We might soon be able to use solar energy collected from space.

Since at least the late 1960s, there has been interest in the concept of space-based solar power (SBSP), which involves utilizing satellites to gather solar energy and "beam" it to collecting locations on Earth. Despite having enormous promise, the concept has not taken off enough because of financial and technological barriers.

Are some of these issues currently solvable? If so, SBSP might play a significant role in the global switch from fossil fuels to renewable energy.

We already use the sun's energy. It is directly gathered using what we typically refer to as solar power. This includes a variety of technologies, including solar thermal energy and photovoltaics (PV). The energy from the sun can also be captured indirectly; one example of this is wind energy, which is produced when the sun's uneven heating of the atmosphere results in breezes.

These green energy technologies are not without their drawbacks, though. They are constrained by the amount of light and wind available and take up a lot of space on land. Solar farms, for instance, don't collect electricity at night and do so less frequently throughout the winter and on cloudy days.

The onset of the night won't put a cap on PV in orbit. Over the course of a year, a satellite in geostationary orbit (GEO), which is a circular orbit about 36,000 km above the Earth, is exposed to the Sun for more than 99% of the time. This enables it to continuously produce green energy.

When energy needs to be transmitted from the spacecraft to an energy collection, or ground station, GEO is perfect.

because the Earth-fixed satellites are immobile here. It is anticipated that there will be 100 times more solar energy accessible from GEO than there will be people on the planet in 2050.

Wireless power transmission is needed to deliver the energy gathered in space to the Earth. By using microwaves for this, even in foggy skies, the amount of energy lost in the atmosphere is minimized. The ground station will receive the satellite's microwave beam, which will be sent there to be processed by antennas into electricity.

At high latitudes, the ground station must have a diameter of 5 km or more. Even yet, this is still less land than is required to generate the same amount of electricity using solar or wind energy.

Changing ideas

Since Peter Glaser's original concept from 1968, many different designs have been put forth.

A portion of the energy used in SBSP is lost as heat after being transformed multiple times (from light to electricity to microwaves to electricity). 10 GW or more of power will need to be collected by the satellite in order to inject 2 GW of power into the grid.

Two 2km-wide steerable reflectors make up the Cassiopeia idea, which was recently developed. These direct the sun's rays onto a collection of solar panels. These 1,700 meter-diameter power emitters can be directed at the ground station. According to estimates, the satellite might weigh 2,000 tonnes.

Another architecture called SPS-ALPHA varies from Cassiopeia in that the solar collector is a massive structure made of a great number of tiny, modular reflectors called heliostats, each of which may be moved individually. They are produced in bulk to cut costs.

Scientists at Caltech launched MAPLE in 2023. It was a little satellite experiment that transmitted a very modest quantity of power back to the university. MAPLE demonstrated that the technology might be utilized to supply electricity to Earth.

Both domestic and foreign interests

Although the government's current strategy does not mention SBSP, it could be essential to achieving the UK's net-zero goal by 2050. By 2050, the SBSP could produce up to 10 GW of power, or 25% of the UK's current demand, according to an independent analysis. A safe and reliable electricity source is provided by SBSP.

In addition, it will generate 143,000 jobs nationwide and a multibillion-dollar sector. With its SOLARIS effort, the European Space Agency is at present assessing the SBSP's potential. By 2025, the technology might have a complete development strategy.

Other nations have lately declared their plans to upgrade to larger systems and beam energy to Earth by 2025.

An enormous satellite

Why is SBSP not being deployed if the technology is available? The fundamental constraint is the large mass that must be launched into space and the price per kilogram of doing so. Heavy-lift launch vehicles are being developed by businesses like SpaceX and Blue Origin with a focus on reusing portions of those vehicles after they have flown. This might reduce the venture's cost by 90%.

The SBSP satellite will need hundreds of missions, even with SpaceX's Starship rocket, which can send 150 tonnes of payload into low Earth orbit. Some parts, such as lengthy structural trusses, which are structural elements made to span considerable distances, might be 3D printed in space.

Complexities and dangers

The dangers associated with an SBSP mission must still be thoroughly evaluated. Although the electricity generated is entirely green, it is hard to forecast how much pollution will be produced by hundreds of heavy-lift launches.

Furthermore, managing such a massive structure in space will require a significant quantity of fuel, requiring engineers to work with occasionally quite dangerous substances. Degradation will have an impact on the photovoltaic solar panels, decreasing efficiency over time from 1% to 10% per year. However, maintenance and refueling might be utilized to virtually forever extend the satellite's life.

Anything in the path of a powerful enough beam of microwaves that might reach the ground would suffer damage as well. Therefore, the power density of the beam must be limited for safety.

Although it may seem difficult to construct platforms like this in space, solar power in the area is technically possible. Large-scale engineering is necessary for it to be commercially viable, which necessitates a long-term and resolute commitment from governments and space agencies.