POWER December 2021 - 10

GLOBAL MONITOR
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 whiteknuckle
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
10
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, FrazerNash
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.
" 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
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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
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
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POWER December 2021

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