While solar energy generation has become significantly cheaper and more efficient in recent years, it still faces inherent limitations: solar panels can only produce power during limited daylight hours, clouds frequently obstruct sunlight, and a considerable amount of sunlight is absorbed by the atmosphere before reaching the ground. But what if we could gather tremendous solar power in space and transmit it down to Earth instead?[1]
Space-based solar power presents exciting opportunities for sustainable energy. In the future, orbital collection systems could gather energy in space and transmit it wirelessly back to our Earth. These systems could provide power to remote areas, complementing the current terrestrial power infrastructure.
Countries all around the world are investing some tremendous amounts in space-based solar power research and development, with international organizations aiming to reduce carbon emissions to net-zero by 2050. NASA is exploring how to best support the development of space-based solar power. A new report from NASA’s Office of Technology, Policy, and Strategy (OTPS), titled “Space-Based Solar Power,” seeks to equip NASA with the necessary information to aid this research. The OTPS report examines the conditions under which space-based solar power could be a viable option for achieving net-zero greenhouse gas emissions compared to other sustainable solutions. It also considers NASA’s potential role in advancing space-based solar power systems.[2]
What is space based solar power?
A typical system involves a network of large, kilometer-scale satellites in geostationary orbit (GEO). Each satellite is equipped with lightweight solar panels and mirrors to focus sunlight onto the panels, producing approximately 3.4 GW of electricity. This electricity is then converted into microwave radiation with an efficiency of around 85%. The proposed microwave frequency is usually 2.45 GHz, which is transparent to the atmosphere and moisture, allowing a net 2.9 GW of power to be beamed to a receiver on the ground.
A secure pilot beam is sent from the ground to the satellite to ensure the microwave beam is accurately targeted. The ground-based rectifying antenna, or ‘rectenna,’ converts the electromagnetic energy into direct current (DC) electricity, which is then passed through an inverter to deliver a net 2 GW of alternating current (AC) power to the grid.[3]
Legal aspect
Implementing space-based solar power (SBSP) projects on a global scale will add additional pressure to international space law. Two key international legal challenges will be particularly significant.
Allocation of orbital slots
The primary legal framework governing outer space is the Outer Space Treaty of 1967 (OST), which includes all major spacefaring nations. This treaty aims to prevent national appropriation of outer space, ensuring it remains free from interstate competition.
The use of orbital slots, both in the geostationary orbit and elsewhere, is regulated by the International Telecommunication Union (ITU). According to the ITU’s Constitution, member states should manage these slots as limited national resources, using them ‘actually, efficiently, and economically’.
In practice, access to orbital slots operates on a ‘first-come, first-served’ basis. States must register the assignment of a specific slot with the ITU to launch a satellite. Although these registrations are made by states, many are submitted on behalf of commercial entities.
Geostationary orbit slots are particularly favored for space-based solar power (SBSP) projects due to their greater stability and exposure to sunlight. If SBSP becomes widespread, competition for these limited slots is expected to intensify, putting additional strain on the ITU’s current regulatory mechanisms.[4]
Responsibility for harm
As space becomes more crowded, the likelihood of SBSP equipment causing or suffering damage from other space objects increases. The risk to launch vehicles and satellites is exacerbated by the growing amount of space debris, resulting from the abandonment or intentional destruction of aging satellites. Congestion in low-earth orbit is also increasing rapidly due to the introduction of satellite constellations.
The Outer Space Treaty (OST) holds states accountable for all activities conducted in outer space, even if these activities are commercial. The 1972 Liability Convention makes launching states liable for any damage caused by their space objects. If the damage occurs on Earth or to an aircraft in flight, liability is absolute (i.e., no need to prove fault). Otherwise, a state is liable if the damage is due to its fault or the fault of those it is responsible for.[5]
Would the beam of SBSP be safe?
Most space-based solar power (SBSP) systems use microwave frequencies to wirelessly transfer power back to Earth. These microwaves operate at a frequency too low to stimulate cells, making them non-ionizing. The primary interaction with living organisms is through energy absorption and subsequent tissue heating.
Microwaves are already prevalent in our daily technology, from low-power applications like mobile networks and Wi-Fi to high-power uses such as microwave ovens. According to the European Commission’s Scientific Committee on Emerging and Newly Identified Health Risks, current scientific research indicates “the results of current scientific research show that there are no evident adverse health effects (of Electric and magnetic fields (EMF) exposure) if exposure remains below the levels recommended by the EU legislation”.[6]
Current SBSP Projects and Progress
Key players in SBSP include China and the US, both of which have made significant strides in technology, partnerships, and launch plans.
China is advancing its efforts to launch into space, with the China Aerospace Science and Technology Corporation planning to deploy small to medium solar satellites in the stratosphere to capture energy from space between 2020 and 2025.
In the US, there are ongoing collaborations and investments. For instance, Northrop Grumman and the U.S. Air Force Research Laboratory have formed over than a $100 million partnership to develop advanced SBSP technology.
Additionally, progress is being made in creating reusable launch systems, which will reduce the cost of space transport and the overall expense of SBSP. SpaceX, for example, is currently developing reusable launch vehicles for space missions.[7]
Conclusion
Although this technology currently appears to be expensive and maybe inaccessible, it is anticipated that it will soon be utilized for energy production. This technology holds significant potential for facilitating the energy transition and mitigating climate change. Consequently, the associated legal and environmental implications must be prioritized and addressed proactively.
[1] https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/Space-Based_Solar_Power_overview
[2] https://www.nasa.gov/organizations/otps/space-based-solar-power-report/
[3] https://spaceenergyinitiative.org.uk/space-based-solar-power/
[4] https://www.lexology.com/library/detail.aspx?g=349730f0-43c3-4021-aacc-301df167f8d3
[5] Op.cit.
[6] https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/FAQ_Frequently_Asked_Questions_on_Space-Based_Solar_Power
[7] https://www.greenmatch.co.uk/blog/2020/02/space-based-solar-power
Étudiant en master 2, droit et gestion des énergies et du développement durable, Université de Strasbourg
