Flat plate solar collectors
Flat plate collectors work on copper pipes running through a glass covered collector, often connected to a water storage tank on the roof. The sun heats the copperpipes and the resulting hot water is thermo-siphoned out of storage tank.
Evacuated tube solar collectors
Evacuated tubes use (as the name suggests) consist two glass tubes fused at the top and bottom. The space between the two tubes is evacuated to form a vacuum. A copper pipe (called a heat pipe) running through the centre of the tube meets a common manifold that is then connected to a slow flow circulation pump that pumps water to a storage tank below, thus heating the water during the day. The hot water can be used at night or the next day due to the insulation of the tank.
The evacuation tube systems are superior as they can extract the heat out of the air on a humid day and don’t need direct sunlight. Due to the vacuum inside the glass tube, the total efficiency in all areas is higher and there’s better performance when the sun is not at an optimum angle – such as when it’s early in the morning or in the late afternoon.