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Japanese firm proposes ring of solar panels around the moon

Posted: Sat Jun 05, 2010 5:10 pm UTC
by Josephine
http://www.physorg.com/news194706618.html

Spoiler:
The Shimizu Corporation, a Japanese construction firm, has recently proposed a plan to harness solar energy on a larger scale than almost any previously proposed concept. Their ambitious plan involves building a belt of solar cells around the Moon’s 6,800-mile (11,000-kilometer) equator, converting the electricity to powerful microwaves and lasers to be beamed at Earth, and finally converting the beams back to electricity at terrestrial power stations. The Luna Ring concept, the company says, could meet the entire world's energy needs.

Shimizu envisions that robots would play a vital role in building the Luna Ring. Teleoperated 24 hours a day from the Earth, the robots would perform tasks such as ground leveling and assembling machines and equipment, which would be done in space before landing them on the Moon. A team of astronauts would support the robots on-site.
Due to the massive amount of solar panels and other materials needed for the project, Shimizu proposes that lunar resources should be used to the fullest extent possible. The company’s plans call for producing water by reducing lunar soil with hydrogen imported from Earth. Lunar resources could also be used to make cementing material and concrete, while solar-heat treatments could help produce bricks, glass fibers, and other structural materials needed for the project.
The Luna Ring itself would initially have a width of a few kilometers, but could be extended up to 400 kilometers wide. The electric power generated by the solar cells would be transmitted by electric cables to transmission facilities on the near side of the Moon, which is constantly facing Earth. After the electricity is converted into microwave beams and laser beams, 20-kilometer-diameter antennas would beam the power to receivers on Earth. A guidance radio beacon would ensure accurate transmission to the receivers. The energy would then be converted back to electricity and supplied to grids, or possibly converted to hydrogen for fuel or storage.
Shimizu points out that one of the biggest advantages of the Luna Ring is that, since the Moon has virtually no atmosphere, there is no bad weather or clouds that could inhibit the efficiency of the solar panels. As such, the Luna Ring achieves 24/7 continuous clean energy generation, potentially ending our reliance on limited natural resources.


I like the idea, even if it's a little out of reach.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 5:38 pm UTC
by phillipsjk
What could possibly go wrong?

I think this may be a good idea if and only if the power is not beamed to Earth.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 6:14 pm UTC
by Josephine
Maybe Shimizu is planning on a supervillain-style hold-the-world-hostage scenario...

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 6:47 pm UTC
by Dibley
Are the efficiency gains high enough to outweigh the absurd cost? It's not as though we've run out of sunny places to put solar panels. Wouldn't it be significantly cheaper to just put them in the Sahara, and use wires, rather than microwaves?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 6:48 pm UTC
by mmmcannibalism
Based on this and other recent things(like the robot base) either Japan has the craziest scientists in the world or they are going to be taking over the world by 2020.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 7:28 pm UTC
by silent man
Dibley wrote:Are the efficiency gains high enough to outweigh the absurd cost? It's not as though we've run out of sunny places to put solar panels. Wouldn't it be significantly cheaper to just put them in the Sahara, and use wires, rather than microwaves?
Building solar cells on earth will always result in a patchwork, meaning that depending on the time there will be varying amounts of power available. Also, most places on earth have some form of weather and are covered by the atmosphere, both of which can cause wear and corrosion on equipment. Finally, the much slower rotation and lower gravity of the moon make it easier to have the cell arrays track the sun.

Personally, I'm wondering why they're going to the moon instead of simply putting the solar arrays in the various Lagrangian points (except maybe L2 and L3). It'd need even less supporting structure and you'd always have all the cells working at full capacity.
There're probably some problems with construction in microgravity and the orbits not being stable that I haven't thought of, but I still think it's a cool idea.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 7:48 pm UTC
by Dibley
Yes, terrestrial cells are less efficient. They're also thousands of times cheaper, which I think probably makes up for it.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 8:24 pm UTC
by Iv
Dibley wrote:Are the efficiency gains high enough to outweigh the absurd cost? It's not as though we've run out of sunny places to put solar panels. Wouldn't it be significantly cheaper to just put them in the Sahara, and use wires, rather than microwaves?

Probably but the Sahara is not in Japan.

Anyway don't fream too much anyway. As far as I can remember, Japanese companies routinely propose "pie in the sky" projects. Few of them are seriously considered, but I think they like to know which options they have given the current tech. A healthy R&D exercise if you ask me.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 9:28 pm UTC
by PCal
There are plenty of great idea out there but feasibility makes it hard to do a lot of them. Also is some how this does come to be how do they keep the lasers microwaves or whatever constantly aiming at the same collection point on earth?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 10:27 pm UTC
by G.v.K
As such, the Luna Ring achieves 24/7 continuous clean energy generation, potentially ending our reliance on limited natural resources.


except that the sun is also a limited 'natural resource'.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 11:16 pm UTC
by Omegaton
A high-energy laser from a moon-sized object? Why does that seem so familiar?

Spoiler:
Image

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sat Jun 05, 2010 11:31 pm UTC
by Steax
So the moon will be populated with robots, who have nuclear mining capabilities, rockets aimed at earth, and now they have more energy to consume than earth itself. Plus a pre-built laser system that fires towards earth. Awesome.

G.v.K wrote:
As such, the Luna Ring achieves 24/7 continuous clean energy generation, potentially ending our reliance on limited natural resources.


except that the sun is also a limited 'natural resource'.


I think for short-term purposes we can think of it as a free energy source. For the next 2 billion years or so, probably.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 12:37 am UTC
by EmptySet
Well, the sun is going to burn out whether we collect solar energy or not. Putting up solar panels doesn't make it die faster. So in that sense it's free energy, it's just that the gravy train will eventually stop.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 12:55 am UTC
by G.v.K
Is it a goal to 'end our reliance on natural resources'? What does that really mean? Whether the timeframe is 50 years or 2 billion years doesn't really alter that question.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 2:27 am UTC
by Glass Fractal
G.v.K wrote:Is it a goal to 'end our reliance on natural resources'? What does that really mean? Whether the timeframe is 50 years or 2 billion years doesn't really alter that question.


Having energy for the next two billion years is a lot more useful than having energy for the next 50 years, unless we all die between now and 2060. The resources of our planet are very very limited and take forever to replenish where as stars are being made en masse all the time.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 3:43 am UTC
by mmmcannibalism
Glass Fractal wrote:
G.v.K wrote:Is it a goal to 'end our reliance on natural resources'? What does that really mean? Whether the timeframe is 50 years or 2 billion years doesn't really alter that question.


Having energy for the next two billion years is a lot more useful than having energy for the next 50 years, unless we all die between now and 2060. The resources of our planet are very very limited and take forever to replenish where as stars are being made en masse all the time.


We die in 2012 obviously...

That being said, I'm in the sun is free energy side of this debate since we will probably work out antimatter generation or cold fusion or efficient fusion well before the sun burns out.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:22 am UTC
by G.v.K
Glass Fractal wrote:
G.v.K wrote:Is it a goal to 'end our reliance on natural resources'? What does that really mean? Whether the timeframe is 50 years or 2 billion years doesn't really alter that question.


Having energy for the next two billion years is a lot more useful than having energy for the next 50 years, unless we all die between now and 2060. The resources of our planet are very very limited and take forever to replenish where as stars are being made en masse all the time.


i wasn't really thinking about usefulness, but whether or not at some point in the future we would exist in such a way as not to require the intake of 'natural resources' for our sustenance. that seemed to be the implication of the initial quote to me. just a quibble really.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:33 am UTC
by Kain
Considering that the sun will keep releasing photons regardless of how many we capture, we would hardly be consuming it with solar cells. That said, I would almost pity the poor plant or two that would have just barely scrapped by with the reflected photon that one of these cells might happen to capture :)

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 2:41 pm UTC
by Arancaytar
After the electricity is converted into microwave beams and laser beams, 20-kilometer-diameter antennas would beam the power to receivers on Earth. A guidance radio beacon would ensure accurate transmission to the receivers.


So it's a very accurately transmitted potential orbital death ray. How bad could it be?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 3:48 pm UTC
by redgrowth
Our problems are with consumption not generation. Eventually the power and other resources we get from the moon will not be enough and then what? Maybe there will be something new to use up, maybe not. At some point we are going to run out of new resources to use (up).

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:22 pm UTC
by Iv
Arancaytar wrote:So it's a very accurately transmitted potential orbital death ray. How bad could it be?
Nope. From a previous discussion about this very subject, it appears that the receiving end would have an area of several hundreds square meters and have to be a carefully designed antennas field in order to get any energy. There is not guarantee you won't have health problem if you go unprotected in the area, but you shouldn't be instantly fried. The frequency that is likely to be chosen will be one that can go through the atmosphere easily and with all probabilities it will go through your body easily as well with few interactions.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:27 pm UTC
by Steax
Wikipedia on 'Space-based Solar Power#Safety' wrote:At the Earth's surface, a suggested microwave beam would have a maximum intensity at its center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline (the receiver's perimeter). These compare with current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves, which are 10 mW/cm2, - the limit itself being expressed in voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes. A beam of this intensity is therefore at its center, of a similar magnitude to current safe workplace levels, even for long term or indefinite exposure. Outside the receiver, it is far less than the OSHA long-term levels. Over 95% of the beam energy will fall on the rectenna. The remaining microwave energy will be absorbed and dispersed well within standards currently imposed upon microwave emissions around the world. It is important for system efficiency that as much of the microwave radiation as possible be focused on the rectenna. Outside of the rectenna, microwave intensities rapidly decrease, so nearby towns or other human activity should be completely unaffected.


Looks safe enough?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:33 pm UTC
by Zuwow
redgrowth wrote:Our problems are with consumption not generation. Eventually the power and other resources we get from the moon will not be enough and then what? Maybe there will be something new to use up, maybe not. At some point we are going to run out of new resources to use (up).

So we shouldn't try to find any new power sources because eventually we'll need more?

Because that train of thought doesn't make any sense. Consumption will continue to grow regardless of generation, until consumption and generation are the same, obviously. Wouldn't it then make the most sense to use what resources there are to maximize generation?

Also, for all intents and purposes, light from the sun is free and won't be running out any time soon. I fail to see how that could be "used up" besides our consumption becoming greater than what the power supplies however that doesn't make it stop supplying power, we'll just need to find another source to augment our power already received from the moon.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 4:38 pm UTC
by Technical Ben
I was about to post that it fails from moon dust erosion. But then I realised I was thinking of Mars, which has an atmosphere and massive dust storms. However, if the dust is kicked up during construction it could be a problem. If the materials can be made and placed dust free, it could succeed.

Oh, and if they paint one side blue, and the other red... (now where is my photoshoped version of the Moon with adds on?)
[Edit. Found it!!!]
Image

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 5:32 pm UTC
by Iv
Steax wrote:
Wikipedia on 'Space-based Solar Power#Safety' wrote:At the Earth's surface, a suggested microwave beam would have a maximum intensity at its center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline (the receiver's perimeter). These compare with current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves, which are 10 mW/cm2, - the limit itself being expressed in voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes. A beam of this intensity is therefore at its center, of a similar magnitude to current safe workplace levels, even for long term or indefinite exposure. Outside the receiver, it is far less than the OSHA long-term levels. Over 95% of the beam energy will fall on the rectenna. The remaining microwave energy will be absorbed and dispersed well within standards currently imposed upon microwave emissions around the world. It is important for system efficiency that as much of the microwave radiation as possible be focused on the rectenna. Outside of the rectenna, microwave intensities rapidly decrease, so nearby towns or other human activity should be completely unaffected.

Looks safe enough?

Actually that was the kind of text I had in mind but it triggers a crowd of questions : How are we supposed to get a significant amount of energy from a radiation that is at 1/4th of the solar irradiation constant ? Wouldn't that mean that if you built solar panels instead of rectenna on the same area you would get similar energy ?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 5:46 pm UTC
by redgrowth
Zuwow wrote:
redgrowth wrote:Our problems are with consumption not generation. Eventually the power and other resources we get from the moon will not be enough and then what? Maybe there will be something new to use up, maybe not. At some point we are going to run out of new resources to use (up).

So we shouldn't try to find any new power sources because eventually we'll need more?

Because that train of thought doesn't make any sense. Consumption will continue to grow regardless of generation, until consumption and generation are the same, obviously. Wouldn't it then make the most sense to use what resources there are to maximize generation?

Also, for all intents and purposes, light from the sun is free and won't be running out any time soon. I fail to see how that could be "used up" besides our consumption becoming greater than what the power supplies however that doesn't make it stop supplying power, we'll just need to find another source to augment our power already received from the moon.

That's exactly what I meant, unless our consumption stabilizes and stops growing we will always need to find new sources of power. It doesn't matter if these sources of power are renewable or not because we will consume beyond their capacities and need more. This is an unsustainable process. I am trying to say that I think this Japanese firm is solving the wrong problem.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 5:51 pm UTC
by Iv
redgrowth wrote:That's exactly what I meant, unless our consumption stabilizes and stops growing we will always need to find new sources of power. It doesn't matter if these sources of power are renewable or not because we will consume beyond their capacities and need more. This is an unsustainable process. I am trying to say that I think this Japanese firm is solving the wrong problem.

What problem ? Let's admit that we are cosntantly climbing the Karaschev scale and let's begin to build our Dyson sphere

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 5:56 pm UTC
by TheGrammarBolshevik
Technical Ben wrote:Oh, and if they paint one side blue, and the other red... (now where is my photoshoped version of the Moon with adds on?)

Well, it would be the new logo, which might cause tide problems and who knows what else with the gravitational effects.

redgrowth wrote:This is an unsustainable process.

The universe is an unsustainable process. Efficiency is good, but there's nothing we can do to escape the Second Law of Thermodynamics.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 7:03 pm UTC
by Josephine
Iv wrote:
redgrowth wrote:That's exactly what I meant, unless our consumption stabilizes and stops growing we will always need to find new sources of power. It doesn't matter if these sources of power are renewable or not because we will consume beyond their capacities and need more. This is an unsustainable process. I am trying to say that I think this Japanese firm is solving the wrong problem.

What problem ? Let's admit that we are cosntantly climbing the Karaschev scale and let's begin to build our Dyson sphere

And unfortunately, a type III civilization is the only type that is capable of building a Dyson sphere.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 7:06 pm UTC
by Glass Fractal
nbonaparte wrote:
Iv wrote:
redgrowth wrote:That's exactly what I meant, unless our consumption stabilizes and stops growing we will always need to find new sources of power. It doesn't matter if these sources of power are renewable or not because we will consume beyond their capacities and need more. This is an unsustainable process. I am trying to say that I think this Japanese firm is solving the wrong problem.

What problem ? Let's admit that we are cosntantly climbing the Karaschev scale and let's begin to build our Dyson sphere

And unfortunately, a type III civilization is the only type that is capable of building a Dyson sphere.


Why would you need the mass and energy of an entire galaxy at your command to build a Dyson sphere?

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 7:10 pm UTC
by Vaniver
Iv wrote:Actually that was the kind of text I had in mind but it triggers a crowd of questions : How are we supposed to get a significant amount of energy from a radiation that is at 1/4th of the solar irradiation constant ? Wouldn't that mean that if you built solar panels instead of rectenna on the same area you would get similar energy ?
Solar radiance is over a very wide range of frequencies, which makes it difficult to capture more than a small fraction of it. This microwave radiation would (most likely) all be at the same frequency, making it trivial to get near 100% efficiency in transfer (though the solar panels on the moon would face the same ~30% efficiency that panels on Earth would face, though with a few upwards adjustments thanks to the lower temperature, more predictable weather, and lack of an atmosphere).

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 7:51 pm UTC
by Iv
Vaniver wrote:Solar radiance is over a very wide range of frequencies, which makes it difficult to capture more than a small fraction of it. This microwave radiation would (most likely) all be at the same frequency, making it trivial to get near 100% efficiency in transfer (though the solar panels on the moon would face the same ~30% efficiency that panels on Earth would face, though with a few upwards adjustments thanks to the lower temperature, more predictable weather, and lack of an atmosphere).

But that still sounds incredibely useless. That means that for every square meter of solar panel built on the moon, you'll have to build more two or three square meter of rectenna on earth. That sounds silly... One of the data must be wrong.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 8:11 pm UTC
by Vaniver
Iv wrote:But that still sounds incredibely useless. That means that for every square meter of solar panel built on the moon, you'll have to build more two or three square meter of rectenna on earth. That sounds silly... One of the data must be wrong.
No, the ratio would be roughly 1-1. You'd still get the benefits of constant power generation (unless the microwave beam can be blocked by weather, which seems likely). Most likely a higher intensity transmission beam would be used- if you go up to solar radiance, then you're starting to get significant savings (neglecting the phenomenally larger cost of building things in orbit).

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 10:20 pm UTC
by phillipsjk
Arancaytar wrote:
After the electricity is converted into microwave beams and laser beams, 20-kilometer-diameter antennas would beam the power to receivers on Earth. A guidance radio beacon would ensure accurate transmission to the receivers.


So it's a very accurately transmitted potential orbital death ray. How bad could it be?


To be clear, my objection had nothing to do with the beam: it can be done safely; for example, point it at sparsely populated areas.

My objection is that such a scheme would effectively increase the surface area of the earth. We already have problems with global warming, along with Geo Engineering proposals to reduce the amount of light hitting the Earth's surface by nearly 2%.

What a solar network on the moon would be good for is space travel: Boost out of the Earth's gravity well, refuel from the moon, then continue on your journey. A solar panel network could also be used for moon based mining and manufacturing facilities. The moon can also be used to beam power to space stations in orbit. If the right angle is used (a portion of the beam would travel through the upper atmosphere), a beam of radiation may be able to "boost" a space station (with enough surface area) to make up for atmospheric drag. Edit: A moon-based beam can also be used to push loose debris in orbit into the atmosphere to burn up.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Sun Jun 06, 2010 10:44 pm UTC
by Iv
Vaniver wrote:
Iv wrote:But that still sounds incredibely useless. That means that for every square meter of solar panel built on the moon, you'll have to build more two or three square meter of rectenna on earth. That sounds silly... One of the data must be wrong.
No, the ratio would be roughly 1-1. You'd still get the benefits of constant power generation (unless the microwave beam can be blocked by weather, which seems likely). Most likely a higher intensity transmission beam would be used- if you go up to solar radiance, then you're starting to get significant savings (neglecting the phenomenally larger cost of building things in orbit).

Even 1-1 seems useless...
The number I'm using is the one Steax put forward : 1/4th of the solar irradiation (presumably the irradiation on earth below the atmosphere). Which roughly means that a 30% efficient solar panel would be a more slightly more sensible use of the area (only 12h a day but you don't expect a moon-earth link to be active 24h a day either).

Re: Japanese firm proposes ring of solar panels around the m

Posted: Tue Jun 08, 2010 9:31 pm UTC
by lcole95067
This seems like a pretty cool concept. It's the first I've heard of it, so I'll have to follow to see what happens.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Wed Jun 09, 2010 2:00 am UTC
by ++$_
Iv wrote:The number I'm using is the one Steax put forward : 1/4th of the solar irradiation (presumably the irradiation on earth below the atmosphere). Which roughly means that a 30% efficient solar panel would be a more slightly more sensible use of the area (only 12h a day but you don't expect a moon-earth link to be active 24h a day either).
If you look at the number of 23 mW/cm2 provided, that translates to 230 W/m2. The solar irradiance at the surface, averaged over the year and over the entire surface area, is 342 W/m2. So it's more like 2/3 of the solar irradiation in an average location.

On the other hand, of course the moon does not generously stay directly overhead. A geostationary satellite does, but then the power station would probably be on the equator, where you will get more than the average of 342 W/m2 anyway.

Re: Japanese firm proposes ring of solar panels around the m

Posted: Wed Jun 09, 2010 4:09 am UTC
by thc
phillipsjk wrote:
Arancaytar wrote:
After the electricity is converted into microwave beams and laser beams, 20-kilometer-diameter antennas would beam the power to receivers on Earth. A guidance radio beacon would ensure accurate transmission to the receivers.


So it's a very accurately transmitted potential orbital death ray. How bad could it be?


To be clear, my objection had nothing to do with the beam: it can be done safely; for example, point it at sparsely populated areas.

My objection is that such a scheme would effectively increase the surface area of the earth. We already have problems with global warming, along with Geo Engineering proposals to reduce the amount of light hitting the Earth's surface by nearly 2%.

You know what else "effectively" increases earth's surface area? Burning fossil fuels. Assuming high transmission efficiency, it would produce no more warming due to entropy than fossil fuels or nuclear would. That is to say, not very much.