Dusseldorf In space, the sun shines 24 hours a day, seven days a week. There is no sunset in space. And the sunlight is ten times more intense than on Earth. This always available, inexhaustible source of energy could be the solution to one of the biggest renewable energy problems on earth. So-called space-based solar energy is still little more than an idea on paper.
Scientists at the European Space Agency (ESA) want to change that now. The project, appropriately named “Solaris” (from the sun), was given the green light in November last year. With a budget of 60 million euros, the researchers now have three years to test whether full development of space-based solar energy is really worthwhile.
“The technology has been around for decades. It is theoretically possible. We now want to find out whether it is practically possible and cost-effective,” says ESA Director Josef Aschbacher.
The idea of a base load capable, always available green energy in times of climate change is meanwhile an interesting research object for many countries. The UK, US, Japan, Australia, South Korea and China all want sunlight that can be harvested 24/7.
Because as sustainable as wind and solar energy are, the generation of electricity with the eco-systems is just as weather-dependent. Electricity is only available when the wind is blowing or the sun is shining. And she only does that here on earth for a few hours a day. Completely different than in space.
If the idea of space-based solar energy becomes more than just a theory, 800 terawatt hours of green space energy could theoretically be generated annually from 2050 onwards. This is the finding of a study by the consulting firm Frazer-Nash on behalf of the British government.
For comparison: The European Union consumed just over 3000 terawatt hours in 2020. Solar energy from space could therefore cover around a third of current electricity requirements and squeeze fossil fuels out of the European mix. But there is still a long way to go until then.
transport in microwaves
Although the technology behind it is surprisingly simple: the energy would literally be “beamed” to earth. Thousands of high-performance solar cells would capture the sun’s energy 35,000 kilometers from Earth. The electrons would then be converted into microwave radiation so that the energy could be sent wirelessly to Earth. There, a field of antennas would pick up the microwaves. Then the radiation would have to be converted back into electricity, which could eventually be fed into the grid and thus to the socket. At least that’s the idea.
“This requires an infrastructure several kilometers long that has to be screwed together and assembled in space,” explains Aschbacher. Experts estimate that for one to two gigawatts of electricity, which roughly corresponds to the output of a nuclear power plant, an area of almost 15 square kilometers would be needed in space, about the size of 2,000 soccer fields. The solar modules alone would spread to about four square kilometers. The cost of materials would be immense.
Nevertheless, the first tests with significantly smaller solar tiles have already been started. However, in the US. The California Institute of Technology (CalTech) from the USA sent a small spacecraft into orbit in January. Also on board was the so-called Space Solar Demonstrator (SSPD).
In space, the device, which weighs around 50 kilograms, is supposed to arrange several PV modules, which only then unfold like a kind of solar sail. 32 different solar cell types are on board to test which are particularly effective and stable in space. They should capture the energy and send it bundled over a distance in orbit.
According to the CalTech researchers, the system is already working on Earth: “There are still many risks, but after going through the entire process, we have learned valuable lessons. We believe that the space experiments will now provide us with a lot of additional information,” says Ali Hajimiri, one of the senior directors for the project. For him, the experiment is a giant step. Even if there are still a lot of hurdles.
Solar systems in space are bulky and expensive
Solar panels are bulky and heavy, making them expensive to ship into space. They also require extensive wiring to transmit power. This will require new architectures, materials, and structures for a system capable of making solar power practical in space, while being light enough to be inexpensive for mass deployment and strong enough to withstand the harsh space environment.
The huge solar systems then have to be assembled in space by robots that don’t yet exist. Above all, the technology of wireless energy transmission that works on Earth has yet to be tested on the much longer distance through space.
However, there has already been a successful attempt on terrestrial soil. Last year, Esa and the European aviation company Airbus presented a first test together with the New Zealand start-up Emrod.
>> Also read: This is how you get the best out of your solar system
Near Munich, the 2.5 kilowatts of power from a solar panel were converted into microwaves and transmitted over a distance of 36 meters in the form of a microwave beam using a transmitter. The microwaves were converted back into electrical power and used to light a model city, build a refrigerator and produce green hydrogen using a small electrolyser.
The efficiency losses during the conversion were surprisingly limited, says energy expert Martin Hoyer from the consulting firm Roland Berger. A loss of just 30 to 50 percent would be expected when converting electricity to microwaves and then back to electricity.
However, significant advances in several conversion technologies are still needed to achieve the required level of efficiency. While these advances are theoretically possible, they have yet to be demonstrated through actual hardware development and testing.
“One challenge is the upscaling and efficiency of the technology. The other is building the structure in space,” explains Hoyer. These are the two most research-intensive fields.
Two gigawatts of capacity cost over ten billion euros
Hoyer led the feasibility study on solar energy from space at Roland Berger on behalf of Esa. The result: “Although many of the building blocks are based on existing or emerging technologies for space and ground applications, significant developments are still required to enable such a system,” the authors write.
Above all, the question of cost is an important point. For a capacity of two gigawatts, Hoyer expects costs of over ten billion euros. This is perhaps less than one might have assumed, but it would still mean system costs of between 70 and 250 euros per megawatt hour. For comparison: the same amount of electricity cost between 25 and 50 euros until the crisis year 2022.
“The key to feasibility is weight. The tons determine the costs,” explains Hoyer. What is meant are the tons of raw materials that are needed to build the necessary facilities on earth, but above all in space in the first place. Up to 4000 tons of photovoltaic modules alone could be necessary. Depending on how efficient they are and how cheap or expensive the rocket launches are to bring the modules into space, the costs can vary greatly depending on the weight.
>> Also read: “We had to pull the emergency brake”: Why the new German solar boom is faltering
The fact that more and more countries are currently dealing with space-based solar energy is mainly due to the fact that the overall costs for such a project have already fallen significantly in recent decades. And through private companies like SpaceX, founded by Elon Musk. Numerous rocket launches are required to bring the material into orbit. And they were significantly more expensive 15 years ago than they are today. More efficient rocket launches are suddenly making solar energy from space more than just fiction.
The British government is already investing the equivalent of around 19 billion euros in this. Over 60 technology companies are already part of the UK Space Energy Initiative, including heavyweights such as aerospace group Airbus, the University of Cambridge and satellite manufacturer SSTL. They are convinced that solar energy can be beamed down to earth from space.
However, experts do not expect the first pilot projects to start before 2040. Even if the research is successful, Esa director Aschbacher believes that it could be at least another 15 years before the first all-based solar energy arrives on earth.
Many rocket launches are needed to get the equipment into orbit. If the fuel conversion to green hydrogen succeeds in the 2030s, “we would at least be largely climate-neutral here”.
Then structures would have to be set up in orbit, similar to what happened at the International Space Station ISS. And then the power plant needs to be installed and turned on. “But imagine, it really works. That would be phenomenal,” enthuses the researcher.
series “These green ideas could change the world“: From wave power plants, carbon-free cement and solar panels in space to energy-giving species of algae, there are ideas with the potential to change the world. Only a few make the breakthrough. We present some of the most interesting innovations. The series is scientifically supported by the independent think tank Future Cleantech Architects.
More: Artificial Intelligence: “I speak, therefore I think…”