After the German physicist Hertz discovered the photoelectric effect in 1887, solar energy began to show its application prospects.

　　It is the improvement of photoelectric conversion efficiency that can truly make it commercialized on a large scale. For every 1% increase in conversion efficiency, the cost of solar energy will drop by more than 5%.

　　Before the conversion efficiency reached 10%, solar energy was mainly used in aerospace technology and military applications. In 2004, the conversion efficiency of polysilicon increased to about 10%, and Europe began to guide the development of solar energy through government subsidies. Since then, technological progress has continued to accelerate, with an increase of about 1% every year. In 2019, the conversion efficiency of polysilicon has exceeded 22.8% (created by Canadian Solar), and monocrystalline silicon has reached 24.03% (created by Longi).

　　The cost of monocrystalline silicon is higher than that of polycrystalline silicon, so in the past solar energy mainly used polycrystalline silicon. However, because the conversion efficiency of monocrystalline silicon is higher than that of polycrystalline silicon, the final use cost is lower than that of polycrystalline silicon. Therefore, after 2016, monocrystalline silicon solar cells have begun to explode, and their proportion is getting higher and higher.

　　The theoretical maximum limit of crystalline silicon solar cells is 29.1%, so there is not much room for improvement in conversion efficiency. But the new discoveries made by researchers at MIT and Princeton University in the past few years may increase the theoretical maximum limit to 35%. They published a paper on the results of this research in the journal Nature on July 3, 2019.

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate batteries are a perfect replacement for lead-acid batteries, and they are the first choice for grid-connected peak shaving, off-grid energy storage, photovoltaic energy storage, UPS, data center and other industries.

　　Solar power generation system with lithium battery energy storage system is a very promising clean energy.