Evacuated Tube Solar Collectors
Evacuated tube solar collectors function according to the same principle as the thermos bottle; the sun's rays enter the tube and the heat remains trapped inside. Cool to the touch on the outside, the inside reaches very high temperatures and the vacuum-sealed tubes prevent heat loss. The heat produced is then transferred to the building's water supply.
The method by which the heat in the solar collectors reaches the building's water supply is relatively simple. The solar collectors gather the sun's energy and conduct the heat that is generated to a "solar fluid." The solar fluid consists mostly of water with some food-grade gycol added to the mix to prevent freezing. This fluid is circulated in a closed loop between the collectors on the roof and the heat storage tank in the basement. Through heat exchangers the heat produced in the solar collectors is transferred to the heat storage tank and in turn, that heat passes to your building's existing plumbing system.
The materials and technology are very well developed, keeping heat loss to a minimum. The system is able to maintain 70-80% efficiency; meaning that 70-80% of the energy collected is delivered to your building's hot water or heating system.