GB2485356A

GB2485356A - Power supply having first and second energy stores

Info

Publication number: GB2485356A
Application number: GB1018938.9A
Authority: GB
Inventors: Theodorus Jansen
Original assignee: SCIENTECH FZC
Current assignee: SCIENTECH FZC
Priority date: 2010-11-09
Filing date: 2010-11-09
Publication date: 2012-05-16
Also published as: WO2012062756A1; GB201018938D0

Abstract

A power supply unit configurable as a stand-alone unit for remote applications has an energy module 12 to store energy in a first energy store 20 and a second energy store 22. Input 14 receives energy from a renewable resource, e.g. a wind turbine, and each energy store is charged with charger 18.The first and the second energy store have different storage methods, and are configurable in a loop such that the first energy store can charge the second energy store, and the second energy store can charge the first energy store. The output 16 has an electrical output 16a and a mechanical output 16b. The energy stores are connected to a transducer 24 that is connected to the outputs. The first energy source may be a battery and the second energy source may be a hydraulic storage device or a compressed air storage device.

Description

Power Supply [0001] The invention relates to a power supply, and in particular to a power supply for a remote or isolated building that requires long service intervals, such as a telecommunication tower. The invention also relates to a stand-alone system comprising such a power supply, and to a method of configuring such a system.

Background of the invention

[0002] Power supply units for telecommunication towers and such buildings often require long service intervals because they are located in remote and climatically harsh environments, without reliable local services such as electricity. Not only does their location make them difficult to service on a regular basis but the conditions can be detrimental to the performance of the components therein. Known power supply units use a combination of electrical batteries and back-up combustion-engine driven generators to provide power.

[0003] Unfortunately, known units have relatively short service intervals and/or they are expensive to configure and maintain because a large number of electrical batteries are required to lengthen the service interval. Not only are these batteries expensive, but an electrical battery can become unstable and deteriorate in extreme environmental conditions, such as a desert environment, thus reducing the performance of the unit.

Renewable energy sources can top-up an electrical battery's energy level, but back-up combustion-type generators are required to provide power and re-charge the batteries when batteries go flat. Generators require their fuel supply regularly replenished.

Summary of the invention

[0004] The invention provides a system having improved stability, greater and efficient energy storage and longer service intervals. In one aspect, the invention resides in a power supply unit configurable as a stand-alone unit for remote applications, the unit having: an energy module configured to store energy in a first energy store and a second energy store, wherein the first and the second energy store have different storage methods, and wherein the first energy store and the second energy store are configurable in a loop such that the first energy store can charge the second energy store, and the second energy store can charge the first energy store; an input configured to receive energy from a renewable resource and charge the or each store in the energy module; and an output configured to convert energy stored in the energy module to provide electrical and/or mechanical power. In other words, the energy storage methods are different types of energy storage means, or devices.

[0005] The provision of a first energy store and a second energy store enables the system to be more stable because the majority of the energy can be stored in a medium best suited for the environment in which the power supply is to be used, thus making the supply more robust. By way of example, a secure location, such as an airport, can have a main storage method of dry-cell batteries rather than one of combustible fuel. And a desert type environment can use compressed air because temperature extremes can have a detrimental effect on a battery's performance.

[0006] Further, the method of energy storage can be selected to minimise the effect on the environment by inhibiting pollution damage in the event of an accident, or minimising the resource, or "carbon footprint", created by the energy storage method or its manufacture. For example: diesel pollutes the atmosphere; a battery has an energy intensive, complex manufacturing processing and contains hazardous materials; but a flywheel, or a compressed air energy storage (CAES) system can store energy in a more environmentally friendly way.

[0007] The invention can have a minor and a major energy store and the major energy store can have a storage method that has a lower environmental impact than the first energy store. The energy stored in the major energy store can be carbon neutral. In other words, the energy stored in the carbon neutral energy store can come from a renewable energy source and the delivery of energy, or return of energy from that store, can be achieved without using another resource and/or being detrimental to the environment. The energy module can have two or more energy stores. The loop can function to transfer energy between the energy stores. The loop can have a converter to convert the energy stored in one energy store and transfer it to another energy store. The loop can form a circuit, or a chain, around which energy can be transferred and/or distributed and/or balanced.

The purpose of the loop can be to store an appropriate amount of energy in each energy store, which store energy using different methods, according to the load required on the output. The loop can have an electrical and/or a mechanical input to receive energy from an external source. The loop can have an electrical and/or a mechanical output to deliver energy to an external source.

[0008] The energy module can be configured to require minimal resource and/or minimal energy loss through energy transfer between energy stores. By way of example, energy can be transferred from one energy store to another via a single-stage converter, thus minimising energy loss during conversion.

[0009] The energy module stores and manages energy to function as a power supply. The energy store can be an accumulator. The first energy store can be an electrical battery and the second energy store can be an air tank that functions to provide a compressed air energy storage unit.

Alternatively, the energy storage method can be chemical, biological, electrochemical, electrical, mechanical, thermal or a combination thereof. By way of example, a second or additional energy store can be a flywheel.

[0010] The air-tank, when charged with compressed air, can be configured to power an air-engine. The air engine is a standard piston-type engine, or can be a Wankel-type engine. The air-tank can be configured to decompress into another air tank prior to driving the air-engine. The other air tank can be used to reduce the pressure from a larger air tank that has a greater capacity and can store air at a higher pressure, such as a pressure of bar, while the other air tank can be of a lower capacity and have a lower pressure, such as a pressure of 10 bar. Nominal atmospheric air pressure at sea-level is 1 bar. The air-engine can be operable at an air pressure of approx. 2 bar, or at a pressure fractionally greater than atmospheric air pressure.

[0011] The difference in air pressure across the air engine, i.e. between the inlet on the outside and the chamber on the inside, can be greater than 0 (zero) bar for the engine to rotate. In other words, the engine can be configured to rotate when the air pressure is sufficient to overcome the frictional resistance in the engine. The air pressure difference can be greater than 0.5 bar. Optimal performance can be achieved when the air pressure between the outside and the inside is approximately 1 bar or greater.

[0012] The or each energy store can have two or more sections, or stages. The stages can be used to control the dissipation of energy by decompression, stepping down or gearing down the output from the energy store. In other words, the invention can use two or more stages to regulate the energy being dissipated. This can improve the stability of the invention and minimise inefficient "spikes" or surges in energy. Surges of energy are difficult to harness and often result in lost or wasted energy that cannot be used. By way of example, if energy is stored in a CAES unit at 20+ bar then stepping down the air pressure to drive an air engine at a pressure of 2 bar requires careful regulation. Therefore, a further stage can be reduced to dissipate the energy stored at 20 bar down to 10 bar, and perhaps via a further stage down to 5 bar, before being regulated for input to the air engine using control mechanisms, such as solenoids.

[0013] The power supply unit can be configured with a charger, or charger controller, that can receive energy from a renewable energy source device and charge the or each store. The renewable energy source device can have a wind-turbine, photo-voltaic panel, wave generator, Pelton wheel, Peltier-effect device and the like. The charger can also charge a battery therefrom and/or receive and convert mechanical forces to charge a second energy store by, for example, increasing the pressure of the air stored in an air-tank.

[0014] The output can have an inverter configured to convert electrical energy stored in the battery to an output voltage, such as 230V a.c.

Additionally or alternatively the output can have a mechanical drive configurable to drive an apparatus such as an air-conditioning compressor.

[0015] In another aspect, the invention resides in a system for providing energy to a substantially autonomous unit, the system having: a power supply unit as described herein; a device for harvesting energy from a renewable resource; and a load device configured to manage the unit.

[0016] By way of example, the invention resides in a unit such as a telecommunications tower that is located in a remote location, without services, that is difficult to access. Renewable energy devices can be configured to provide power to the unit, and the power supply unit having an energy store regulates the power from the renewable energy store to provide power and drive to the autonomous unit.

[0017] The invention can be used in applications where a low-maintenance energy store is required. The power supply unit is configured to manage the energy stored therein to provide energy in the form required by an autonomous or low maintenance unit.

[0018] Not only can the provision of a first energy store and a second energy store enable the system to be more stable, but the majority of the energy can be stored in a medium that requires minimal upkeep. By way of example, a liquid fuel source may require heating to prevent freezing, or a battery and associated electronics may require cooling. The method of energy storage can be selected to minimise the continuous maintenance level on a day-to-day basis.

[0019] The invention also resides in a method of configuring a system for providing energy to a substantially autonomous unit, the method involving: configuring a device to harvest energy from a renewable resource; connecting the device to an energy module to store energy in a first energy store and a second energy store, wherein the first and the second energy store have different storage methods; configuring the first energy store and the second energy store in a loop such that the first energy store can charge the second energy store, and the second energy store can charge the first energy store; configuring an input configured to receive energy from a renewable resource and charge the or each store in the energy module; and providing an output to convert energy stored in the energy module to provide electrical and/or mechanical power. The invention can reside in a method of configuring the above mentioned energy module, system or apparatus.

[0020] The method of energy storage in the energy stores can be selected according to the particular application. An energy store can be chosen to enable versatility and require fewer ancillary components to control and utilise the energy stored. On the other hand, an energy store can be selected for its stability and capacity. In each case, many factors such as cost and the environmental can be considered. The energy stores are by way of example an electrochemical battery for flexibility and compressed air for duration, stability and output drive.

Brief description of the Figures

[0021] In order that the invention can be more readily understood, reference will now be made, by way of example, to the drawings in which: Figure 1 is a block diagram of a power supply unit according to the present invention; and Figure 2 is a block diagram showing in more detail a system having the power supply unit of Figure 1.

Detailed description of embodiments

[0022] Figure 1 is a block diagram showing the main components of a power supply unit 10 having an energy module 12 having an input 14 and an output 16. The output 16 has an electrical output 16a and a mechanical output 16b. The input 12 is connected to a charger 18 within the energy module 12 and the charger 18 is connected to a first energy store 20 and a second energy store 22. The energy stores 20, 22 are connected to a transducer 24 that is connected to the outputs 16a, 16b.

[0023] The energy module 12 is configured such that the first energy store 20 is connected to the second energy store 22. The transducer 24 also has a connection to the first energy store 20. A loop is defined by the connection from the first energy store 20 to the second energy store 22, which is in turn connected to the transducer 24 that finally connects back to the first energy store.

[0024] The energy module 12 can have one or more inputs 14. Each input is connected to the charger, or charger controller 18, which converts and/or manages the energy received at the input for storage in the first energy store 20 or the second energy store 22. By way of example, an electrical input 14 from a wind turbine is regulated by the charger 18 for storage in the first energy store 20, such as a battery. The charger can also be configured to regulate mechanical energy from, for example, a windmill and store the energy in the second energy store 22, which can be a hydraulic storage device or a Compressed Air Energy Storage (CAES), such as an air-tank.

[0025] The transducer 24 is configured to convert energy from the electrochemical first energy source 20 via a DC-AC inverter to provide an electrical output 16a. Similarly, the transducer is also configured to convert mechanical energy from the CAES of the second energy store 22 to a mechanical drive output 16b via, for example, an air-engine.

[0026] The first energy storage 20 can be configured as a smaller unit storing less energy than the second energy store 22, but charging the second energy store 22 incrementally. The second energy store can store more energy and, in this way, the loop from the second energy store 22 via the transducer 24 can be configured to charge the first energy store 20 from reserves in the second store 22. The second energy store, therefore, functions as the main reservoir of energy.

[0027] The above mentioned configuration has numerous advantages.

The power supply unit 10 can, for example, select the most appropriate energy store for providing the required output, which can be useful when the energy unit is required to start and run a device such as an air-conditioning unit. Air-conditioning units are typically driven by induction motors that require significant starting currents. Therefore, a mechanical output can be used to drive the motor until it is up to operating speed before switching to the electrical output, thus avoiding the need to draw so much electrical power from the energy sources, which would require higher rated components just to support an initial start up using the electrical output 16a.

Therefore, when the first energy store is an electrical battery the relative size and cost can be scaled down relative to the load requirements of the energy module 12.

[0028] The mechanical output can be used to drive the shaft of a cooling device when in operation. In other words, the mechanical output can be used to drive an air-conditioning compressor during normal operation, and not just during start-up. The mechanical output can also drive a cooling fan, or similar device that is configured to dissipate and/or transfer heat. Figure 2 shows, by way of example, the components of an energy module 12 that are configured to receive and store energy to provide a 23OVAC power supply and a mechanical drive for an air-conditioning compressor. Like reference numerals are used to describe like features common to Figure 1 and Figure 2.

[0029] The input 14 of the energy module 12 of the power supply unit is configured to receive an electrical output from a solar cell 26 and a windmill 28 comprising a DC generator. The electrical energy received from the solar cell and the windmill 28 is received by the charger 18 and regulated to charge a battery 20. The battery is connected to a transducer 24 in the form of a DC to AC inverter 24 to provide a 23OVAC output power supply 1 6a.

[0030] The battery 20 is also connected to an air-compressor 30 having a DC motor, and is configured to charge an air tank 22. A plurality of air-tanks can be used.

[0031] The air tank 22 is configured to power an air engine 32 that has a mechanical drive output 16b configurable to drive a compressor 34 of an air-conditioning unit. The air engine is assembled from two reciprocating cylinder engines.

[0032] A starter 36 and a control unit 38, powered by the battery 20, are configured to drive the air engine. Air from the air tank 22 into the cylinders of the air engine is regulated by solenoids (not shown) that are controlled by the control unit 38. The solenoids are energised using solid-state relays. The timing and actuation of the solenoids is determined according to the position of the pistons of the air engine. Proximity sensors (not shown) are configured adjacent the pistons to determine their position and are connected to the control unit 38 to enable efficient and cyclic operation. The proximity sensors can optimise the start up and performance of the air engine by establishing the relative position of the sensors at any given time and injecting air at an appropriate pressure according to the cycle. The control unit 38 can regulate the input of air, using the input from proximity sensors, to ensure smooth and efficient cyclic action.

[0033] The air tank 22 can have a main storage tank and smaller air tank for holding depressurised air. Air can decompress directly into the cylinders of the air engine directly, or can first be depressurised into smaller tanks before being fed into the air engine.

[0034] The speed of the air engine 32 is self regulating. Therefore, irrespective of the air pressure that is fed into the air engine the speed of the engine is constant. The pressure is directly converted into torque. By way of example, the consumption of air by an air engine is 200 litters for 7 mm, when the air is stored at 10 bar and decompressed to a working pressure of 2 bar. The minimum operating pressure can be 2 bar. The minimum air-pressure that can be input to the air engine is the air-pressure required to displace a cylinder head within the engine to cause it to rotate and provide a mechanical output. Depending upon the load the pressure fed to the engine is varied. A flywheel (not shown) manages fluctuations on the output of the air engine. The flywheel can stabilise the mechanical output. The output air from the air engine is fed back into the air tank 22. Additionally, or alternatively, the proximity sensors and/or pressure sensors can determine the air pressure expelled from the air engine and direct the expelled air to charge the main air tank 22 and/or one of the smaller air tanks, downstream of the main tank, which are used to depressurise the main air tank and store air at a lower pressure.

[0035] The air engine 32 is also configured to drive a DC generator 40 that is configured to recharge the battery 20.

[0036] The power supply unit takes energy from a renewable source and stores the energy, incrementally, in the air tank 22. The level of output energy from a solar cell 26 or a windmill 28 is not suitable for direct application to electrically powered devices and, therefore, a battery is the most suitable method of storing energy in this particular application. The charger 18 and battery 20 function to regulate and store low levels of energy input to the energy module 12. Practically, the battery is an efficient and low cost way of providing power to the inverter 24. Surplus energy, however, is more suitably stored in another media in the form of compressed air in the air tank 22. As required, energy stored in the air tank 22 can be released to power the air engine 32 and drive a generator, such as the DC generator 40 and provide a DC voltage supply that can recharge the battery 20 and /or supply a DC voltage to the inverter 24.

[0037] The energy in the battery 20 and in the air tank 22 is maintained to be substantially balanced. In other words, the energy stored in the battery and the air tanks is balanced so that there is enough energy in the battery to control the charging of the air tanks when energy is received from a renewable energy source, and at the same time there is sufficient energy stored in the air tanks to be able to drive the air engine and the DC generator to charge the battery so that there is enough energy in the battery to control the charging of the air tanks. At least two of the methods of storing energy in the power supply can have a symbiotic relationship that can maintain such a balance.

[0038] In theory, the renewable energy source is infinite and the power supply unit is scaled to maintain an adequate reserve of energy for a predetermined device to be powered. In practice, the battery 20 or air-tank 22 require infrequent charging.

[0039] The present invention has been described above purely by way of example, and modifications can be made within the spirit and scope of the invention, which extends to equivalents of the features described. The invention also resides in any individual features described or implicit herein or shown or implicit in the drawings or any combination of any such features or any generalisation of any such features or combination.

Claims

CLAIMS1. A power supply unit configurable as a stand-alone unit for remote applications, the unit having: an energy module configured to store energy in a first energy store and a second energy store, wherein the first and the second energy store have different storage methods, and wherein the first energy store and the second energy store are configurable in a loop such that the first energy store can charge the second energy store, and the second energy store can charge the first energy store; an input configured to receive energy from a renewable resource and charge the or each store in the energy module; and an output configured to convert energy stored in the energy module to provide electrical and/or mechanical power.
2. A power supply unit according to claim 1, wherein the first energy store is an electrical battery and the second energy store is an air-tank.
3. A power supply unit according to claim 2, wherein the air-tank is configured to power an air-engine.
4. A power supply unit according to claim 3, wherein the air-tank is configured to decompress into one or more smaller air-tanks prior to driving the air-engine.
5. A power supply unit according to claim 3 or 4, wherein the air-engine is operable at an air pressure of 2 bar.
6. A power supply unit according to any preceding claim, wherein the input is configured with a charger that can receive energy from a renewable energy source device and charge the or each store.
7. A power supply unit according to claim 6, wherein the charger can charge a battery therefrom and/or receive and convert mechanical forces to increase the pressure of air stored in an air-tank.
8. A power supply unit according to any preceding claim, wherein the output has: an inverter configured to convert electrical energy stored in the battery to an output voltage, such as 230V a.c.; and/or a mechanical drive configurable to drive an apparatus such as an air-conditioning compressor.
9. A system for providing energy to a substantially autonomous unit, the system having: a power supply unit according to any proceeding claim; a device for harvesting energy from a renewable resource; and a load device configured to manage the unit.
10. A method of configuring a system for providing energy to a substantially autonomous unit, the method involving: configuring a device to harvest energy from a renewable resource; connecting the device to an energy module to store energy in a first energy store and a second energy store, wherein the first and the second energy store have different storage methods; configuring the first energy store and the second energy store in a loop such that the first energy store can charge the second energy store, and the second energy store can charge the first energy store; configuring an input to receive energy from a renewable resource and charge the or each store in the energy module; and providing an output to convert energy stored in the energy module to provide electrical and/or mechanical power.