The European Space Agency (ESA) has unveiled a plan to harvest the sun’s energy in outer space and beam it back onto earth. The technology, which is still in its nascent stage, aims to develop a 15km²-long space-based solar power (SBSP) structure orbiting 35,786 km above the earth to create a renewable baseload capacity similar to that of nuclear power plants.

The ESA proposed SOLARIS in August as preparatory technology development and maturation program to advance key aspects of the concept of SBSP plants.

The development of SBSP might allow Europe a way to be powered by giant floating solar panels orbiting the axis of the earth. Through this, the continent would extend the technological state-of-art in a diverse set of key technologies relevant to earth and space applications, such as high-efficiency solar cells, wireless power transmission, and robotic in-orbit assembly.

“[Such a project] would ensure that Europe becomes a key player– and potentially leader – in the international race towards scalable clean energy solutions for mitigating climate change,” the ESA said.

How does it work

Space-based solar power is the concept of collecting solar power with a spacecraft in earth’s orbit and distributing it to earth. Unlike terrestrial systems, SBSP has the advantage of collecting solar energy in space, generating a higher collection rate given the lack of a diffusing atmosphere and a longer collection period by placing a solar collector in an orbiting location.

The system converts the sunlight to electricity, which is beamed to earth wirelessly, most likely by radio frequency waves. The energy beam must be accurate and reliable and retain as much power as it travels through the earth’s atmosphere. One system would have the capacity of 2 GW at a single ground location or 500 MW or less at multiple ground locations.

“Considering the climate and energy crises and the rapid strides we’re making in space capabilities, now is the time to investigate if Space-Based Solar Power can be part of the solution – it’s the responsible thing to do,” said Sanjay Vijendran, ESA’s lead for the SOLARIS proposal.

If scientists can come close to the theoretical transmission efficiencies, they could roughly produce 400 W of electricity per square meter on receivers on earth. This would account for about two to three times the amount received from the same area of the terrestrial PV panel, and as a green energy source, SBSP could provide green electricity to the grid 24/7.

An SBSP system comprises three main segments: the space segment, the ground segment, and the launch segment. The space segment contains the platform in orbit, composed of elements such as reflectors, energy conversion, and wireless power transmission systems. The ground segment contains all elements needed to receive, convert, and transmit the energy into the terrestrial grid. The launch segment comprises the launch systems to deliver the infrastructure into orbits, such as heavy reusable launchers or orbital transfer vehicles.

Benefits of SBSP

SBSP would not compete with terrestrial solar power plants but rather complement them. Unlike terrestrial solar power plants, SBSP would provide continuous, stable, baseload (non-intermittent) power to an electrical grid equivalent to nuclear, hydro, coal and gas power plants.

The areas dedicated to receiving the power transmitted from the orbiting power generation satellites could be on land or the sea and are expected to be usable in parallel for other applications, such as agriculture, or combined with a utility-scale ground-solar or wind farm. This will potentially allow the maximization of power generation from areas already set aside for renewable power generation purposes.

Technical Challenges

SBSP technologies are still in their very early stages of development, and factors such as relatively high upfront costs for the implementation and skepticism from decision-makers have so far restricted their development.

The use of wireless networks to enable the operation of a complex and large system in space represents a major technological challenge. Implementing conventional wired-data-harness architecture would significantly increase the system mass and complicate the elements’ interfaces. Around two million components will need to be monitored and controlled wirelessly, including sensors and actuators, and such large sensor-actuator wireless networks do not currently exist in this form.

Moreover, significant developments in the transmit antenna technologies will be needed to improve the efficiency and mass to enable high-efficiency, long-distance wireless power transmission. Low-cost, high-cadence, heavy-lift launchers are also necessary to enable SBSP. Even with the largest and most powerful launchers available today, it would still require a very high launch cadence and a drastic reduction of launch costs to deliver the infrastructure necessary for a fully operational SBSP.

According to ESA, space experts believe that by 2040, reusable launch systems, which will conduct aircraft-like services (launch, land, refuel, launch again), will be available on the market, thus with the potential to enable SBSP.

The ESA will discuss the SOLARIS project in November.

In July, the United Kingdom government announced a £3 million (~$4 million) grant for space-based solar projects to collect the sun’s energy using solar panels orbiting the earth.

Last year, researchers at the National Renewable Energy Laboratory said they would send perovskite solar cells into space to evaluate their potential use in space and assess the durability of materials used to lower the cost of specialized photovoltaic panels to generate electricity in space.