Rather than processing and converting solar energy the way photovoltaic systems do, solar thermal set-ups simply collect the sun’s heat as it arrives and use it to heat a supply of water. In some arrangements, collector pipes exposed directly to the sun’s rays heat a steady stream of flowing water as it circulates through them before being emptied into a large-capacity water tank. The flow can be kept going for as long as is required, and such a system is capable of heating a fairly significant amount of water in a short period of time. There are also closed-loop indirect thermal systems that pass the heat collected to a fluid with a low freezing point such as glycol, which in turn transfers that heat via exchange coils to water that is already stored inside tanks.
Because solar thermal relies on a much simpler technological arrangement than solar photovoltaics, it has attracted the attention of many do-it-yourselfers, and there are plenty of good designs available on the Internet for anyone who would like to put together their own solar hot water system from cheap or recycled materials.
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