Design and principle of operation of a pressurized water heater
Design:
The solar collector consists of vacuum tubes made of borosilicate glass. The vacuum between the two glass layers acts as an excellent insulator and prevents heat loss. In a triple magnetron metallization process, an absorber is applied (a compound that absorbs solar rays and converts them into thermal energy). Additional absorber layers are designed to retain as much energy as possible inside the tubes and prevent heat loss through infrared radiation. The new special absorption layer, ALN/AIN-SS/CU with copper added, represents the next generation of absorption coatings. Succeeding the AL/N/AL layer, it features higher efficiency (by up to 12%) and excellent absorption properties for both direct and diffuse solar radiation. The inside of the vacuum tube can heat up to as much as 300°C.
A so-called "heat pipe" is installed inside the vacuum tubes. Following the principle that the boiling point drops as pressure decreases, the pressure inside the heat pipe was lowered by evacuating the air. The liquid inside the heat pipe exchanger boils at a temperature as low as 25°C. The copper used for production is oxygen-free, ensuring long and reliable operation. Aluminum fins located inside the vacuum tubes assist in transferring energy to the copper heat pipes.
The tank is made of SUS 304 stainless steel with a thickness of 1.3 - 2.0 mm and is insulated with polyurethane foam with a thickness of at least 50 mm. The entire set is factory tested at a pressure of 10 bar and can be connected directly to the water supply network. Hot water flows out of the tank, pushed out by cold water (under the exact same pressure as in the water mains).
Principle of operation:
Under the influence of solar radiation, the inside of the vacuum tubes heats up. Through the aluminum fins, heat is transferred to the heat pipes. When a temperature of 25°C is reached, the liquid in the heat pipe starts to boil and turns into vapor. The vapor rapidly rises to the top into the exchanger head, where it cools down and condenses again after releasing its heat. It then flows back to the bottom of the heat pipe to repeat the entire process. The high efficiency of the collector results from its ability to absorb diffuse solar radiation (e.g., on cloudy days) and minimize heat loss. Energy is obtained not only from direct sunlight but also from light reflected off snow.
The system does not require pumps, controllers, or expansion tanks to operate properly, making it highly reliable. Water is located only in the tank and flows out of it under pressure. The set can be placed on the ground and can supply water to higher floors of the building.
In case of damage to a vacuum tube, the whole system still works. Only the efficiency of the system decreases. There are no liquids inside the vacuum tubes, which means a tube can be dismantled at any time without having to empty the system.
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.
- Damage to a vacuum tube with a heat pipe does not shut down the entire system, it only reduces its efficiency.
- No possibility of collector clogging (unlike flat-plate collectors or those based on U-pipes).
- Easy servicing and self-assembly possibilities.