How to Harvest Terawatts of Solar Power on the Moon

By David Warmflash | April 22, 2016 1:03 pm

(Credit: Shimzu)

Planet Earth isn’t the most ideal place for solar power to thrive. Sunsets and weather afford solar panels a significant amount of downtime.

But there’s a place not too far from here where the sun never stops shining.

A handful of researchers, and more recently the Japanese corporation Shimizu, have been gearing up to develop solar power on the moon.

Shimizu took off with the idea in 2013 in the aftermath of Japan’s 2011 Fukishima accident, which produced a political climate demanding alternatives to nuclear power plants. Shimizu’s plans call for beginning construction of a lunar solar power base as early as 2035. The solar array would be 250 miles wide and span the lunar circumference of 6,800 miles. They’re calling it the Luna Ring.

Lunar Solar Power (LSP) arrays would receive higher energy density from sunlight than we get through Earth’s atmosphere, avoid weather, and could beam energy to any part of Earth facing the moon. LSP could, theoretically, even satisfy 100 percent of our energy needs. That would be approximately 18 TW today and possibly 24 TW by mid century.

Microwave Beaming

The key to lunar-based solar on Earth is microwave transmission. Energy from the sun can be converted into microwaves in the same way radar beams are generated.

The technology has been around for many decades, and it’s dependable and efficient. A few weeks ago, the National Space Society’s (NSS) proposal on space-to-space transmission of energy as microwaves was rated in the top 1 percent of ideas presented at the D3 Innovation Summit, hosted by the Department of State in January.

The NSS wants to demonstrate the feasibility of space-based solar power, which the US is government taking seriously as an advanced energy system. Still, space-based energy would require massive satellites orbiting Earth. Space entrepreneur Elon Musk and others have criticized space-based energy for a simple reason: the cost of delivering such systems into space would overshadow any benefits gained in terms of energy density.

Lunar Power: How It Could Work

During Project Apollo in the 1970s, Dr. David Criswell, of the University of Houston, was researching how best to utilize lunar materials. He discovered that all the materials needed for manufacturing photovoltaic cells were present in lunar rocks and dust.

In other words, no bulk materials would have to be boosted from the Earth’s surface into space. Instead, space-energy firms could send equipment to the moon whose job would be to manufacture more equipment, such as excavator and ore processing machines and specific-task robots. A high school student in California recently published a paper in New Space describing a self-replicating, robotic factory that could autonomously manufacture solar panels from lunar materials.


(Credit: Shimzu)

Criswell’s idea may have been dreamy back in the 70s, but by the 80s all of the technology for building the equipment, robots, and massive amounts of PV cells on the moon had been invented.

To be sure, the lunar solar arrays would be enormous, but the photovoltaic cells themselves could be tissue thin, since the moon has no weather or air.

Consider also that half of the moon is in sunlight at any one time, so it’s clear why Shimizu wants to ring the moon with arrays. Such a system could provide the needed 24 TW of energy, or more. But how might LSP compare with Earth-based solar, which, after all, requires no rocket launches at all?

Here on Earth

Almost weekly, we hear about a new photovoltaic electric plant. Morocco recently completed the first of three phases of what will be the largest solar thermal power plant on Earth.

The Moroccan plant is at the edge of the Sahara Desert, but even the Sahara receives heavy rainfall, or sandstorms that reach hurricane velocities. Thus, Earth-based systems have to be reinforced with glass and metal, which translates into money — so much money LSP becomes more pragmatic as you scale up to multiple terawatts.

In an economic assessment of LSP, which Criswell updates continuously with respect to current trends in Earth-based solar power, such a system would cost something on the order of half a trillion dollars to build. Earth-based solar for multiple terawatts would cost about five times as much.

With an LSP system in place, new beams could be added continuously for additional customers buying into the power, and receivers anchored to earth would be cheap and low tech. The community linking into space power would place its receivers in a designated safe area, and the beam system would be issued new programming to feed the new receiving zone.

Plus, building LSP would yield the added benefit of an infrastructure on the moon, including a human-occupied lunar base that could grow into a colony and serve as a staging location for missions deeper into space, including human exploration and colonization of Mars.

  • Uncle Al

    1 TW =10^12 W, 1 kt (nuclear) = 4.186×10^12 J.
    18 TW = 4.3 kilotons/second or 15.5 megatons/hour. Yer gonna beam that down to Earth, are ya? It’s gonna leave a mark. It’s gonna thrust the moon! Do the satellites yer gonna fry in geosynchronous, GPS, and polar weather and surveillance orbits, count toward the bottom line?

    rated in the top 1 percent of ideas presented at the D3 Innovation Summit, hosted by the Department of State” Monkeys and typewriters. Hasten to join shock brigades of exemplary labor to end Klimate Kaos! Youtube v=FS5CH-Xc0co Klimaschutzstaffel! Die Fahne hoch, die Reihen fest geschlossen…” Further the daily struggle!

    • polzzlop

      “It’s gonna thrust the moon!”?

      Radiation is already redirected by the Moon.
      How is the path of the Moon affected?

      “Do the satellites yer gonna fry in geosynchronous, GPS, and
      polar weather and surveillance orbits, count toward the bottom line?”

      If watts per square meter is significant, shield the satellite.
      Satellite plinks are already compromised, for short periods, by the Sun.

      • Uncle Al

        Thrust? The photon stream will be directed re Yuri Milners light sail ” Breakthrough Starshot.” The sun cyclicly radiates the entire lunar globe. The 18 TW photon emitter is local and unmoving (plus an RCH of libration). Find a rocket chemical thruster with I_sp above 500 seconds. Photon thruster I_sp = 30+ million.

        Local mean solar constant is 1367.7 W/m^2. 18 terawatts over 100 mi^2, 2.59×10^8 m^2, is 65,000 W/m^2. It will leave a mark.

  • polzzlop

    Rail gun from the Moon to build Lagrange Point, power complexes.
    “The L4 and L5 points make equilateral triangles with the Earth and Moon”

    • Keith

      Considering beem spread and distance, wouldnt it be better to collect power from the sun in geosynchronous orbits around the earth?

      • polzzlop

        Yes, you are correct. Beaming to Earth would would be best from closer.
        Perhaps use geosynchronous as a relay point?

        In the far future, enormous arrays to beam power in the Solar system?

        • Keith

          What happens to all this extra energy beemed to earth? We will use what we can of it, but virtually all of it will end up as heat eventually.

          • polzzlop

            Estimate global average surface temperature from;
            “Unified Theory of Climate Anthony Watts”
            T = (25.3966 (1366 + 0.0001325)^0.25)* exp(0.233001*(98888.2)^0.0651203 + 0.0015393*(98888.2)^0.385232 )

            1366 is Solar radiation — 98888.2 is pressure, appears twice.
            How much will we increase incoming radiation?

          • Keith

            The articles plan talks about 24Terawatts by mid century. You mentioned the far future were presumably far more power could be beemed to earth. This beegs several questions. How much would be too much energy beemed to earth?

          • polzzlop

            “his beegs several questions. How much would be too much energy beemed to earth?”

            Ballpark guess from Nikolov ans Zeller equation — adding 200 watts/square meter
            T = (25.3966 (1366+200+0.0001325)^0.25) exp(0.233001×98888.2^0.0651203+0.0015393×98888.2^0.385232)
            T = 297.602°K

            Yes we can — Optimize the climate and design the weather, we must.

  • OWilson

    I don’t know what all the fuss is about.

    As the author says, “:A high school student in California recently published a paper in New Space describing a self-replicating, robotic factory that could autonomously manufacture solar panels from lunar materials”.

    Great. Lets do TV’s , cars, buses, trains and rocket ships, too.

    How about self replicating gold bars, Iphones and Coke too? All while we sleep.

  • JC Hamner

    There’s this oblate spheroid that’s a lot larger than the moon that also gets constant sunlight. Might want to look into creating a global power grid there. I hear tell of global networks being created there before. Might help solve some other problems, too…

  • Keith

    Wouldnt it be far better to make a Lunar based electromagnetic rail gun to launch pv cells into geosynchronous orbit? There they would recieve light 24 hours a day 7 days a week every month all year long, unlike on the moon which recieves sun less than 1/2 the time.

    • Ciprian Danea

      Man, we scorched the earth, built cities and consider roadkill trivial. The moon looking different is the last thing we’ll consider in our works to preserve the species. The moon is changing by itself, nothing is staying the same.
      I’m more concerned with beams frying sparrows and freaking out my kids.
      Also, as Musk sais, we still have clean ground options to exhaust: fusion, thorium unknown magic being developed in a lab somewhere, all before the solar freaking moon is THE only way left.

      • Keith

        Haha, instead of sun burns, well be concerned about light from the moon burning sparrows and such.

  • jayanth

    i wanted to know how the energy is transimitted from the space in the form of micro waves and laser rays, but how it is possible, i know that information can be transmitted with the microwaves.can any help me plss…

    • Keith

      Light is composed of alternating both electric and magnetic waves. Electromagnetic waves induce alternating voltages or currents in antennas that can either be use for Sensing a signal or if the waves are strong enough, provide power. Microwave have a fairly narrow beem spread when compared to radio waves but they spread out more then visible lazer beem.

      It is interesting to note that wifi and some microwaves ovens use frequencies not that far apart from each other.

  • Collapsar

    OI thought that I heard that Lunar dust could be an issue. Won’t minning on the lunar surface cause dust to levitate above the surface? Won’t that dust accumulate and cling on the surface of photovoltaic cells reducing their efficiency? I hope someone seriously looks into the before spending tons of money.

    W!ould beaming the much energy density to earths surface be harmful to birds flying through it?

    Just a few questions that came to me when I read this article. Let’s keep pushing the boundaries of innovation!

    • Friz Martin

      We’ll have to figure in the cost of a man with a dustrag to maintain the facility. And we could feed the fried birds to the hungry.

  • Tari Nai

    Sure, there is no weather and atmosphere on the moon to disrupt the solar production, but everyone forgot how the surface of the moon look like? Its bombared with asteroids, dudes! So still think no maintenance is needed?

    • Mike Richardson

      Yes, micrometeorites would be an issue, especially with so much surface area occupied. The moon has an advantage with in situ materials that can be harvested for building and repair, but it is still further from the earth than any orbiting array, so you’d need on-site repair and maintenance on the moon. Not to mention issues of beam divergence over the earth-moon distance. It’s an interesting concept, but definitely faced with serious technical issues.

  • DS

    Haven’t we already seen this twice…in Star Wars? Didn’t they call them the Death Star and Starkiller? I’ve always heard $1 million per pound to launch payload into space. The cost for this project would be astronomical (pun intended). I really hope no one is receiving any funding for even exploring the idea of this. If so, I want to get paid for coming up with outlandish ideas.

    • OWilson

      High school science:

      “He (Criswell), discovered that all the materials needed for manufacturing photovoltaic cells were present in lunar rocks and dust. In other words, no bulk materials would have to be boosted from the Earth’s surface into space.

      His contemporary, Carl Sagan, said that all the materials needed for manufacturing humans were present in “star stuff”. In other words, no bulk materials (or people), would have to be boosted from the Earth’s surface into space.

      With a little (at first) more money, and a few more studies, who knows where this research could lead, or what “spin offs” could result :)

  • Kenny Sono

    Plenty of advancements have started with partially valid theories. It would not surprise me if the first steps to getting energy back to Earth ended up being more like space shuttles with enormous batteries inside “Trailer Ships” they tow back to Earth, and then plug into something like Electric Generator power plants. Looking at what is currently (pardon the pun) happening with batteries, this approach would not surprise me. In time, that approach might change to individual “energy ships” flying automatically when they’ve filled up with solar power, to their destination, parking themselves and plugging themselves in, until they are empty again. One of things MOST noticeable about this entire concept is the phrase UNLIMITED ENERGY. Any company (such as Shimizu) willing to stake their reputation on such ideas have to be looking at the promise of huge amounts of prosperity by considering them.


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