Space as a Source of Solar Energy?

The concept of solar panels beaming down energy from space has long been discussed and considered before but did not materialize and push through due to the cost and practicality. Many scientists and researchers dropped the idea as this for them is “unachievable” in the future – not in Japan. The seemingly unimaginable and unattainable thing to happen in the future has found its place due to the longing solution for global energy crises and concerns about the environment.

Just like with the recent series of Japanese based anime Mobile Suit, the depletion of fossil fuels has forced humanity to turn to space-based solar power generation as global conflicts rage over energy shortages. The sci-fi saga is set in the year 2307, but even now real Japanese scientists are working on the hardware needed to realize orbital generators as a form of clean, renewable energy, with plans to complete a prototype in about 20 years (source: Farming Solar Energy in Space article).

Japanese researchers recently produced up to 180 watts of laser power from sunlight. They began ground tests of a power transmission system designed to send energy in microwave form to Earth. The laser and microwave research projects are two halves of a bold plan for a space solar power system (SSPS) under the aegis of Japan’s space agency, the Japan Aerospace Exploration Agency (JAXA). Specifically, by 2030 the agency aims to put into geostationary orbit a solar-power generator that will transmit one gigawatt of energy to Earth, equivalent to the output of a large nuclear power plant. The energy would be sent to the surface in microwave or laser form, where it would be converted into electricity for commercial power grids or stored in the form of hydrogen (source: Farming Solar Energy in Space article).

According to Hiroaki Suzuki of JAXA’s Advanced Mission Research Center, they are doing this in preparation for finding solutions to the challenges posed by exhaustion of fossil fuels and global warming. JAXA says its potential advantages are straightforward: in space, solar irradiance is 5-10 times as strong as on the ground, so generation is more efficient; solar energy could be collected 24 hours a day; and weather would not pose a problem. The system would also be clean, generating no pollution or waste, and safe. The intensity of energy reaching Earth’s surface might be about five kilowatts per square meter—about five times that of the sun at noon on a clear summer day at mid-latitudes. Although the scientists say this amount will not harm the human body, the receiving area would nonetheless be cordoned off and situated at sea (source: Farming Solar Energy in Space article).

At a facility in Miyagi, Suzuki and JAXA researchers are testing an 800-watt optical-fiber laser that fires at a receiving station 500 meters away. A mirror reflecting only 1,064-nanometer-wavelength light directs it into an experimental solar panel. (He chose that frequency of light because it easily cuts through Earth’s atmosphere, losing no more than 10 percent of its pop.) A key task will be finding a material that can convert sunlight into laser light efficiently. A leading candidate is an yttrium-aluminum-garnet ceramic material containing neodymium and chromium (source: Farming Solar Energy in Space article).

The challenges are more than just the basic science that they have started doing. There are a lot more tests to be done that requires big structures in space: thin-film condenser mirrors, solar panels and a microwave transmitter stretching for kilometres and weighing 10,000 metric tons, as well as a 100-unit laser array of 5,000 metric tons that would be 10 kilometres long. The ground-based microwave antenna would have to be two kilometres long. So the big question is, are we ready for that big change? For that big challenge? If Japan, is trying out their best to find alternative ways and help preserve our planet Earth, we can also find simple ways in contributing to that and be open to changes when that happens.