The future of clean energy was the subject of a show by engineers at the European firm. They used solar panels, microwaves, and electricity to turn sunlight into microwaves, light up a model of a city, and transform it into microwaves. Is it time to resurrect a scheme long derided as science fiction and launch giant satellites to collect solar energy in space? They could generate power from clouds and nighttime and send it down to Earth.
Jean-Dominique Coste says that the problem is an engineering one. It hasn't been done at a large scale.
Proponents of space solar power believe that the need for green energy, cheaper access to space, and improvements in technology could change that. Someone will make a commercial investment and it will bloom. It could be a trillion-dollar industry according to a former NASA researcher.
Billions of dollars are likely to be invested in the future, but there are still many questions about whether power down to the planet can be done efficiently. The idea is moving from concept papers to a lot of tests on the ground. Next month, the European Space Agency will propose a program of ground experiments to assess the viability of the scheme. Up to £6 million in grants was offered by the U.K. government. The Chinese, Japanese, South Korean, and U.S. agencies are all working on small projects. According to the author of an assessment NASA plans to release in the coming weeks, the tone of the discussion has changed. Karen Jones says that it may now be a matter of pulling it all together and making it work.
The idea of space solar power was investigated by NASA. A proposed space demonstration mission would have cost $1 trillion. Mankins said that the idea was off the table and that many at the agency still don't want to talk about it.
Both space and solar power have changed in recent years. The efficiency of photovoltaic solar cells has increased over the past decade. The telecoms industry uses microwave transmitters and receiver. The development of robots to repair and refuel satellites could lead to the creation of giant solar array.
Falling launch costs have boosted the idea. It will take hundreds of launches to build a solar power satellite large enough to replace a typical nuclear or coal powered station. It would need a large-scale construction site in the middle of the universe.
The idea has been made more plausible by the private space company. The price of a Falcon 9 rocket is $2600 per kilogram, less than 5% of what it costs on the Space Shuttle, and the company promises rates of just $10 per kilogram on its gigantic Starship. Jones said it was changing the equation. It's all about economics.
The cost of space hardware is being reduced. Satellites are usually built with high-priced components. The Perseverance rover costs $2 million per kilogram. Starlink can be made for less than a thousand dollars per kilogram. Mankins has long argued that the approach could work for giant space structures made of many low-cost components. The economics of space solar power become obvious when combined with low-cost launches.
The economics could be more favorable with better engineering. Coste says that the demo in Germany was 5% efficient and compared the input of solar energy with the output of electricity. When the Sun shines ground-based solar panels do a better job. Recent studies show that space solar could compete with existing energy sources on price.
The cost calculus will be improved by lower weight parts. There are pizza box–size devices with photovoltaic cells on one side, electronics in the middle, and a microwave transmitter on the other. If you put thousands of these together like a tiled floor, they will form the basis of a space solar satellite. Researchers have been testing prototypes on the ground for a long time, but in 2020 a team at the U.S. Naval Research Laboratory got its aboard the Air Force's X-37B experimental space plane.
The leader of the project says that it is still in the air. The panel does not send microwaves to Earth. The Air Force will be testing a sandwich panel next year. The prototype panel will be launched by the California Institute of Technology.
The disadvantages of sandwich panels are that the microwave side must always face toward Earth and that the photovoltaic side can turn away from the Sun. Mirrors can be used to illuminate the side of the satellite that has a power source. A 2012 NASA study by Mankins proposed a design in which a bowl-shaped structure with thousands of individually steerable thin-film mirrors directed light onto the photovoltaic array.
Ian Cash is the Managing Director of the International Electric Company. The whole structure rotates to keep the mirrors pointing sunward as he proposes a satellite. The power from the cells is converted to microwaves and fed to 1 billion small antennas, which act as a "phased array" to steer the beam towards Earth. Cash says that this design makes it the most competitive economically.
Power generated from a space station will need to get to the ground safely and efficiently. Teams in Japan, China, and South Korea have similar efforts after a recent ground-based test. Current transmitters and receiver have less input power. Vijendran says that space solar needs at least 80% efficiency.
Testing is needed for the safety of gigawatts through the atmosphere. Most designs aim to produce a beam kilometers wide so that any spaceship, plane, person, or bird that strays into it only receives a small portion of the 2 gigawatt transmission. Jones says that receiving antennas need a lot of real estate because they are cheap to build.
Europe is where public agencies are most focused on space solar power. There is a commitment that you don't see in the U.S. Two cost/benefit studies of space solar were done last year. Vijendran says they found it could match ground-based renewable sources on cost. It's around the clock availability would make it competitive even at a higher price.
The technical hurdles will be assessed in November by the member states. Plans for a full effort will be laid out if the news is positive. Vijendran says that the European Space Agency can put a megawatt-scale demonstration facility in space by 2030. It is like a moon shot.
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