Could a Swarm of Space Mirrors Replace Much of Europe’s Solar and Wind by 2050?

The idea of beaming solar power down from space might sound like science fiction, but it’s being taken seriously by a growing number of governments. A new analysis shows it could significantly lower the cost of Europe’s 2050 net zero commitment.

Space-based solar power was first conceived in 1968 but largely remained on the fringes of energy policy discussions. However, as countries around the world committed to rapidly reducing greenhouse gas emissions, the idea started to gain traction.

Space agencies in the US, Europe, Japan, and China are now actively developing and testing space-based solar power concepts. But the technology is still nascent and extremely expensive, which raises serious questions about whether it could truly contribute to net zero goals.

A new analysis in Joule takes a stab at predicting whether the technology could play a role in the energy transition, based on current projections. The researchers found that two designs currently under development at NASA could potentially help. They might, according to the paper, even reduce the cost of achieving a carbon-free grid in Europe by 2050 by 7 to 15 percent.

“This is the first paper to put space-based solar power into the energy system transition framework,” senior author Wei He, at King’s College London, said in a press release. “We’re currently at a stage to transfer this blue-sky idea into testing at a large scale, and to begin discussing regulation and policymaking.”

The European Union has committed to reducing overall carbon emissions to net zero by 2050, which would mean replacing almost all fossil fuel energy production with low-carbon sources such as wind, solar, and nuclear power.

This will require significant changes to the grid, most notably massive increases in energy storage capacity to cope with the intermittent nature of renewables. Space-based solar could potentially simplify things, because it would provide power around the clock.

“In space, you potentially have the ability to position solar panels to always face the sun, which means power generation can be nearly continuous compared to the daily pattern on Earth,” says He. “And, because it’s in space, the solar radiation is higher than on the Earth’s surface.”

The new study considered two designs currently under development at NASA that are at varying levels of sophistication and technological readiness. The first, known as a planar array, is essentially a large satellite with solar panels on one side and equipment to beam power down to Earth in the form of microwaves on the other. The second is a more advanced design known as a heliostat swarm. This approach features a group of steerable reflectors that redirect sunlight to a central collector that then beams it down to Earth.

The first design is significantly more mature, the authors note, and so could likely be deployed sooner. However, because the transmitting face has to point towards the Earth it can’t always maintain the best angle for collecting sunlight. That means that over the course of a year, it’s only able to generate power 60 percent of the time.

In contrast, the heliostat can move its mirrors to maintain optimal sunlight collection at nearly all times. But the design is much further from real-world realization, the authors write, and building it would require huge advances in our ability to autonomously construct arrays in orbit using robots.

However, despite their embryonic states of development, NASA has forecasts for how much each of these technologies is likely to cost out to 2050. The researchers compared these projections against forecasts for renewable energy costs over similar time frames.

They found that space-based solar would become commercially viable if costs dropped below 14 times the projected 2050 cost for solar power. If costs dropped below 9 times that amount it could potentially provide almost all of Europe’s required power. This is because, despite the still-high price tag, these satellites could beam power anywhere on the continent almost around the clock, translating to big savings on transmission and energy storage infrastructure.

Based on NASA’s cost projections, the researchers found that the heliostat design could reduce total energy system costs by 7 to 15 percent by 2050, replace up to 80 percent of Earth-bound wind and solar installations, and reduce battery usage by over 70 percent. Some long-term hydrogen storage may still be required to tide the continent over during the winter months though.

The planar design would not be economical, but the researchers said its higher maturity level means it should still be pursued as a technology demonstrator that could help prove out the concept.

The authors note that regulatory challenges and public acceptance may present significant hurdles. Satellites that beam high-power microwaves down to Earth come with considerable safety concerns and the receiver stations may need to be enormous—on the order of several square kilometers.

Still, this study is one of the first to provide a concrete analysis of the technology’s potential to help fight climate change. And given the scale of the challenge we currently face, we could do with as many options as possible.