Space-Based Solar Power May Be Closer Than You Think
The vision sounds far-fetched: If a kilometer-scale satellite could be outfitted with a hybrid array of photovoltaic (PV) and concentrating solar power (CSP) panels and launched into orbit 22,400 miles above Earth, it could continuously harvest 3.4 GW of solar power and beam it down to Earth via microwave radiation for grid consumption, potentially delivering 2 GW of dispatchable and baseload power. But according to a whole systems" set of detailed engineering and economic feasibility studies conducted by systems, engineering, and technology-oriented Frazer-Nash Consultancy for the UK government, this concept of a typical space-based solar power (SBSP) system is both technically and economically feasible-and it can be achieved within the next 18 years.
While still at an early stage of technical maturity, SBSP systems research and development has progressed steadily since the 1970s, spearheaded by several government space programs, including in the U.S., Japan, China, South Korea, and the European Union. And while it has existed for more than a century-it derives from Nicolas Tesla's grand vision for wireless power transfer (WPT)-the world's white-knuckle fight against climate change in the context of energy security, affordability, and scalability is making SBSP an extraordinarily attractive pursuit, noted Martin Soltau, lead of Frazer-Nash's Space business, and a lead developer of the report for the UK government.
It can provide baseload power but it can also provide this dispatchable power," said Soltau, who notably also co-chairs the Space Energy Initiative, a UK-based alliance of research and commercial energy, space, materials, and manufacturing entities that are dedicated to space power delivery by 2050. But then it's got these other real exciting advantages," Soltau told POWER at the end of September as the UK's Department for Business, Energy, and Industrial Strategy (BEIS) endorsed the SBSP feasibility studies. It doesn't produce waste, it doesn't have problems with fuel supply, it's very environmentally clean, and the carbon payback is very short," he said.
Also notable is that SBSP's terrestrial" footprint-which essentially only requires a receiving antenna and a conversion facility-is also much smaller, only a third of the size compared to terrestrial solar, and only about 3% of the size of an equivalent wind farm," Soltau said. As uniquely, it is possible to beam energy to other parts of the world," opening up new international collaboration to net-zero, potentially helping developing nations to decarbonize, and even shaking up traditional power markets.
The Frazer-Nash Consultancy study is especially significant because it represents one of the world's first whole system" space power-based independent assessments. The UK's interest in space power stems from an economic opportunity to establish a foothold in rapidly burgeoning civil and defense space activities around the world, essentially boosting private investment, and capitalize on its unique engineering and manufacturing strengths, like satellite manufacturing. But Soltau said the study, which stems from a government-sponsored innovation competition," could also offer international insight through its stakeholder-reviewed findings, which were gleaned over a six-month period and encapsulated two phases: one focused on technical opportunities and challenges, and the other on costs.
In its study Frazer-Nash recommended that the SBSP system concept be established to define user and system requirements, which would ultimately align more focused research activities. The UK government told POWER that as a next step, it is already exploring how it can potentially support innovation in the development of these dual-use" space power and terrestrial power systems.
The undertaking is markedly broad. As part of its engineering study, Frazer-Nash proposed a typical" SBSP system based on three leading concepts, which it chose as reference designs for its investigation. The typical system comprises a massive kilometer-scale satellite that would be launched to Geostationary Earth Orbit (GEO, about 36,000 kilometers above a point on the Earth) to enable gigawatt-scale generation.
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2. Frazer-Nash's study focused its cost modeling on CASSIOPeiA, a prototype satellite solar power design developed by International Electric, which features a helical structure with high-concentration solar PV (HCPV) panels. The panels are oriented to face north and south to collect light reflected off of mirrors at either end of the structure. Frazer-Nash also notably highlighted another design, the SPS Alpha, designed by John Mankins, an American. It concluded that both designs are technical and economically viable," and their development could be completed well before 2050." Courtesy: International Electric |
At this altitude the Sun is visible over 99% of the time," it noted. The satellite harvests solar power using large lightweight solar panels, often with a system of mirrors to reflect and concentrate sunlight onto the panels (Figure 2). That generated power is then converted into microwave radiation and beamed-in a safe" frequency of 2.45 GHz and intensity 230 W per square meter (which is one quarter of the intensity of midday sunlight)-to a rectifying antenna (or rectenna") on the ground. The ground rectenna then converts the electromagnetic energy into direct-current electricity, which can be converted and transformed to provide power to the grid with acceptable characteristics.
Significantly, the concept envisions a complete system that would comprise a constellation" of such satellites with a combined 10 GW capacity. However, the study also embeds the core generating system into a larger power study that includes enabling systems," such as spacelift, control station construction, ground station maintenance, and even potential legislation, permits, international agreements, and standards.
According to Soltau, the study concluded that leading satellite power concepts do not require any substantial advance in materials' technology or performance, but building them economically will require two principal capabilities that are today immature but rapidly developing: robotic in-orbit assembly, and a low-cost reusable space transportation infrastructure. This poses a substantial undertaking," he noted, given that the size of the system, and the need to assemble and integrate them in space, would be an order of magnitude larger in mass and extent than any spacecraft currently in orbit." Key to achieving the scale and ambition of the system will be to address the considerable engineering risk" through a program of design and technology demonstration, he said.
The study also identified an array of technical challenges, from maintaining the angle between the sun-pointing solar collector and the ground-pointing microwave transmitter, to the size and scaling of the microwave antenna. Optimizing the specific power of SBSP satellites-which have a mass of several thousand tons-and managing their components' thermal aspects will also be crucial.
Finding an optimum choice of power beaming frequency will also require a trade-off between the satellite orbit, satellite sizing, power level transmitted, power beaming efficiency, the transmitter diameter and receiver diameter, the thermal limits on the sandwich panel, and the upper safe limit of Radio Frequency (RF) intensity at the center of the received beam," the study acknowledges. Keeping frequencies at 2.45 GHz for larger (2 GW) systems, and 5.8 GHz for lower-power, lower-mass systems, may be a good guideline, it concluded.
The given technical challenges (and scope of engineering risks), the relatively low technical maturity of several technologies, and the diversity of technical concepts that have been proposed pose a long list of methodology limitations when assessing SBSP costs, the study acknowledges. However, by developing a bespoke cost model" that addresses uncertainty and focuses only on the CASSIOPeiA design, the study concludes that a typical SBSP could deliver a levelized cost of electricity (LCOE) of between35 ($47)/MWh and79 ($107)/MWh, assuming a successful development program.
The cost analysis included end-to-end production, launch, assembly, operational service life, and decommissioning," Soltau noted. The LCOE we calculated is for the nth of a kind, which would be quickly reached in the fourth or fifth system," given the modularity and repeatability of the design, he said. Each solar power satellite is highly modular, so you reduce production costs when you've got high production runs," he said.
Assuming a system is commissioned in 2040, the LCOE at the midpoint of50/MWh includes this very high hurdle rate of 20%" to account for estimate uncertainty as required by institutional investors, he noted. And what you'd expect is as the development proceeded, and we matured the technology, and all the development risk was retired, that the hurdle rate is going to fall well under 10%. At a 10% hurdle rate, the LCOE is only26/MWh-that's cheaper than the cheapest renewable technology in the UK at the moment," he said. This is why our government is excited, because it's actually looking not only at the technology's great characteristics, but it's actually very affordable as well."
Still, for now, to propel research and development, the UK government is looking at a net present value-a representation of overall development costs-of about16.3 billion ($22.1 billion), the study suggests. Another1 billion will also be necessary to support operating expenditure over the life of the system.
In its policy roadmap, however, Frazer-Nash suggests the public sector may only need to fully fund Phase 1, totaling350 million ($474 million) over the first five years. Thereafter the private sector could reasonably be expected to start investing an increasing proportion as shown," it says. As an incrementally valuable benefit, the program would potentially provide broader spillover economic benefits," including in areas that span wireless power transmission, semiconductor technology, PV technology, space grade electronics, robotics, space freight and transportation, and general skill development to support space activities, it said.
-Sonal Patel is a senior associate editor for POWER.
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