Evacuated Tube Solar Thermal Collectors

The HRSFUNKE evacuated tube solar thermal collectors comprise a set of glass tubes fitted to a header pipe. The tubes are coated externally with an absorbent film. Internally, the glass tube has a copper pipe (also known as a heat pipe) with the solar fluid within the copper tube. Between the copper tube and the glass tube, the air is removed to create a vacuum. This lets the solar radiation in to heat the copper tube but stops any heat escaping back out because of the vacuum, thereby making them more efficient in the winter than flat plate collectors. The fluid heated within the tube rises during the natural convection process to the top in the header and is replaced by cooler water which is heated during the heating cycle. This is circulated through the heat exchanger to transfer the heat to the hot water system. The solar water is cooled during this process as its heat is transferred to the domestic hot water, the solar heating cycle then starts again.