GB2461756A - Compressed air energy storage - Google Patents

Abstract

High pressure air is provided by a various sources and is stored as a means of storing energy. A pneumatic motor driving a generator is used to convert the energy into electrical energy when required. The air may be provided by a wind turbine, or a compressor powered by a diesel or petrol generator, or by off-peak electricity from a grid.

Description

Storing electrical power from solar or national grid sources as air pressures.

This invention relates to the ability to store energy produced by wind driven air pumps, wind driven electrical turbines, photovoltaic tiles, water turbines or off-peak grid power by converting it to air potentials. The high air pressure produced by the wind driven air pump is stored directly in a vessel [11 while the high air pressure produced by the solar devices is stored in vessel [1] after being converted. The high air pressure produced in this way and stored in vessel [1] is then fed to a designed air motor which drives a generator. The cycle, electrical power to air pressure and back to electrical power is complete.

The demand for energy from fossil sources is exceeding the supply and damaging our environment (C02 and general pollution is causing so many problems).

Replaceable energies from environmental sources can be used; these are all valuable but can be very intermittent and unreliable (they depend on so many factors). The answer to the sustainable growth of these units must be a cost-effective storage system. For instance, the energy produced by a solar source during the morning when the wind is blowing hard and the sunlight is intense may not be required, but in the afternoon (in the same conditions) a demand for more power than that being produced could be made. If a storage unit is fitted (with the correct wiring) the total energy available in the afternoon could be that produced and stored in the morning plus the energy being produced at that point in time in the afternoon. Without the storage unit the energy produced in the morning would have been lost.

According to the present invention there is provided an extremely high air pressure supplied by a commercial 240V AC electric motor (powered by the output of the solar sources) driving a screw/piston type air compressor [4] (the HP of the electric motor on the compressor [4] will depend on the energy available from the sources).

Alternately and preferably, if the system involves only wind driven air compressors feeding directly into the vessel [1] then losses due to the conversion (electrical to air) will not be involved; the air motor will drive the generator and no other circuitry will be required other than the safety valve. The commercial unit [4] will only be required if it is intended to store electrical power from solar devices or the national grid.

The unit [4] pressurises a high capacity air vessel [I] constructed using cross woven fibreglass matting. A very strong stretchable inner liner is fitted inside vessel [1] (or a number of these vessels in parallel); for external support the vessels [1] should be positioned underground. The air motor [3] is then driven by the potential between the high air pressure in vessels [1] and atmospheric pressure. Two pistons operate on one drive shaft; these are known as the active piston and the inactive piston. All the residual air above the inactive piston is fully removed allowing it free movement to TDC while at the same time the high air pressure is applied to the active piston. This results in two power strokes being generated by the designed air motor for each revolution of the drive shaft. The output power could be increased by increasing the area of both pistons or flexibility can be achieved by having a number of air motors operating from the same high pressure with each driving its own generator. As the demand for power falls or increases the air motors can be switched into and out of the high pressure supply from the vessels [1].

A specific embodiment of the invention will now be fully described hereinafter, by way of example, with references to the accompanying drawings in which: -Figure 1 describes the modifications to a commercial air pump to make it an air motor by fitting four air valves.

Figure 2, (please view with Figure 1). Reed switches and button magnets control air valves via a relay to give maximum efficiency and accurate timing of the air motor. Two systems can be used, two banks of reed switch (marked Si, S2 etc) or alternately one bank of reed switches and one relay; the second version gives a more efficient operation and longer component life.

Figure 3 shows the LP (low pressure) magnetic air valves (V2 and V4) venting directly (without restraint) into the atmosphere.

Figure 4 is the electrical diagram of the components.

Figure 5 and 5A shows the construction of the wind driven air pump.

A commercial air pump was used to make the magnetic air motor [3] (this commercial air pump is made in large or small power visions or one can be constructed specially). The demonstration version (a DVD is available showing the unit operating) is a small unit with twin pistons operating on a single drive shaft. Conversion involved replacing the existing cylinder head which had held the two one-way valves with a 1/4inch steel plate. This was drilled and tapped to take the four air valves.

This air motor replaces that described in the patent GB 2410930 "An air driven environmentally friendly vehicle".

Referring to the drawings and diagrams attached Figure 1/4. The LP valves are 1,4 inch diameter and the HP valves are 1/4 inch in diameter, both are heavy duty. The total wattage taken by the motor (no matter what the output power is) will be around 40 watts.

In Fig la the piston P1 is shown at TDC and valve VI, when open, will inject high pressure air onto the top of P1 for the full period of its travel. At the same time Piston P2 is ready to return to TDC so valve V4 will open for the full period of its travel. Any air pressure built up above P2 during its travel towards the head will be removed In Fig lb the pistons are shown in the reverse state; nowV2 will remove pressure from above P1 while valve V3 will apply high pressure to P2, again for the full period of its travel.

Figure 2 is the wiring diagram for the air motor; this shows the two methods adopted to control the switching and timing.

All contacts are as shown in the drawing without power on.

For the first method (shown in figure 2 fig 2a) the V-Belt pulley wheel revolving on the driveshaft carries the three button magnets Ml, M2 and M3; the magnets and the V-Belt pulley revolve in front of the board carrying the reed switches (position sideways). As the V-Belt pulley rotates, the reed switches are switched into the "on/off" condition by the nearness of the passing button magnets. Two banks of reed switches are fitted.

One bank controls the first half of the drive shaft rotation and the other controls the second half of the drive shaft rotation. In this operation the reed switches carry the full current of the two air valves. The timing itseff is achieved by fitting the reed switches in the precise point on the backing board that matches the actions required.

In the second method the efficiency and component life is increased; a relay is used to reduce the current load on the reed switches and to give a steady "on" period of the air valves (no pulsing).

Relay RA is operated by the 24V DC on SI (SI is any. of the reed switches in the active bank) during 180 degrees of the drive shafts rotation. This is achieved by the magnets attached to the "V'1 belt pulley closing each reed switch as it passes. RA relay operating operates four sets of change over contacts RAI, RA2, RA3, and RA4 (RA4 is not used).

Referring to Figure 1/4. Only one bank of reed switches is used for this method. RA relay normal not operated; no reed switches involved for this 180 degrees of travel. RA 1 is in the normal state, no function. RA 2 normal state applies the 24V to the air valves V2 and V3. V3 applies high pressure to P2 while V2 vents P1.

The pistons turn the drive shaft 180 degrees taking the magnets round to operate the reed switches SI, S2, etc. Now the reed switches in this bank put out 24V to operate the relay.

All the change-over contacts of RA relay are changed from the normal state. RA 1 applies the 24V to VI and V4 and at the same time RA 2 disconnects V3 and V2. Referring to Figure 1/4 again VI applies high pressure to P1 and V4 vents P2. The drive shaft travels the next 180 degrees and the operation is repeated. RA 3 also changes over and as it carries a capacitor it connects it across the coil of RA relay at points marked I and 2.

As the magnets travel over the reed switches there may be very short periods where none of them are fully operated, RA relay could release and operate quickly; the capacitor on RA3 slugs the relay preventing chatter which of course would reduce the efficiency of the magnetic air motor.

Figure 3 is the layout and shows the positions of the entire components involved.

The extremely high air pressure is provided by a commercial (preferably screw type) pump compressor unit [4] taking its power from all the environmentally friendly power sources, the grid or the back up petrol/diesel generator. The commercial unit {4} functions independently (having all the required air valves fitted) and pressurizes the large capacity air vessel or vessels [1].

The 24V outputs of the photovoltaic tiles, wind driven electric turbines and any other device producing electric power is converted to 240V AC by inverters to feed the air compressor [4].

The air pressure produced by the wind driven screw type air compressor is fed directly into the vessels [1]. Vessel or vessels [I] are constructed in the form of very strong cross woven fibreglass. A strong stretchable inner liner fitted inside vessel [1] forms an extra air seal and maintains the pressure for as long as possible if the pressure is falling. The vessel [1] is best positioned underground for extra external support; if more than one vessel [1] is used they are connected in parallel. The air pressure valve {5} fitted to the air vessel [I] has two settings; the first setting operates the electrical contacts fitted to it; the second setting vents excessive air pressure (safety only). The high pressure air from vessels [1] is fed to the high pressure valves V3 and VI to drive the magnet air motor. The spent air is released by the low pressure valves V2 and V4 into the atmosphere.

The HP (current drawn) of the commercial electric motor on unit [4] will be matched to the available output power of the sources.

Figure 4 is the electrical diagram.

The outputs of all the devices are converted to 240 volts AC and then fed across relay RAM; the operational voltage of relay RAM will be set to match the conditions required by the consumer. The inverters will prevent any feedback through an inactive source. The consumer will draw any power required between the point marked "Live Direct" and neutral. If the consumer tries to take more power than is being produced, the voltage across the connections of relay RAM will fall and relay RAM will release. When the required voltage across relay RAM can be realised, RAM relay will operate. The operating voltage of relay RAM will be set to give the results required by the consumer i.e. the load the consumer wishes to apply to the wind turbines/photovoltaic tiles before the voltage fails to operate RAM relay. This in turn will take into account the current required by the motor on the commercial air pump [4] (the two demands will have to be matched). When relay RAM does operate the contacts fitted to relay RAM will connect all current generated by the wind turbines/photovoltaic tiles to the commercial air pump [4] and the commercial air pump will store any further power produced as air pressure. The wind driven air compressor will continue to charge the air vessels [1] despite all the above operations. Venting will only be triggered by the safety valve if the maximum safety pressure of vessel [1] is exceeded. The grid will only be connected by the timer to the air pump motor [4] during the off peak-times set by the grid and only if the wind turbine or photovoltaic tiles are not producing sufficient voltage (the environmental source is given priority) Figure 5 shows the construction of a wind driven screw air pump. The fin turns the air pump to face the wind and the pressurised air is fed directly into vessel [1] (this does away with the losses incurred by the conversion from electricity to air pressure when using a turbine). The nylon in the horizontal swivelling support gives an airtight bearing. Water on the base of the vessel [1] can be removed by slackening the drain point cap. As the wind driven screw air pump feeds directly into vessel [1] the safety valve [5] must vent into the atmosphere regardless of any other setting as soon as the safe pressure of vessel [1] is exceeded. A horizontal spoiler can be fitted to compensate for lack of weight, ensuring an airtight seal on the nylon bearing.

The contacts fitted to the safety valve [5] will become open circuit before the safety valve vents isolating the commercial air pump from any power source. The safety valve will vent into the atmosphere if the safe pressure is exceeded and electrical contacts fitted on the safety valve are faulty (permanently closed).

Under the condition where the contacts are as shown in the drawing and the timer contacts are made, the grid (if fitted) will be connected permanently to the commercial air pump by the contacts of relay RAM until again the contacts on the safety valve are open circuited by the excess pressure, or the timer switches "off'. However if the voltage across relay RAM from the environmental source (wind or photovoltaic tiles) is sufficient to operate relay RAM, then when the timer contacts operate no current will be drawn from the grid (the environmental source is given priority).

The reed switches 2/4 are shown wired horizontally for ease of circuit description but they are in actual fact mounted vertically on the board to give a suitable operation time of the valves Vi, V2, V3 and V4. Between the electrical switch fitted in the 24V DC circuit to the four valves and the air switch fitted as part of the commercial air pump, full control of the air magnetic air motor is obtained.

Under the condition where the wind driven compressor unit is to light and the system is loosing air pressure, a horizontal fin can be added above the unit to apply a downward thrust on the nylon bearing.

The intention is to make the system flexible and able to cope with large or small systems (making it interesting to as many users as possible). This could be achieved by modifying a number of larger air compressors. One very large air storage fibreglass vessel would then feed a number of these modified air motors; the electrical output power would then be adjustable to match the demand by switching in one, two or three of the motors (with its alternator) into circuit.

The vessel [1] could be formed by concrete, stone or a ceramic berried deep in the ground; it would have to be lined with a pressure resistant shell.

Sighting the environmental sources and vessels [1] and the magnetic air motor will depend on the cost of heavy copper conductors compared to the cost of a high-pressure hose! The high air pressures is constantly maintained by feeding 240V AC from one or the other of the sources to the unit [4] as well as air pressure from the wind operated air compressor.

Claims (8)

1. CLAIMS1) A storage unit for electrical energy comprising a pressure substantially above atmospheric pressure drive means for driving a 240V AC generator wherein the drive means comprises an air motor drivable by the pressure difference between the substantially high pressure and atmospheric pressure. All actions are performed automatically using electrical relays and reed switches.
2. 2) An air driven motor as claimed in Claim I wherein the electric power from environmental friendly sources, diesel/petrol generator or the off peak grid system is always applied to power a commercially produced screw type or piston air pump [4j 3) An air driven motor as claimed in Claim I wherein if the high air pressure is derived solely from wind driven air compressors then the commercial air compressor [4] will not be required and the air motor will drive the generator direct 4) An air driven motor as claimed in Claim I plus Claim 2 wherein the high-pressure vessel is protected by a safety valve fitted with electrical contacts. The electrical contacts remove any power source from the air pump (4) when the high pressure vessel (1) reaches it capacity. In case of a failure of the electrical contacts the excess is vented into the atmosphere.5) An air driven motor as claimed in Claim 1, 2 and 4 wherein the high pressure air vessel [1] is constructed of cross woven fibreglass matting with a very strong stretchable inner liner Inside it is fitted and stored underground for extra support.6) An air driven motor as claimed in 1, 2, 4 and 5 wherein the electrical power is reproduced as 240V AC and supplied to the consumer as and when required.7) An air driven motor as claimed in 1, 2, 4, 5 and 6 wherein the size of the air vessels [I] dictates the electrical storage capacity.8) An air driven motor as claimed in 1, 2, 4, 5, 6 and 7 wherein a number of air motors each driving a generator can be switched on to the high pressure air in vessel [I] to matching the demand for power.9) An air driven motor as claimed in 1, 2, 4, 5, 6, 7 and 8 wherein the commercial air pump is of the screw type producing minimum noise reducing disturbance and giving maximum air pressure.10) An air driven motor substantially as described herein with reference to Figures 1 -5 of the accompanying drawings.11)An engine suitable for driving a generator as defined In claim I Amendments to the claims have been filed as follows Claims.1. A storage unit for environmental energy comprising a pressure substantially above atmospheric pressure drive means for driving a 240V AC generator/alternator wherein the drive means comprises of a newly designed air motor [3] requiring a minute amount of local electrical power to control the timing while the output power of the motor is generated purely by the potential difference between anticyclone pressures (the electrical output of environmental sources drive commercial electrical air compressors to produce the high pressures while wind powered air compressors feed vessels [1] directly) and atmospheric pressures wherein the electrical output power reproduced in this way is in a near clean sine wave form and at a potential of 240V AC. The air pressures in vessels [1] are constantly maintained at a maximum by off peak grid systems and environmental sources. All actions of the full unit are performed automatically using electrical relays and reed switches. The motor has two power strokes per revolution of the driveshaft.2. An air driven motor as claimed in Claim I wherein the high pressure air in vessels [1] is derived dually from wind driven air compressors and the high air pressure produced by electrical power from environmental sources wherein both sources of high air pressure are stored in the same vessels [1]. A number of air motors can then be driven directly from the high pressure air stored in vessels [1]; each motor driving an alternator/generator thereby produces clean electrical power.
3. 3. An air driven motor as claimed in Claim I and 2 wherein vessels [I] can withstand the extremely high anticyclone pressures by being formed out of multiple cross woven fibreglass matting, which has been lined with a strong stretchable inner liner and sited underground for extra support.
4. 4. An air driven motor as claimed in 1, 2 and 3 wherein the capacity of the total air vessels forming vessels [1] dictates the electrical storage capacity.
5. 5. An air driven motor as claimed in 1, 2, 3 and 4 wherein the wind driven air compressor is fitted with a twin surfaced reinforced nylon bearing between it and the tower [fig 5A] for lateral rotation. To ensure an airtight seal on the nylon bearing a horizontal spoiler compensates for lack of weight under high wind conditions and a one way valve in the tower retains the pressure in vessel [1].
6. 6. An air driven motor as claimed in 1, 2, 3, 4 and 5 wherein a number of the designed air motors each driving a generator/alternator can be switched into or out of the high pressure air in vessels [1], making the system flexible while producing clean output power.
7. 7. An air driven motor substantially as described herein with reference to Figures 1 S...: -5 of the accompanying drawings.
8. 8. An air motor suitable for driving a generator/alternator as defined in claim I.