If a solar cell has an area of 154 square centimeters, and is illuminated by standard AM1.5G light, it will have an energy output of 15.4W. If the tested cell power output is 2.6 watts, then its conversion efficiency is 2.6/15.4 = 16.88%. In 2011, after adopting DuPont's 17A positive silver paste, the average conversion efficiency of solar cells on production lines exceeded 18%. Due to differences in standards and testing equipment among manufacturers, the specific figures may vary. Improving the conversion efficiency of solar cells can accelerate the reduction in their manufacturing costs, ultimately leading to the same grid connection price as conventional energy sources.
What is a solar cell?
To effectively study the conversion efficiency of solar cells, it's essential to first clarify the concept of a solar cell, that is, to understand what a solar cell is and how it works. A solar cell, as the name suggests, is a device used to convert solar energy into electrical energy. This device is typically flat, hence the name solar panel. Solar cells are also called photovoltaic cells, primarily based on their function and characteristics. The development of solar cells in my country is relatively recent, only a few decades old, but it has already achieved a considerable scale.
Solar cell conversion efficiency:
As an energy-saving and environmentally friendly product, the conversion efficiency of solar cells is of utmost concern to people. The conversion efficiency of a solar cell refers to the percentage of sunlight it can convert into electrical energy. The working principle of a solar cell is mainly to convert solar energy into electrical energy directly or indirectly through the photoelectric effect. Due to current technological limitations, it is difficult to convert all collected solar energy into electrical energy; therefore, conversion efficiency is used to describe its working capacity.
Currently, my country's solar energy utilization technology is not very advanced, as the conversion efficiency of solar cells is not very high. At present, the photoelectric conversion efficiency of monocrystalline silicon solar cells in my country is around 24%, and this is under optimal conditions. That is to say, if 100 units of solar energy are collected, only 24 units can be converted into electricity for human use after passing through solar panels. This conversion efficiency is actually very low. Further efforts are needed to improve the conversion efficiency of solar cells.
Solar panels are devices that absorb sunlight and convert solar radiation energy directly or indirectly into electrical energy through the photoelectric effect or photochemical effect. The main material of most solar panels is silicon. When sunlight shines on the surface of a solar cell, some photons are absorbed by the silicon material; the energy of the photons is transferred to silicon atoms, causing electrons to jump and become free electrons. These free electrons accumulate on both sides of the PN junction, creating a potential difference. When an external circuit is connected, under the influence of this voltage, a current will flow through the external circuit, generating a certain output power. Essentially, this process is the conversion of photon energy into electrical energy.
Solar panel power calculation
A solar AC power generation system consists of solar panels, a charge controller, an inverter, and a battery; a solar DC power generation system does not include an inverter. To ensure the solar power system provides sufficient power to the load, the components must be selected appropriately based on the power consumption of the appliances. The following example, using a 100W output power system and 6 hours of daily use, illustrates the calculation method:
1. First, the daily watt-hours consumed (including inverter losses) should be calculated: If the inverter's conversion efficiency is 90%, then when the output power is 100W, the actual required output power should be 100W/90%=111W; if it is used for 5 hours a day, the output power is 111W*5 hours=555Wh.
2. Calculation of solar panel output: Assuming 6 hours of effective sunshine per day, and considering charging efficiency and losses during charging, the output power of the solar panel should be 555Wh/6h/70% = 130W. Here, 70% represents the actual power used by the solar panel during charging.
According to the latest certification report from the Hamelin Solar Energy Research Institute (ISFH) in Germany, LONGi Green Energy's independently developed silicon heterojunction solar cell has achieved a conversion efficiency of 26.81%, breaking the five-year-old record for silicon solar cell efficiency.
Martin Green, the "father of solar energy" and professor at the University of New South Wales, announced via video on November 19 that LONGi Green Energy's 26.81% battery efficiency is currently the highest record for silicon-based solar cells in the world, regardless of the technology used.
This is the latest world record set five years after a Japanese company set a record of 26.7% efficiency for single-crystal silicon cells in 2017. It is also the first time in the history of photovoltaics that a Chinese solar energy technology company has set a world record for silicon cell efficiency.
Improving conversion efficiency and reducing the cost per kilowatt-hour are the eternal themes of the photovoltaic industry's development. Li Zhenguo, founder and president of LONGi Green Energy, stated at the press conference that solar cell efficiency is the beacon of photovoltaic technology innovation; the ultimate efficiency of crystalline silicon solar cells determines and demonstrates the development potential of photovoltaic technology and the direction of the photovoltaic industry.
