Installing solar panels on the roof not only generates income from solar power but also provides insulation and heat insulation, cooling the indoor temperature during hot summer days. However, how effective is the roof solar panels' cooling and heat-insulating properties and can it really achieve a cooling effect for the indoor temperature? We analyze the fundamental principles and actual measurement data to see what the facts actually are.
1. Fundamental principles of solar insulation and heat insulation
Photovoltaic power generation is a technique that converts solar energy directly into electricity using the photovoltaic effect at the semiconductor interface. When sunlight shines on the photovoltaic panel, the panel absorbs most of the solar energy and converts it into electrical energy, with very little light being reflected. The structure of the photovoltaic panel is tempered glass on the surface and an opaque polymer back sheet on the back, making it a good cover. Based on these two points, the sunlight shining on the roof is mostly absorbed to generate electrical energy, not heat energy, and the shading property of the photovoltaic panel can block sunlight and maintain the indoor temperature. This is the fundamental principle of why photovoltaics have excellent heat insulation performance, which far exceeds the pure physical insulation and heat insulation effects of general heat insulation materials.
2. Actual temperature measurement of photovoltaic system components
On a hot day in Shanghai, China in the summer of 2020, some data records were taken using an infrared temperature gun. The following are the results:
Figure 1: Temperature of the inverter surface
The inverter is installed on the north eaves, and the surface temperature is 44.4 degrees, which is about 5 degrees higher than the air temperature. The overall heat dissipation performance is good.
Figure 2: Temperature of the electrical switch
The contact temperature of the main switch of the grid-connected cabinet is 36.8 degrees, which is lower than the air temperature and shows good surface appearance.
Figure 3: Temperature of the photovoltaic surface
Figure 4: Temperature of the roof surface
It can be seen that under the conditions of an air temperature of 40 degrees, clear sky, and noon at 12 o'clock, the roof temperature reaches 68.5 degrees, which is hot enough to cook an egg. The temperature of the photovoltaic panel surface was measured to be 57.5 degrees, which was close to the roof temperature when touched with the hand. The photovoltaic panel will generate some heat during power generation, which is a normal phenomenon, because solar energy is converted into electrical energy. The temperature of the roof surface under the photovoltaic panel without direct sunlight was about 48 degrees. It can be seen that the maximum temperature difference of the roof surface depends on whether it is directly exposed to sunlight.
This fully shows that the photovoltaic panel has excellent insulation and heat insulation properties, which can reduce the heat absorption of the roof surface and indirectly reduce the temperature of the top floor room, achieving double energy-saving effects. According to actual measurement data and feedback from owners, after installing the roof photovoltaic, the temperature on the top floor can be reduced by 5-8 degrees during high temperature weather.
3. Multiple benefits of photovoltaic cooling and heat insulation
The new function of reducing indoor temperature by installing a roof photovoltaic power plant brings many benefits to photovoltaic users. For ordinary household users, reducing the indoor temperature during high temperature weather greatly saves air conditioning electricity expenses. For large factories, the heat insulation and cooling function of the roof photovoltaic panel is a huge "sunshade umbrella."
1. Physical cooling of the factory building
In summer, it is difficult to be in the factory, and power outages often occur, seriously affecting the production schedule. Installing solar power photovoltaics can not only provide the electricity required for production but also have a shading and cooling effect to achieve physical cooling of the factory building.
2. Reduce enterprise energy consumption
The roof covered with solar panels will have an average summer temperature 5C-8C lower than non-covered roofs, and air conditioning energy consumption can be reduced by 30%-40%.
3. Improve employee working environment
After the factory's temperature drops, it can greatly improve the working environment of employees, avoid heat stroke, improve production efficiency, and reduce production costs.
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