Space-based solar power has been around for more than 60 years: in fact, in 1958, the U.S. satellite Vanguard 1 was the first spacecraft to use a sub-one-watt power panel to operate a radio transmitter. The satellite stopped working a few years later, but it’s still in orbit: not only did it pave the way for the use of solar energy in space, it’s also the oldest human-made object orbiting the Earth. In the meantime, technology has advanced: today the International Space Station is equipped with more than 400 square meters of panels, which provide it with more than 240,000 times the energy of that first small installation on Vanguard 1.

But if it’s possible to supply solar power to spacecraft, can thisrenewable energyalso be beamed back to Earth, continuously and constantly, with greater efficiency, at all times of the day and without weather conditions interfering? That’s the challenge the SOLARIS project will be focusing on in the coming years.

Driving a petrol or diesel car instead of an EV costs the average household £700 a year in fuel bills, according to the ECIU report.

The European Space Agency’s goal with the SOLARIS project, which started in 2023, is to generate energy in space to be used on Earth. The Enel Group is also taking part, thanks to our expertise in photovoltaic technology, grids and storage and, in general, in the creation of large-scale renewable energy generation plants and the subsequent management of the energy produced. In the SOLARIS project, Enel has made an important contribution in the preliminary identification of potential business models and in determining the size of the solar power plants that will be in orbit, as well as giving the basic guidelines for the installation of the stations that will receive energy from space.

Missed insulation upgrades have cost UK households an average £235 a year on their energy bills, according to the ECIU.

The idea is to set up space-based solar power plants 36,000 km above the Earth's surface, in a geostationary orbit: that is, a circular orbit around the equator which coincides with the Earth's rotation period. The panels would be exposed to the Sun at all times, thus producing energy at practically all hours of the day and in all seasons, except for a few days a year, during the period of the equinoxes (the transition from winter to spring and from summer to fall), due to the conical shadow created by the Earth.

Space-based solar panels are not like those normally used in photovoltaic systems on Earth. They’re lighter and multi-junction, which means they’re made of several layers, each of a different semiconductor material and therefore able to absorb a different part of the solar spectrum, thus extracting more energy in the same amount of exposed surface area. They don’t use silicon, but rather materials such as indium arsenide or gallium arsenide, and they can reach higher levels of efficiency: they currently have an efficiency of 30%, but are expected to reach 40% within 10 years (those used for generation plants on Earth currently top out at 21-22%, while the HJT panel developed in our 3Sun factory in Catania reaches 24.5%).

Driving a petrol or diesel car instead of an EV costs the average household £700 a year in fuel bills, according to the ECIU report.

The first important date for SOLARIS is set for next year, 2025. By then, it will be necessary to assess what the actual transmission efficiency is: that is, how much of the energy produced in orbit would reach Earth. Not through a giant cable or space elevator – for the moment, that’s still science fiction – but through a wireless system. Microwave energy will be beamed to Earth and "captured" by a series of antennas that will turn it into electricity and feed it onto the grid.

Power transmission from space was first accomplished in 2023, thanks to technology developed by the California Institute of Technology and used by the Space Solar Power Demonstrator (SSPD-1) satellite. It was an experiment that demonstrated technical feasibility by turning on two LED lights.

The question now, however, is the industrial and economic feasibility and sustainability of the process. A one-gigawatt power plant would have an approximate weight of about 11,000 tons, and it would take 100 launches to get all the material into orbit. To be an economically sustainable system, the transmission efficiency – that is, the share of the energy produced in orbit that would reach Earth, which to date is still unknown – would have to be more than 90%.

If all goes well, then the next step, around 2030, will be to send the first solar farm into orbit: a 1-MW power plant that’s already assembled and capable of automatic extension.