Is Solar Energy from Outer Space in Our Future? – Part One: Building a Geosynchronous Solar Power Plant

Two different concepts for delivering solar energy from space are being considered in plans developed by China and the United Kingdom (UK) on the one hand, and the United States (US) on the other.

Both concepts wish to take advantage of uninterruptible solar energy which has been an aspirational goal for a long time but no single country as of yet has developed a feasible project. The reasons to do it, however, are tantalizing: 100% renewable energy for as long as the Sun continues to shine without interruption.

Today a state-of-the-art solar panel on Earth can convert between 20 to 30% of the energy it collects from sunlight into electricity. At night solar panels here contribute nothing. But in space with nothing to block the Sun, that same Earth-based solar panel becomes thirteen times more efficient. And that is enough of an incentive to consider solar power from space.

The Chinese and UK models are massive arrays located in geosynchronous orbit while continuously beaming energy to receiving stations here on Earth.

The US model is different using a constellation of solar power generating satellites. These would be in relatively low orbits and interconnected to form a mesh network. The total network would generate continuous energy beaming it to the surface even when a portion of it gets blocked when the satellites enter the night side of the planet.

In this two-part posting, we look at the Chinese and UK models.

China and the UK Propose Monster Solar Arrays

What experience to date can we apply to build what both China and the UK are proposing – monster arrays that would span multiple square kilometres in geosynchronous orbit? There are quite a few telecommunications satellites today in geosynchronous orbit. None are the size of what is being proposed. But we know how to get there from Earth.

Building something big in space has only one current model. It currently orbits 400 kilometres (248 miles) above the Earth and is the International Space Station (ISS), a structure several football fields in size. The ISS was built from modules and components delivered to the low-Earth orbit site and then assembled. It took ten years and $150 billion US  and costs about $3 billion for annual maintenance, not including astronaut visits and provisioning for the onboard crews.

A solar power array of the size being contemplated could be built from modular components sent into space where assembly could occur in low-Earth orbit in a similar fashion to the ISS. China has some experience already in building its own space station, Tiangong, using a similar technique. But the solar power array as envisioned by China would be a structure 25 times larger than the ISS. The simple math would suggest for such a structure costs could be 25 times higher. That means to build it could run up a $3.7 trillion bill.

If the site of the build is a low-Earth orbit, the solar power array would after completion have to be moved to a geosynchronous orbit 35,786 kilometres (22,236 miles) above the Earth. A move of this type at this scale would be unprecedented. Likely the means of propulsion would be plasma or ion thrusters, or maybe a novel use of a series of solar sales which could be deployed to move the completed array to its permanent location. Then finally there needs to be a receiving station on Earth that can capture what the array sends back to Earth in the form of microwave beams. There is the experience we have in building large radio telescopes and networks of them, and we know how to build large solar farms. But the antenna array will need to collect energy from the array that when transmitted to Earth must be diffuse enough to not harm anything or any creature flying through it. At the same time, there should be little in the way of energy loss in transmission from space.

From a recent UK feasibility study that looked at building a solar power array in space similar to what China is envisioning, British engineers have concluded that a geosynchronous orbiting power station is viable and can be built from materials launched from Earth. The study calculated the need for 300 launches equivalent in capacity to SpaceX’s current Starship. That would be enough to deliver materials for the assembly of a demonstrator array several kilometres in size by 2035 and capable of generating Gigawatts of electricity. The UK proposed array would be built by robots in the geosynchronous orbit location. Once the demonstration proves it works the array would continue to grow in size encompassing a significant space footprint.

The British call their project CASSIOPeiA which stands for Constant Aperture Solid-State Integrated Orbital Phased Array. (I wouldn’t have considered this particular acronym because if my Greek mythology is right, Cassiopeia was a vain African queen who was punished for her hubris by Poseidon and tied to an upside-down chair where she hangs today as the constellation that goes by her name.)

There is a Downside to a Geosynchronous Solar Power Station

The first question that comes to mind is — is one of these things enough? Redundancy in infrastructure makes for better outcomes as telecommunications companies will tell you. They learned about redundancy in their networks by overbuilding relays and substations to meet a five 9s standard. That’s 99.999% uptime or no more than 2 minutes of downtime for dial tone annually.

Power companies on Earth aspire to get close to five 9s but the cost to build redundancy into generation and delivery comes at a much higher cost. Even then utilities can be hit by unanticipated extreme events that normally would seldom interrupt dial tone. We are talking about hurricanes, tornadoes, wildfires, earthquakes, and tsunamis.

For a geosynchronous orbiting power array, there are space equivalents to extreme events that happen here on Earth. I can name three.

1. Geomagnetic storms caused by solar eruptions eject massive amounts of material into space. Referred to as coronal mass ejections (CMEs), these consist of magnetically charged particles that seriously disrupt satellites and even ground-based infrastructure. They last from hours to days. A recent Starlink SpaceX launch suffered a loss of 40 of its satellites because of a CME. Starlink operates in orbits much closer to Earth and therefore is more protected from CMEs and other space weather. But a geosynchronous solar power array would be far more exposed and the damage to it could be significant.
2. Solar radiation storms are another form of solar eruption. These are solar flares that are less spectacular than CMEs but nonetheless pose considerable danger. A stream of particles from solar radiation storms can cause radio blackouts on Earth. It can damage satellites and humans on the ISS need to find shelter in special areas of the structure when one of these phenomena erupts.
3. Solar x-ray emissions stream from the Sun and negatively impact radio and telecommunication signals here on Earth. These emissions also can cause radio blackouts. They interfere with GPS and can alter the positioning and operation of satellites in low-Earth orbit. For an array parked in geosynchronous orbit, the negative impact of x-ray emissions would be the threat to communications from Earth for the purpose of doing operational maintenance.

If we are to build solar power arrays as conceived by China and the UK then we will need to ensure that these massive projects in orbit will not suddenly go dark on us. We will have to build self-repair capacity into the structures, and to a degree overbuild them beyond 100% performance capacity. The question we have to ask is not can we build it, but more can we afford it?

But the US may have a solution that would make the vulnerabilities we have identified for a geosynchronous solar solution go away. And that’s what we will describe in Part Two.