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Nov. 09, 2022

NASA and several other national space agencies have recently revived their lunar colonization programs. One key factor that needs 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 BIDR'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 supply the main energy consumer ultimately: 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 fuel, 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 87° contains the PV arrays. The locations of 4 O2 factories at a slightly higher margin 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 circle of PV arrays to its diametrically opposite end, such that the factories can be powered by solar 100% of the time.

"My solution has a specific mass far below all alternatives, 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 concerning 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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