How to choose the installation location and inclination of solar collectors?
Solar collector installation location
Choosing a suitable installation location on the building surface is the key to ensuring the functional requirements of the solar water heating system. The most ideal installation location is the roof of the building, followed by the facade of the building, such as walls, balconies and other parts (due to the limitation of the installation angle of the collector, the radiation gain will be affected to a certain extent), should avoid installation at the bottom of the building facade, the place blocked by the surrounding greenery or the shape of the concave part of the building. General high-rise residential buildings are suitable for installing solar collectors as shown in Figure 1.
Solar collector inclination
The installation inclination of the solar collector has a great influence on the amount of solar radiation obtained by its surface. In order to obtain the maximum amount of radiation, it is best for the collector to track the sun’s trajectory or adjust the angle regularly, but this will greatly increase the initial investment, and there are also certain difficulties in operation. Therefore, most of the solar collectors currently installed are stationary. In general, in order to obtain the maximum annual solar radiation, the inclination of the collector should be consistent with the local latitude (p). If the system is used in summer, its inclination should be the local latitude minus 10°, and if the system is mainly used in winter, its inclination should be the local latitude plus 10°. This is because the maximum annual direct solar radiation can be obtained when the inclination of the collector is consistent with the local latitude. In summer, the altitude angle of the sun is larger, and the inclination angle should be slower; in winter, the altitude of the sun is smaller and the inclination is steeper. However, many studies have shown that the installation inclination of the collector is not only related to the local geographic latitude, but also related to the climatic conditions, solar radiation, atmospheric transparency, and system use time. Due to different climate, radiation conditions, geographical location and other factors in different regions, the optimal installation inclination will also be different. For solar water heating systems used in winter, the optimal angle is generally (4+18°), and only the Chengdu Plain, Chongqing, Guizhou and other places have the best inclination angle (4+10°); for solar water heating systems used in summer, the optimal installation inclination angle is (4-25°) (if the calculated value is less than 0, the inclination angle value shall be 0, that is, set horizontally). Taking the Hangzhou area as an example, we calculated the monthly average daily radiation at different inclination angles in the due south direction, and obtained the best monthly installation inclination angle. For the calculation of the optimal annual installation inclination of the fixed-installed collector, the results show that when the installation inclination of the collector is 22°, the accumulated solar radiation is the largest throughout the year; except in summer, the angle that maximizes the total amount of solar radiation in spring, autumn and winter is 30°; the angle that maximizes the amount of solar radiation received by the surface of the collector in winter (January, February, and December) is 48°; if the hot water load is considered, when the heat collection area of each household is 2~2.5m², the optimal installation inclination angle is 40°~45°. The solar collectors arranged on the roof should be arranged according to the best inclination angle as far as possible. The collectors of high-rise buildings are mostly installed on the walls or balcony railings (poles). Due to factors such as aesthetics and safety, the angle is generally large, or even placed at 90°, which will sacrifice a certain heat collection efficiency.
Further reading: Classification of solar collectors