Satellite Beams Solar Power Down To Earth, In First-of-a-Kind Demonstration (science.org) 75
Researchers at the California Institute of Technology (Caltech) have successfully demonstrated the capability of steering power in a microwave beam from a satellite to targets in space, as well as transmitting some of that power to a detector on Earth. Science Magazine reports: The Caltech mission, funded by the Donald Bren Foundation and Northrop Grumman Corporation, aimed to go a step further with lightweight, inexpensive, and flexible components. The microwave transmitter was an array of 32 flat antennas packed onto a surface slightly larger than a dinner plate. By varying the timing of signals sent to the different antennas, the researchers could steer the array's beam. They pointed it at a pair of microwave receivers about a forearm's distance away and switched the beam from one receiver to the other at will, lighting up an LED on each.
The transmitted power was small, just 200 milliwatts, less than that of a cellphone camera light. But the team was still able to steer the beam toward Earth and detect it with a receiver at Caltech. "It was a proof of concept," says Caltech electrical engineer Ali Hajimiri. "It indicates what an overall system can do."
The Caltech spacecraft still has two more planned experiments. One is now testing 32 different varieties of solar cell to see which best survives the rigors of space. The second is a folded piece of ultralight composite material that will unfurl into a sail-like structure 2 meters across. Although the sail will not hold any solar cells, it is meant to test the kind of thin, flexible, and large deployments required for a future power station.
The transmitted power was small, just 200 milliwatts, less than that of a cellphone camera light. But the team was still able to steer the beam toward Earth and detect it with a receiver at Caltech. "It was a proof of concept," says Caltech electrical engineer Ali Hajimiri. "It indicates what an overall system can do."
The Caltech spacecraft still has two more planned experiments. One is now testing 32 different varieties of solar cell to see which best survives the rigors of space. The second is a folded piece of ultralight composite material that will unfurl into a sail-like structure 2 meters across. Although the sail will not hold any solar cells, it is meant to test the kind of thin, flexible, and large deployments required for a future power station.
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Actual orbital power information. (Score:2)
https://en.m.wikipedia.org/wik... [wikipedia.org]
Most of the questions that these articles spawn, and the rampant speculation that follows, can be answered by reading the wikipedia entry.
How is this a proof of concept? (Score:5, Insightful)
Sending waves towards earth is what satellites do, no?
The interesting question is not whether this is possible. I find it quite clear that it is. The question is does it make any sense? Were those 200mW what was sent or what was received... and what was the delta?
If you need to generate a GW of solar power in space (meaning getting several tons of panels up there, situated and protected from debris) just to produce one MW the whole thing becomes rather moot.
Re:How is this a proof of concept? (Score:4, Interesting)
Re:How is this a proof of concept? (Score:5, Informative)
Yes. The receiver and transmitter were both on board the satellite. A foot apart. The beam was "detectable" on earth. Disappointing based on what the headline suggests.
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Re:How is this a proof of concept? (Score:4, Informative)
Source: https://www.science.org/conten... [science.org]
I would tend to read it as "sent" and thus "emitted". But yeah, without knowing what power was emitted and then received, it's not very useful to know it only one way or only the other. They also write that they were able to detect it with a receiver, which also doesn't say a lot, because with modern instruments we can detect relatively weak signals.
No we could make educated guesses based on our understanding of the composition of our atmosphere and how its properties attenuate electromagnetic energy at various wavelengths. But since we're only provided with "microwave transmitter" which is a range from 1 mm to 1 m waves, that is also difficult to say with a greater degree of certainty. Sub 5cm waves for example experience a lot more attenuation than a 1m wave for example. We already see this in practice with 5G cells.
Naturally I would think that they used wavelengths where attenuation is very low. In that case a main concern for losses would be the inverse square law for example, where ways need to be found to focus the beam so that its waist is very close to the receiver. For this they used a phased array antenna.
These antennas are great for beam steering, without involving moving parts, but they're not very energy efficient. So that would be a concern if you're developing an energy transmission system.
But ultimately, all of this is based on some basics that were taught in University some 17 years back. And I haven't worked actively in that sector ever since, so perhaps this state of knowledge is somewhat dated and there's someone who can provide more accurate information.
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...Naturally I would think that they used wavelengths where attenuation is very low.
Yep. Until you get to frequencies well above X band, atmospheric attenuation (and in particular, cloud and rain attenuation) is low. The demo is somewhere around 5 GHz, I think, C-band. It should penetrate clouds and even rain with not much loss.
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Normally, engineering efficiency isn't that critical in renewable energy systems, because you're not paying for the energy source. It doesn't matter if a wind farm loses most of the energy flowing through it, as long as it can be built and operated at a profit. Profit is where the idea of space based power falls down; to make a profit at market prices you have to be able to deliver power to the grid at the same or lower prices than terrestrial sources.
The one clear advantage of space based solar over most
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Getting it to work 100% of the time is a bit tricky. Assuming a satellite is in GEO, it still has brief periods where it's eclipsed by Earth. It's not much though, between 1 and 70 minutes near local midnight per day plus/minus 20 days from the equinoxes.
You need multiple satellites a few degrees apart to have one cover the other during the outages to get to 100%.
It's exciting technology. I wish TFA would have talked about link budget and losses. :|
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If you have no storage you must design for peak load instead of average load
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One of those pie-in-the-sky concepts that you see in
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The potential advantage of solar panels in orbit isn't getting more energy, it's getting energy even when it's cloudy. You can transfer the power on frequencies that don't interact as much with water vapor, so you can beam the power through the clouds. People love to complain about how you can't rely on solar power, this is an answer.
Well, it's a potential answer, obviously, since we can't do it today.
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Solar panels in space are subject to extreme heating, cold and radiation. And yes, debris too.
We have had functional solar panels in orbit for decades.
And you need to put them there to start, which takes energy.
What doesn't take energy to start?
And then you have the safety problem of a powerful energy beam pointing down at you.
This one we agree on.
And you have to convert this energy back to electricity (guess how?).
Erm... a rectifying antenna?
Electromagnetic radiation readily converts to electricity.... Didn't build an AM radio as a kid?
Re:How is this a proof of concept? (Score:5, Informative)
They demonstrated some key technologies needed to make space based solar commercially viable.
The array they used is made of small, low cost, lightweight, flexible antennas. They were folded up for launch, and then unfolded in space.
Because they were flexible, exact alignment when unfolded is not possible. The system has to adapt to slightly misaligned and even broken antennas, and still be able to send power back to Earth. While this sort of thing has been done before, this is a considerable advancement of the technology.
Protecting from debris probably isn't such a big deal. Solar arrays are typically made to keep working if some of the cells go bad, e.g. due to collision with very small bits of junk.
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However, it does not need to be aimed at the receiver all the time. If needed, it could be aimed at some military base or something. 1MW of microwaves should cook everything and everyone in that base quite thoroughly.
Intensity [Re:How is this a proof of concept?] (Score:2)
However, it does not need to be aimed at the receiver all the time. If needed, it could be aimed at some military base or something. 1MW of microwaves should cook everything and everyone in that base quite thoroughly.
Not when you account for beam spread, no. At the distance from geosynchronous orbit to the Earth's surface, diffraction physics says the beam MUST spread, and the intensity at the surface is sunlight intensity or less.
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The achievement is not that they send microwave energy from a satellite to Earth's surface, but that they did it using an aimed beam at much higher power.
A typical communications satellite in LEO will have a transmitter power of about 1KW and just kind of "shine" the energy onto the Earth in a directional, but wide, beam. The power seen at the ground is measured in femptowatts.
This demonstration has a power density some 14 orders of magnitude higher than most satellite communications.
=Smidge=
Low power [Re:How is this a proof of concept?] (Score:2)
The achievement is not that they send microwave energy from a satellite to Earth's surface, but that they did it using an aimed beam at much higher power.
That would be a good demonstration, but no, the power beamed to Earth was very low, only 200 milliwatts [science.org] (of which only a tiny fraction was received on the ground-- enough to detect, not enough to power anything.).
The value of the demonstration was in showing that their low-cost solid-state phased array transmitter worked as predicted in space. Showing that your hardware works in space is a step toward actual usable power levels, even if only a small step.
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Sending waves towards earth is what satellites do, no?
Yeah, and we have loudspeakers too, so why does everyone carry a point-to-point communication device in their pocket? Makes no sense, right? </s>
Satellite signals are usually sprayed all over the ground, rather than being focused at a specific point. DirectTV wasn’t aiming specifically at your house. Neither is GPS. Nor was Sputnik. Not even Starlink focuses on a specific terrestrial point. They’re all spraying signal all over the ground, and that’s fine when you’re sending dat
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Reportedly [satmagazine.com] for Starlink, "The diameter of the cell on the surface of the Earth to which the beam from the satellite covers is 15 miles"
I think a receiving dish that big would be a little costly!
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Let's ser....by putting solar panels in space we can potentiallu *increase* the amount of solar radiation reaching the earth. Great.
Oh, just think of the weapons potential though...
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Annual energy use of humans per year: 580 million terajoules.
Each hour 430 quintillion Joules of energy from the sun hits the Earth.
Humans use 1.34883721 × 10^-12 of the power in a year that hits the Earth in a hour.
I don't think this project will alter that in a signifcent way.
no chance of accidents (Score:4, Funny)
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Soletta [Re:no chance of accidents] (Score:2)
I remember talking about this with my father 40 years ago. It of course what we do all the time, but can we do it so it makes sense. Can we concentrate sunlight by a factor of two or three over a large area, where there are solar panels and minimal air traffic.
Hard to do. To concentrate sunlight by a factor of two, the apparent size of the mirrors or lenses in orbit has to be the same size as the apparent disk of the sun. Since anything in orbit is quite far away, that means the mirrors or lenses would have to be enormous.
More importantly, can we have a network of these satellites so that the solar panels are supplied 24/7.
There isn't really an orbit that can be simultaneously over the ground station and in the right position to redirect sunlight, and stay in that position. So you would need a lot of such lenses or mirrors in orbit to provide 24/7 illumination.
(do
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Since what they are talking about is microwave transmission, that is clearly not the idea being tested.
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Faraday cages need to be grounded, so you're also going to be nailing them to the floor.
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I know you are joking, but realistically this technology might not be deployable due to the potential for misuse. Just think what the reaction would be if China announced it.
It's got many of the same issues as nuclear power. Concerns that it could be weaponized, requiring a considerable amount of technical expertise and regulatory oversight for a country to operate it, and high cost compared to the alternatives.
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This comes up every time.
No, it is not possible to weaponize it. Energy density will be less than sunlight.
It will need an enormous antenna array to focus the beam on a few square km of receiver site.
To make the microwave beam tighter, so it can cook things, would mean a vastly bigger transmitter array in space, which would be very obvious if not impossible.
There are much better ways to make space-based weapons.
however . . . (Score:2)
. . . Parisian pedestrians are less than thrilled by this redirection . .
(well, at least the ones that managed to dodge the first day, but anyway . . .)
ORBITAL DEATH RAY!!! (Score:2)
I'm sure this has no military applications, at all.
Saw this in the late 1970's (Score:2)
Steering a beam, only headed in the reverse direction.
The Reflex Gun [youtu.be]
There is no master but the Master (Score:2)
And QT-1 is his prophet.
Re: There is no master but the Master (Score:2)
Very good!
That was my first thought too....
My second one was about the Lost Cometary Colony. Now that's even obscurer reference.
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"Very good!
That was my first thought too....
My second one was about the Lost Cometary Colony. Now that's even obscurer reference."
Obscure? The Master? Ssssssssssssssssssssssss!
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I think building this power plant could also make the giant death robot appear, if you had disasters enabled.
Re:Simcity 2000 (Score:2)
I didn't play that game, but I do remember one of the random disasters caused the beam to move away from the receiver for awhile and could do damage. So the smart thing to do was to place the receiver site outside the city.
Since the tech is probably sending microwaves down, it makes sense to do just that, set up a large receiver in a remote location. Microwaves could be tuned to cut through the atmosphere with fairly low loss. But I wonder how much better this would be than ground-based solar? I suppose
Put the tinfoil hats on! (Score:2)
Otherwise they will cook your brain!
Where are the cellphone tower protestors ... (Score:2)
I for one.. (Score:1)
+1 for global warming (Score:2)
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You can pick frequencies that get through the clouds better than visible light does, so that's theoretically a bonus. But while I think it could be very useful in the future, I still don't think it really makes sense at this point. It's only when you have the bulk of the manufacturing in space that you want to put the panels there. By then, some strategies for dealing with the space trash that generally makes it a bad idea could emerge.
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I suggest you look at the total energy the Earth receives from the Sun in a year, compared to the energy we use for civilization. The Earth receives more power from the Sun in 1 hour than the human race generates in a year.
Getting all our power beamed in would make no difference and without carbon pollution to trap heat
What about possible RFI (Score:2)
200 milliwatts. (Score:1)
BBQ chicken from heaven, what's not to like? (Score:1)
remember the Kzinti lesson: (Score:2)
Hey awesome! (Score:2)
Just love it when defense contractors get to test new "totally not something we could use as a weapon" platforms!!
Because defense contractors are the first people I think of when I think of stuff beneficial to mankind, you know?
(Can't wait for people to tell me I'm paranoid, because of course I am! Who would be foolish enough to trust any of them?!)
Interesting but oversold. (Score:2)
Indeed interesting proof of concept. Dispatchable solar energy.
That said when Mr. Bucknell says "Space solar is the only clean, firm, scalable energy technology [with] a credible path to actual zero carbon emissions." he is not correct. Every source, including this one has a carbon footprint. If he means "doesn't emit greenhouse gases while used" then it is not the only one. Tidal, thermal solar, photovoltaic solar, some of the hydroelectric dams, nuclear plants, wind turbines and geothermal power do not em
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You have to combine them with Moron Waves to work. MTG used to be the key source.
Why I'm skeptical (Score:2)
I saw a documentary where a lady with spirally hair buns tried to prevent a dude with asthma from using a bigass satellite to bake her planet doing this. The damned robots argued too much, they must be married. Asthma Dude should have baked the damned bots instead.
In Other News (Score:2)
While tuning this laser beam that is shot from Space towards the surface of the Earth large swathes of Canada were lit on fire.
Film At 11
Getting Microwatts from Kilobucks (Score:2)
What's the price per KWH delivered on the ground?
Beware, the robots might get religion! (Score:2)
Asimov warned us of the dangers of letting robots run one of these stations.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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He showed that it's perfectly safe, so long as you don't try to mess with their reasoning.
2001 shows us what happens when you do that.
fiction becomes reality (Score:2)
Robert Heinlein incorporated this concept into some stories back in, I think, the 1940s. I'm sad he didn't live to see it become reality.
Stop touching yourself (Score:2)
I heard that God blew the top off the house of the guy responsible for this with an excess of popcorn.
We don't need no oil... (Score:2)
Home on Lagrange (The L5 Song)
by Bill Higgins and Barry Gehm
Copyright 1978 by William S. Higgins and Barry D. Gehm
(Sung to the tune of "Home on the Range")
Oh, give me a locus
Where the gravitons focus
Where the three-body problem is solved
Where the microwaves play down at three degrees K
And the cold virus never evolved
CHORUS:
Home, home on Lagrange
Where the space debris always collects
We possess, so it seems,
Two of our greatest dreams:
Solar power and zero-gee sex!
We eat algae pie, and our vacuum is high
Our bal
How is this news, except for debunking solar sail (Score:2)
Pointing a phased array antenna has be done for half a century at least.
Interesting is the deployment of a 'sail-like' solar array. Wouldn't that just send the satellite wafting off in to the void ... or was Thomas Gold [wikipedia.org] correct and the whole solar sail thing is a scam?
Oh, 200 mW (Score:1)
I thought they said 200 MW. If they could receive that on earth, they'd have a better proof of concept.
Oh wait, they transmitted 200 mW, not received on earth. Just barely detectable. Well, keep going, guys. Let's see if you or fusion power reaches commercial use first.