by The concept of space-based solar power (SBSP) – using satellites to collect energy from the sun and “inject” it into collection points on Earth – has been around since the 1960s. Despite its great potential, the concept has not gained enough traction due to cost and technological constraints.
Can some of these problems be solved? If so, SBSP could be an important part of the world’s transition from fossil fuels to green energy.
We are already harvesting energy from the sun. It is collected directly from what we generally call solar energy. This includes different technologies such as photovoltaics (PV) and solar-thermal energy. Solar energy is also collected indirectly: wind energy is an example of this, because wind is created by the uneven heating of the atmosphere by the sun.
But these green energy production methods have limitations. They take up a lot of space on the ground and are limited by the presence of light and air. For example, solar farms do not collect energy at night and collect less in winter and on cloudy days.
PV in orbit will not be blocked at the beginning of the night. A satellite in geostationary orbit (GEO) – orbiting around 36,000 km from Earth – is exposed to the Sun more than 99% of the time throughout the year. This allows generating green energy 24/7.
GEO is suitable when power needs to be sent from a spacecraft to an energy collector, or ground station, because the satellites here are stationary with respect to the Earth. It is estimated that there is 100 times more solar energy available in GEO, than the projected energy needs of humanity in 2050.
Transmitting energy collected in space to Earth requires wireless energy transmission. Using microwaves for this reduces the energy lost in the air, even in cloudy skies. The microwave beam sent by the satellite will be directed towards a base station, where antennas convert the electromagnetic waves back into electricity. A substation would need to be 5 km wide, or even more at high latitudes. However, this is still less than the land area needed to produce the same amount of energy using the sun or wind.
Changing thoughts
Many designs have been proposed since the original idea by Peter Glaser in 1968.
In SBSP, energy is converted several times (light to electricity to microwaves to electricity), and some is lost as heat. In order to add 2 gigawatts (GW) of power to the grid, about 10 GW of power would need to be collected by satellite.
A recent concept called CASSIOPeiA consists of a 2-kilometer-wide array of control reflectors. These devices reflect sunlight onto a series of solar panels. These energy conveyors, about 1,700 meters in diameter, can be seen from the base station. It is estimated that the satellite could weigh 2,000 tons.
Another architecture, SPS-ALPHA, differs from CASSIOPeiA because the solar collector is a large structure made up of small numbers, featuring modules called heliostats, each of which can be moved independently. They are mass produced to reduce costs.
In 2023, Caltech scientists launched MAPLE, a small satellite experiment that beamed small amounts of energy back to Caltech. MAPLE proved that the technology could be used to transmit energy to Earth.
National and international interest
The SBSP could play an important role in meeting the UK’s net-zero target by 2050 – but the current government plan does not include that. An independent study found that SBSP could generate up to 10GW of electricity by 2050, one quarter of the UK’s current demand. SBSP provides secure and stable power supply.
It will also create a multi-billion pound industry, with 143,000 jobs across the country. The European Space Agency is currently evaluating the performance of the SBSP and its SOLARIS initiative. This can be followed by a comprehensive technical development plan by 2025.
Some countries have recently announced the goal of lighting up the Earth’s energy by 2025, moving to large-scale projects in the next two decades.
A large satellite
If the technology is good, why not use SBSP? The main measure is the amount of mass that needs to be launched into space, and its cost per kilogram. Companies like SpaceX and Blue Origin are developing heavy-lift launch vehicles, aiming to reuse parts of those vehicles after they fly. This can reduce the cost of the business by 90%.
Even using SpaceX’s Starship vehicle, which can launch 150 tons of cargo into low Earth orbit, the SBSP satellite will require hundreds of launches. Some components, such as long structural trusses – structural elements designed to travel long distances – can be 3D-printed in space.
Challenges and risks
The SBSP mission will be challenging – and the risks still need to be fully assessed. While the electricity generated is entirely green, the pollution impact from hundreds of heavy-lift launches is difficult to predict.
Additionally, controlling such a large structure in space would require large amounts of fuel, which involves engineers working with sometimes toxic chemicals. Photovoltaic solar panels will be affected by degradation, reducing efficiency over time from 1% to 10% per year. However, servicing and refueling can be used to extend the life of a satellite almost indefinitely.
A microwave beam strong enough to reach the ground can damage anything that interferes. For safety, then, the energy density of the beam will have to be limited.
The challenge of building platforms like this in space may seem daunting, but space-based solar power is technologically possible. To be economically viable, it requires great engineering, and therefore a long time and a firm commitment from governments and space agencies.
But with all that in place, SBSP can make a fundamental contribution to bringing us to net zero by 2050 with sustainable, clean energy from space.
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Matteo Ceriotti, Senior Lecturer in Space Systems Engineering, At the University of Glasgow
This article is republished from The Conversation under a Creative Commons license. Read the first article.
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