Transmit solar power from space to Earth

 Japan to make history as the first country to Beam Solar Power from Space to Earth

The Sun never sets in space and Japan has found a way to harness this unlimited energy. Forget rooftop panels, Japan is ready to take solar power to space. The country is gearing up to test its space-based solar power station, which is designed to beam power back to Earth. The project, dubbed OHISAMA, is named after the Japanese word for ‘sun’. And while it won’t be powering cities just yet, it’s an exciting leap towards clean, round-the-clock energy straight from orbit. Following are the some of the important points:-  

Japan’s OHISAMA project will beam solar power from space to Earth

This demonstration paves the way for future orbital solar stations               

A small satellite will wirelessly transmit 1 kilowatt of energy

The energy beamed from space won’t be enough to run more than a coffee maker, but if all goes according to plan, Japan will soon make history by transmitting solar power wirelessly from orbit to Earth. This year, a 400-pound satellite will launch into low Earth orbit and attempt something that once seemed confined to science fiction. Using solar panels and microwave transmission, the satellite will send about one kilowatt of power, roughly enough to run a dishwasher for an hour, down to a ground antenna. The solar power will be converted into microwaves. Koichi Ijichi, and adviser at Japan Space Systems, laid out the details of the project at the International Conference on Energy from Space, held in London in April 2024. The test spacecraft will be compact, weighing just 400 pounds. Using a 22-square-foot solar panel, it will collect sunlight in orbit and store the energy in an on-board battery. Because spacecraft travel very quickly, at speeds close to 17,400mph, the antennas on Earth have to be spread out over 25 miles. The antennas also have to be strategically placed at a distance of three miles from each other to receive the energy, which will be transmitted via microwaves.

“It will be a small satellite, about 180 kilograms [400 pounds], that will transmit about 1 kilowatt of power from an altitude of 400 kilometers,” Koichi Ijichi, one of the researchers and an advisor at Japan Space Systems (JSS), said. The project, called OHISAMA, is part of a growing international push to harness solar power from space as a means to reduce dependence on fossil fuels and help curb climate change. Space solar farms can produce energy all day. It may seem too futuristic to be true, and that is because the project is still in its infancy. The satellite is only projected to transmit about 1 kilowatt of power from an altitude of 250 miles. This translates to having enough energy to run a small household appliance, like a dishwasher, for an hour. Clearly, this is not sufficient for commercial use, yet the Japanese researchers are hopeful that the test will be a step forward. Still, Japan has been testing this technology for years, and they’ve had good results thus far.

The idea of collecting solar power in space and beaming it to Earth was first floated in 1968 by Peter Glaser, a scientist working on the Apollo program. At the time, it seemed outlandish. The costs were too high. The required structures, too massive. The engineering challenges, too daunting. But things have changed. Advances in robotics, wireless transmission, and orbital logistics, particularly the promise of SpaceX’s Starship rocket, are starting to make the once-impossible look feasible. The JSS satellite will be equipped with a 22-square-foot (2 square meters) solar panel. This photovoltaic panel will collect sunlight and charge an on-board battery. The crucial part is how this stored energy will be sent back down to us. In the case of a regular solar panel, the collected energy is turned into electricity and is transmitted via wires. However, supplying solar energy from space to Earth through wires is not feasible. So the satellite will convert the electricity into microwaves and send it wirelessly in the form of an energy beam to a specially designed receiving antenna on the ground. 

In 2015, they wirelessly transmitted 1.8 kilowatts of power over 55 meters, while later tests managed to send 10 kilowatts over 500 meters. Japan hopes to one day launch huge solar power satellites into geostationary orbit, each capable of producing up to one gigawatt of clean energy. A gigawatt translates to one million kilowatts, which is certainly a big step up. This would power hundreds of thousands homes, and be a game changer for disaster zones, remote areas or any place where reliable electricity is hard to come by. Moreover, since the satellite will be traveling at an incredible speed of about 17,400 miles per hour (28,000 km's per hour, the typical speed of satellites in low Earth orbit), the receiving antenna on Earth will need to be quite large, potentially stretching across several km's. However, for now, such large antennas are not required because the satellite will currently serve as proof of concept. Thirteen receivers spread over a 600-square-meter area in Suwa (a city in Japan) will capture microwaves sent from its energy panels and convert them into electricity. The best part about space solar panels is that they can collect energy day and night, regardless of weather conditions, unlike Earth-based solar farms. While it’s still early days, and challenges remain, Japan’s OHISAMA project is proving that the future of clean energy might just be out of this world.

If this demonstration is successful, the Japanese agencies will launch bigger satellites capable of transmitting much more solar energy. Japan isn’t alone in exploring the potential of space-based solar power. The US has also been actively researching this area. For instance, in May 2020, the US Naval Research Laboratory (NRL) conducted a significant experiment called the Photovoltaic Radiofrequency Antenna Module (PRAM). This experiment resulted in the launch of the X-37B Orbital Test Vehicle, which, for the first time, successfully demonstrated the key technology of converting sunlight into microwave energy in space and wirelessly transmitting it back to Earth. Then, in March 2023, researchers at Caltech launched a space-based prototype called MAPLE (Microwave Array for Power-transfer Low-orbit Experiment). It offers a lightweight and low-cost approach to supply solar energy from space to a desired location on Earth. Not everyone is convinced the dream can become reality. In January, NASA released a report casting doubt on the feasibility of space-based solar power. The agency estimated that such systems could cost as much as 61 cents per kilowatt-hour. That’s over ten times more expensive than the cheapest Earth-based solar or wind energy, which can cost as little as 5 cents per kilowatt-hour. Whether the mission will successfully achieve this goal remains to be seen. JSS and its partners haven’t yet announced an exact launch date, but in their latest statements, they confirmed the mission is scheduled in the near future this year.