How Space-Based Solar Power Plants Could Be Built By Robots On the Moon (blastingnews.com)

MarkWhittington writes: The concept of space based solar power has been around for decades. The late Gerard K. O'Neill proposed building them as a way to finance space colonies in the 1970s. Recently Popular Science reported on a modern approach to building space based solar energy stations. Instead of relying on massive, orbiting space colonies filled with construction workers to put the plants together, why not automate the entire process?

Comments

Bahahahaha

[Anonymous Coward]

Where is Solaren's 2016 installation?

https://en.wikipedia.org/wiki/...

Oh, not even a single bolt in orbit yet? Oh I guess it'll just magically happen in the next nine months?

These space fantasies always follow the same pattern:

1) Uncritical support from people raised on sci-fi and proficient in software, but with no knowledge of the physical sciences and engineering
2) Failure to deliver anything
3) Upping the ante to ever more ridiculous concepts

Not far fetched at all

[ickleberry]

Given that its been quite a while since someone landed anything on the moon. It would be a victory for space exploration if someone sent up a robot and dug a hole. People in the 60s would have expected a decent size lunar colony by now

capitalism filter

[Ritz_Just_Ritz]

I'm sure the instant someone can make more selling electrons generated from orbit than it costs to produce them (without siphoning tax dollars off of the rest of us clods), you'll see such a business materialize, the world will be a better place, oceans will stop rising, etc.

Until then, let's continue with the research but utilize what's the most cost effective now.

Fer God's sake, fusion energy is just around the corner... :)

Re:capitalism filter

[blindseer]

"Fer God's sake, fusion energy is just around the corner... :)"

And nuclear fission is here now.

A good measure of the quality of an energy source is the energy return on energy investment (EROEI). Oil, natural gas, wind, and nuclear fission all can get 10:1 or better. Hydro and coal can get near 100:1 or better. We see ground based solar getting less than 10:1 with 2:1 being common. For space based solar to work it'd have to compete with what we have now and whatever else might come along in the time it'd take to get this going.

I've seen estimates that we could quadruple the output for a given solar panel by taking it from the ground and putting it into orbit. Part of this is because the air shields the panels from about 1/3 of the sun's power but most of the gain comes from getting only 4 to 12 hours of sun (based on location) per day to getting 23.99 hours of sun (even the best orbits will be in Earth's shadow for several minutes every year and changing orbits takes a lot of energy). That means a 10:1 solar panel on Earth gets to be a 40:1 EROEI, but a more realistic number would be more like the 10:1. We'd get that same 10:1 if we only optimized the panels on Earth and not have to deal with having to launch it from the moon. It would also be much easier to optimize ground based solar because to get to the proper height would require an 8 foot ladder instead of a rocket.

If we rule out coal because coal is bad, and we rule out hydro because we just can't dam any more rivers, then we're still left with the 10:1 EROEI that wind and nuclear fission can provide with current technology. If we allow for some advancements in technology and economies of scale then we could easily see wind double its EROEI. With nuclear fission we've really only begun to try new technologies, we're doing fission today much like we did 50 years ago. If we get some sane policies on nuclear power then we could see fission get 100:1 EROEI quite easily. Some speculate 1000:1 EROEI using molten salt reactors with a breeding cycle.

Other technologies like bio-diesel, ethanol (corn or sugar beets), geothermal, and such get EROEI that barely exceed 1:1, which makes them barely worth considering. They might have value within narrow parameters but these are not technologies to use as a primary energy source to drive a modern economy.

I see a future that is driven by nuclear fission, nothing else can compare.

Re:capitalism filter

[KGIII]

> Fer God's sake, fusion energy is just around the corner...

You laugh and it's a rather traditional joke around here but it *does* look like they're getting closer and closer. Of course, I'm old and fusion power has been anywhere from five to thirty five and even fifty years away. The funky looking machine the Germans are building is claimed to have some potential - they've had it spun up and run it at some pretty high temperatures - if I understand their last press release properly.

Hmm... I'm 58. It was 5 years away when I was a kid. It was 50 years away when it was the 1970s. It was 35 years away in the 1980s. It was 50 years away during the 1990s. It was 35 years away in the 2000s. It's 5 years away now.

It probably won't happen in my lifetime. ;-)

This sounds familiar

[beatle11]

An object in space beaming energy down to a planet. Sounds a lot like a Death Star to me.

Re: This sounds familiar

[syntheticmemory]

Sounds like solar panels on earth to me.

the economics don't work out

[ooloorie]

The economics of space based solar power make little sense. You gain maybe a factor of three in terms of energy captured, but at the cost of massive launch costs, expensive maintenance, expensive transmission systems and large ground based stations, and the risk of having what amounts to energy beam weapons in space. If you think solar energy is cost effective, just put three times as many solar panels on the ground (in the Sahara and Mojave) and you still come out ahead.

As for self-replication, that would be a neat trick to master just on earth and is probably still a long ways off; but once we do, it works just as well on Earth. Furthermore, the moon is still a fairly deep gravity well; for any kind of orbital construction, it makes much more sense to divert an asteroid into orbit and use that as the raw material for solar panels, space stations, or whatever, rather than launching from the moon.

Re:the economics don't work out

[DanielRavenNest]

Actually, the ratio is 7:1 in space vs an average location on Earth. 24 vs 4-5 hours/day of usable sunlight, and 36% brighter Sun above the atmosphere. The economics of space power then boil down to if you can provide power from space for less than 7 times as much as the same solar system on the ground, space makes sense. Otherwise it doesn't. Per your arguments against:

* Launch costs - The point of using local energy and materials in space is to avoid those massive launch costs. Orbital mining has mass return ratios of hundreds to thousands to 1 (depends on where you mine, and how), so the amount you need to launch from Earth is greatly reduced.

* Expensive maintenance - Communications satellites typically last 15 years with zero maintenance (though they do carry spare hardware). They consist of solar panels, and microwave transmitters. Solar power satellites have the same parts, just way way bigger. So maintenance should be minimal, and what there is can be automated, since the SPS has lots of copies of the same items.

* Expensive transmission systems - Klystrons and Gyrotrons are pretty simple devices. If you can make solar panels in space, you can make those too. You will need thousands, so you would automate the production.

* Large ground-based stations - Solar farms on the ground need that too, so that cost is a wash.

* Beam weapons - The power beam can't be focused smaller than a few km, so the beam intensity is less than or equal to sunlight. The focusing is determined by the wavelength, size of the transmitter antenna, and distance from space to ground. I wouldn't recommend standing in the beam, but I wouldn't recommend being inside a coal plant furnace or a nuclear reactor either.

* Putting 7 times as many panels on the ground - This is the correct answer today. Launch costs would have to come down a lot, or mining and production in space would have to be well developed and efficient for space power to make economic sense. Those don't exist yet, but that is not an argument to stop research. It's just an argument to not build space power plants *today*.

* Self-replication - this is very difficult, but not required. Automated machine tools today can make parts for more automated machine tools. They don't make *all* the parts, just the metal ones. Mostly automated machinery that can make most of the parts in space is sufficient. The remainder of the hard-to-make parts are sent from Earth, and humans on-site or by remote control do the tasks that automation can't handle. You are correct that this works just as well on Earth. A starter set of machines that can mostly copy itself and make parts for other machines is called a "Seed Factory". Working on that concept is my day job. See https://en.wikibooks.org/wiki/... for a path that starts on Earth and uses the seed factory idea to expand into space.

* Moon vs asteroids - The various types of asteroids (metallic, carbonaceous, etc.) are different compositions from each other and from the Moon. Depending what raw materials you need, you will likely want to mine both. Asteroids don't stand still. Even if they have an easy to reach orbit, they are not always in the right place in that orbit. So your departure windows are limited. The Moon has a more limited range of elements available, but it's always nearby, and has a low enough orbit velocity you can mechanically throw cargo into orbit. The right answer will depend on a detailed assessment of actual needs, which as far as I know, nobody has done using up-to-date information.

Flaw in the idea

[DanielRavenNest]

> "The problem with regular solar power is that the sun isn't always up." (from the article)

This problem exists on the Moon too. It makes sense to get raw materials from the Moon, but not to put your factory there. It takes about 900 MJ to produce a square meter of silicon solar panel, and their output is about 245 W/m^2 in space. So they make back the energy to copy themselves in 3.67 million seconds, or 42.5 days. Typical working life against radiation damage is 15 years, so the panel can copy itself 128 times in orbit away from the Moon, but only 64 times on the surface, where sunlight is available 50% of the time.

Space Station era space solar panels had a power output of 55W/kg, so a square meter has a mass of about 4.5 kg. Kinetic energy of escape from the Moon is 2.83 MJ/kg, so launching the materials for the solar panel require 12.75 MJ/m^2. The panel in orbit can make back that energy in 14.5 hours, so the extra energy to launch the materials is small compared to the 7.5 years of extra output you get.

Automation was nowhere near as good in the 1970's as it is today, so by all means use automated factories. But put them in high orbit so they get full-time sunlight to operate with. The Moon and Near Earth Asteroids serve as sources of raw materials to feed the factories. The reason you want both is the various asteroid types have different compositions than the Lunar surface and each other. So you get a wider range of materials to work with. In particular, some asteroid types are nearly pure iron-nickel alloy, and others have lots of carbon and water. Those are not easily obtained from the Moon, and any mining engineer will tell you to go for the highest grade ore, because it's less work to extract the product.

Simcity 2000

[hooiberg]

And how exactly are we going to get this energy back to Earth? With the Simcity 2000 cityzapper?

Re:Simcity 2000

[DanielRavenNest]

The standard method is a microwave beam aimed at a large ground receiver. Antenna elements and diodes convert the beam to DC electricity. It's about 75% efficient, and the beam is always on, so you collect more energy per day than the same area covered with solar panels.

Elon Musk on Space Based Solar Power

[ebob]

The comments of someone who knows a thing or two about the economics of space transport: "While Musk loves electric cars and spaceflight, there's one thing he hates: space solar power. "You'd have to convert photon to electron to photon back to electron. What's the conversion rate?" he says, getting riled up for the first time during his talk. "Stab that bloody thing in the heart!""

"Wirelessly beam it to the ground"?

[jenningsthecat]

Um, if we manage to figure out how to 'wirelessly beam' energy over great distances with an efficiency that's anywhere near useful, and if we manage to solve the problem of what happens when a satellite or an airplane or a flock of birds or whatever flies through the beam, then maybe it'll be time to talk about automating the building of solar power plants on the Moon.

OTOH, if we manage the sci-fu and eng-fu to accomplish those things, maybe we can just efficiently generate and distribute cheap solar electric power right here on Earth, and forget about space robots and moon shots. Just a thought.

Say wha?

[msauve]

"Global warming is the greatest challenge our species will face in the next 100 years," says Justin Lewis-Weber. Currently a high school senior in California...

Sure, and B.o.B says the earth is flat. I'm not buying from either the rapper or the fortune teller.

Bonus points for why "wirelessly beam[ing]" planetary scale power isn't a good idea. The article ignores the problem of how that even happens, or how a small targeting error doesn't take out Manhattan.

H1B visas From Outer Space?

[Required Snark]

So will that mean there will be hoards of robot H1B visa applicants from the moon taking jobs away from Earthlings? They'll work 24/7 for electricity and get paid using bulk shipments of raw materials to space that are easier to get from a inhabited planet with infrastructure.

How can a carbon based biological organism compete?

Earth-based solar cells

[Tijaska]

The referenced paper says that to meet our energy needs through solar power alone we would need an area 92% of Nevada covered in solar cells. Nevada is 286,367 square kilometers in area. 92% of that is about 286,000 square kilometers. There are an estimated 1.7 billion buildings on planer Earth (see https://github.com/svendvn/sam...). If their combined area is less than the area needed for solar cells to power Earth then their average floor space area is less than 168 square metres each (about 1,700 square feet each). A 13 metre (43 foot) square building beats that. Sure, our power needs keep climbing as our population increases. So does the number of buildings required to house and service the extra people. Solar cells are too expensive to put on every roof today, but Moore's law applies. Standard roof tiles will one day come with some level of photovoltaic capability baked in.