GB2429343A

GB2429343A - Low voltage power supply system

Info

Publication number: GB2429343A
Application number: GB0516923A
Authority: GB
Inventors: Dmitry Frolov; Yury Spirin
Original assignee: SOUVENIR
Current assignee: SOUVENIR
Priority date: 2005-08-18
Filing date: 2005-08-18
Publication date: 2007-02-21
Also published as: GB0516923D0

Abstract

A low voltage (3V DC) power supply system comprises a plurality of different sources of electrical energy 4, 5, 9, 10, 11, an array of alkaline battery cells, a battery regenerator 14 for charging the battery cells, and a low voltage electrical load 15 adapted to be powered by the array, a plurality of different sources being adapted to be connected selectively to the battery regenerator to regenerate the battery cells and thereby supply the load. The sources may be wind generators 5, solar panels 4, rainwater driven turbines 9 mounted in down-pipes 8, steam generators 10 or a solar panel 11 mounted on a vehicle roof. The batteries are conventional alkaline cells regenerated by a very low current. The system can be augmented by power derived from the mains 13 through a transformer 16.

Description

LOW VOLTAGE POWER SUPPLY SYSTEM

Field of the Invention

The present invention relates generally to power supply systems. The invention relates more particularly, but not exclusively, to power supply systems for low-voltage supply systems in a domestic or other environment.

Background to the Invention

There are many reasons why domestic power supply systems would benefit from conversion from the traditional systems operating at comparatively high voltage (e.g. a nominal 110 volts in the USA and 230 volts in Europe and most other parts of the world) to a lower voltage, perhaps as low as 3 volts.

Apart from safety aspects, there are obvious benefits to be derived by taking advantage of "free" energy from non-fossil fuel sources. So called, "al- ternative" or "renewable" energy sources, such as wind power, solar power, wa- ter-driven turbines, geothermic reservoirs and so on, have become more acces- sible to the public as their prices fall with rising demand and as public aware- ness increases.

Low voltage supply systems require measures to store energy and to make it available on demand as load variations occur. It is not expected that such low voltage systems would necessarily meet the demands of a modern domestic lifestyle but it could be tailored to supply the demands of trends to- wards low voltage lighting, for example, that have become popular in recent years. Low voltage supply systems might be arranged to run alongside conven- tional mains power supply systems so that the latter could be used to top- up the former if need be. This could be done overnight on a cheaper tariff so as to re- duce the cost to the consumer. In addition, the use of a separate low voltage supply would reduce demands on the national grid and preserve ever-depleting fossil fuels.

It has also been discovered that single-use alkaline cells normally regarded as "non-rechargeable" can in fact be regenerated if the conditions are properly set and controlled. Very low trickle currents over an extended time pe- riod have been shown to be very effective at regenerating "non- rechargeable" cells, and our co-pending Application GB0415639.4 is directed to a method and apparatus for regenerating such cells. It has also been found that the same re- generation process, i.e. the application of a low trickle current over an extended period, can advantageously be applied to rechargeable cells, such as nickel- cadmium and nickel-metal-hydride cells, as well.

The present invention therefore aims to provide a single low voltage power supply system that is capable of taking advantage of "free" or renewable energy sources whilst still meeting the demand requirements of a domestic or other environment.

It is known from JP10122124 to provide a wind generator on a roof top and it is known from DE4205331 to provide a vehicle with a solar panel supplying energy to top up an in-house power supply system. It is also known from JP113I 8037 to provide an array of batteries in which strings of parallel cells are connected to a sensor which switches out a good cell in one string to balance a faulty cell in another string, whereby to maintain a good supply. US6057665 describes a system for optimising the maximum power available from a variable energy source to charge batteries.

Summary of the Invention

In accordance with the invention, a low voltage power supply system comprises a plurality of different sources of electrical energy, each source being connected to supply electrical energy to a respective group of batteries within an array of batteries, all the batteries in the array being connected in parallel to an electrical load, each of said sources being arranged to supply energy as a voltage substantially equal to the maximum e.m.f. of the batteries.

Each battery preferably consists of at least one replaceable cell, and more preferably two or more cells connected in series to provide an output volt- age which is a multiple of the approximately I.5V cell e.m.f.

While rechargeable cells such as nickel-cadmium or nickel-metal-hydride cells can be used, the cells are preferably single-use alkaline cells. Each source of electrical energy is preferably arranged to supply each battery in the respective group with a regeneration current below 35 mA.

The system is preferably provided in, on and/or around a building.

One of the different sources may be at least one solar panel, which may be mounted on a roof of the building or on a roof of a vehicle adjacent the build- ing.

One of the different sources may be at least one wind generator, which may be mounted on a roof of the building.

One of the different sources may be at least one water-driven turbine, which may be located in one or more down-pipes adapted to carry water from a roof of the building.

One of the different sources may be at least one steam-driven generator.

One of the different sources may be at least one geothermal generator.

The array of battery cells preferably comprises a plurality of seriesconnected battery cells, the plurality of said series-connected battery cells being connected in parallel with one another.

The cells may conveniently be of standard size "AA", and the array may consist of, for example, 100 such cells. Since alkaline single-use cells can only be regenerated a limited number of times, for example 50-70 if fully discharged and then fully regenerated, it will be necessary periodically to replace the cells.

The use of alkaline single-use cells, however, permits this to be done very cheaply as compared with ordinary rechargeable cells, such as nickelcadmium and nickel-metal-hydride cells.

The low voltage power supply system may further comprise a trans- former connected between a supply of mains voltage and a respective group of batteries in the array.

The battery array is conveniently adapted to provide electrical energy to the load at substantially 3 volts, based on a normal cell voltage of 1.5, but bat- teries may consist of more than two cells in series, to provide higher voltages, if desired.

Brief Description of the Drawings

The invention will be described with reference to the drawings, in which: Figure 1 is a schematic representation of a typical low voltage power supply system incorporated in a house; and Figure 2 is a simple circuit diagram of the supply system shown in Figure 1.

Detailed Description of the Illustrated Embodiments Referring first to Figure 1, a typical house I is shown having a roof 2 and walls 3. The roof 2 is provided with one or more solar panels 4 and one or more wind generators 5 mounted on supports 6, which may be the chimney stacks of the house. Windows and doors are omitted from the drawing for the sake of clarity.

Rainwater gutters 7 of the house are connected to down-pipes 8 carrying rain water to a conventional drainage system or surface discharge outlet. Lo- cated intermediate the down-pipes are turbines 9 that are driven by the rain- water flow to generate electricity. Other peripheral electricity generating de- vices, such as a steam-driven generator 10 and a further solar panel 11 mounted on a vehicle 12, may also be integrated into the system, as will be ex- plained shortly.

Although not illustrated in Figure 1, further wind generators and/or solar panels may be mounted in static or dynamic positions around the house, such as in trees or on dedicated supports. The mains inlet to the house is shown diagrammatically at 13.

All of the devices mentioned so far are connected to a battery array 14 whose output supplies a load indicated generically at 15. The load could be any number of appliances inside or outside the house, such as lighting, sound sys- tems, low power devices such as shavers, radios and small television sets, alarm monitoring systems, security systems and so on. The mains inlet 13 is also connected via a transformer/rectifier 16 to the array 14.

Although appliances could be redesigned to operate on low-voltage di- rect current, existing appliances might be operated by providing an inverter unit between the battery array and the appliance providing a higher-voltage alternat- ing current.

More significantly, as far as the present invention is concerned, the battery array contains a plurality of sets of cells. These may be of the alkaline sin- gle-use type, which are not normally regarded as rechargeable. However, as previously mentioned, a low current applied over a long period has recently been proved to regenerate such cells, so that they can again provide a useful amount of stored energy, as well as being suitable for regenerating conven- tional rechargeable cells.

The cells are preferably grouped in an array of say 100 cells. Using AA cells, which typically have a capacity of 2600mAh, this would potentially yield a system capacity of 260Ah. A larger number of cells would give greater output capacity.

As an added bonus, the house wiring circuits do not require significant adaptation to transfer to a low voltage supply system. One could, for example, disconnect a lighting circuit from the mains supply and connect it alternatively to the low voltage system according to the invention, replacing the light fillings and lamps with low-voltage fittings and lamps. The system according to the inven- tion can be regarded as supplementing the mains supply. It is clear that the more generating devices that are provided, the less power that needs to be drawn from the mains. Conversely, the mains supply system can be used to top-up the battery-powered supply system during periods of low energy con- sumption or when the low voltage supply system cannot meet total demand.

It is envisaged that the power system will be configured as a modular system, so that additional generating components can be added as required and perhaps according to the season of the year. It is also envisaged that dif- ferent groups of batteries will be regenerated by different generating devices.

However, other configurations are possible and may be preferable according to circumstances. Whatever connection configuration is adopted, all of the battery arrays are connected to a common output to supply the load 15.

In operation, the regeneration current can be limited, if necessary, by simple resistors. The batteries themselves are used as simple low-cost switch- ing elements. Once a cell reaches the regeneration voltage, no further current is drawn. Consequently, no voltage regulators are required. The electrical en- ergy drawn from the mains is via the transformer/rectifier 16 and would there- fore be substantially constant. On the other hand, the individual generators would be configurable to operate at a substantially constant voltage.

Figure 2 illustrates diagrammatically the system electrical configuration.

The array 14 of individual alkaline cells 20 as illustrated are all connected in parallel, providing a system voltage equal to the single cell voltage of approxi- mately 1.5. In practice, it would be desirable to form individual cells into batter- ies each containing two or more cells in series, to provide an output voltage which is a multiple of the cell voltage, for example 3V. Different energy sources are connected to respective groups of batteries (whether taken to be single cells or multiple cells in series) the sources being such that the voltage does not ex- ceed the final cell e.m.f., and the current delivered to an individual cell is, in the case of a single-use alkaline cell, less than 35mA at any time. This may be achieved, if necessary, by current-limiting resistors in series with the cells, or simply by dividing the likely current output from the source over the appropriate number of batteries. Thus, for example, the wind turbines 5 may be connected individually to respective groups of batteries, or collectively to a wind turbine group, and similarly the solar panels 4, the rain-water turbines 9, and the mainssupplied transformer/rectifier 16 may be connected such that each individual device, or each different type of source, supplies a respective individual group of batteries 20.

It will be appreciated that, while Figure 2 shows five batteries as consti- tuting a group of batteries, this is for the sake of convenience of illustration, and the actual number in a group will depend on factors such as the power output of the relevant source or group of similar sources, and on the required regenerat- ing current.

The present invention provides an integrated approach to supplying power to a domestic or other suitable environment in a way that reduces the overall fossil-fuel power consumption of the house etc and maximises the bene- fit in terms of safety, reliability and cost to the household.

Claims

1. A low voltage power supply system, comprising a plurality of different sources of electrical energy, each source being connected to supply elec- trical energy to a respective group of batteries within an array of batteries, all the batteries in the array being connected in parallel to an electrical load, each of said sources being arranged to supply energy at a voltage substantially equal to the maximum e.m.f. of the batteries.

2. A low voltage power supply system according to Claim 1, wherein each battery consists of at least one replaceable cell.

3. A low voltage power supply system according to Claim 2, wherein each battery consists of a plurality of replaceable cells connected in series.

4. A low voltage power supply system according to Claim 2 or 3, wherein the or each cell in each battery is a single-use alkaline cell.

5. A low voltage power supply system according to Claim 2 or 3, wherein the or each cell in each battery is a rechargeable cell.

6. A low voltage power supply system according to any preceding claim, wherein each source of electrical energy is arranged to supply each battery in the respective group with a regeneration current below 35 mA.

7. A low voltage power supply system according to any preceding claim, wherein said system is provided to supply a building.

8. A low voltage power supply system according to any preceding claim, wherein one of said different sources comprises at least one solar panel.

9. A low voltage power supply system according to Claim 8, wherein at least one said solar panel is mounted on a roof of a vehicle adjacent the building.

10. A low voltage power supply system according to any preceding claim, wherein one of said different sources comprises at least one wind generator.

11. A low voltage power supply system according to any preceding claim, wherein one of said different sources comprises at least one water-driven turbine.

12. A low voltage power supply system according to Claim 11 when dependent from Claim 7, wherein at least one said turbine is located in a down- pipe adapted to carry water from a roof of said building.

13. A low voltage power supply system according to any preceding claim, wherein one of said different sources comprises at least one steam- driven electricity generator.

14. A low voltage power supply system according to any preceding claim, wherein one of said different sources comprises at least one geothermal generator.

15. A low voltage power supply system according to any preceding claim, further comprising a transformer connected between a supply of mains voltage and said battery array.

16. A low voltage power supply system, substantially as described with reference to the drawing.

17. A building supplied with electrical energy by a low voltage power supply system, substantially as described with reference to the drawing.