Solar energy reaches the upper limit of the Earth’s atmosphere, about 1367W per square meter. The highest conversion efficiency of PV modules is about 21%, which means that the maximum power that can be produced in one square meter is 210W, but the remaining 1157W energy goes where?
1. Half of the energy is absorbed and reflected by the atmosphere.
There are thousands of kilometers of atmosphere above the earth, divided into troposphere, stratosphere, intermediate layer, thermal layer and outer layer. About 30% of the sun’s energy is reflected into space, and about 19% of the energy is absorbed by the clouds and the atmosphere. It became a wind, thunder and rain, and the energy reaching the surface of the earth accounted for about 51%. That is to say, the solar energy reaches the surface of the earth, the average power per square meter is about 690W, and the standard test condition of the custom solar panel is 1000W per square meter. The illumination in most places cannot reach this condition, of course. In a few places, the irradiance may exceed 1000W at a particular time.
2. Photovoltaic cell module absorbs the energy of visible light.
Spectral knowledge of sunlight: Sunlight is a mixture of continuously varying wavelengths of light, containing light of various wavelengths: infrared, red, orange, yellow, green, blue, enamel, purple, ultraviolet, etc. Red, orange, yellow, green, sputum, blue, and purple are visible light, visible to the human eye. The region with the largest radiant energy is in the visible part, accounting for about 48%, the radiant energy in the ultraviolet spectral region accounts for about 8%, and the radiant energy in the infrared spectral region accounts for about 44%. In the entire visible spectrum, the maximum energy is in the wavelength. At 0.475 μm, the solar cells can only absorb part of the energy and convert it into electrical energy. The ultraviolet spectral region cannot be converted into energy, and the long wavelength in the infrared spectral region can only be converted into heat.
At present, solar panels can only absorb the energy of visible light. If OEM solar panels can absorb all energy, the maximum efficiency can reach about 48%, but no photovoltaic technology can achieve such a wide bandwidth, when the band width is 1.0~1.6. At eV, the maximum conversion efficiency of the PERC crystalline silicon PV cell is below 44%, and the ultimate efficiency of the crystalline silicon solar cell is predicted to be 29%. In March 2017, the Japanese Chemical Manufacturing Company developed an outdoor solar cell with a conversion rate of 26.3%.
3. The encapsulation loss of photovoltaic module.
After being laminated into a solar module, the product area is larger than the area of photovoltaic cells, and the total area efficiency is lost by about 2%. Secondly, the light loses 0.5% through solar glass. Again, the light loses 0.5% through the EVA film. Furthermore, the power loses 1% because of the resistance the interconnect strip/sink strip. Finally, a total of about 4% was lost. With the continuous development of solar module technology, multi-busbar solar cell modules, double-glass photovoltaic modules, and MWT back-contact multi-busbar photovoltaic cell modules are now available, which can reduce small solar panels to less than 1%.