Somerset Solar Thermal Energy

Solar Thermal Heat pipes within an Apricus heating system might seem like a new concept, but the chances are that you are using them everyday without realising it. Many laptop computers use small heat pipes to help keep the CPU cool and air-conditioning system commonly use heat pipes for heat conduction.

The principle behind heat pipe's operation is very simple.

Structure and Principle

The heat pipe itself is hollow with the space between the pipes being evacuated, in a similar way to the solar heat collection tube. Although, this is not for insulation, but affect the liquid inside. Water behaves differently at different pressures, within a vacuum water boils at a much lower temperature.

By having a vacuum in the heat pipe, the water will boil at a more efficient temperature and move to the top of the pipe. In fact in the heat collector, the water will boil at just 30^oC (86^oF). So as soon as the heat pipe gets to 30^oC (86^oF) the water vaporizes. This temperature can be reached quickly within the collector tube, even on a cloudy day in Britain. The vapour rises up the heat pipe, transferring the heat from the sun to the condenser. At the heat is asorbed out of the condenser, the water returns to a liquid and flows back down the heat pipe.

At room temperatures the water will form a ball (similar to mercury when poured onto a flat surface)this can be heard rattling inside the heat pipe if it is shaken. It is only water, but it will sound like a small piece of metal rattling around inside because of the very low pressure it is under.

This may make our heat pipes sound like very simple constructions; a hollow copper pipe with the air sucked out and a drop of water. This is correct, but to achieve what our heat pipes can do, more than twenty strictly controlled manufacturing procedures are needed.

Quality Control

The quality of the materials used is essential to creating good quality heat pipes. Any impurities on the copper of the heat pipe will have an affect on the performance. The copper itself must also be very pure, we use copper containing trace amounts of other elements, otherwise these can leach into the vacuum preventing the heat pipe from working properly.

Some inferior heat pipes are forced to use a capillary system to improve the flow of the liquid. Apricus Solar Collector heat pipes used have an incredibly smooth interior surface, allowing the efficient flow of liquid back and forth. Also, as we do not install our heat pipes horizontally we can create savings by not worrying about horizontal fluid flows.

Freeze Protection

Even in the vacuum within the heat pipe, the freezing point of water will still be 0°C (32°F). Because the heat pipe is insulated against external air temperature by the evacuated glass tubes, the water inside will not freeze even if the overnight temperature drops to -20°C (14°F).

Regular heat pipes for solar hetnig systems can be damaged by repeatedly freezing. But the water inside an Apricus heat pipe will still freeze under cold enough conditions, but it will freeze in a completely controlled way, ensuring that no damage occurs to the copper pipe.