Japanese satellites will transmit solar power to Earth

Japan is preparing to transmit solar energy from space to Earth next year, in the form of microwaves .

Japan is preparing to transmit solar energy from space to Earth next year, two years after American engineers achieved the same feat. This development marks an important step toward a space-based solar power station that could help the world cut fossil fuels amid the fight against climate change, Space reported on April 19.

Simulate the solar power production system in space. (Photo: AFRL).

Speaking at the International Conference on Energy from Space held this week, Koichi Ijichi, an advisor at the Japan Space Systems research institute, outlined a roadmap for testing small solar power plants in space, broadcasting wireless energy from low orbit to Earth. According to him, it will be a small satellite, about 180kg, transmitting about one kilowatt of electricity from an altitude of 400km. One kilowatt is equivalent to the amount of electricity needed to run a household appliance such as a small dishwasher for about an hour, depending on size. Therefore, this experiment cannot be compared to the scale for commercial use.

The spacecraft will use a 2 m2 solar cell to charge the battery pack. The accumulated energy will then be converted into microwaves and transmitted to receiving antennas on Earth. Because the spacecraft moves very fast, about 28,000 km/h, the antennas need to spread over 40 km, each 5 km apart, to be able to transmit enough energy. According to Ijichi, transmission only takes a few minutes, but when the battery runs out of power, it takes several days to fully charge.

The mission is part of the OHISAMA project (which means Sun in Japanese) and will launch in 2025. Researchers have tested wireless transmission of ground-based solar power from a fixed source. They plan to conduct transmissions from planes in December this year. The aircraft will be equipped with solar batteries similar to those used on spacecraft and transmit power over a distance of 5-7km.

The idea of ​​producing solar power in space was first described in 1968 by former Apollo engineer Peter Glaser. Unlike most renewable electricity generation technology on Earth, solar power in space is constantly available because it is independent of weather and time of day. Currently, nuclear power plants and thermal power plants use coal or natural gas to meet demand when the wind stops blowing or the Sun goes down. Recent technological advances may help solve part of the problem in the future. But researchers have yet to find a way to ensure uninterrupted and carbon-free electricity supply by the middle of the 21st century.

The development of autonomous technology and wireless power transmission , especially the birth of the giant Starship rocket, could make solar power in space a reality. Last year, a satellite built by Caltech engineers on the Space Solar Power Demonstrator mission transmitted solar power from space for the first time. The mission ends in January 2024. However, according to a NASA report, the energy required to manufacture, launch and assemble the power station in orbit makes the electricity price of the production facility too high, more than 12 times higher than wind and solar power on Earth. Earth.