Space-based solar power technically has the potential to provide near limitless renewable energy and to direct it almost instantly to where it is needed at any given time. The space-based solar concept involves power being generated by an orbiting solar power station. This could use either photovoltaic panels or a concentrated solar plant that focuses the sun onto a boiler to drive a steam turbine. The power would then be beamed to receiving stations on earth using microwaves or laser beams. The receiving stations would be connected to local power distribution grids. A network of satellites could beam energy anywhere on Earth, directing power where it is needed.
The problem is that the cost of building space-based solar power stations has been estimated to be 1,000s of times more than the cost of current earth-based renewable power installations. The main reason for the high cost is that a commercial power station weights 1,000s of tons. It either has to be launched into orbit or the materials have to be mined in space, with the materials processing and all manufacturing carried out in orbit. Until recently, this has all looked ridiculously expensive compared to just building a solar array on the land. However, with companies like SpaceX rapidly bringing down launch costs and developments in lightweight photovoltaics, space-based solar is starting to look more feasible.
A number of governments and corporations around the world are now predicting that space-based solar will become a commercial reality within the next few decades. That makes active research and development necessary today to be part of this emerging industry. The announcement by China of a roadmap to a commercial power plant is an exciting development.
History of Space-based Solar Power
The concept of a satellite beaming energy back to Earth was originated by Asimov in his 1941 short story Reason. A more futuristic version of this was actually described earlier by Olaf Stapledon in his 1937 novel Star Maker, which envisaged, “every solar system... surrounded by a gauze of light traps, which focused the escaping solar energy for intelligent use.” In 1960 the physicist Freeman Dyson published a paper arguing that a technological civilization would inevitably construct such a structure around their star. Such structures, now referred to as Dyson spheres, are considered something we might look for to identify advanced civilizations in space.
The first technical paper describing how we might achieve space-based solar power was published by Peter Glaser in 1968. Feasibility studies were then carried out by NASA in the 1970s, with a number of technical reports setting out what could be achieved. Both photovoltaics and concentrated solar plants were considered, as well as microwave or laser power transmission. The most ambitious proposals involved capturing an asteroid near Earth into Earth’s orbit and mining it to create a massive solar power station. One such asteroid could provide many times more electrical power than all the power stations on Earth.
Current Major Players
Japan passed its Basic Space Law in 2008, which makes achieving space-based solar power a national goal. Initially, small demonstration satellites will be launched and then a commercial 1-gigawatt station by 2030. Japan Aerospace Exploration Agency (JAXA) is developing a number of solar-collecting satellite designs, all intended to be placed in geosynchronous orbit at an altitude of 36,000km. A satellite with a fixed photovoltaic panel would not always be pointing at the sun. JAXA is therefore investigating a concept with multiple mirror satellites focusing sunlight from different directions onto a central photovoltaic satellite. It intends to use a pilot signal from the Earth station to allow the satellite to aim as the receiving station. In 2015, JAXA made an initial demonstration of its microwave transmission technology, sending 1.8 kilowatts over a distance of 55m.
A number of different groups are working on space-based solar in the U.S. The U.S. Naval Research Lab (NRL) is researching modular solar and transmitter units for space deployment but have no plans for a full-scale demonstration. Caltech is also developing an ultralight module able to collect solar power and wirelessly transmit it. This is currently less than 1kg/m2 and incorporates beam steering. Solaren is a California-based startup that plans to launch a 200 megawatt space based power station in the mid-2020s.
China’s Roadmap to Commercial Space Based Solar
Chongqing University, the China Academy of Space Technology and Xidian University will collaborate at a new test facility being built on a 13.3 hectare site in Chongqing's Bishan district. Projected to be completed in two years, the research center will investigate a number of issues related to space-based solar.
At the initial test facility, microwave power transmission technologies will be developed and tested. The effects of the microwave beams on plants and animals will also be tested. Four to six tethered balloons will be used to carry solar panels to an initial height of 1,000m and then beam the energy back to the ground. This would already be a significant improvement of the 100m that the researchers involved have currently beamed energy.
The next stage will see balloons deployed to the edge of space to fully demonstrate the feasibility of beaming power to earth from satellites. Construction of a small- to medium-sized power station using this principle to place a solar array in the stratosphere is planned to take place between 2021 and 2025.
The next stage of the project would be a megawatt power station orbiting at an altitude of 36,000km. Construction is scheduled to begin in 2030 with a launch before 2040. The station would be positioned to provide power 99 percent of the time.
Finally, a gigawatt commercial space based solar power station would be launched by 2050, supplying power to earth and beaming it to spacecraft for deep-space exploration.