GB2053270A - Storage and use of solar energy - Google Patents

Abstract

Solar energy collected by a panel 2 heats a fluid which is stored in a tank 14. The solar photoelectric energy is fed to a hydrogen generator 16 and hydrogen generated is used to fuel a heater 38 in which fluid from the storage tank or from a mains supply can be heated. Both forms of energy, heat and electrical, are thus capable of being stored and used in accordance with operating requirements and weather conditions. <IMAGE>

Description

SPECIFICATION A method and a system for utilization of solar energy This invention relates to utilization of solar energy by means of a collector system in which a fluid is used as a heat collecting and transmitting medium, and the invention is mainly related to domestic energy supply.

It is known that solar energy may alternatively be collected as photoelectric energy, but for domestic use the heat collectors are the preferred energy generators.

It is the purpose of the invention to provide an improved method for the collection of and accumulation solar energy.

The invention is based on the combined use or collection of both heat energy and photoelectric energy from the sun, and means are provided for separately accumulating the heat energy, viz. in an accumulating medium such as water in a storage tank, and the electric energy, viz. by using it to produce hydrogen and accumulating the hydrogen in a separate accumulator. The hydrogen, either when needed or in case of surplus production is fed to a burner in a fluid heater connected to the storage tank such that both types of energy may be eventually stored as heat in the tank or supplied as heat to the domestic heat consumption system.

In this manner it is possible in an effective manner to utilize both of the said types of energy with advantageous accumulation possibilities including a common tank accumulator enabling the hydrogen accumulator to be designed with a reasonably small capacity.

The method according to the invention is correspondingly specified in claim 1 and the system according to the invention in claim 2.

Another important aspect of the invention is that the collectors for heat energy and photoelectric energy, respectively, may be materially combined in a single collector element when this is of the well known type having a flat fluid filled space between a black rear side and a transparent front wall, the space being top- and bottomwise provided with connector pipes for connecting the fluid in a fluid circuit. Such an element may be provided with solar cells adjacent the said rear side thereof, whereby the cells will receive the light when it has passed through the front wall and the fluid (water, transparent oil or other), and thus the radiation will produce both heat and electricity when it hits the rear wall. The electrical connections to the cells may even be constituted by the exterior fluid pipes if these are made of copper.

The invention is described in more detail in the following, reference being made to the accompanying drawing, in which: Fig. 1 is a schematical view showing an embodiment of a solar energy system according to the invention, Fig. 2 is a sectional view of an equalizing valve for use therein, and Fig. 3 is a perspective view of a preferred solar panel element.

The solar energy system shown comprises a collector panel 2 which is water filled behind a glass front plate and is provided with several groups of solar cells. The energy collected by the panel 2 is led into a collector system through copper tubes 4 and 6 as warm water and electric current, respectively. The uppermost copper tube 4 is provided with a thermostatic valve 8 controlling the water outflow from the panel 2.

The tubes 4 and 6 are connected to a storage tank 14 through separation connectors 10 serving to electrically connect the tubes 4 and 6 to a control unit 12.

The electrical energy is used to energize a hydrogen generator 16 adapted to decompose water electrolytically into oxygen and hydrogen.

The water used in the hydrogen generator may be supplied from the mains and need only pass a simple water purifying unit 1 8. The DC voltage used in the generator 1 6 between electrodes 20 and 22 is preferably 3V and the DC current is about 7-10 A. At the left (+) electrode 20 oxygen is generated while hydrogen is generated at the right (-) electrode 22. The hydrogen generator 1 6 is provided with safety valves 26 and with a constant level sensor 24.

The oxygen produced by the generator 1 6 at one side of a partition 23 is led to the atmosphere through a particular equalizing valve 28 which is described in detail below. The produced hydrogen is pressed through a non-return valve 30 into a first hydrogen accumulator 32 filled with a hydride material, preferably ferric-titanium (FeTi), which as weil known is able to absorb hydrogen at any temperature between -200C and +800C, i.e. this accumulator is operative at ambient temperature.

The primary hydrogen accumulator 32 is provided with a combined cooling and heating coil 34, by means of which heat may be drawn out during the filling of the accumulator while the coil 34 may be used to heat the accumulator 32 in order to force the hydrogen out again.

The primary hydrogen accumulator 32 is connected in known manner to a secondary hydrogen accumulator 36 containing another hydride material such as magnesium (Mg) which is able to absorb hydrogen in considerable quantities, though at a relativeiy high temperature level - about 3000C - which means that the secondary hydrogen accumulator 36 must be correspondingly cooled and heated during the filling operation and the emptying operation, respectively.

From the secondary Mg-accumulator 36 the hydrogen is fed to a burner in a water heater 38 in which the hydrogen is used as fuel, but as shown in dotted lines the burner may also be supplied with hydrogen directly from the primary FeTiaccumulator 32. In the heater 38 the hydrogen is burned for heating a coil system 40 belonging to a central heating system 42 which is also connected to the heat storage tank 14. In periods of time where the heat consumption is low the surplus heat may be stored in the heat storage tank 14 for use in periods of high heat consumption. The heater 38 may furthermore or alternatively be energized from a bottle of gas 44, if necessary.

In practice it may be advantageous that the FeTi-accumulator 32 and the Mg-accumulator 36 are built as partially integrated units in order to minimize the lengths of the necessary tube connections and in order to obtain a combined cooling and heating system for use during the filling and emptying operations, respectively.

The system shown also comprises an electric power supply unit 46 by means of which the hydrogen generator 16 and the control unit 12 may be energized, e.g. in emergency situations.

Furthermore the system may be combined with other alternative energy systems, e.g. with a windmill as indicated in the drawing.

The equalizing valve 28 is shown in detail in Fig. 2, it comprises a cylindrical housing 48 the opposite ends of which communicate directly with the oxygen and the hydrogen chambers of the hydrogen generator 16 through tubes 50 and 52, respectively. Inside the housing 48 is reciprocally arranged a sliding piston 54 which is springloaded at its right end by means of a coil spring 56. The sliding piston 54 is provided with three sealing rings (O-rings) 58, 60 and 62. The housing is furthermore provided with an oxygen outlet 64 open to the atmosphere.

As the oxygen pressure is built up on the left side of the piston 54, this piston is moved towards the right against the counter-pressure of the spring 56 and against the smaller hydrogen pressure until the O-ring 58 passes the outlet 64 and lets the oxygen escape to the atmosphere.

Of course the equalizing valve 28 is adjusted in accordance with the closing pressure of the nonreturn valve 30 (Fig. 1).

Fig. 3 shows the collector panel 2 which is a flat box having a front wall of glass and a rear wall provided with solar cells 3. The front sides of these are black or dark as is the remaining rear surface. The cells 3 may be mounted behind a transparent plate or sheet if they should be isolated from the water in the panel 2.

Briefly, the hydrogen accumulator system operates to receive hydrogen in the primary unit 32 under release of heat, whereby the water in the tank 14 is used for cooling the coil 34. When further cooling is impossible (or the cooling is switched off) the surplus hydrogen will leave the top of the accumulator at increased pressure and get forced into the secondary accumulator which is effectively coolable by the water from the tank 14. When it is desired to use the hydrogen the coil in the accumulator 36 should be heated to a high temperature as initially obtainable by burning gas from the bottle 44 in the heater 38 and thereafter by the burning hydrogen itself, a heat exchanger 37 for the coil inside the unit 36 being arranged adjacent the flue outlet from the heater 38. The process is controllable by means of a throttle valve in the connection between the coil and the heat exchanger.

Claims (7)

1. A method for utilization of solar energy in a solar energy collecting system using a fluid as energy collecting and transporting medium, characterized by collecting solar heat energy and solar photoelectric energy by suitable collector means, storing heated fluid in a storage tank, using the electric energy to energize a hydrogen generator, accumulating the hydrogen in a hydrogen accumulator, using the hydrogen as fuel in a hydrogen fired fluid heater connected to said storage tank, and utilizing the energy stored hereby, said steps being controlled individually dependent of the actual weather and consumption conditions.

2. A solar energy system for performing the method according to claim 1, characterized in that it comprises solar panel means for collecting heat by means of a fluid and electricity by means of solar cells, a storage tank for heated fluid, a hydrogen generator energized by the solar electric power, a hydrogen accumulator for storing the hydrogen produced hereby, a hydrogen fired fluid heater receiving hydrogen from the accumulator and supplying heater fluid to said storage tank, and control means for controlling the operations of the system.

3. A system according to claim 2, characterized in that the solar panel consists of a unitary flat panel element of the type having a liquid filled space behind a transparent front wall, said space having a dark rear portion, and that a plurality of solar cells is mounted in connection with said rear portion.

4. A system according to claim 2, characterized in that said hydrogen generator consists of a water decomposing unit energized by the solar cells, and that the oxygen produced by the unit is led out to the atmosphere through an equalizing valve, while the hydrogen is pressed into said hydrogen accumulator by virtue of the pressure in the hydrogen generator.

5. A system according to claim 3, characterized in that the solar panel is connected to the remaining system through electrically conducting fluid tubes used for the transmission of both heat fluid and cell current.

6. A system according to claim 2, characterized in that the hydrogen accumulator is a two stage unit of the hydride type, in which the first stage is controlled by a heat connection with the storage tank, while the second (high pressure) stage is coolable by the tank water and heatable by means of a heat exchanger mounted adjacent the flue outlet from the hydrogen burner.

7. A system according to claim 4, characterized in that the equalizing valve is a cylinder having a slide piston, which is subjected to the respective hydrogen and oxygen pressures on opposite ends thereof, the oxygen being exhaustible through an escape opening in the side of the cylinder in - response to the oxygen forcing the piston against a bias to partially uncover the escape opening.