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Optical Concentrator To Make Solar Power Cheaper
Posted by
Soulskill
on Sat Feb 21, 2009 12:22 PM
from the bright-ideas dept.
from the bright-ideas dept.
Al writes "Researchers at a company called Morgan Solar have developed a simple solar concentrator that promises to cut the cost of solar energy. The Light-Guide Solar Optic (LSO) consists of a specially-molded acrylic optic that traps light and guides it toward its center using total internal reflection. At the middle of the concentrator another optic made of glass receives the incoming light, amplifies it and directs it toward a small solar cell at the very center of the device. Unlike other concentrators, the light doesn't leave the optic before striking a solar cell so there's no air gap, and there's no chance of fragile components being knocked out of alignment. This could significantly reduce the cost of manufacturing this type of solar cell."
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Submission: Optical Concentrator to Make Solar Power Cheaper by Anonymous Coward
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Cool (Score:5, Interesting)
That's actually pretty cool. By concentrating the light, they need less photovoltaic material per square foot of land used for solar. I'm curious how the efficiency of photovoltaic cells varies with the concentration of light. Will 1 square foot of sunlight concentrated into a few square inches of photovoltaic cells produce as much power as 1 square foot of unconcentrated photovoltaic cells?
Re:Cool (Score:5, Interesting)
The efficiency actually goes up relative to PV material in straight unmagnified sunlight. I'm sure there's a saturation point where that stops. This is one reason concentrating light on PV is a plus. Of course, the other is that it involves less PV material cost.
Parent
Another "investor opportunity"? (Score:4, Insightful)
The article, A Cheaper Solar Concentrator [technologyreview.com], referenced in the Slashdot story says, "With a flat bottom and convex, mirrored top, the [Morgan Solar [morgansolar.com]] optic receives the incoming barrage of light at a concentration of about 50 suns and amplifies it to nearly 1,000 suns before bending the light through a 90-degree angle."
The article does not explain how there is a concentration of 50 times before the light reaches the optics. The article is wrong in using the word "amplifies". The correct word would be "concentrates".
To have a 1,000 times concentration, the area of the optics must be 1,000 times larger than the area of the solar cell. That delivers 1,000 times the heat, also.
Morgan Solar's investors page [morgansolar.com] says, "Morgan Solar was incorporated in June 2007 and is currently well funded by a start-up investment from our angel investor and Chairman, Eric Morgan." Apparently the company was funded by the inventor or someone in his family. It says, "Our plans call for securing our next round of investment funding by Q1 2009. If you are a venture capital company or a potential partner-investor interested in exploring investment opportunities with our company, please contact us."
Was a Slashdot editor paid to allow this story? Did Slashdot profit? Was Technology Review paid to run the story? I think that articles about companies that are soliciting investments should have a statement about whether or not someone was paid.
Parent
Here's the link ... (Score:5, Informative)
... about concentrating solar power [wikipedia.org].
Parent
Re:Cool (Score:5, Informative)
That's actually pretty cool. By concentrating the light, they need less photovoltaic material per square foot of land used for solar. I'm curious how the efficiency of photovoltaic cells varies with the concentration of light
For a constant temperature, efficiency goes up logarithmically with light concentration. A solar cell with 1 sun on it is going to be less efficient than one with 500 suns on it assuming you have a way to cool the cells. Past a certain point the efficiency drops like a rock due to lack of cooling the cells and this reduces the voltage you can produce by about 2.3mV/C past room temp.
Parent
Re: (Score:2)
Re:Cool (Score:4, Interesting)
Won't work. This thing has to face the sun directly. Which means that it has to be a fixed installation, and it won't work when it's cloudy.
The article briefly mentions some other group at MIT that's developing a concentrator that works with diffuse light - so presumably that would take care of both those problems.
Parent
Tilting is overrated (Score:4, Insightful)
A flat panel can be pointed at the position of the midday sun, and left stationary would have a reduced aperture to the sun as a result of the angle in the morning and evening. Turning the whole assembly helps. But, if there are many panels, they would have to be spread out or else some will shadow parts of others. Basically, it comes down to capture area. If you have a 10 meter by 10 meter area, there's only so much sun that enters it. In the morning and evening, there is less sun entering that area because of the angle. If you have one giant 10m by 10m panel that in there that gets tilted, its shadow will be outside the area, and you're actually capturing sun that would go outside. If you are have lots of small 100cm x 100cm panels, tilting them doesn't help because of the shadows. Remember, there's less total sunlight to get at an angle. Tilting is only an advantage when you have less than 100% coverage, and are willing to lose sun at midday.
Tilting is also a mechanical thing which means some kind of control mechanism, more exposure to failure, and greater maintenance costs.
An optical structure that would funnel light from any angle over a reasonably wide angle range would be the ideal solution. It would handle the change from morning to midday to evening, and would handle the diffuse light of cloudy weather. That's the thing to work on.
Parent
neat idea. What do they do with the heat though? (Score:5, Interesting)
Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?
Re: (Score:3, Interesting)
Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?
About 80% of the energy is absorbed across the entire solar spectrum. Yes, it will radiate some heat away as IR, but mostly the heat is convected away by the surrounded air. You're right, though--this is a design concern for these devices, as temperature effects efficiency and lifetime.
Re:neat idea. What do they do with the heat though (Score:5, Interesting)
They keep them in the dark so they don't get hot.
or from wikipedia:
The solar cells require high-capacity heat sinks to prevent thermal destruction and to manage temperature related performance losses...In May 2008, IBM demonstrated a prototype CPV using computer chip cooling techniques to achieve an energy density of 2300 suns.
Parent
Re: (Score:2)
My first thought was, why are they using a PV cell in the first place, instead of using the heat to drive a turbine?
waste heat (Score:4, Interesting)
Or use the waste heat to drive a stirling engine as a booster perhaps. I know just regular solar panels get wicked hot on the backs of them when sitting in full direct sun, I mean it is black stuff sitting behind a clear surface and stuck on a metal backing, it gets *hot*. Just doubling that heat would turn it into some sort of decent viable optional energy source.
And why PV? Instant electricity from it, solid state, no moving parts, pretty spiffy stuff. Big solar concentrators with turbines are cool too, we have those for giant megawatt scale production now, but we don't have them for joe homeowner yet or joe back packer, PV fits the bill for those purposes.
Parent
Re: (Score:3)
Re: (Score:3, Insightful)
Heat water with the waste heat.
When the water tank gets too hot you heat the house with it (or dump the heat outside).
I'd use an oil loop between the collectors and an over-sized water tank.
It's just a fresnel lens (Score:5, Interesting)
From the picture, it looks a lot like a fresnel lens [wikipedia.org].
Re: (Score:3, Interesting)
There are some key differences. In a fresnel lense the ridges just bend the light passing through a small amount. It is basically the surface of a regular lense stepped into a flat surface. Thus it acts almost exactly like a standard lense and has a focal point somewhere behind that all the light is reflected to.
From the sound of it, this lens bends all the incoming light 90 degress or more, sending it towards the center through the lens itself to a secondary optic area which concentrates the light and r
Re: (Score:2, Informative)
Re:It's just a fresnel lens (Score:4, Informative)
Parent
solex agitator (Score:2, Informative)
Watch out for the man with the golden gun...
Does this have to be aimed? (Score:2)
Does this thing have to be aimed at the sun? In 1D or 2D? If it needs 2 pointing axes, it's too complex. 1D, maybe; there are trough-like concentrators at Mojave which are driven to move with the sun.
Re: (Score:2)
It would appear that it must track the sun precisely.
Re: (Score:2)
Why does that make it "too complex"? Finding the sun is not a particularly hard engineering problem.
Burn, burn your little b*%^&rds & solar sm (Score:2, Funny)
My house has an nearly unbeatable infestation of small ants, and I can't help but think just what a magnificent burning lens one of these would make minus the solar chip.
But aside from that, there are some other pretty nifty uses for concentrated sunlight. I am definitely curious whether the lens can be scaled up to a square meter or more, enough to possibly melt glass or aluminum.
Re: (Score:2)
I am definitely curious whether the lens can be scaled up to a square
You're thinking of solar furnaces, like the one in Odeillo http://en.wikipedia.org/wiki/Solar_furnace [wikipedia.org] (already in production for over 20 years ...)
transmission lines (Score:5, Interesting)
I live in LA. To the east of us is the Mojave Desert, and there's already quite a bit of solar power out there right now [wikipedia.org]. The big issue is transmission lines to get the energy from the Mojave to LA. Building transmission lines requires political action, and that's slow and uncertain because of NIMBY. I have photovoltaics on my roof, but objectively, if you look at the price of land where I live versus the price of land in the Mojave Desert, it's pretty clear where you should be building these things.
Shadow lines (Score:2)
That's the thing about alternatives. Storage. Also unlike wind solar panels block the ground underneath big time. One has to wonder about the effect if solar becomes a bigger source.
Re: (Score:2)
I'm thinking effects similar to forest.
Shade, cooler, a little less evaporation, only shade tolerant bushes underneath.
Of course you don't want plants overgrowing your solar power plant anyway.
Re:Shadow lines (Score:4, Interesting)
Which is why in actual practice the land under the solar collectors is made as sterile as they can afford to make it. We need to accept that getting most of our energy from desert solar will probably require destroying the ecology of several percent of the deserts of the southwest. I think that's an acceptable trade off, but for those who insist on a "greener" solution I suggest they push for nuclear power.
Parent
Re: (Score:2)
Re: (Score:3, Interesting)
Huh? My post, which you were replying to, didn't say anything about storage.
LA's problem with lack of capacity shows up on hot days in the summer, when everyone is running their air conditioner. That's exactly when the Mojave plants will be running at their maximum production. Because of this excellent match between peak production and peak demand, there isn't really an issue with storage. It's a perfect fit.
Re: (Score:2)
Wow, just in time (Score:2, Funny)
I object to the word "amplify". (Score:5, Insightful)
There is no "amplification" taking place at all, merely concentration. Those are two VERY different things.
An unstated benefit (Score:3, Interesting)
of this particular solar advance means not only greater efficiency and lower cost, but also MUCH MUCH greater feasability for wider adoption by areas of higher latitudes. In addition, this particular advance would appear to reduce the detriment of partial occlusion by some factor.
This concentrator technology also reduces the manufacturing use of rare metals for these systems and that is another huge benefit also.
Concentration is not amplification (Score:2)
> optic made of glass receives the incoming light, amplifies it
I'm sorry, but an "optic made of glass" can not amplify light. All it can do is concentrate it.
In fact the whole this just sounds like packaging a solar cell and an elaborate magnifying glass to me.
No net decrease in surface area. No proven increase in efficiency.
Re: (Score:3, Informative)
No net decrease in surface area. No proven increase in efficiency.
There's a third axis; cost per watt. Acrylic is cheaper than PV silicon.
(Actually the relationship of surface area and efficiency is fixed, so it's really a second axis.)
-Peter
Can you put it in place of glass windows? (Score:2)
If this material concentrates all of the sunlight onto the PV chip in the center does that mean that NO OTHER light will pass through it? From the description of something that will take (sun)light from any angle and direct it towards the center does that mean someone behind it will only see black?
If not, it might be a good surface to use on the millions and millions of square feet of windows that covers office buildings. You could conceivably generate ALL of a buildings energy needs that way. (The power
Re: (Score:3, Funny)
Caution
Cf. holographic concentrators (Score:2)
Interesting to compare this to a holographic concentrator [prismsolar.com]. This optical concentrator has a much higher concentration ratio and thus allows the use of much less silicon, but on the other hand it requires a mechanical tracker and a heat sink, which the holographic concentrator does not.
I hope to see both these technologies in production soon. $/W is the big barrier for photovoltaics.
"Cheaper" Power Cells (Score:3, Interesting)
Re:"Cheaper" Power Cells (Score:5, Insightful)
Because they used to be insanely, ridiculously, incredibly damned expensive. Now they are merely damned expensive. In a decade or so they will be down to expensive. Someday they will be cheap, but the sun may go out first.
Parent
Re: (Score:2)
Someday they will be cheap, but the sun may go out first.
Hmmm I can see the ads.
"Purchase Duke Nukem Forever now, and get a free pack of solar cells!"
They've just re-discovered (Score:2)
Re:They've just re-discovered (Score:4, Informative)
Not really a lens of any type. Its an example of non imaging optics [wikipedia.org]. A lens, Fresnel or otherwise, or a mirror, produces an image of an object at its focus. So, as the sun moves across the sky, its image would move across the plane of focus. So you'd either have to make that image plane big enough to contain the imaged sun track over a day or move the apparatus. Non imaging optics reflect or refract incoming light rays from any direction on to a single point as well as focus the light from a large aperture onto a smaller area.
While the idea of non imaging optics in general isn't novel, the design of this device might be.
Parent
Wait... (Score:2)
Plastics make Problems (Score:3, Insightful)
The plastic is the problem. Can't we do it with all glass? If you use a solar furnace you can make it with solar energy. Alternately, if you get enough PV, you can run an electric furnace. Either way, plastic is nasty and sand is everywhere. (Some of the additives in glass are nasty, to be fair. But not all glass is nasty. All plastic is either nasty or has a short life when exposed to UV. Much is nasty AND has a short life.
Re:Not an original idea? (Score:5, Informative)
Parent
Very original idea (Score:3, Insightful)
Amplifying light with a glass 'optic' would be quite original. Concentrating it yes, but amplifying it?
I would be very impressed if they have actually achieved it.
Re: (Score:2)
A science reporter at a magazine published by MIT? Yeah, I guess it is asking too much.