Energy from Orbit
Plans to capture solar energy from “solar farms” in space and beam it to earth were reported by Pallab Ghosh in a recent BBC news report (Ghosh, 2022). The article anticipated approval of a three-year feasibility and economic study aimed at eventually sending gigawatts of power to earth from space to help address future energy shortages.
A few days
later Olivia Allen reported that ESA, the European Space Agency, had approved plans
for further research into Space Based Solar Power, SBSP (Allen, 2022). The
project, known as SOLARIS, “will carry out research with the aim of developing
huge orbiting satellites fitted with solar panels that can collect the sun’s
energy and wirelessly beam it down to Earth.” Allen traces the concept back to
the 1970s, but regards the technology as only now close to what is needed to
realise the idea. Orbiting solar panels would receive continuous sunlight and so
provide continuous power to receivers on earth, transmitting energy over a distance
of 36,000km. Allen notes that “there is still a way to go” from the successful
transmission over a distance of 30m achieved in Munich earlier in the year. “China,
the USA, and Japan are also in the processes of developing plans for SBSP and a
UK company, Space Solar, is aiming to demonstrate beaming power from space
within the next 6 years.”
The UK is a
member of ESA (which is not an EU organisation) and some of the questions which
may occur to readers of the two articles referenced above have been addressed
in the paper “Space based solar power: de-risking the pathway to net zero” which
reports an independent study for BEIS by the Frazer-Nash Consultancy Ltd.
(BEIS, 2021). The Executive Summary of
the report begins by stating that there are challenges to the UK Government’s
legal commitment to reach Net Zero emissions by 2050, and that the risks could
be reduced by the novel generation technology of Space Based Solar Power. The
plan is to place “a constellation of very large satellites in a high earth orbit,
where the sun is visible over 99% of the time, collecting solar power and
beaming it securely to a fixed point on the earth.” This could provide clean
baseload energy independent of weather and of time of day or year. SBSP is seen
as viable and economically competitive, capable of providing an acceptable Levelised
Cost of Electricity (LCOE) and of bringing “substantial economic benefits for
the UK.” The report recommends incorporating SBSP into government policies and
initiating “a staged technology development and demonstration programme.”
The argument
for SBSP is developed in the rest of the report, beginning with a forecast
doubling of the global energy demand in the next thirty years, and continuing
with discussion of the concept and comparison with more conventional power
generation. The satellites which will capture solar energy are to be located in
geosynchronous orbits where they will be in sunlight more intense than that
received on earth for 99% of the time, making the energy storage associated
with ground based solar farms unnecessary.
Solar Power
Satellites are spacecraft on the order of a kilometre in scale, with lightweight
solar panels generating power in the region of 3 Gigawatts (GW). This is
converted to radio waves and transmitted to antennae on earth; the proposed
frequency is in the 1 to 10GHz range, where atmospheric conditions have little
effect on wireless power transmission. The receiving antennae convert the radio
waves to electricity, delivering an expected 2 GW to the grid, comparable to
the output of a nuclear power station. The ground antenna array (or ‘rectenna’)
is “a large open net structure, holding the small dipoles, or aerials which
capture the radio wave energy and convert it to DC electricity.” The radio beam
intensity must be kept low for safety reasons, and a figure of 240W/m2 is
suggested, “about a quarter of the intensity of the sun at the equator.” This
implies a very large array “typically an elliptical shape at UK latitudes,
measuring about 6.7km x 13km.” The size and power output lead to an overall
figure of about 29W per m2 of ground area, about three times greater than would
be produced by a solar array on the ground in the UK. The report suggests that
rectennas could be co-located with offshore wind farms, using existing grid
connections.
Satellite
construction is expected to be highly modular, using large numbers of a few types
of unit. This makes mass production possible, with assembly in orbit by
autonomous robots; it also gives resilience to damage, along with production
costs low enough to produce electricity at an acceptable price. Launching satellite
hardware into orbit is a dominant cost, but launch costs have fallen with the
development of reusable vertical launch rockets, and the demand which SBSP is
likely to create could increase this trend.
Assembly would be carried out in Medium Earth Orbit (MEO) to avoid the
risk from space debris in Low Earth Orbit and the harsh radiation environment
of the inner Van Allen belt. The satellite could then use its own solar power
to ascend to geostationary orbit. The satellite would be “an order of magnitude
larger in mass and extent than any spacecraft currently in orbit” and its power
to mass ratio (kW/ kg) is a key consideration: a figure in the range 0.5 - 1.0
kW/kg is considered “ambitious but feasible”. By the early 2040s a “constellation
of solar power satellites” could be delivering a substantial part of the UK’s
energy. An outline of the time framework shows ground based satellite and
balloon trials up to 2026, a 40 MW low orbit demonstrator by 2031, a 500 MW
satellite in operational orbit by 2035, a 2GW production prototype satellite
operational by 2039 and 15 % of UK energy delivered from orbit in 2042.
The paper mentions
ESA activity along with reviews of activity outside the UK. The USA is
conducting Space Solar Power research and development under a defence budget
and the Naval Research Lab is experimenting with power collection and
conversion in space on the X-37B spaceplane, but there is currently no civil
energy policy on SBSP from the US Department of Energy. Japan has undertaken SBSP research since the
1980s, focussing on wireless power transmission, with in-space experiments.
Japan has established space solar power as a national goal, and the Japan
Aerospace Exploitation Agency has a roadmap to commercial SBSP, demonstrating
kW scale transmission in 2015. The China Academy for Space Technology has a SBSP
programme and a development roadmap. The Chongqing Collaborative Innovation
Research Institute for Civil-Military Integration is constructing a facility
for Space Based Solar Power testing. South Korea is pursuing a number of power
beaming activities through the Korea Electrotechnology Research Institute and
private organisations. Both Australia and Canada have expressed interest in
SBSP, but without mention of government supported activities. There is thought
to be scope for the UK to take a political leadership role, either open or
focussed on strategic international partners, and exploratory discussions have
taken place.
Projected
cost comparisons for the UK between SBSP comprising five 2GW grid connected
power stations and other methods are presented, taking into account end to end
production, launch, assembly, operational service life and decommissioning: SBSP
appears slightly more expensive than onshore wind, but cheaper than Combined
Cycle Gas Turbine plus Carbon Capture and Storage (CCGT + CCS), Nuclear and
Biomass. The Net Present Value of overall development costs is estimated at
£16.3 billion, with full funding of £350 million in the first five years coming
from the public sector. The paper recommends that “the UK should integrate
Space Based Solar Power into key Government policies, and take a leadership
role in developing the technology.”
The
political risks listed include the large areas of land needed for the ground
antenna arrays; maintenance of development timescales; security of operations;
and the uncertainties of international collaboration. Economic uncertainties
involve the evolution of other forms of renewable energy; the predictability of
the cost of space launches; and the development of industrial capability. In
the social domain, there may be opposition to the technology involved and its
perceived dangers. Technological
uncertainties surround the techniques of robotic assembly and maintenance in
orbit; the manufacture of suitable panel modules; the efficiency of wireless
power transmission; beam control and operational life. Legal questions may
arise over regulation and spectrum and orbit allocation. Environmental issues
may raise difficulties regarding site development and lifetime carbon footprint,
and it may be difficult to prove that long term safety and decommissioning
strategy will be adequate.
There are other
perspectives on SBSP: Pagel (2022) is concerned with the military applications
of the technology, exploring its utility in U.S. Department of Defense operations
“at the tactical edge, serving the warfighters at forward operating bases as
well as expeditionary forces where power infrastructure is problematic” and
claiming that “The international community is already aggressively underway in
SBSP system design.” The military aspect of SBSP does of course imply issues of
defending SBSPs designed for peaceful use in time of war.
Wallach
(2021) focusses on legal issues such as whether SBSP power contracts can be
used to satisfy regulatory targets for renewable energy; who owns the right to
the "slot" located at the geosynchronous orbit above a particular
rectenna; how long the rights to operate a satellite array in such a location
last; and whether the International Telecommunications Union has obligations to
reserve spaces for developing nations. Aside from the legal issues, Wallach
provides an introduction to the technical side of the subject which is a useful
supplement to that of the BEIS paper.
The Space
Energy Initiative has among its aims the establishment of an International
Partnership for the development of Space Based Energy, securing funding and
promoting research. Its website provides insights into the current range of
interested parties, and links to relevant articles, news and resources (SEI,
2021).
References
Allen, O.,
2022, ESA approves plans for research into Space Based Solar Power, The Oxford
Scientist, online,
accessed 27 Dec 2022
https://oxsci.org/esa-plans-space-based-solar-power/
BEIS, 2021, Space
based solar power: de-risking the pathway to net zero, Department for Business, Energy &
Industrial Strategy, online, accessed 27 Dec 2022
Ghosh, P.,
2022, Esa mulls Solaris plan to beam solar energy from space, BBC news, 22 Nov.
2022, online, accessed 27 Dec 2022
https://www.bbc.co.uk/news/science-environment-62982113
Pagel, J.,
2022, A STUDY OF SPACE-BASED SOLAR POWER SYSTEMS, Monterey, CA; Naval
Postgraduate School, online, accessed 28 Dec 2022
https://core.ac.uk/download/pdf/543795437.pdf
SEI, 2021, Space
Energy Initiative, online, accessed 30 Dec 2022
https://spaceenergyinitiative.org.uk/
Wallach, M.,
2021, Legal Issues for Space Based Solar Power, Online Journal of Space
Communication, online, accessed 28 Dec 2022
https://ohioopen.library.ohio.edu/spacejournal/vol9/iss16/18/
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