Main types of collector
There are two main types of collector, flat plate and evacuated tubes.
Flat plate consists of a black metal plate which either has pipes bonded to it or two metal plates which the water is trapped between. The collector has a layer of insulation behind it and a glass or clear plastic cover to trap more of the light energy. As water flows through the plate it is warmed by the sunlight.
An evacuated tube collector contains a small copper collector which is painted black. The glass evacuated tube prevents heat loss by conduction and convection. The glass tube also traps more of the suns light energy. The ends of the copper tubes are all sealed and are placed so they warm water circulating to the hot water tank. Evacuated tubes are more efficient than flat plate collectors but they are more expensive to produce. They are best for situations where space is limited.
