How Solar Water Heaters Work

The operation of the solar collector is as follows:

1. Solar Absorption: Solar thermal energy is absorbed within the evacuated tubes and is converted into usable concentrated heat.

2. Solar Thermal Transfer: Copper heat pipes transfer the thermal energy from within the solar tube into the copper header.

3. Solar Thermal Storage: A thermal transfer solution (water or glycol mixture) is pumped through the copper header. As the the solution circulates through the copper header the temperature is raised by 5-10 oC / 9-18 oF.

Evacuated Tubes: The most efficient thermal collector on the market, the glass tubes absorb solar thermal energy for use in water heating. The tubes have a double wall, the area between the inner and outer layers of the wall are evacuated ( a vacuum). This acts as a thermos to keep heat from escaping into the atmosphere.

The evacuated tubes are glass tubes manufactured from strengthened borosilicate glass. The tubes have a double outer layer; the outer layer is fully transparent to allow solar energy to pass through unimpeded. The inner layer is treated with a selective optical coating which causes energy absorption without reflection. The inner and outer layer are fused at high temperatures at the end leaving an empty space between the inner and outer layers. All air is pumped out of the space between the two layers (evacuation process) creating the thermos effect which stops conductive and convective transfer of heat which might otherwise escape into the atmosphere. Heat loss is further reduced by the low-emissivity nature of the type of glass that is used.

Heat Pipe: Inside the glass tube is the copper heat pipe. It is a sealed hollow copper tube that contains a small amount of proprietary liquid, which under low pressure boils at a very low temperature. In fact the liquid contained in the heat pipe boils at only 86 oF (30 oC).

The header is enclosed in the manifold (above).

This heat pipe rapidly and efficiently transfers the captured thermal energy through the evacuated tube and delivers it to the manifold (header) as the liquid boils and rises. As the heat is removed from the heat pipe by the copper header, the liquid condenses and gravity returns it to the base of the heat pipe so that the process is continually repeated.

Because the evacuated tubes are round, they serve as a passive tracking solar collector maximizing their performance.