Design and principle of operation of a non-pressurized water heater
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, 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 tank is made of SUS 304-2B stainless steel and is insulated with polyurethane foam with a thickness of at least 50 mm.
Models from the JNHX series have a copper coil installed inside the tank, which can be connected directly to the water supply network. For automatic water replenishment in the tank, they are also equipped with a small expansion tank. Once completely filled, the inlet valve is automatically closed by means of a float.
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 tank. The water undergoes continuous circulation between the tank and the vacuum tubes, 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. The collector also performs excellently in winter. It obtains energy not only from direct sunlight but also from light reflected off snow.
The installed small expansion tank serves to automatically replenish the water in the tank directly from the water supply network. Systems from the JNHX series have a copper coil installed inside the tank and can be connected directly to the water supply network. In this case, the water in the tank is not used; it serves only as a heat buffer for the pressurized water flowing through the coil. The advantage of this solution is the possibility of obtaining domestic hot water at higher pressure. There is no need for gravitational draining or using pumps. Instead of water, a glycol solution can then be placed in the tank, which can additionally circulate in the central heating system.
The system does not require pumps and controllers to operate properly, making it highly reliable. The open circuit ensures that even if the water boils, it does not cause a pressure increase inside the tank. Thanks to this, the system is failure-free and safe.
Advantages:
- Higher efficiency of the vacuum collector than a standard flat-plate collector.
- Simple design, low failure rate - tube lifespan exceeding 15 years.
- Direct connection between the collector and the tank (no heat loss).
- Excellent tank insulation (daily water temperature loss of 6 - 10 degrees C).
- No need for pumps and controllers.
- Simple installation that does not require modification of the existing system.
- Easy servicing and self-assembly possibilities.