Space-based solar power could eventually prove to be an alternative source of electricity for Japan, as the country struggles to find the best energy mix to lessen its dependence on thermal and nuclear power.
The Japan Aerospace Exploration Agency (JAXA) has been conducting studies in the hopes of erecting huge solar panels in space to generate electricity in the near future.
The basic idea is simple: Build a solar power station in geostationary orbit to gather sunlight; convert the energy to solar electricity, and then direct it via microwaves or laser beams to receiving antennas on Earth.
The Space Solar Power System (SSPS) would be able to collect the same amount of solar energy almost 24 hours a day, since it would not be affected by the weather. It could generate five to 10 times more power compared to solar power operations on Earth, JAXA says.
One SSPS with a 2.5 km by 2.3 km panel would have the capacity to generate 1 gigawatt of electricity, the agency says, which is about the same as a nuclear power plant.
For a country with few natural resources, an SSPS sounds like it would be a dream come true, and currently Japan is leading the world in research on space-based solar power.
Making the program into a reality, however, won’t be an easy job, as the agency still needs to overcome many hurdles.
“This is a grand project. I think we will be facing more unclear issues as we proceed,” Tatsuhito Fujita, an associate senior engineer at JAXA’s Aerospace Research and Development Directorate in Tsukuba, Ibaraki Prefecture, told The Japan Times in a recent interview.
JAXA is currently focused on developing the technologies to build a huge structure in space, and on ways to transmit energy to Earth by microwaves or laser beams.
The agency is also studying a system to fold solar panels into a rocket and have then unfold in space as one large panel, Fujita said.
Technology to accurately send microwaves or lasers over long distances is also crucial, because the SSPS would be located some 36,000 km above Earth-based receiving antennae.
If the angle of the sending beam were off by just one degree, it could result in a difference of 600 km on the ground, Fujita said.
“We must transmit the energy accurately to a pinpointed area. So we need a system that can control beams to the 0.0000- something degree,” Fujita said.
JAXA initially aimed to conduct space-based demonstration experiments in fiscal 2017, and start commercial use sometime in the 2030s. But that schedule is looking increasingly unrealistic, and Fujita said JAXA is planning to come up with a new time frame within the next few years.
Another huge issue is cost, Fujita said. JAXA initially estimated ¥1 trillion for the total expenditure to build the SSPS, but he admitted that it is a very ambitious goal.
The 2.5 km by 2.3 km panel with a solar array and microwave generator that JAXA is currently studying would be about 750 times the size of the International Space Station — the largest structural object currently orbiting Earth — and would weigh about 26,600 tons.
It would also require a great many trips between Earth and space to transport all the components necessary to build the SSPS, he said.
“It now costs about ¥10 billion to launch an H2A or H2B rocket, for example. If we are to launch it (to carry materials) for construction of SSPS . . . it would be a gigantic number,” Fujita said, adding that electricity bills using power produced in this way will be way more expensive than current ones.
If JAXA adopts laser beams to transmit solar energy from space to Earth, the size of the SSPS could be smaller, he said. But while microwaves can be transmitted under any weather conditions, laser beams cannot penetrate clouds, he said.
“We are targeting to provide (electricity with) a price that every one can use,” Fujita said.
But to do that, they need to find ways to reduce the massive costs, such as developing cheaper transportation systems to space, he said.
The safety of microwaves — which are used in mobile phones — also needs to be examined. Although they are generally considered safe, their impact on the environment and on people’s health need to be fully studied, he said.
Despite all the difficulties, if JAXA is successful, SSPS could be one of Japan’s core energy sources in the future. Moreover, the country in principle export the solar energy from space, transmit it to any place with a receiving antenna.
If it can develop a much cheaper transportation system to space, the agency could also boost space-related businesses such as space travel, Fujita said.
If JAXA succeeds in commercializing the SSPS, it would have a “huge impact” on energy development, he said.
“I’ve been doing this research for nearly nine years. Back then, nobody really paid much attention to this project,” Fujita said.
But the project has been garnering more attention since the 2011 triple meltdown at the Fukushima No. 1 nuclear power plant, he said.
“It’s great that more people recognize the project now. But there are still lots of issues,” Fujita said. “We hope to come up with technologies that many people can use.”