Cornwall Solar Thermal Heating

Solar energy may sound laughable with the typically changeable British weather, but with Apricus Solar Heating systems and the incredibly efficient evacuated tubes they use, you can be assured of hot water all year round.

Apricus Solar Heating systyems use evacuated tubes to absorb the suns energy. The solar energy is easily converted into usuable heat for domestic use. Evacuated tubes have been used for years in Europe, Canada and China, but new advances in production techniques have made them even more efficient. Apricus collectors use "twin-glass" tubes which are known for their reliability, high performance and low manufacturing cost.

Each evacuated tube is composed of two very strong borosilicate glass tubes. The outer of the tubes is transparent, this allows light rays to pass through. The inner of the tubes is coated with a special dark coating designed to absorb the suns heat and reflect as little as possible. The ends of the tubes are fused together before the space between the two layers of glass being evacuated. This evacuation simply means all of the gasses in the space being sucked out to form a vacuum. This cuts down on the ability of heat to escape back out of the tube.

Why is a vacuum important? A vacuum is an excellent insulator, this is why thermos flasks use a vacuum to stop heat from transferring through the body. This is important for the tubes because once it had absorbed the suns heat we don't want to escape back out into the atmosphere. The vacuum helps prevent this without preventing the tube from absorbing the heat in the first place. The insulation that the vacuum offers is so good that the inner tube can reach temperatures of 150°C (304°F) while the outer tube is still cold to the touch. This gives a solar heating system using evacuated tubes excellent performance even in colder or cloudy weather.

To maintain this vacuum in the space between the glass tubes, a barium getter is used (the same device is used in in the tubes inside CRT TVs). During the manufacture of evacuated tubes this getter is subjected to high temperatures which will coat the bottom of the tube with a layer of pure barium. This layer will actively absorb gases (CO, CO₂, N₂, O₂, H₂O and H₎₂from the tube during storage and operation. This assists in maintaining the vacuum correctly. The barium layer also acts as a visual indicator as to whether the vacuum is holding or not. While the vacuum is present, barium layer will be silver, turning white should the vacuum be lost. This means you can see at a glance if a tube is in working order.

The efficiency of a solar water heater depends upon a whole range of factors, possibly the most important being the level of solar radiation (insolation) your home receives. More about insolation levels is available here.