Beaming solar power to Earth: feasible or fantasy?

It’s always interesting when we are presented with very different and knowledgeable perspectives about the feasibility of a proposed technological advance. I recently had this experience when I saw two sets of articles about the same highly advanced concept within a short time window, but with completely different assessments of their viability.

In this case, the concept is simple and has been around for a long time in science fiction and speculative stories: capture gigawatts of solar energy using orbiting structures (I hesitate to call them satellites) and then beam that energy down to Earth.

The concept has been written about for decades, is simple to describe in principle, and appears to offer many benefits with few downsides. In brief, the plan is to use huge solar panels to intercept some of the vast solar energy impinging on Earth, convert it to electricity, and then beam the resultant electrical energy to ground-based stations from where it could be distributed to users. In theory, this would be a nearly environmentally “painless” source of free energy. What’s not to like?

It’s actually more than just an “on paper” or speculative concept. There are several serious projects underway, including one at the California Institute of Technology (Caltech) which is building a very small-scale version of some of the needed components. They have been performing ground-based tests and have even launched some elements in orbit for in-pace evaluation in January 2023 (“In a First, Caltech’s Space Solar Power Demonstrator Wirelessly Transmits Power in Space”). The Wall Street Journal even had an upbeat article about it, “Beaming Solar Energy From Space Gets a Step Closer”.

There are many technical advances to be resolved in the real world (actually, they are “out of this world”) issues that have to be addressed. Note that the Caltech project is funded thus far by a $100 million grant, all from a single benefactor.

The Caltech Space Solar Power Project launched their Space Solar Power Demonstrator (SSPD) to test several key components of an ambitious plan to harvest solar power in space and beam the energy back to Earth. In brief, it consists of three main experiments, each tasked with testing a different key technology of the project, Figure 1.

Figure 1 Caltech’s Space Solar Power Demonstrator from their Space Solar Power Project has three key subsystems, encompassing structure, solar cells, and power transfer. Source: Caltech

The three segments are:

• Deployable on-Orbit ultraLight Composite Experiment (DOLCE): A structure measuring 6 feet by 6 feet that demonstrates the architecture, packaging scheme and deployment mechanisms of the modular spacecraft that would eventually make up a kilometer-scale constellation forming a power station, Figure 2;

Figure 2 Engineers carefully lower the DOLCE portion of the Space Solar Power Demonstrator onto the Vigoride spacecraft built by Momentus. Source: Caltech

• ALBA: A collection of 32 different types of photovoltaic (PV) cells, to enable an assessment of the types of cells that are the most effective in the punishing environment of space;
• Microwave Array for Power-transfer Low-orbit Experiment (MAPLE): An array of flexible lightweight microwave power transmitters with precise timing control focusing the power selectively on two different receivers to demonstrate wireless power transmission at distance in space.

Scaling a demonstration unit up to useable size is a major undertaking. The researchers envision the system as being designed and built as a highly modular, building-block architecture. Each spacecraft will carry a square-shaped membrane measuring roughly 200 feet on each side. The membrane is made up of hundreds or thousands of smaller units which have PV cells embedded on one side and a microwave transmitter on the other.

Each spacecraft would operate and maneuver in space on its own but also possess the ability to hover in formation and configure an orbiting power station spanning several kilometers with the potential to produce about 1.5 gigawatts of continuous power. A phased-array antenna would aim the 10-GHz power beam to a surface zone about five kilometers in diameter.

The concept is certainly ambitious. Perhaps most challenging is the very harsh reality that scaling up power-related projects from a small-scale bench-size demonstration unit to full-scale functioning system is a highly nonlinear process. This applies the battery storage systems, solar and wind energy harvesting, and other sources.

Experience shows that there’s an exponential increase in difficulties and issues as physical size and power levels; the only question is “what is that exponent value?” Still, the concept makes sense and seems so straightforward; we just have to keep moving the technology along and we’ll get there, right?

I was almost convinced, but then I saw a strong counterargument in an article in the June 2024 issue of IEEE Spectrum (“A Skeptic’s Take on Beaming Power to Earth from Space”). The article’s author, Henri Barde, joined the European Space Agency in 2007 and served as head of the power systems, electromagnetic compatibility, and space environment division until his retirement in 2017; he has worked in the space industry for nearly 30 years and has reality-based insight.

He looked at various proposed and distinctly different approaches to capturing and beaming the power, including CASSIOPeiA from Space Solar Holdings Group; SPS-ALPHA Mark-III from a former NASA physicist; Solar Power Satellite from Thales Alenia Space; and MR-SPS from the China Academy of Space Technology (there’s a brief mention of the Caltech project as well).

He discusses key attributes, presumed benefits, and most importantly, the real obstacles to success as well the dollar and technical cost to overcoming those obstacles—assuming they can be overcome. These include the hundreds, if not thousands, of launches needed to get everything “up there”; the need for robotic in-space assembly and repair; fuel for station-keeping at the desired low earth orbit (LEO), medium earth orbit (MEO), or geostationary orbit (GEO); temperature extremes (there will be periods when satellites are in the dark) and associated  flexing; impacts from thousands of micrometeorites; electronic components capable of handling megawatts in space (none of which presently exist), and many more.

His conclusion is simple: it’s a major waste of resources that could be better spent on improved renewable power sources, storage, and grid on Earth. The problem he points out is that beamed solar power is such an enticing concept. It’s so elegant in concept and seems to solve the energy problem so cleanly and crisply, once you figure it out.

So now I am perplexed. The sobering reality described in Barde’s “downer” article wiped out the enthusiasm I was developing for these projects such as the one at Caltech. At some point, the $100 million seed money (and similar at other projects) will need to be supplemented by more money, and lots of it (easily, trillions), to take any of these ideas to their conclusion, while there will be substantial risk.

Is beamed solar power one of those attractive ideas that is actually impractical, impossible, too risky, and too costly when it meets reality of physics, electronics, space, and more? Do we need to keep pushing it to see where it can take us?

Or will the spigot of money as well as the personal energy of its proponents eventually dry up, since it is not a project that you can do part way? After all, with a project like this one, you’re either all in or you are all out.

I know that when it comes to the paths that technology advances take, you should “never say never.” So, check back in a few decades, and we’ll see where things stand.

Related Content

• Keep solar panels clean from dust, fungus
• Lightning as an energy harvesting source?
• The other fusion challenge: harvesting the power

References

• IEEE Spectrum, “A Skeptic’s Take on Beaming Power to Earth from Space”
• IEEE Spectrum, “Space-based Solar Power: A Great Idea Whose Time May Never Come”
• IEEE Spectrum, “Powering Planes With Microwaves Is Not the Craziest Idea”
• IEEE/Caltech Technical Paper, “The Caltech Space Solar Power Demonstration One”
• Caltech, “Solar Power at All Hours: Inside the Space Solar Power Project”
• Caltech, “Space Solar Power Project Ends First In-Space Mission with Successes and Lessons”
• Caltech, “In a First, Caltech’s Space Solar Power Demonstrator Wirelessly Transmits Power in Space”
• Caltech, “Caltech to Launch Space Solar Power Technology Demo into Orbit in January”
• The Wall Street Journal, “Beaming Solar Energy From Space Gets a Step Closer”

The post Beaming solar power to Earth: feasible or fantasy? appeared first on EDN.