NASA and several other
national space agencies have recently revived their lunar colonization
programs. One of the key factors that need to be solved is how to power a
future colony. Can uninterrupted solar power feasibly be realized without
energy storage? On Earth, providing 100% of electricity demand 100% of the time
solely from renewables, but without energy storage, is unfeasible.
This earth-bound mindset has been challenged recently by a paradigm shift
developed by BGU's Prof. Jeffrey Gordon, which he was invited
to present to NASA in late August. His idea was published earlier this year in
the premier journal Renewable
Energy.
On the Moon, solar is the sole available renewable resource. The overriding
challenge is to completely supply the main energy consumer: factories that need
to continuously (24/7, 365 days a year) produce thousands of tons of oxygen
(O2) per year from the lunar soil, for rocket propellant, orbiting satellite
refueling and human sustenance. A large part of the challenge derives from any
location on the Moon on average spending half of the lunar rotational period of
29.5 days in the dark.
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Above: Artist's rendition of an
individual electrically-driven O2 production reactor on the Moon.
In his paper, Gordon documents a feasible strategy where uninterrupted
electricity would be produced by photovoltaic (PV) arrays installed around a
360° latitudinal ring close to (but not at) a lunar pole, with transmission
lines installed to the O2 plants for which there would then be substantial
remote siting flexibility.
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Above: Photograph looking down on the
Moon's north pole, restricted to 5° of latitude. The red dashed ring at a
latitude of 87° contains the PV arrays. The locations of 4 O2 factories at a
slightly higher latitude are shown in yellow (the number four is arbitrary, for
illustration). Transmission lines from the ring of PV arrays to the O2
factories are indicated in green, each extending from a power collection point
on the ring of PV arrays to its diametrically opposite point, such that the
factories can be powered by solar 100% of the time.
"My solution has a specific mass far below all alternatives so far,
namely, record low kg/kW, a key figure of merit for affordable and feasible
lunar installations, with launch and installation costs currently exceeding
$1,000,000/kg. Our new strategy is more than a factor of 100 better than solar
with battery storage. It is also at least a factor of 6 superior to the
solution now being contemplated by NASA of nuclear reactors driving
conventional turbines and generators."
"I was invited to present my findings at NASA's headquarters for solar
power in space in August at the Glenn Research Center in Cleveland, Ohio. NASA
scientists expressed preparedness to rethink the plan to power lunar colonies
with nuclear energy instead of solar energy," says Gordon.
The concept exploits the unique combination of (a) the absence of a lunar
atmosphere, (b) the near-zero tilt of the Moon's polar axis with respect to the
ecliptic plane, (c) lunar conditions being amenable to low-mass inexpensive
transmission lines, and (d) a lunar diameter far smaller than that of Earth.
Prof. Gordon is a member of the Department of Solar Energy & Environmental
Physics, Jacob Blaustein Institutes for Desert Research of Ben-Gurion University.
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Above: Photograph of a commercial PV array for space, comprising 3 modules of high-efficiency solar cells, each module is 1.1 m wide, dimensions that are commonplace for space missions. Around 30,000 such modules would suffice to power the expansive envisioned lunar colony.
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