

20

The invention also relates to a method for generating and / or storing electrical energy in the form of high-pressure gas by means of a piston engine and an electric generator / engine, the piston engine comprising at least one piston device, which piston device comprises at least one opening with a valve connected to a high-pressure gas line and which comprises at least one opening with a valve connected to a low-pressure gas line, wherein in expansion cycles electricity is generated by burning fuel in the piston device and / or high-pressure gas allowing pressure from a gas reservoir to flow through the piston device such that the generator / engine is driven, and / or where electrical energy is stored in compression cycles by driving the piston device by means of the electric generator / engine such that gas in the gas reservoir is being pumped.

According to another aspect of the invention, at least one piston device is set for a neutral cycle, in which a second valve remains closed. Preferably, the two first valves are open and closed one after the other for at least one revolution one after the other. Preferably, the piston device set for the neutral cycle in a subsequent revolution is set for the opposite cycle of the cycle of the other piston device.

Such a method makes it possible to adjust the mass flow from the high-pressure line to the low-pressure line or vice versa by having at least one of the piston devices run in the neutral cycle, or even in the opposite cycle.

By the opposite cycle it is meant that when the piston device operates in a compression cycle, the relevant piston device is controlled for the expansion cycle and vice versa. After all, the mass flow through a piston device running in a neutral cycle is interrupted and when a piston device operates in the opposite cycle, the net mass flow through the piston engine is further adjusted. By adjusting the number of piston devices, starting from a piston engine with a plurality of piston devices, which run in a neutral or opposite cycle, the power of the piston engine 30 can be adjusted. The use of the neutral cycle makes it possible to make this adjustment in power of the piston engine while the piston engine is in operation; the engine does not have to be stopped.

8

According to another aspect of the invention, at least one piston device for the compression cycle and the other piston device for the expansion cycle are set.

5

The invention will be further elucidated with reference to the exemplary embodiment shown in the figures, in which:

Figure 1 schematically shows the device operating as a conventional cogeneration unit;

Figure 2 schematically shows the device operating in the expansion cycle; Figure 3 schematically shows the device operating in the compression cycle;

Figure 4 schematically represents the device in which the power of the motor is adjusted; 20

Figure 5 schematically represents a piston device; and

Figure 6 schematically shows the control of the valves in a piston device when a starting cycle is switched to a target cycle.

The device 1 for generating electricity and storing electrical energy in the form of high-pressure gas is used in Figure 1 as a combined heat and power unit. An electric motor / generator 3 is connected with a crankshaft 3a to a piston engine 6, which comprises 8 piston devices 8, which act as expanders, and 2 compressors 7. Through a supply of gas 18a, which for example consists of a "supercharger", 9 through an open valve 10 via a line 9 the gas is supplied to the compressors 7. Via a high-pressure line 4 and an open valve 15 the gas in the piston devices 8 burned with the addition of fuel (not shown), whereby the crankshaft 5a drives the electric motor / generator 3, whereby electricity is generated. The gases are discharged via a low-pressure line 5 with an open valve 13 and via open valve 17 to an outlet 19, which consists of a "turbo expander". An inlet of gas 18b is closed by means of a closed valve 16, 10, just like a connecting line 20, which is closed by a valve 14. A gas reservoir 2 is also closed from the line 9 by a valve 11 and from the high-pressure line 4 by a valve 12.

In Figure 2, the device 1 operates in the generation cycle, wherein the piston engine 6 is driven by the gas from the gas reservoir 2 and thus the engine / generator 3 is driven, whereby electricity is generated. High-pressure gas is led from the gas reservoir 2 via the open valve 12 to the high-pressure pipe 4 through the open valve 15. The valve 11 is now closed. The 20 supplies of gas 18a and 18b are closed with valves 10 and 16. No mass now flows through the compressors 7. The high-pressure gas is burned in the piston devices 8 after fuel has been supplied, so that the engine is driven via the crankshaft 3a / generator 3 is driven, whereby electricity 25 is generated. The combustion gases are discharged via the low pressure line 5 with open valve 13 via the open valve 17 to the outlet 19. The connecting line 20 is closed with the valve 14.

When the pressure of the gas in the gas reservoir falls from 2 to 70 bar, the valve 12 is closed and the valve 11 is opened, whereby the gas flows via the pipe 9 through the compressors 7 to the high-pressure pipe 4, whereby the pressure is increased.

10

In Figure 3, the device 1 operates in the storage cycle, wherein the engine / generator 3 uses electricity to drive the piston engine 6 via the crankshaft 3a to compress the gas and store it in the gas reservoir 2. Gas is supplied via the inlet 18b, which consists of a "supercharger", is led via the valve 16 to the low-pressure line 5, which is now divided by the closed valve 13 into parts 5a and 5b. The high-pressure line 4 is also divided by the closed valve 15 into parts 4a and 4b. The outlet 19 is closed by the valve 17. Low-pressure gas is led from the low-pressure line 5a through the piston devices 8a, where it is compressed because the crankshaft 3a is driven by the engine / generator 3. The compressed gas is supplied via the high-pressure line 4a and the connecting line 20 through the open valve 14 to the low-pressure line 5b, which now contains gas under higher pressure. The compressed gas is further compressed by the piston devices 8b and via the high-pressure conduit 4b stored by the open valve 12 in the gas reservoir 2. The valve 10 is also open and the valve 11 is closed, whereby gas is introduced via the inlet 18a and the pipe 9 supplied to the compressors 7, which deliver high-pressure gas to the high-pressure line 4b and then to the gas reservoir 2.

In Figure 4, the device 1 also operates in the storage cycle, such as in Figure 3, with the difference that a piston device 8c runs in an expansion cycle. As a result, pressurized gas is returned from the high-pressure line 4a to the low-pressure line 5a, whereby the total mass flow from the low-pressure line 5a to the high-pressure line 4a decreases.

Figure 5 shows a piston device 21, for example a piston device as known from the international patent application WO 2006/025743, which is designed with 3 valves.

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The piston device 21 comprises a piston 22, a chamber 23 and three valves 24, 25a and 25b. A high-pressure valve 24 is connected to the high-pressure line 4 and low-pressure valves 25a and 25b are connected to the low-pressure line 5. A valve as known from international patent application WO 2004/092550 is suitable. Furthermore, the piston device is provided with means for fuel supply and heat recovery (not shown).

Figure 6 shows the control of the two low-pressure valves 25a and 25b and the high-pressure valve 24 of the piston device 21 of Figure 5 on transition from the output cycle to the neutral cycle and from the neutral cycle to the target cycle, each during three rotations of the crankshaft . The shaded bars for each of the valves 25a, 25b and 24 indicate when the relevant valves are open. For example, at time V in Example I, the low pressure valves 25a and 25b are open and the high pressure valve 24 is closed, as can be seen in Figure 5.

Example 1 has as its starting cycle an expansion cycle 26. Hereby gas flows from the high-pressure line 4 under high pressure during a short opening of the high-pressure valve 24 of the upper dead center (TDC) of the piston 22 to 30 ° after TDC, into the chamber 23 due to the fall of the piston 22 and is expanded after the high-pressure valve 24 has been closed. From 180 ° after TDC to TDC, 25 low-pressure valves 25a and 25b are opened and the gas from the chamber 23 is forced into the low-pressure line 5 by the upward movement of the piston 22.

Example III has as its starting cycle a compression cycle 28. Here, gas from low-pressure line 5 flows into the chamber 23 through low-pressure valves 25a and 25b through the downward movement of the piston 22 from TDC to 180 ° after TDC. The low pressure valves 25a and 25b are closed 12 at position 180 ° after TDC and the subsequent upward movement of the piston 22 compresses the gas, after which the gas can flow out through the opening of the high pressure valve 24 at 30 ° before TDC in the high pressure line 4 .

5

For the transition from, for example, an expansion cycle 26 to a compression cycle 28, use is made of the neutral cycle 27, wherein the low-pressure valves 25a and 25b are alternately open and the high-pressure valve 24 remains closed, as shown in the third revolution of example I.

Example 1 shows a transition 29a from the expansion cycle 26 to the neutral cycle 27. During the transition 29a, the low pressure valve 25a is not opened and the valves 24 and 25b continue to follow the expansion cycle 26. In a subsequent revolution of the piston 22, the low pressure valve 25a follows the compression cycle 28 and low pressure valve 25b still follows the expansion cycle 26. The high pressure valve 24 is closed / this is the neutral cycle 27.

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Example II shows a transition 29b from the neutral cycle 27 to the compression cycle 28. During the transition 29b, the low pressure valve 25b is not opened, the low pressure valve 25a continues to follow the compression cycle 28 and high pressure valve 24 is opened according to the compression cycle 28. In a subsequent revolution, the low pressure valve 25b is also driven according to the compression cycle 28, after which all valves follow the compression cycle 28.

Examples III and IV show in a similar way the transition from the compression cycle 28 via the neutral cycle 27 to the expansion cycle 26 via transitions 29c and 29d.

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Valve times other than those indicated in Figure 6 are also possible; for example, it is possible to overlap the low pressure valves 25a and 25b in the neutral cylinder 27. As long as the high pressure valve 24 remains closed, the mass flow is interrupted by the piston device. However, it is important that the valves are closed at TDC, due to possible damage to the valves by the piston as a result of the very small harmful volume of the piston device.

Claims (17)

Method for generating and storing electrical energy in the form of high-pressure gas by means of a piston engine and an electric generator / engine, the piston engine comprising at least one piston device, which is at least one opening with a valve that is connected to a high-pressure gas line and which comprises at least one opening with a valve connected to a low-pressure gas line, wherein electricity is generated in expansion cycles by burning fuel in the piston device and / or extracting high-pressure gas from a gas reservoir through the piston device flowing in such a way that the generator / engine is driven, wherein electrical energy is stored in compression cycles by driving the piston device by means of the electric generator / engine such that gas is pumped into the gas reservoir, with changing between said cycles from the starting cycle 20 to the target cycle, characterized in that during the change from an output cycle to a target cycle, a neutral cycle is set in which one of the said valves remains closed. The method of claim 1, wherein the valve that remains closed during the neutral cycle is connected to the high pressure line. 3. Method as claimed in claims 1 or 2, wherein the piston device comprises at least three valves, of which at least two first valves are each connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line, the two during the neutral cycle, first valves are open one after the other for one revolution and close after each other within one revolution. The method of claim 3, wherein during the neutral cycles, one of the first valves is set for the target cycle and the other first valve remains set for the exit cycle. A method according to claim 3 or 4, wherein during the transition from the last starting cycle to the first neutral cycle, one of the first valves is closed for at least one revolution and is set for the target cycle in a subsequent revolution. 6. Method as claimed in claims 3 to 5, wherein during the transition from the neutral phase to the target cycle, the valve set for the output cycle is closed for at least one revolution and is set for the target cycle in a following revolution. The method of claims 3 to 6, wherein a first valve opens at the upper dead center (TDC) and the other first valve closes at the upper dead center (TDC). 25 8. Device for generating and storing electrical energy in the form of high-pressure gas, comprising a gas reservoir, a piston engine and an electric generator / engine, the piston engine comprising at least one piston device, which has at least one opening with a valve connected to a high-pressure gas line and which comprises at least one opening with a valve connected to a low-pressure gas line and which piston device comprises at least one supply of fuel, the device being adapted to generate electricity by fuel in expansion cycles to be burned in the piston device and / or to allow high-pressure gas from a gas reservoir to flow through the piston device such that the generator / engine is driven, the device being further adapted to store electrical energy in compression cycles by starting the piston device drive through the electric generator / motor such that gas is in it gas reservoir, characterized in that the device comprises a control device for controlling the valves, which is adapted to set a neutral cycle during the change from an output cycle to a target cycle, in which one of said valves remains closed ft. 9. Device as claimed in claim 8, wherein the piston device comprises at least three valves, of which at least two first valves are each connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line, wherein during the neutral cycle the two first valves are open one after the other for at least one revolution and closed one after the other within one revolution. 10. Device as claimed in claims 8 or 9, wherein the piston engine comprises at least one compressor to increase the pressure of the gas in the high-pressure pipe to at least a minimum operating pressure level. Device as claimed in claims 8, 9 or 10, wherein the minimum operating pressure level is at least 10 bar, preferably at least 50 bar, and more preferably at least 70 bar. 12. Device as claimed in claims 8 to 11, wherein the piston engine comprises at least a first piston device, at least a second piston device and a closable connecting line between the high-pressure line and the low-pressure line, wherein the gas flow in the pressure lines can be adjusted in such a way by means of valves state that gas is passed through the connecting line after compression in the first piston device through the second piston device for further compression to at least the minimum operating pressure level. Device as claimed in claim 12, wherein the connecting line comprises a heat exchanger for extracting heat from the gas. 14. Method for generating and / or storing electrical energy in the form of high-pressure gas by means of a piston engine and an electric generator / engine, the piston engine comprising at least two piston devices, said piston devices having at least one opening with a valve which is connected to a high-pressure gas pipe and which comprises at least one opening with a valve which is connected to a low-pressure gas pipe, electricity being generated in expansion cycles by burning fuel in the piston devices and / or high-pressure gas from a gas reservoir 30 flowing through the piston devices such that the generator / engine is driven, and / or electrical energy being stored in compression cycles by driving the piston devices by means of the electric generator / engine such that gas is pumped into the gas reservoir with the characterized in that at least one piston device for a neutral cycle wo is set in which one of the said valves remains closed in order to control the mass flow through the piston engine. 15. Method according to claim 14, wherein the piston devices each comprise at least three valves, at least two of which are first valves connected to the low-pressure line or the high-pressure line and the other, second valve is connected to the other line, wherein during the neutral cycle the two first valves are open one after the other for at least one revolution and closed one after the other within one revolution. 16. Method according to claims 14 or 15, wherein the piston device which is set for the neutral cycle in a subsequent revolution is set for the opposite cycle of the cycle of the other piston device. 17. Method for generating and / or storing electrical energy in the form of high-pressure gas by means of a piston engine and an electric generator / engine, the piston engine comprising at least two piston devices, said piston devices having at least one opening with a valve which is connected to a high-pressure gas pipe and which comprises at least one opening with a valve which is connected to a low-pressure gas pipe, electricity being generated in expansion cycles by burning fuel in the piston devices and / or high-pressure gas from a gas reservoir by allowing the piston devices to flow such that the generator / engine is driven, and / or where electrical energy is stored in compression cycles by driving the piston devices by means of the electric generator / engine such that gas is pumped into the gas reservoir with the characterized in that at least one piston device for the compression cycle e n the other piston device is set for the expansion cycle.