Japanese company has plan to harvest energy from moon-based solar plant
China's Jade Rabbit rover may have renewed humanity's acquaintance with the moon, but it's a Japanese company that has the biggest plans for our permanent satellite. Its proposal, called "Luna Ring", envisions the construction of a gigantic solar power plant on the moon, with a belt of solar cells around its equator harvesting energy to transmit to earth as microwaves and lasers.
Will the project see the light of day? As solar energy becomes more critical and more common, situating a solar generation plant away from earth's surface makes sense; earth-based solar power plants can only produce energy during daylight hours, and are all susceptible to cloud cover. Since the moon doesn't have an atmosphere, it isn't cloudy and doesn't deflect the sun's energy. Yes, there are a couple of total lunar eclipses each year when the sun doesn't shine on the moon at all, but that doesn't change the fact that solar power generation would theoretically be five times more efficient on the moon than it is on earth.
The driving force behind construction company Shimizu's lunar ambitions is, of course, a desire for unlimited clean energy. The way it works is ingenious. The first step is to construct a massive belt of solar panels a few kilometres wide around the moon's 11,000-kilometre-long equator, but instead of transporting millions of tonnes of building materials up there, Shimizu's plan is to use the powdery material found on the moon itself. This so-called regolith can be mixed with hydrogen to make water, which in turn can be mixed with more lunar soil and gravel from earth to manufacture everything from concrete to ceramics. They also claim that solar-heat treatments would allow the manufacture of glass and solar cells.
Such a project would require a major reliance on robots. "Robots will play a vital role on the lunar surface," reads the matter-of-fact brochure, "tele-operated 24 hours a day from earth." Although the robots will level the ground to ready for the installation of the solar panels - and assemble machines and other equipment in space before landing them on the moon - human astronauts will acts as overseers on the surface. Eventually the solar belt could extend to 400 kilometres wide. Shimizu has said that building could begin in 2035.
However, it's how Shimizu plans to beam back the energy that's truly awesome. Antennas some 20 metres high will use high-density lasers to transmit radio-guided solar power to a receiver on earth, probably out at sea, that could convert them back into direct current and straight into a power grid.
Such an idea recalls the space solar power "Sun Tower" concept studied by Nasa at various times in the past 40 years. Although that idea relied upon multiple satellites - or "solar birds" - covered in solar panels, it also involved wirelessly transmitting power to an earth-based power station through microwave transmitters or lasers.