Solar hot water is water heated by the use of solar energy. Solar heating systems are generally composed of solar thermal collectors and a fluid system to move the heat from the collector to its point of usage. Systems may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use.
Solar hot water systems are used to produce hot water for wide variety of uses, including home, business and industrial uses. Heating swimming pools, underfloor heating or energy input for space heating are more specific examples.
The evacuated tube solar hot water systems are the most efficient type for most Australian conditions. A thorough comparison of evacuated tube vs. flat plate collectors can be found under http://en.wikipedia.org/wiki/Solar_thermal_collector
Key determinents for choosing the collector type are
- Application – if using for pool heating it would appear flat plate are favoured
- Amount of direct sunlight – if cloudy and cool conditions do not occur at your location, it would appear a flat plate are favoured
- Cost – if the cost differential is great, it would appear flat plate are favoured
Otherwise evacuated tube are favoured.
Some systems now use an efficient electric heat pump to heat water. The heat pump uses a compressor to take heat from outside air, concentrate it and transfer it to water.