Space Solar Power Microwave Transmission Array SolarBeam Initial Network Completed: Continuously Transmitting Clean Power from Space to Ground

Space Solar Power Microwave Transmission Array SolarBeam Initial Network Completed: Continuously Transmitting Clean Power from Space to Ground

SolarBeam, a space solar power project jointly promoted by the Japan Aerospace Exploration Agency (JAXA) and SoftBank, announced the completion of its initial network on August 23, 2030. Three satellites equipped with solar panels and microwave transmitters completed networking in geostationary orbit (36,000 kilometers altitude), successfully transmitting 200 kilowatts of power continuously to a ground receiving station in Hokkaido.

SolarBeam's principle is to collect solar energy in space and transmit it to the ground via microwave beams. In space, there is no atmospheric obstruction or day-night cycle, allowing solar panels to operate 24 hours a day, with per-unit-area generation efficiency 5 to 10 times that of ground-based solar power stations.

Each SolarBeam satellite has a wingspan of 50 meters, covered with high-efficiency triple-junction gallium arsenide solar panels achieving 38% photovoltaic conversion efficiency. The satellites convert solar energy into microwave beams (frequency 5.8 GHz) and precisely direct them to the ground receiving station via phased array antennas. The ground receiving station consists of a 300-meter-diameter rectenna array that converts microwave energy into direct current electricity.

JAXA SolarBeam project lead Professor Susumu Sasaki said: "SolarBeam demonstrates the technical feasibility of space solar power generation. Although 200 kilowatts is still small, it validates the complete technology chain for precisely transmitting energy from 36,000 kilometers away."

Technical challenges focus on two areas. First, precise pointing control of the microwave beam — a 1-degree deviation over 36,000 kilometers means a 630-kilometer offset, requiring sub-arcsecond pointing accuracy. Second, microwave transmission efficiency — the end-to-end efficiency from solar energy to final electricity is currently 12%, with significant room for optimization.

SoftBank CEO Masayoshi Son said at the launch event: "SolarBeam is the ultimate solution for human energy. Space solar power is unaffected by weather, seasons, and day-night effects, and can theoretically provide unlimited clean energy. Our goal is to build a gigawatt-class space solar power station by 2035."

However, space solar power costs remain extremely high. The initial 3 satellites required a total investment of $2.8 billion, with per-kilowatt-hour costs approximately 20 times that of ground-based solar power. JAXA estimates that with mass satellite production and declining launch costs, space solar power's per-kilowatt-hour cost could drop to comparable levels with ground-based solar by 2035.

Environmental organizations have expressed concerns about the safety of microwave transmission. JAXA responded that the microwave beam's power density has been strictly designed to be below 1% of safety standards at the edge of the ground receiving station, posing no harm to humans or wildlife.