The definition of solar collector is absorbing solar radiation and generating heat to transfer to the device of heat transfer medium. It contains abundant meanings, it is a kind of device to absorb solar radiation, generate heat, and transfer heat to the heat transfer medium. Although the solar collector is not the terminal products to the consumers directly, but the solar collector is the key component to compose different solar energy heat utilization systems. No matter it is the solar water heater china, solar oven, active solar house, solar greenhouse or solar dryer, solar industrial heating and concentrating solar power, none of them can work without the solar collector, all of them use the solar collector as the system dynamics or the core parts.
The solar collector can be divided into some classification as follows:
1. According to the working medium of heat transfer , the solar collector can be divided into liquid collector and air collector.
2. According to the solar radiation of the press enter the day lighting whether can change direction points or not, there are concentrating collectors and not concentrating collectors.
3. According to the collector is tracking the sun or not, the solar collector can be divided into tracking collector and non tracking collector.
4. According to the vacuum space inside the collector is divided into flat-plate collectors and vacuum tube collector.
5. According to its working temperature range, there are the low temperature collector, the temperature collector and the heat collector.
6. According to the materials which are used in the collector, there are pure copper panels, copper aluminum composite panels and aluminum panels.
For example, the flat-plate solar collectors, it consists of a transparent cover plate, insulating layer and the shell and so on. The flat-plate solar water heater is also composed of the flat solar collector water heater. When the solar collector does work, the solar radiation though the licid cover plate will project on the absorber plate, then transferred into heat energy to the heat transfer fluid of the absorber plate to raise its temperature as the useful energy output. At the same time, after the temperature rising, the absorber board should reject the heat to all around by conduction, convection and radiation, which will become the loss of the collector.
One of the most basic kinds of the solar collectors is flat-plate solar collectors, its structure is very simple, can operate reliably, its cost is appropriate, and there are some characteristics of it, such as bearing strong pressure, big absorbed area, is one of the best choice of collectors for the combination of the solar power and the building. The other example is vacuum tube collector, which is a kind of heat pipe thermal solar collector by vacuuming of the space between the endothermic body and the transparent cover. The vacuum tube water heater is the water heater which is composed by vacuum tube collector.