How much energy from the sun can be absorbed by solar panels

Solar energy is a kind of energy produced by the nuclear fusion of hydrogen in the sun. The energy emitted by the sun is only about one in 2.2 billion to reach the range of the earth's atmosphere, reaching the upper boundary of the earth's atmosphere, which is about 1367W per square meter, It reaches the photovoltaic module and converts it into direct current. According to the current efficiency of 18.3% of the single crystal 300W module, it is about 183W. Where does the 1184W energy in the middle go?

1. Absorbed and reflected by the atmosphere

There are thousands of kilometers of atmosphere above the earth, which are divided into troposphere, stratosphere, mesosphere, thermosphere and exosphere. About 30% of the sun's energy is reflected into space, and about 19% of the energy is absorbed by clouds and atmosphere. It becomes wind, thunder and rain, and about 51% reach the earth's surface. Since most of the earth's surface is covered by oceans, the energy that can really reach the land surface is only about 10% of the radiant energy that reaches the earth. Nevertheless, using this energy can be equivalent to 35,000 times the current global energy consumption.

2. The battery module only absorbs the energy of the visible light part

Spectral knowledge of sunlight: sunlight is a mixture of continuously changing light of different wavelengths, including light of various wavelengths: infrared, red, orange, yellow, green, blue, indigo, violet, ultraviolet, etc. Red, orange, yellow, green, indigo, blue, and violet are visible light that can be seen by the human eye. The longer wavelength part is red light, the longer wavelength part is infrared light, the shorter wavelength part is violet light, and the longer wavelength part is ultraviolet light, although the wavelength range of the solar spectrum is very wide, from a few angstroms to several angstroms. Ten meters, but the distribution of radiant energy by wavelength is uneven. Among them, the region with the largest radiant energy is in the visible light 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 0.475μm, the solar cell can only absorb part of the energy and convert it into electrical energy. The ultraviolet spectral region cannot perform energy conversion, and the long wavelength in the infrared spectral region can only be converted into heat.

In the solar spectrum, different wavelengths of light have different energies and different numbers of photons. Therefore, the number of photons generated by the solar cell when exposed to light is also different. In general, silicon solar cells do not respond to ultraviolet light with wavelengths less than about 0.35 μm and infrared light with wavelengths greater than about 1.15 μm, and the peak response is in the range of 0.8 to 0.9 μm. Determined by the solar cell fabrication process and material resistivity, the spectral response peaks at about 0.9 μm when the resistivity is low. In the spectral response range of solar cells, the region with longer wavelength is usually called long-wave spectral response or red light response, and the region with shorter wavelength is called short-wave spectral response or blue light response. Essentially, the long-wave spectral response mainly depends on the lifetime and diffusion length of minority carriers in the matrix, and the short-wave spectral response mainly depends on the minority carrier lifetime in the diffusion layer and the recombination velocity on the front surface.

At present, there are two ways to improve battery efficiency. One is to study new battery materials and widen the range of response spectrum. For example, cascaded solar cells integrate sub-cells made of semiconductor materials with different spectral responses together to make full use of solar energy. Each wavelength of the spectrum can be used to improve utilization through multi-junction cell technology. The second is to correct the cell technology, such as diamond wire cutting, surface passivation technology, laser processing technology, etc., to improve the utilization rate of solar energy.

 3. Component packaging loss

After encapsulation into modules, because the module area is larger than the total area of ​​the battery, the overall area efficiency is lost by about 2 percentage points; secondly, due to the loss of 0.5 percentage points of light transmission and absorption of photovoltaic glass; 0.5 percentage points of light transmission absorption loss of EVA film; Third, the resistance of the interconnect bar/bus bar loses 1 percent. In total, it lost about 4 percentage points. With the continuous development of module technology, multi-busbar battery modules, double-glass aluminum-free frame modules, and MWT back-contact busbarless battery modules are now introduced, which can reduce the packaging loss of modules to less than 1%.