There is more than one way to make a solar power “water battery”. All of them take sunlight in one way or another and store it in order to generate electrical power at a time when there is little or no solar input. One method is to collect and store solar generated heat in water which can then be used to boil low temperature fluids in order to drive a small turbine. Another method is to use solar cells to collect electrical power into a standard deep cycle lead acid battery, which is then used to run household appliances through an inverter. A third method is to use solar cells to make hydrogen which can then be filtered through a Ballard type Fuel cell to make electricity later when it is dark and when and where it is needed most. There is even a fuel cell that can generate electricity using polluted water. We will look at each in turn.

Running a turbine on low temperature “steam” is accomplished by heating water in coils exposed to concentrated sunlight. This is typically done using a sun facing parabaloid with a tube “circuit” full of water paced at the focus. The water is filtered by gravity to an insulated collection tank which is placed higher than a cold water tank. Cold water sinks and hot water rises, so eventually all the water in a closed system is heated. The heated water is used in a heat exchanger to boil a low temperature fluid like Freon or ammonia. This steam is directed to a turbine generator pair that generates electricity. This kind of unit can built to any size from household size to industrial sized for whole cities. The solar heated water acts as a kind of storage battery to generate electricity on demand.

Charging a large deep cycle standard RV battery is done by connected several 12 volt solar cell arrays in series-parallel. A voltage regulator and diode is incorporated to keep the charging power at 12 volts and the diode prevents discharge by back leakage through the solar array when it is not exposed to sunlight and in charge mode. A typical deep cycle battery consists of lead plates and water based sulphuric acid mix. Many stores sell amorphous solar cells today that can be used to charge a car battery directly through the cigarette lighter. This design is for heavier applications and is coupled with an inverter to run standard 60 cycle household appliances like a refrigerator, power tools and entertainment electronics.

The most radical and advanced design uses water to make hydrogen from sunlight which is stored to make