Aeronautics - Space - Defence

Orbital solar power plants: the new innovation in clean energy production?

Published on 09 February 2024 Read 25 min

The concept of a solar power plant is not new, in fact we have to go back to the end of the 1960s to see the first representation. At the time, the objective was to provide access to clean energy, especially in the context of the 1970s oil crisis. However, the constraints of assembly, maintenance and cost quickly put a stop to the various projects of the time. Today, major technological advances, the cost of access to space, which is much lower than 50 years ago, and the desire of various countries to have a certain degree of energy independence, from a variety of sustainable sources, seem to have revived the momentum for orbital solar power plants. At least that is what the growing number of programs seems to indicate. Alcimed comes back on the development opportunities and describes the stakes of this new means of energy production.

The pioneers in this field are the United States and China, the latter announcing an operational station before 2030. Other promising initiatives come from Japan, the United Kingdom, and more broadly from Europe, with a desire to have solar power plants in orbit by 2040-2050.

  • For more than a year, the US Air Force and the Naval Research Laboratory (NRL), using the X-37B robotic spacecraft, have been conducting experiments in low earth orbit (about 400 km) to test the capture of solar energy and its conversion into direct current electrical energy in space. The test of power transmission to Earth is expected to be conducted by the Air Force Research Laboratory (AFRL) in 2025. Northrop Grumman, partner of the AFRL, has received USD 100 million in funding to carry out the test.
  • In China, the “Daily Project” team, led by Duan Baoyan of Xidian University in Shaanxi province, said the group has set a goal of having a solar power plant in space by 2028. The tests in Xidian were carried out using a 75-metre-high steel structure built on the university’s campus.
  • In the UK, the government’s commitment to Net Zero led to the launch of the Space Energy Initiative in early 2022, bringing together the government with research organisations and industrial companies. Their goal is to have a first low-earth orbit solar power plant demonstrator by 2030 and a first operational system by 2040. The UK design would bring 2GW of power to the grid.
  • At the European level, ESA has launched a call for new ideas for Space-based Solar Power Station (SPS or SSPS). By the end of 2021, 85 ideas were proposed, 16 were selected and will receive funding.
  • In Japan, the Japan Aerospace Exploration Agency (JAXA) announced in 2014 a technology roadmap to build orbital solar power plants with a combined capacity of 1 GW by 2030. JAXA aims for a fully operational plant by 2050. In parallel, Japan Space Systems has announced that it will launch a demonstrator into orbit in 2025.

Increased interest over the last 10 years

The number of scientific publications, as well as patent applications, has increased sharply since the beginning of the 2010s. This is in line with the announced willingness of the various international entities to put into orbit these space-based solar power stations.

Figure 2 – Number of scientific publications on space-based solar power station since 1970 (source: Scopus)
Query: TITLE-ABS-KEY ((space-based AND solar AND power AND station) OR (space-based AND solar AND power AND satellite))

Figure 3 – Number of patents filed and granted (source: The Lens)
Patent query: space-based AND solar AND power AND station

The technological challenge of orbital solar power plants

For an orbital solar power station (CSO or SPS for Space-based solar Power Station), the transmission of solar energy captured in space remains a technological challenge. Two approaches coexist and still present major technical, economic and regulatory challenges.

DescriptionSolar energy is collected by two large networks of mirrors, then converted into a microwave and transmitted to a field of receiving antennas with a diameter of 8 km in order to be converted into an electric current. This type of CSO is in geostationary orbit, at an altitude of around 36 km.In principle, laser energy transmission systems are very similar to microwave energy transmission. The main difference lies in the wavelengths used. While most wireless energy transmissions are based on microwave frequencies of 2.45 or 5.8 GHz (0.12-0.05 m), laser energy transmission takes place in the visible or near infrared frequency spectrum (1.5 pm). This type of CSO is in low orbit, i.e. at an altitude of less than 2,000 km.
AdvantagesStable, continuous transmission of energy into the atmosphere (rain, clouds, etc.).

Each CSO can supply more than 1 GW of energy to the terrestrial receiver.

The intensity of the energy transmitted does not exceed that of the sun.

Mature, mature technology.

Much lower cost than microwave satellites.

Only one launch is required per satellite, reducing costs and risks.

The small diameter of the laser makes it easier to receive on the ground.

Because the satellite is in low orbit, maintenance is easier.

DisadvantagesThe production cost of the power station is extremely high, estimated at several tens of billions of dollars.

The large size of the satellite would require several launches and assembly in space.

As the satellite is in geostationary orbit, and therefore very far from the Earth, it would not be easy to maintain.

The relatively low power of each satellite, of the order of 1 to 10 MW, would require several satellites to have a real impact.

This solution raises a number of concerns about the use of lasers, such as the blinding and militarisation of space.

Interactions with the atmosphere (absorption, dispersion, turbulence) complicating the transmission of power through clouds and rain.


Orbital solar power plants: a subject of innovation to be followed closely

Despite the fact that the progress of current projects is still limited, and that the number of publications and patents on the subject of orbital solar power plants is still relatively low, the challenges linked to clean energy are growing rapidly.

Technological innovation in the field of energy will play a crucial role in achieving the objectives of carbon neutrality by 2050, as well as in strengthening the energy sovereignty of States.

Technological innovation in the field of energy will play a key role in achieving the objectives of carbon neutrality by 2050, as well as in strengthening the energy sovereignty of States. Alcimed can support you in your projects related to carbon neutrality.

About the author, 

Alexis, Consultant in the Chemistry and Materials team of Alcimed in France

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