Space-Based Solar Power -
Generating Electricity Above Earth

Deploying vast arrays of solar panels in space for energy production may seem like a far-fetched idea, but it has gained serious momentum in recent years. Several countries are now locked in a competitive race to develop the necessary technology. The British government, for instance,  recently invested over four million pounds to advance the concept, with the UK Space Agency collaborating with several universities and private companies to develop technology capable of supplying up to a third of the country’s energy within two to three decades. Similarly, the Japanese government and the Japan Aerospace Exploration Agency (JAXA) have been working on the technology for years, with plans to conduct space-based tests in the near future. The European Space Agency (ESA) aims to lead a trillion-dollar industry, while China has entered the race with determination, with some suggesting it is already in the lead. Meanwhile, the United States, which first promoted the idea in the 1970s, has renewed its interest, with the participation of players such as NASA, along with U.S. security agencies, actively researching and funding this technology, having already conducted a successful space-based trial. But why invest billions in placing solar panels in space when they work perfectly well on Earth?

The solar arrays will orbit about 36,000 kilometers above Earth's surface, transmitting energy through electromagnetic waves to arrays of antennas on the ground. Depicted: A pioneering project to generate power from solar energy in space | Source: ESA©

The Great Promise

Renewable energy sources, such as wind turbines and solar farms—large arrays of solar panels spanning wide areas—provide low-cost electricity without emitting greenhouse gases. However, they come with a significant drawback: their power generation is intermittent and inconsistent. The intensity of the wind varies constantly, which affects the rotation speed of wind turbines and, consequently, the power output they generate. Similarly, while the sun may provide abundant energy at midday under clear skies, it offers much less at other times, especially on cloudy days or at night. Nuclear power plants and hydroelectric dams can produce continuous and clean electricity, but they are not suitable for every location,  and their construction often faces technical challenges or social opposition. These constraints underscore the need for alternative energy solutions.

In space, the sun always shines. At a sufficient distance from Earth, the planet no longer blocks sunlight, allowing for a continuous stream of sunlight to be harnessed. Without clouds or an atmosphere to absorb or scatter sunlight, the intensity of solar radiation in space is approximately ten times greater than the average solar radiation reaching the Earth's surface. To take advantage of these conditions, most proposals suggest placing a vast array of solar panels in a high, geostationary orbit, synchronized with Earth’s rotation. At an altitude of approximately 36,000 kilometers, the array would orbit the planet once per day, remaining fixed above the same point on the surface. This configuration ensures that the panels receive near-continuous sunlight, interrupted only briefly during predictable periods when the Earth casts a shadow.

To transmit electricity to Earth, the vast solar array will convert the energy into powerful microwave beams, which will be directed in a concentrated manner to specialized antenna fields that will convert the waves back into electricity. Since microwaves are minimally affected by clouds and weather, they offer the potential for a stable, year-round supply of solar energy. Additionally, these antenna fields could serve multiple purposes, such as supporting crop cultivation between the antennas or hosting conventional solar panels.

The solar array can be positioned above any country, providing energy to different regions worldwide.  The system can redirect microwave beam transmissions to various locations, supplying electricity to another country within seconds. Unlike generating electricity from nuclear fusion, "it’s not new science, it’s an engineering problem," according to Jean-Dominique Coste, Senior Manager at Airbus Blue Sky, involved in developing the technology. "But it’s never been done at [large] scale.”

The cost of launching into space today is about one-tenth of what it was a decade ago, with further decreases expected in the coming years. In the diagram:  The cost of launching per kilogram of material over time, along with SpaceX’s optimistic projections for 2030 | Source: Visual Capitalist

Drop in Launch Costs

The concept of placing a solar array in space is not new. Isaac Asimov explored the idea as early as 1941, in his science fiction story "Reason", In 1968, aerospace engineer Peter Glaser outlined a design of such an array - a concept NASA hoped to pursue amid the energy crises and lunar missions of that era. However, the prohibitive cost of launching and assembling such a large-scale project has long hindered its progress. A NASA report from early 2024 estimates that a space-based solar array with a capacity of around two gigawatts -  comparable to the Diablo Canyon Nuclear Power Plant in California  - would span 10 to 20 square kilometers and weigh up to 10,000 tons. For perspective, this is more than the combined weight of 4,000 SpaceX Starlink satellites and fourteen times the mass of the International Space Station (ISS).

NASA estimates that positioning the solar array in its designated orbit will require at least 2,300 launches. Twelve out of every thirteen launches will focus on refueling and transferring components from low Earth orbit—similar to the altitude of the International Space Station—to geostationary orbit. The total project cost is estimated to exceed 280 billion dollars, with launch expenses projected to account for about 70 percent of that amount. When measured against its electricity generation capacity, the cost of the space-based solar array is substantially higher than that of existing power generation technologies.

However, the report also offers a reason for optimism. While the cost may seem astronomical, launch expenses have decreased significantly compared to the past. In recent years, satellite launchers with reusable components have been developed, such as SpaceX's Falcon 9, introduced in 2010, considered a milestone in technological development, as it can take off and land multiple times, allowing for substantial cost reductions. Reusing components significantly reduces costs, and they continue to decrease: currently, the cost of launching one kilogram of material into space is just under 3,000 US dollars; NASA estimates that by 2050, the launch cost could drop to around 1,000 dollars per kilogram, while SpaceX predicts even lower costs, potentially as low as  200 dollars per kilogram with its giant Starship launcher and reusable satellite components. 

Additionally, advancements in solar-powered electric propulsion technology could allow the solar array to be transported from low Earth orbit directly to geostationary orbit, eliminating the need for additional refueling launches. If achieved, this development could significantly reduce launch costs, making the entire project economically viable. In an especially optimistic scenario, the cost of electricity generated by the space-based solar array could become comparable to that of electricity produced by terrestrial solar farms.

Beyond high launch costs, this mega-project will require complex technological advancements.  For instance, sophisticated autonomous robots will need to assemble, transport, and maintain the entire solar field without human intervention.  Moreover, the microwave transmission and reception system must be significantly more efficient than those used in recent experiments, ensuring the successful transfer of as much energy as possible to a small area on Earth.

The video presents the European Space Agency’s (ESA) SOLARIS program for establishing space-based solar arrays:

The Tank in the Room

Technological developments may help us mitigate the climate crisis, but it seems that the race for space-based electricity is also driven by security considerations. According to the US Air Force, for example, the technology could provide energy to remote military bases, , including those situated behind enemy lines, obviating the perilous need for fuel supply convoys vulnerable to attacks. A military base could rely on a relatively small solar field, making the technology worthwhile even at a high cost. The technology could also facilitate in-flight recharging of military aircraft and grant unmanned aerial vehicles virtually limitless flight endurance. "Electricity from space" could also prove beneficial for civilians in disaster or conflict zones, or when terrestrial electricity infrastructure is compromised, akin to the utilization of space-based internet during conflicts like that in Ukraine.

While the idea of harnessing space for electricity generation may seem far-fetched, much of the necessary technology already exists. Although unprecedented in human history, the continued reduction in space launch costs could soon make this feasible, especially for military applications. Will space-based solar fields become commonplace in the foreseeable future? The answer may become clear in the coming years. What is certain is that, in the meantime, we must continue transitioning to renewable energy sources here on Earth.