Using the sun to heat water
A collector is placed on the roof of a structure, and water is pumped through it, and is heated.
The collector can be a simple glass topped box with copper pipes in it, or a set of metal tubes surrounded by a evacuated (near vacuum) glass cylinder. A parabolic mirror can also be added to concentrate the sun's light on the tube.
A simple water heating system would pump cold water out to a collector to be heated, the heated water flows back to a collection tank. There are even ways to do this without a pump, using natural convection. This type of collector can easily provide enough hot water for a family, for very little or no monthly cost. Temperature regulators are required to mix the hot water from the tank with cold water because at peek times the water from the collector can reach very high temperatures. Using some of the more advanced collectors, it is possible to get much higher temperatures (well above the boiling point of water) therefor a medium with a boiling point over the operating temperature is required, and many are available. This heated fluid would, by way of a heat exchanger, heat water.
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