Europe's 1st and Foremost Consultancy for Space-based Solar Power!
Europe's 1st and Foremost Consultancy for Space-based Solar Power!
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Space Energy Insights' definitive guide to space-based solar power. Do you have more questions? Contact us here.
Space-based solar power is the concept of collecting solar energy in space with solar power satellites, and beaming it wirelessly back to Earth for distribution.
Space-based solar power involves putting huge solar farms or mirrors up in space, capturing or reflecting solar energy and transmitting it wirelessly to receivers on Earth, where it can then be converted into electricity.
As with terrestrial solar farms, space-based arrays will range in size, depending on the required power output, from around 100 metres in diameter (generating Megawatts of power) eventually up to kilometre-scale structures (generating Gigawatts).
The generated power would be transmitted wirelessly through modular transmitters to the receiving antennas on the ground (referred to as rectennas), typically through the use of safe, low-intensity radio frequencies, similar to those used for Wifi, mobile phones and satellite communications. The chosen frequency would allow the beam to reach the receivers with almost no loss through the atmosphere, whatever the weather conditions, providing a continuous and reliable source of clean power 24/7.
An alternative way to send solar energy down is by reflecting sunlight using orbiting mirrors and capturing the energy with ground-based solar farms. However, this form of energy transfer would be affected by atmospheric absorption and weather conditions, just like normal sunlight.
Once the energy from the Sun has been transmitted to Earth it will be captured by a receiving station called a rectenna. The captured energy will be converted into electricity and added to the power grid, and distributed in the normal way – perhaps to your own home!
Geostationary orbit (GEO) or inclined orbits reaching out to GEO distances are the most favoured orbits for large space-based solar power platforms due to their continuous sunlight and large coverage over the Earth. Low Earth orbit (LEO) constellations are attractive for lower cost and potentially earlier commercially-viable applications. Sun synchronous orbit may also be considered for supplying power twice a day to locations all around the globe at specific times where additional power from space is most valuable, e.g. at dawn and dusk.
Advantages and disadvantages of geostationary orbit for space-based solar power platforms
Geostationary orbit is about 36,000 km above Earth’s equator. Satellites orbit at the same rotational speed as Earth, remaining fixed over a single location on the surface. Most large-scale space-based solar power concepts envision large solar farms in GEO to provide stable, baseload power for grid applications.
Advantages and disadvantages of low Earth orbit for space-based solar power platforms
Low Earth orbit covers altitudes ranging from about 160 km to 2,000 km above Earth. For the mirror concept, LEO is necessary to reduce the spot size of the reflected light to the minimum possible (around 5-10km) in order to minimise light pollution of surrounding areas.
Rectenna stations, which receive microwave power beams from space-based solar power satellites and convert them into electricity, are similar in size to large-scale ground-based solar farms that are increasingly being built today around the world.
Typical rectenna sizes for a gigawatt (GW) power output are on the order of 20 km² or more. Due to safety and atmospheric heating limits, the microwave beam footprint on Earth must be large to keep local radiation intensity safe, which also dictates the rectenna's large area.
Nevertheless, the average power intensity delivered by the rectenna into the grid is many times greater (~30-50 W/m²) than the average power intensity delivered by a terrestrial solar farm, especially in mid-latitudes like Europe (~10 W/m²). Therefore, space-based solar power uses much less land to generate the same amount of electricity compared to ground solar, and very much less than wind farms.
Almost! A solar power satellite in geostationary orbit can see the Sun for well over 99% of the time. It is only in the Earth’s shadow for a maximum of 72 minutes a day, for about three weeks around the spring and autumn equinox. These completely predictable and short gaps can be covered by a modestly-sized battery storage system, thereby easily providing true 24/7 clean power.
There is an urgent need for clean, affordable, scalable and secure energy sources to support decarbonisation for mitigating global warming, increased energy supply for new applications and increased energy access to regions of the world still without electricity. Space-based solar power, thanks to its unique characteristics, could ultimately provide the elusive solution to the 'Energy Trilemma' of sustainability, affordability and security throughout the globe.
While the idea of space-based solar power has existed for over 50 years, it has gained renewed importance in recent years in Europe and worldwide due to the climate crisis. In parallel, recent advances in space capabilities – particularly reusable launchers and satellite mass production – have greatly improved the prospects of space-based solar power being an economically-viable proposition.
Numerous studies have repeatedly shown that space-based solar power, used effectively in complement with other clean energy sources such as ground-solar and wind, can help accelerate the decarbonisation of societies. Without reliable sources of clean power like space-based solar power, decarbonisation of our societies will take longer, be more expensive and more environmentally damaging than otherwise.
Space-based solar power can also be used at smaller scales to reach applications and communities too remote for reliable, affordable energy access. For example, small island states, remote mining communities, and heavy industry in areas with fragile or overstressed grids. It can also help in emergency and disaster situations, where simple infrastructure can be deployed to receive power beamed from space when other ground-solutions are rendered unavailable.
Not initially, no. Rather, space-based solar power is seen as complementing other renewable sources of energy by providing reliable, uninterrupted power. Various new technologies are being developed in other areas, such as fusion, geothermal or tidal, and together they could work in complement to help accelerate decarbonisation.
Space-based solar power’s baseload reliability means it fills gaps left by intermittent sources, potentially sharing locations with terrestrial renewables and maximising use of dedicated energy zones.
In the longer term, as space-based solar power scales up and costs fall further, the prospect is for it to eventually become cheaper than all other forms of energy on Earth, thereby displacing further deployment of terrestrial renewables as our need for energy grows into the future. Space-based solar power is scalable to ultimately provide all the energy the Earth needs in the future.
It’s true that solar, wind, and batteries will be the backbone of our clean energy future: they’re available now, costs continue to go down, and they’re being deployed at unprecedented speed. However, while integrating such technologies into the energy mix is relatively easy early on, as we push towards a fully decarbonised grid, we encounter some significant challenges that become prohibitively expensive to solve with batteries alone.
Think of it like this: getting to 60-70% renewable energy with solar, wind, and batteries is achievable and increasingly cost-effective; this is indeed the target in the International Energy Agency’s Net Zero 2050 Roadmap. But the remaining 30-40% and especially the last 10-20% – ensuring the lights stay on during a week of cloudy, windless weather in winter – becomes disproportionately expensive.
Here’s why: as renewable penetration increases beyond 80-90%, you need massive amounts of storage or other backup options that sit idle most of the time, used only during rare but critical periods. A 2024 study of Australia’s transition to 100% renewables found that achieving the last 18% (from 82% to 100%) requires as much investment as the first 82% combined. The storage alone would need to provide backup power for 2-4 days and handle 15-40% of peak demand.
To put this in perspective, transitioning Australia alone to 100% renewables would require:
• 13 times more battery storage capacity than exists today
• 40 times more energy storage capacity than currently deployed
Now imagine scaling this globally, especially in regions like Northern Europe where solar resources are limited and seasonal variations are extreme. In such cases, the amount of storage, plus all the transmission lines needed, becomes totally uneconomic.
A 2025 study by King’s College London on what the impact of space-based solar power could be on the European energy system found that, using the reference concepts from NASA’s 2024 report, space-based solar power could reduce Europe’s total power system costs by 7-15%, representing potential annual savings of €35.9 billion. This substantial cost reduction comes from avoiding the exponential expense of achieving very high renewable penetration with batteries alone.
Most significantly for the “last mile” cost problem, space-based solar power could:
• Offset up to 80% of wind and solar deployment needs
• Reduce battery usage by over 70%
• Dramatically reduce transmission infrastructure requirements
Europe faces particularly acute challenges due to:
• High population density limiting available land for renewable installations
• Northern latitudes with severe seasonal solar variations
• Complex cross-border grid integration requirements across the 33 countries analysed in the study
The researchers found that achieving net-zero with terrestrial renewables alone would require massive overbuilding of capacity to handle the worst-case scenarios (winter months with limited sun and wind), along with enormous battery installations that would sit idle most of the time.
The study identified specific cost benchmarks where space-based solar power (SBSP) becomes competitive:
• Complementary role: When SBSP costs reach roughly 14x the 2050 solar PV capital cost
• Dominant technology: When SBSP costs fall to 9x the 2050 solar PV costs
• At 3x the 2050 solar PV costs, SBSP could provide 99% of electricity generation on an economically competitive basis.
This is where the energy experts’ consensus becomes clear: the most cost-effective path isn’t to rely solely on solar and batteries, but to complement them with sources of reliable, dispatchable clean power that can run regardless of weather.
The two leading candidates are nuclear fission and space-based solar power. Both can provide the steady baseload power that reduces the need for massive solar overbuild and battery installations. Studies consistently show that mixed clean energy systems – combining intermittent renewables with dispatchable clean sources – cost significantly less than battery-only approaches while increasing energy security. This is why we are seeing a resurgence of interest in nuclear power by many countries as well as large energy users like cloud/AI firms who have high energy and high reliability needs.
Solar, wind, and batteries will absolutely dominate our clean energy future and provide the majority of our electricity. But for a truly resilient, fully decarbonised grid that never needs fossil fuel backup, we likely need multiple clean technologies working together. Space-based solar power could be the reliable partner that makes the entire system both cheaper and more secure, thereby accelerating our replacement of fossil fuels.
Space-based solar power involves significant costs primarily driven by development, deployment, and operational factors. Previous studies, most of which envisioned large government programmes driving quickly to gigawatt-scale solutions, have estimated relatively high upfront development costs in the many billions of Euros. For example, according to a cost-benefit study performed by ESA in 2022, the development costs for a gigawatt-scale space-based solar power system would be in the same range as other large energy infrastructures like nuclear power, with the deployment costs for the very first gigawatt-scale systems estimated around 10 billion euros per gigawatt.
However, there are private investor-led startup approaches being developed as well in Europe and the US, which take a more stepped-development approach starting with much smaller systems serving high-value customers in specific regions of the world (where energy access is particularly challenging and expensive) and then scaling up gradually from there. These approaches suggest that the first space-based solar power systems could be in operation delivering commercially-viable power from space to some early customers far sooner and for far less money than the traditional government-led roadmaps focused on societal decarbonisation.
Initial electricity costs per megawatt-hour (MWh) are expected to be comparable to nuclear power but will decrease over time as space-based solar power plants are scaled up in number and size as well as through technological advancement. International studies repeatedly confirm that space-based solar power can eventually become cheaper than all alternative forms of firm, reliable energy (i.e. renewables plus storage, nuclear, geothermal, and fossil fuels).
The key cost drivers for space-based solar power include:
Launch costs have historically been a major hurdle for economic viability, but recent advancements in reusable launchers are driving costs down.
The challenge ultimately is to reduce the setup and operations costs sufficiently, such that the electricity, when sold at market prices on Earth, will result in a commercially profitable enterprise. As launch and manufacturing costs fall and deployment ramps up, global studies show space-based solar power could become as affordable – or even cheaper – than ground-based renewables. Plus, it delivers energy 24/7 without the need for storage thereby resulting in lower system-level costs of energy infrastructure, which ultimately reduces prices for users.
Recent international studies suggest space-based solar power could deliver competitively priced electricity within the next decade, assuming current trends in launch and hardware costs continue. Long-term cost estimates for scaled space-based solar power are in the range of €50/MWh or less, making it much cheaper than clean energy sources with similar characteristics, especially when considered at overall system level. This level of cost, for a generation and distribution source like space-based solar power, will finally lead to the reduced energy prices for final users that society demands, while providing decarbonised power. NASA’s 2024 modeling even suggests that space-based solar power could eventually outcompete terrestrial renewables (without storage) on cost, becoming the world’s cheapest, cleanest, and most scalable energy solution.
Recent studies have shown that if rapid technology development continues, space-based solar power could cut Europe’s energy costs substantially and offset a large fraction of the wind and ground-based solar power that would otherwise need to be built in the next 2-3 decades.
Each step, starting with solar collection and moving through conversion to radiofrequencies, transmission, collection by rectennas, and reconversion into DC and eventually AC electricity, introduces losses, reducing the overall end-to-end efficiency of space-based solar power.
However, studies show that even if ‘only’ 10% of the energy falling on the solar panels is delivered to the grid, it will still be economically viable.
While this may sound low, what’s important for the economics is that for whatever remaining energy that is delivered into the grid, at a given price/kWh, that the resulting revenue will pay back all the capital and operational expenditure – that is, launch, assembly and maintenance of the space and ground systems – as well as turn over a profit.
This has indeed been confirmed by numerous studies worldwide and is the foundation of the business case for space-based solar power. This comes substantially from the very high capacity factor, or ‘uptime’ of solar power plants, where in the right orbit, solar energy can be generated 24/7, almost without interruption.
Precise beam-steering will maximise the energy transmission, and improvements in solar cell, DC-RF conversion and rectenna technology will all lead to improved efficiency over time, further reducing the cost of electricity from space.
Read more about the efficiency of the energy conversion chain in our technical challenges of space-based solar power blog post.
Previously, despite its attractive characteristics as a potential global energy source, high launch costs from expendable launchers made space-based solar power economically unfeasible compared to terrestrial solutions.
However, now with the advances in wireless power transmission, mass-production of spacecraft, and with the proof that reusable rockets can dramatically reduce launch costs – with the potential to lower costs even further through upcoming heavy-left launch vehicles like Starship – the construction of dedicated space-based solar power satellites is finally approaching economic viability.
Initial small-scale systems delivering commercially-viable power in high-value markets could be deployed in the next five years, assuming sufficient funding is obtained from investors to develop space-based solar power systems and fully-reusable launch systems are commercially available.
Space-based solar power relies on established technological principles and known physics, requiring no groundbreaking discoveries. However, the primary challenge to do it at scale for a wide-range of applications, lies in the scale of the required structures both in space and on Earth as well as the economics of launching, constructing and operating these structures.
Initial systems will likely be at the smaller end of the scale of power generation and transmission (megawatts) but these will still require relatively large structures requiring in-space assembly and very lightweight, low-cost structures to make it an economically viable enterprise.
The biggest challenges appear to be economic rather than technical, where the cost of transportation, assembly and maintenance needs to drop to much lower levels than today. Some alternative solutions are also being pursued, using laser power transmission, which may allow utilisation of a constellation of smaller free-flying satellites that do not have to be physically connected into a single larger structure. This may get round the challenge of in-orbit assembly, but the scalability of this approach to much higher power levels is still unclear.
Eventually, to serve large-scale users and to supply the grid, power plants in orbit producing hundreds of megawatts to gigawatts of power are required to replace existing non-clean sources such as coal and gas power stations. To gather such levels of solar power, even in orbit where the Sun is more intense, would require solar farms square kilometres in area, with ground-based receiver stations a few kilometres across. This is very much larger than any structure that has been assembled in space today. The construction of such large structures in space would require affordable and regular launches to place the necessary hardware in orbit, as well as reliable and cost-effective autonomous robotic in-space assembly systems. Fortunately, such systems are in development today and will soon be in regular use.
Successful demonstration missions have already proven that wireless power transmission is possible, and other commercial ventures are pushing forward with in-orbit assembly/servicing demonstrations, and developing enabling components. Upcoming in-orbit demos to note include:
At the current rate of progress, and if the in-orbit demonstrations are successful, it is anticipated that privately-funded commercially-driven efforts will be the first to deploy small-scale space-based solar power by 2030, with gradual scaling up during the 2030s limited only by the level of private and public funding available. If concerted efforts are made by both the private and public sector globally, space-based solar power could be supplying a substantial fraction of the Earth’s energy needs in the next 20 years and help accelerate the decarbonisation of societies globally.
Space-based solar power (SBSP) is being actively pursued worldwide, through private, commercial and agency-level entities.
Government agencies and research establishments:
Major corporations:
Notable startups and ventures:
Most space-based solar power systems use microwave frequencies to transmit power to Earth. The specific frequencies and intensities are chosen to minimise atmospheric and biological impact, similar to the applications that are all around us using microwave frequencies: mobile networks, wi-fi, microwave ovens.
Space-based solar power designs have a maximum power density in the beam centre of about 250 W/m², much less than the equivalent peak intensity encountered by standing in the midday Sun at the equator (1000 W/m²).
Even though the peak power densities are low, they are still above regulatory safe limits for public exposure, therefore the entrance to the receiving station (rectenna) sites would be restricted by fencing. Power levels will be below the safe limit of 10W/m² outside of the fencing. Nonetheless, further studies are needed to assess the long-term impacts on health, and international standards need defining to ensure safety and environmental compatibility.
The beam from a space-based solar power system is designed with multiple layers of precision control and safety to ensure it is always correctly directed at the ground receiving station and poses no risk to people or property. The system uses an encrypted and secured pilot beam sent from the ground station to the satellite to precisely steer and align the power beam. If this pilot beam signal is not received or alignment is lost, the power transmission automatically shuts off, preventing any misdirected or stray energy beams.
By design, space-based solar power systems cannot be weaponised or converted into high-intensity beams like lasers or particle weapons. The power beam’s physical characteristics and overall platform design limit peak intensity and prevent focusing the beam beyond safe levels. The system lacks the infrastructure for alternative uses of the transmitted power, ensuring it is dedicated exclusively to safe energy delivery. These safety and anti-weaponization features are integral parts of the ongoing development and regulatory compliance efforts to address societal concerns.
The energy beam from space-based solar power is expected to have a very minimal heating effect on Earth's atmosphere. Although some power loss occurs during energy conversion and transmission steps, initial assessments show that the additional energy introduced by space-based solar power is insignificant compared to the total solar energy absorbed by Earth.
The Sun shines about 170,000 TW of power onto the Earth continuously, with about 70% of it absorbed by the atmosphere and the surface and about 30% of it reflected back into space. Even 1000 solar power satellites, each beaming 2GW of power down to Earth, would only add an additional 0.001% of energy. Furthermore, solar output itself has a much greater variation of about 0.1% over its 11-year cycle.
Radiofrequency power transmission could interfere with satellite, aviation or terrestrial communications, if not properly managed. Thus space-based solar power systems are designed to use narrow spot frequencies below 10 GHz, minimizing interference with existing communication bands. Forming and steering a narrow precise beam will also avoid stray emissions.
Technology development is also ongoing to improve the performance of narrow-band power amplifiers that convert DC electricity to radio frequencies to help with avoiding interference.
Discussions are ongoing with international regulatory bodies to understand issues around the use of power beaming in the Earth and Earth-orbital environments in view of potentially updating spectrum allocation regulations in support of space-based solar power.
A fully realised space-based solar power installation that can produce gigawatts of power may span more than a kilometre wide. It would be large enough to be visible like a star in the night sky due to its vast arrays of solar photovoltaic panels.
However, its position in geostationary orbit (GEO, approximately 36,000 km above Earth) means it appears very small from the ground, much smaller in apparent size than satellites like the International Space Station (ISS), which orbits at around 400 km. For example, to appear as large as the ISS does from Earth, an object in geostationary orbit would need to be about 10 km wide. Because its orbital period matches the Earth's rotation period, the satellite appears stationary in the sky relative to a fixed point on the ground.
Smaller demonstration satellites or low Earth orbit test satellites for space-based solar power would have negligible visibility.
While large in physical size, the visual angle of space-based solar power satellites when viewed from Earth is much smaller than that of lower orbit satellites because of their much greater distance. The high orbit and design considerations minimize their impact on visual sky observations.
Solar power satellites are designed primarily to maximize sunlight collection rather than reflect light back to Earth, so they do not significantly contribute to night sky brightness beyond what is typical for satellites at geostationary orbit.
The specific application of orbital reflector/mirrors for delivering reflected sunlight to locations on the Earth, e.g. solar farms, will be a more significant source of light pollution in areas within a certain distance of the beaming locations. Efforts are underway by companies working in this area to investigate the extent of the potential light pollution and possible mitigation measures that can be undertaken to minimise/eliminate it.
Space-based solar power infrastructure may cover several kilometres, making it vulnerable to collisions from orbital debris. It may itself contribute to the problem if struck by objects or when it reaches the end of its operational life. These installations not only need to withstand impacts from existing fragments in orbit, but also require careful planning to avoid generation of debris during construction and operation, but prevent becoming sources of additional clutter once decommissioned. Design choices can and are being made early on to minimise the potential of the space infrastructure becoming a significant source of debris.
In terms of susceptibility to damage by orbital debris, both natural and human-made, resilience is ensured by the modular architecture of space-based solar power infrastructure, which avoids single points of failure, and allows continued operation even if some modules are damaged. Repair or replacing modules could also be designed into the overall mission concept thanks to in-orbit robotic maintenance capabilities.
Space agencies and private investors are actively investing in debris removal and in-space recycling capabilities to ensure the sustainable use of space. Many of these capabilities will be applicable to space-based solar power, which itself will be a large enough industry to drive the further development of, and provide a sustained market for, these capabilities.
Rocket launches contribute to atmospheric pollution and carbon emissions, raising concerns about the net environmental benefit of space-based solar power. Reusable launch systems and the use of green propellants however, are already reducing the carbon footprint of launches.
Analysis for the UK’s CASSIOPeiA concept suggests an energy payback period of just 23 days for the hydrogen propellant used in launches. This is possible thanks to the near-constant sunshine that is available in high orbit, allowing space solar power plants to provide an abundant clean energy output for the energy that has been invested in making them (both through launches and the manufacturing of the hardware).
Other international studies, including those by the European Space Agency in 2023, confirm that the carbon and energy payback period of space-based solar power can be much better than ground-based solar, making space-based solar power a very environmentally-friendly energy source.
By displacing fossil power stations, space-based solar power plants will result in far less greenhouse gas emissions being produced annually compared to the annual lifecycle emissions from launching and operating the space-based solar power plants themselves.
Nonetheless, today, further research on the environmental effects of large numbers of rocket launches, especially at high-altitude, does need to be performed to improve our understanding of the potential effects on the upper atmosphere so that mitigation approaches can be developed.
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