Space-based electric power – a viable option?

By Björn Carstens
Solar power systems do not produce energy at night, so it would be better to install them where the Sun “shines” with high intensity for 24 hours. That would only be the case in space. Solar energy from Earth’s orbit – a feasible vision or science fiction?
© European SPS Tower concept

In Earth’s orbit the Sun always shines – providing perfect conditions for a solar power station to constantly produce consistent amounts of energy. Motivated by that idea, scientists at the European Space Agency (ESA) had the feasibility of such a mammoth project investigated in recent studies. Putting the outcome in a nutshell: the technology would have huge potential, but there are some high hurdles. Here’s a synopsis:

What the project is about:

  • To achieve the targeted climate neutrality and net-zero greenhouse emissions in Europe by 2050, it is worth focusing on alternative solutions in the field of renewable energies. ESA’s Solaris project – a program for space-based solar energy – might be such a solution.
  • According to the results of recent studies, 20 satellites equipped with solar panels might put an end to Europe’s dependency on import energy. Each panel, says ESA, would have to have a size of 15 square kilometers (5.8 square miles) equating to roughly 200 soccer fields. With those dimensions, one of these stations could produce one to two gigawatts of electricity, like a nuclear powerplant on Earth.
  • An analysis by Frazer-Nash, one of the consultancies commissioned to study the project, revealed that by means of space-based solar power stations 800 terawatt-hours of clean energy could be harvested starting in 2050. That would amount to around one third of the European Union’s power production in 2020.
  • Frazer-Nash calculated a financial benefit of 601 billion euros from the sale of the energy by 2070 versus costs of 418 billion euros.
  • In addition, the Frazer-Nash study found that space-based solar energy could displace fossil energy sources, as well as some of the nuclear energy, from the European energy mix.
Space-based electric power – a viable option?
Leopold Summerer, Head of ESA’s Advanced Concepts team
© ESA - SJM Photography

“To make a major contribution to achieving the net-zero goal for the energy sector by 2050, the technology would have to be demonstrated on a sufficiently large scale in space by the end of the 2030s.”

The technology behind it:

  • Using high-frequency radio waves, the energy generated in space is supposed to be transferred to large receiving antennas on Earth and fed into the local grid as electric power.
  • The energy distribution from the solar power station in Earth’s orbit to the powerplants on Earth’s surface is based on a phase-controlled microwave frequency beam, explains Leopold Summerer, Head of ESA’s Advanced Concepts team.
  • Microwaves in a column with a diameter of about two to three kilometers (1.2 to 1.9 miles) hit an antenna with similar dimensions on Earth’s surface.
  • Ultralight solar cells developed in recent years are regarded as a key technology for this form of wireless energy transfer.
  • Due to the evolutions achieved in space robotics, the panel of experts is confident that huge in-orbit solar systems are feasible. In-orbit robots would have to assemble them from single components.
To prepare Europe for future decision-making on space-based solar energy, ESA has proposed a program named SOLARIS for the next meeting of ESA’s Ministerial Council in November 2022. At that time, the council is supposed to discuss if the ESA member states would support such a complex and costly program.

These are the hurdles:

  • The project entails massive costs and complexity of several hundred million euros to mature its technical feasibility, according to ESA. For instance, it would require a reusable heavy-lift rocket lifting off more than once a week to haul components into orbit. However, ESA has not yet deployed such a rocket.
  • The spatial requirements in orbit and on Earth would pose another problem. Any terrestrial station to which the electric power could be transferred would have to have a size of about 70 square kilometers (27 square miles), according to the study, roughly covering the area of a small town. However, a parallel use for agricultural purposes might be feasible.
  • Solar panels the size of 200 soccer fields are exposed to a high risk of being hit by space debris. According to ESA, more than 32,000 space debris objects are currently orbiting the Earth.
  • To what extent the project is truly environmentally friendly or conserves resources remains largely unclear.
Space-based electric power – a viable option?
This ESA infographic shows how the space-based energy beam is supposed to be captured using photovoltaic cells or an antenna© ESA
Not a new concept

The idea of a wireless transfer of space-based solar energy is not exclusive to ESA. The concept has been investigated, for instance, in the United States as well as in the United Kingdom, China and Japan for years. The feasibility of such an endeavor increases with each technological evolution. A US research team is planning to test the prototype of a satellite in orbit. Researchers have also already achieved a wireless transfer of electric power across several kilometers or miles. However, that’s not enough yet to cover the distance between outer space and Earth.