Design and principle of operation of a solar collector (non-pressurized)
Design:
The solar collector consists of vacuum tubes made of borosilicate glass. The high operational safety of borosilicate glass is achieved through the use of an appropriate mixture of SiO2 and B2O3 oxides, resulting in a product with good chemical resistance as well as extraordinary purity and homogeneity. Borosilicate glass is environmentally friendly and can be recycled multiple times. The application of a thermal tempering process (tempering), combined with the low thermal expansion typical of borosilicate glass, gives it particularly high resistance to temperature changes compared to ordinary glass. The tubes are resistant to hail up to 25 mm in size. The use of tubes with diameters of 47 mm and 58 mm allows for concentric placement of one inside the other. The air between the tubes is pumped out, and the tubes are fused together.
Solar radiation falling on the absorber located on the inner tube is converted into thermal energy, heating the inside of the tube. The vacuum between the tubes acts as an excellent insulator and prevents heat loss to the atmosphere. The collector manifold is made of SUS 304-2B stainless steel and is insulated with polyurethane foam.
Principle of operation:
There is water inside the tank and the tubes. Under the influence of solar radiation, the water in the tubes heats up. Due to convective movements, it rises up into the manifold. The water undergoes continuous circulation between the manifold and the water storage tank, causing a constant increase in water temperature. The high efficiency of the collector results from its ability to absorb diffuse solar radiation (e.g., on cloudy days) and minimize heat loss.
Advantages:
- Higher efficiency of the vacuum collector than a standard flat-plate collector.
- Simple design, low failure rate - tube lifespan exceeding 15 years.
- Easy servicing and self-assembly possibilities.