Industry Case Study: Space Based Solar Power: Meeting the Energy Demand of the Future

Space Universities Network & Industry Case Study

This is a UK Space Universities Network Industry case study, one of a series of case studies aimed at providing teaching exercises for UK higher education. The University of the West of England and the UK startup company Space Solar Ltd. developed this case study.

Introduction

Space Based Solar Power (SBSP) is a conceptual solution for the growing energy demand, and filling the provision gap forecasted in the zero-carbon energy infrastructure.

This case study will introduce the idea of SBSP, net zero and how to integrate SBSP into the energy grid.

Throughout this study, examples are used to illustrate this concept and provide students with an experience of using excel forecasting data in the context of SBSP.

Tell us what you think! We’d love to hear from you to help us improve our case study, and to maximise its utility in teaching. Please comment on this resource using the brief form at the bottom of this page.

Learning Objectives

After completing this case study, you should be able to:

Describe the origins of SBSP
Analyse how SBSP can integrate into a wider energy grid, to help meet net-zero targets.
Calculate the contribution of different types of power generation to net-zero.
Evaluate some of the current challenges with SBSP.

1. What is Space Based Solar Power?

Space Based Solar Power, or SBSP, has its roots in science fiction, with the first record in Isaac Asimov’s 1941 short story “Reason”. In this a space station transmits energy collected from the Sun to various planets using microwave beams.

Figure 1: Cover image for Asimov’s “Reason” published in Astounding Science-Fiction April 1941

The first SBSP concept was described in 1968, with a patent granted to Dr Peter Glaser in 1973 for his method of transmitting power over long distances using microwaves from a large antenna to a much large one. A broad study was conducted NASA in 1974, with the concept showing “enough promise to merit further investigation and research” [1].

In recent years SBSP has been investigated by Japan, China, Russia, India, Europe, the UK and the US. Japan established SBSP as a national goal in 2008, with a roadmap to commercial viability. China began construction of a testing base in 2019, with plans for a 200-tonne station launched by 2035, with capability to generate megawatts of power. Caltech University in the US demonstrated beaming power back to Earth using microwaves in 2023. The European Space Agency has proposed an SBSP concept, SOLARIS, with in-orbit demonstration in the 2030s, and an operational geostationary station capable of generating up to a petawatt of power by 2040. This could supply 14 – 33 % of Europe’s current power . In the UK, the concept of SBSP is based around the CASSIOPeiA architecture, that can be used in various sizes and orbits. Early designs are based around a geosynchronous satellite with 1700 m diameter weighing 2000 tonnes– delivering up to 1GW of power.

SBSP works by transmitting microwaves from a large antenna on a spacecraft, to a much larger one on the ground- known as a ‘rectenna’. The power beaming process is shown in Figure 2.

Figure 2: SBSP Concept of Operations. Image credit ESA.

Clearly, SBSP has the potential to revolutionise the world’s energy needs, but there are also challenges that must be addressed before heavy investment in the idea.

1.1 Advantages of SBSP

24/7 – it is always sunny in space, and with an appropriate orbit, SBSP can generate power for 99% of the year.
Exportable – Some concepts use an RF technique of beam-steering, that allows a single geostationary satellite to redirect its beam between countries in seconds. This is particularly useful for geosynchronous satellites that typically have a view of ~1/4 of the Earth. In the case of CASSIOPeiA, this beam-steering provides both a power generation and transmission system.
Safe – Energy transmission through the atmosphere is at a low power density- just 1/4 the intensity of the midday Sun!
Scalable – designs can be hyper-modular, comprising many similar modules. This would result in the ability to produce several GW per year with a supply chain similar to the automotive or semiconductor manufacturing industry, and leads to good economics though the economics of scale.
Sustainable – Land/Area usage would be 40% of that of terrestrial solar and 8% of that of offshore wind for the equivalent energy output. The carbon footprint is estimated at 26 g CO2 /kWh – which is half of terrestrial solar’s carbon footprint.
Secure and Reliable – The satellites have an encrypted uplink, and a modular design allows tolerance to failures and eases maintenance.
Baseline Power – SBSP provides and known and reliable power, essential for meeting the power demand in a grid dominated by intermittent energy sources (e.g. terrestrial solar and wind).
Cost – From the Levelised Cost of Electricity (LCOE) based on the Frazer-Nash report [1], SBSP should have a similar LCOE to that of renewables, and significantly cheaper that other baseloads (e.g. Nuclear). Baseload is defined as the minimum amount of electric power delivered or required over a given period of time at a steady rate.

1.2 Disadvantages of SBSP

Launch – Relies on low cost to launch. SBSP systems require launching 6.5 kg/kW. Figures indicate that the price to geostationary orbit cannot exceed $200/kg for SBSP to be competitive
Expansive – Airy disc beam spreading neccessitates gigawatt scale stations in orbit. A 1km disc in geosynchronous orbit spreads out to 10km on Earth’s surface, at 2.45GHz.
Loud Spectra – This broadcast frequency requires spatial of SBSP from other satellites using similar frequencies. This is mitigated somewhat by only needing a single frequency, allocated by the International Telecommunications Union (ITU).
Space debris hazard – Risk of damage to the system from space debris – primarily a risk in transit from LEO to GEO. This is mitigated in the CASSIOPeiA architecture by making components thin (<350g/m²), meaning micrometeorites will tear through the system rather than shatter it.
Low efficiency – Loss of energy during multiple photon-electron conversions. The initial conversion from sunlight at a single optimised semiconductor junction is 34% (the Shockley-Queisser efficiency limit) [3]. The conversion on the ground from RF to electrical power is 85-91% efficient [4].
Large Space Structure – a space structure of this scale has never been seen before, and it will present complex and likely sometimes unforeseen engineering difficulties. For example, thermal gradients present a challenge to maintaining the shape of reflectors.
Autonomous – the system must be autonomously or near-autonomously maintained

2. Net Zero for the Future

But why is Space Based Solar Power important? It could provide an alternative approach to boosting the percentage of ‘green’ energy supplied to a national grid. This could be vital for supporting ‘net zero by 2050’ policies.

Organizations around the world are pursuing technologies and policies called “net zero”. According to the UN, net zero means “cutting greenhouse gas emissions as close to zero as possible, with any remaining emissions re-absorbed from the atmosphere by oceans and forests for instance.” Many countries are targeting this by 2050 (or sooner)

Why is Net Zero Important?

In order to avert the worst impacts of climate change and preserve a liveable planet, global temperature increase needs to be limited to 1.5°C above pre-industrial levels. This was exceeded for the first time in 2024. Whilst this alone doesn’t mean the doom of planet Earth, with long-term temperature changes considered on a decadal scale, it is a wake-up call for governments across the world.

Currently, the Earth is already about 1.2°C warmer than it was in the late 1800s, and emissions continue to rise. To keep global warming to no more than 2°C above pre-industrial levels (and indeed targeting limiting to a 1.5°C increase), as called for in the Paris Agreement [7], emissions need to be reduced by 45% by 2030 and reach net zero by 2050. The Paris Agreement is a legally binding international treaty on climate change, adopted at the UN Climate Change Conference (COP2) in Paris.

The G20, an intergovernmental forum comprising of 19 countries (as well as the EU and African Union) accounting for around 85% of gross world product [8], are responsible for around 77% of global greenhouse gas emissions. China, the USA, India, EU, Russia and Brazil, are responsible for 63% of global emissions [9]. 89% of global emissions are produced by countries with net zero emissions targets:

Figure 3: Climate Action Tracker figure showing global emissions covered by national net zero targets

It should be noted the US announced it was pulling out of the Paris Agreement in 2016, less than a year after it first signed up, before officially withdrawing in 2020. It then rejoined following the 2020 presidential election, and left again following the 2024 presidential election. With the US responsible for 14% of global emissions, this is a major concern for global net zero targets.

Achieving Net Zero by 2050

According to the International Energy Agency, the generation of energy in the world is expected to follow the trend shown in Table 1 [11]. In this, “Renewables” include solar photovoltaic, wind, hydro, bioenergy, concentrated solar power, geothermal and marine. CCUS stands for Carbon Capture Utilisation and Storage, and “Unabated Fossil Fuels” are fuels produced and used without interventions that substantially reduce the amount of greenhouse gases emitted.

Table 1: World Electricity Sector – Total Generation [TWh]. Orange highlight indicated projected figures.

	2022	2030	2035	2040	2050
RENEWABLES	8,599	22,532	36,739	50,459	68,430
NUCLEAR	2,682	3,936	4,952	5,583	6,015
HYDROGEN & AMMONIA	–	373	745	1,028	1,161
FOSSIL FUELS (WITH CCUS)	1	220	681	847	996
UNABATED FOSSIL FUELS	17,636	11,066	4,241	1,121	158
TOTAL	29,033	38,207	47,427	59,111	76,838

To achieve net zero, unabated fossil fuel usage must be reduced to zero, leaving an energy gap of over 65 PWh comparing the green electricity generation capacity of 2022 and the predicted demand of 2050. This corresponds to a shortfall of 7.5 TW of power per annum. Currently only ~30% of global energy comes from ‘clean’ energy sources, so not only does energy production need to increase, but 70% of current generation needs to be replaced.

Current UK climate plans would lead to a 2.6% decrease in global greenhouse gas emissions by 2030 (compared to 2019) but to keep global warming <1.5 degrees, global emissions need to be reduced by 43% by 2030. The next Nationally Determined Contribution commits the UK to reducing greenhouse gas emissions by at least 68% by 3020, compared to a 1990 baseline [12]. Despite meeting its 2022 target of reduction of 38% on 1990 levels and that emission levels are currently [12] less than 50% of 1990 levels, the 2030 target is at risk, with only a third of actions covered by ‘credible’ plans.

How can we meet the increasing global energy demand whilst reducing our reliance on fossil fuels? Space Based Solar Power is one option to fill the gap. So, as an example, let us look deeper into the design and figures for CASSIOPeiA- a UK design for an SBSP system.

3. CASSIOPeiA Concept of Operations

CASSIOPeiA stands for Constant Aperture, Solid-State, Integrated, Orbital Phased Array, and is suitable for wireless power transfer in a space environment [13]. The name has been adopted by an SBSP concept being developed by Space Solar and partners, combining the phased array antenna with high efficiency photovoltaic panels.

CASSIOPeiA is to be constructed from ultra-lightweight materials, with detail and conservative modelling showing a 2 GW variant should have a mass of 2000 tonnes – giving a baseload specific power of 1 kW/kg, five times greater than the nearest alternative SBSP concept [13]. The wireless power transmission has been demonstrated by Space Solar terrestrially with their HARRIER system, and the design reached concept maturity level 4 (the same as fusion) in February 2025 [14].

Not only is the 2GW version of CASSIOPeiA about the same mass as a fully fuelled Saturn-V (2800 tonnes) but it would be the largest human-made object in space. Its is expected to be 1402 metres in diameter, and 3957 metres in height. Figure 4 shows an early (slightly larger) CASSIOPeiA compared to the International Space Station, the Eiffel Tower and the current tallest building in the world, the Burj Khalifa.

Figure 4: Size of CASSIOPeiA compared to a selection of the largest human-made objects [15].

Design

CASSIOPeiA has two primary reflectors connected to the helical power core by twist-axis longerons and main longerons, as shown in Figure 5. The power core and main longerons also have utility nodes along them, providing station keeping, shape control and satellite to ground communications.

Figure 5: Main components of the CASSIOPieA SBSP solution [15].

The solar reflectors ensure the sunlight is reflected constantly onto the solar panel array below it, made up of approximately 60,000 layers of photovoltaic cells, all converting the light into high frequency radio waves. The unique solid-state design means that unlike other SBSP architectures, all elements are always in use: all the photovoltaic cells receive constant maximum sun illumination, and all RF elements contribute to the power beam throughout its orbit.

Figure 6: CASSIOPeiA On-Orbit Functions [15].

The helical core of CASSIOPeiA (number 2 in Figure 6), contains both the solar panels to convert sunlight to electrical energy, and dipole antennas to transmit this energy back to Earth. A single element of the core has three omni-directional dipole antennas. Their centres are placed apart, enabling the element to perform beam-steering. This technique involves manipulating the phase and magnitude of each of the antennas, such that they combine to create a directional, steerable energy beam [13]. These antennas are connected at their centre to the element’s solar cells. These are multi-junction 25 m thin-film cells for efficient power generation The final part of an element is a Fresnel lens, which helps to concentrate the incident sunlight onto the next layer of solar cells- increasing efficiency and reducing the number of solar cells needed.

Figure 7: Small-scale CASSIOPeiA phased array. The triple dipole elements are shown [13].

This setup can be seen in Figure 7 and Figure 8. What is also visible from this figure is that the ideal helical shape of the core is able to be discretised into multiple layers of elements. In this way, the antennas themselves are able to be used as the structural support for the core, saving weight. It can also be seen how the Fresnel lenses of one layer act upon the layer below them.

Figure 8: General Arrangement of the Power Core of CASSIOPeiA [15].

So how exactly can CASSEOPeiA help to meet global net zero targets, and to what extent? The next sections detail two exercises that aim to guide you in answering these critical questions…

4. Interactive Exercise 1 – (30 minutes)

This exercise will introduce you to a spreadsheet tool developed by a UK startup called Space Solar who are completing a Phase 2 feasibility study for building a CASSIOPeiA SBSP station, funded in part by the UK government. The spreadsheet aims to investigate the energy balance needed for net zero by 2050 by looking at values for the different types of energy and comparing them.

Download and open the Excel file below “Energy Comparison.xls”. The copyright in this document is the property of Space Solar Group Holdings Limited, with permission given to SUN to distribute this for educational purposes.

Figure 9: Sheets in the SpaceSolarEnergyComparison Excel File.

On opening this, you will land in “Front Sheet”, detailing the usage and copyright policy of the material in the spreadsheet. , highlighting its advantages as an energy generation method.

The “Input” sheet is the first sheet and contains data used in the energy balance investigation. At the top of this sheet is the International Energy Agency’s predictions of the required total generation for several milestone years leading up to 2050: World Electricity Section – Total Generation (TWh).

Figure 10: IEA world electricity generation forecast.

Question 1.1: The formula in cell C14 (needed to be created or replaced) has been accidentally deleted and needs to be restored. Use what you have learned about net zero to re-create this formula.

Hint: assume the current year is 2022, and that you are looking to meet the 2050 requirements.

Following that, energy is converted into power by dividing by time. Then, if we take the number of years left until 2050, the annual additional green energy capacity can be determined.

Figure 11: Determination of the needed annual additional generation from the net zero electricity prediction.

The subsequent 4 blocks each deal with a specific green energy solution with figures taken from real examples of each type of energy generation. These are: Nuclear (Hinkley Point C), Terrestrial Solar (Bhadla Solar Park), Offshore Wind (Hornsea 1) and SBSP (CASSIOPeiA). For each system, the power and energy generation, and cost of each system is presented alongside a few pros and cons. The land area requirement is also included. Following this is an estimate of the number of power stations that can be built in a year, and the time to build one unit – which can be combined to give the number that can be built by 2050.

Question 1.2: What is the formula used for the calculation of how many units of a particular method can be built by 2050?

Hint: The yearly build rate can’t be achieved earlier than: current date + the time to build 1 unit.

Question 1.3: The Terrestrial Solar, and Offshore Wind solutions include a term for the “capacity factor ” in the calculation of energy. What does the capacity factor represent and what can effect the capacity factor?

Question 1.4: The Nuclear solution also has a capacity factor to account for plant down times, but this is not included in the calculation. Change the formula in C22 to account for the capacity factor of Nuclear generation.

Now that you understand how the Input sheet works, we will have a quick look at the ‘Activity’ sheet. The first section of this sheet presents the 4 energy generation solutions from the input sheet and works out how many units of the system are needed for that method to provide 100% of the estimated required power generation capacity in 2050. The second section of the sheet will be explained in the next exercise.

Question 1.5: Taking Just Terrestrial Solar and Just Nuclear as examples, fill in the missing formulae to work out the total number of wind farms, how many are built each year, the total number of turbine, the land area usage and cost for the Just Offshore Wind solution.

5. Interactive Exercise 2 – (1 hour)

On completion of Exercise 1 you should now have a basic working understanding of the spreadsheet and you will have completed all the formulae necessary to proceed.

Question 2.1: Look at the 4 cases where there is only one form of renewable energy generation being used. Critically evaluate the feasibility of each of these cases, and compare advantages and disadvantages of each. Consider the build rate, land area and cost of each solution.

To be able to meet future energy generation needs, a mixture of the 4 types of energy generation is required if we are using only green energy sources. At this point, we need to ba lance the types of energy generation to meet the goal of Net Zero by 2050.
The second half of the “Activity” sheet includes a table with a balance of each of the 4 energy generation techniques providing a percentage of the generation needed.

Figure 12: Energy mixture table.

Figure 12 shows the same calculations as the first section of the sheet. You will note there is conditional formatting on the “Total Plants Needed” column, and this relates to the estimate of yearly build rate from the “Input” sheet – you will note that changing the yearly build rate of SBSP systems to1 built per year, for example, means that all methods are now red i.e the proposed percentage mix requires more units than can be built! Land area, cost and build rate are all competing factors in this balance.
With the smallest land area belonging to Nuclear, it appears at first that the way to minimise the land area needed for power generation is to use only Nuclear plants. But to do this, we see that it would take nearly 2600 reactors (104 per year), which is well above the estimated build rate of 20 nuclear power stations per year.

Answer:The solution is to maximise the Nuclear generation, given the it has smallest land area. Following this, SBSP, Terrestrial Solar and Offshore Wind will be maximised in this order (as the order of decreasing energy density).
Nuclear
From Reactor Startups/Closures, the maximum historic rate seems to be 30 plants being built per year, so the rate maximum deliverable rate (Input!C26) is set to this. This gives us the potential to build 300 reactors by 2050 (note that this can be further increased to 600, by reducing the construction time from 15 years from Hinkley C, to 5 years, an estimate from the 1970s/80s) The capacity factor estimate of 80% seems to be low, and can be boosted to 90% (capacity factor – US EIA).
300 reactors is far short of the 2598 needed for 100% Nuclear , but does allow 11% of the predicted 2050 generation to be made nuclear (with this rising to 23% if we allow the time change mentioned earlier).
SBSP
The next smallest land area is from SBSP, though the numbers on this are the least certain. Space Solar wants to build > 20 GW/year and there are several other SBSP companies. Looking at the numbers in the inputs sheet, we see an estimated time to build of 1 year, and a yearly build rate of 200 stations. With CASSIOPeiA being a 1GW system, Space Solar’s 20GW translates to 20 systems, and the estimate of 200 assumes 9 other companies will do the same. The hyper modularity of SBSP should mean that this has a similar build capacity to that off terrestrial solar. 200 units a year allows SBSP to take 40% of the 2050 energy generation requirement.
Terrestrial Solar
The system with the third lowest land area is Terrestrial solar. The annual build rate is estimated to be around 150 – based upon an additional capacity of 300-400 GW per year (IEA – Renewables). The capacity factor of 24% is consistent with current power stations (capacity factor – US EIA). This gives a total building capacity of 3000 Terrestrial Solar Parks , though allowing the time to build to be reduced to 2 years (IEA – Build Time) allows for 3450 stations. This accounts for 25% and 29% of the 2050 demand respectively.
Offshore Wind
The final power technology is Offshore Wind, taking by far the largest land area. The capacity factor is estimated to be 47%, with it also taking 2 years to build. With an estimated additional capacity of 78GW per year, a yearly build rate of 78 facilities per year can be made (GWEC – Global Wind Report 2023). This accounts for 13% of the estimated demand in 2050.

Table 2: Land area minimisation optimisation.

Power Generation	Percentage [%]
Nuclear	11
SBSP	40
Terrestrial Solar	25
Offshore Wind	13

Using these three power generation strategies, we get a total of 89% capacity generation needed for 2050.

The same process can be used to estimate the:

Ideal ratio to minimise cost.
Ideal ratio to meet goal.

Though given the estimates used in the above answer, the results will be the same.

Interested? Here are some further tasks to challenge yourself with:

The energy mixes that you created in the previous exercise make no assumptions as to energy storage. This is critical for non-baseload methods (Terrestrial Solar and Offshore Wind) which don’t generate power for the entire day.

The Excel model has a final sheet “Activity with Storage”, that looks at how the energy balance is effected by requiring energy storage for Terrestrial Solar and Offshore Wind.

This sheet adds an estimate of the number of hours the non-baseload systems are not generating power per day. The power required to be generated is refined, and the size and cost of battery storage required for the excess power during generation (to be used when the system isn’t actively generating power).

The inputs to the simple battery storage model can be found in the inputs sheet, and cover the storage energy per volume, and the cost per Watt hour of this storage.

Repeat Exercise 2 for this new model.

Can you also account for the capacity factors of the Nuclear and SBSP generation methods?

[1] P. E. Glaser, O. E. Maynard, J. Mackovciak, Jr, and E. L. Ralph, ‘Feasibility study of a satellite solar power station’, NASA CR-2357, Feb. 1974. Accessed: Mar. 17, 2025. [Online]. Available: https://ntrs.nasa.gov/api/citations/19750015611/downloads/19750015611.pdf

[2] Frazer-Nash Consultancy, ‘Space Based Solar Power: De-risking the pathway to Net Zero’, 004456-52265R, 2021. [Online]. Available: https://www.fnc.co.uk/media/e15ing0q/frazer-nash-sbsp-executive-summary-final.pdf

[3] E. Rodgers et al., ‘Space-Based Solar Power’, NASA Office of Technology, Policy, and Strategy, 20230018600, Jan. 2024.

[4] ‘Special deal on photon-to-electron conversion: Two for one!’, MIT News | Massachusetts Institute of Technology, Apr. 18, 2013. Accessed: Jan. 27, 2025. [Online]. Available: https://news.mit.edu/2013/photon-to-electron-conversion-0418

[5] I. Cash, ‘CASSIOPeiA solar power satellite’, in 2017 IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Montreal, QC: IEEE, Oct. 2017, pp. 144–149. doi: 10.1109/WiSEE.2017.8124908.

[6] ‘Net Zero Tracker | Welcome’. Accessed: Jan. 27, 2025. [Online]. Available: https://zerotracker.net/

[7] ‘The Paris Agreement | UNFCCC’. Accessed: Jan. 27, 2025. [Online]. Available: https://unfccc.int/process-and-meetings/the-paris-agreement

[8] ‘About the G20’. Accessed: Jan. 27, 2025. [Online]. Available: https://www.g20.rio/en/about

[9] United Nations Environment Programme et al., Emissions Gap Report 2024: No more hot air … please! With a massive gap between rhetoric and reality, countries draft new climate commitments. United Nations Environment Programme, 2024. doi: 10.59117/20.500.11822/46404.

[10] ‘CAT net zero target evaluations’. Accessed: Jan. 27, 2025. [Online]. Available: https://climateactiontracker.org/global/cat-net-zero-target-evaluations/

[11] International Energy Agency, ‘World Energy Outlook 2023’, 2023. [Online]. Available: www.iea.org

[12] N. Burnett, S. Hinson, and I. Stewart, ‘The UK’s plans and progress to reach net zero by 2050’. Accessed: Jan. 27, 2025. [Online]. Available: https://researchbriefings.files.parliament.uk/documents/CBP-9888/CBP-9888.pdf

[13] I. Cash, ‘CASSIOPeiA – A new paradigm for space solar power’, Acta Astronautica, vol. 159, pp. 170–178, Jun. 2019, doi: 10.1016/j.actaastro.2019.03.063.

[14] ‘Space Solar – Breakthrough in Space-Based Energy: Space Solar Demonstrates World’s First 360° Wireless Power Transmission’, Space Solar. Accessed: Feb. 24, 2025. [Online]. Available: https://www.spacesolar.co.uk/breakthrough-in-space-based-energy-space-solar-demonstrates-worlds-first-360-wireless-power-transmission/

[15] ‘Space Solar, developing and commercialise Space-Based Solar Power’, Space Solar. Accessed: Jan. 27, 2025. [Online]. Available: https://www.spacesolar.co.uk/

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