What is solar thermal collector?
Solar thermal collector convert solar energy received by the absorber into heat and then transfer heat into the useful heat to the flow of hot water just beneath the surface of the absorber. Because the light is only available during the day, then the hot water tank used to store hot water. In addition to the application providing hot water for household, business and industry, solar water heating is also used to heat water in swimming pools and also to heat rooms with under floor heating system.
Based on how the circulation of working fluid into the collector, solar thermal collector can be divided into active systems that use pumps and passive systems without using a circulating pump or by natural or called thermosyphon.
Based on the application and the desired temperature, solar collectors can be divided into several types, namely:
- Unglazed metal and plastic flat plate collectors are used for low temperature applications such as residential pool heating and ventilation air heating for commercial and industrial buildings
- Glazed flat plate and vacuum tube collectors are used for mid-range temperature applications such as domestic hot water and space heating and cooling applications
- Concentrating collectors that focus the sunlight onto a much smaller area are used for higher temperature applications such as industrial process heat, absorption cooling, and large-scale solar thermal power applications to generate steam for electricity generation
Based on the use of direct and indirect heat generation, thermal solar collector system is divided into direct and indirect systems. Indirect Systems: also known as closed loop system. A simple pump moves the antifreeze solution through a loop into the solar collector, through the collector’s pipes, and out of the solar collector. Then, the sun-warmed antifreeze solution flows into a heat-transfer unit where it warms the cool water heading into a conventional hot water tank. The antifreeze solution then returns to the pump and again flows into the solar collector without ever mixing with the building’s water. Direct Systems: knwown also as open-loop system. There is no antifreeze solution; the water heated directly by the sun is the same water used by building occupants. A thermometer and controller sense when the solar collector is warm and ready to heat water. The controller starts a pump that moves cold water into the solar collector, where it is heated. The solar heated water is then stored in a conventional hot water tank.