In July 2016, Bertrand Pirka and Andre Borschberg flew the Solar Impulse 2 solar-powered aircraft developed by a Swiss start-up. It took 16 months to complete a round-the-world flight. The aircraft did not consume a drop of fuel and flew 42,438 kilometers. This flight not only set a record, but also declared to the world: Technically speaking, it is completely possible to travel around the world in an airplane that does not consume any fossil fuels.

　　In 2019, the American company Skydweller bought the intellectual property rights of "Solar Impulse". The new goal of this 115-employee company is to enable solar-powered aircraft to achieve autonomous driving, that is, to create solar-powered drones.

　　Skydweller’s solar-powered drone is not an ordinary aircraft. It has a wingspan of 71.93 meters and 2900 square feet of photovoltaic cells are distributed on it. In addition, a hydrogen fuel cell is installed in case of emergency. The aircraft's flying speed is between 45 kilometers and 90 kilometers per hour, and the flying altitude is between 5 kilometers and 10,000 meters.

　　Skydweller is not the only company developing solar-powered drones. Many private companies in Germany and the United Kingdom are also developing solar-powered drones. According to a recent report on the official website of the German Aerospace Center (DLR), the center is developing a stratospheric solar-powered drone that combines the advantages of aerospace and aviation to ensure future scientific experiments.

　　In 2019, British defense giant BAE Systems tested the solar-powered drone PHASA-35. It has a pair of flat and slender wings with a wingspan of 35 meters, a weight of 150 kilograms, and a load of about 15 kilograms. It can fly at an altitude of 20 kilometers for up to one year. It provides services such as communication, real-time monitoring and remote sensing detection. Traditional satellites are more flexible "pseudo-satellites."

　　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.