Holographic Solar Collectors 189
An anonymous reader writes "The MIT Technology Review is reporting that Prism Solar Technologies has developed a technique to use holograms to concentrate light onto photovoltaic (PV) cells. While the implementation is only about a 10x increase over PV cells without collectors such as mirrors/lenses (mirror/lens approaches can do 100-1000x), it is a great deal simpler, more compact, and cheaper. Also because of the concentration, there is less need for physical PV cell real estate compared to crystalline PV silicon cells of similar output."
Only 10x? That's huge! (Score:5, Interesting)
10x increase for the holographic cell may sound bad compared to 100x-1000x for mirrors/lens. But in the installations I know that use mirrors or lenses they take up most of the area. If 10% of the whole surface was PV cells and 90% were e.g.. mirrors (a very conservative assumption, I think the PV cells will cover less then 1%) you would gain an effective increase of 100x instead of 10x. (This is not entirely true, since these new PV cells are only part energy creating silicon, most of their surface is just the holographic lense. But still a massive space saver compared to classical mirrors.)
Plus you will usually have to place mirrors on the ground due to their weight and the weight of the motors attached to them to make them follow the sun. In contrast you can place PV cells on almost any surface, although you will loose a lot of efficiency if you can not orient them towards the sun.
If you completely ignore that there are theoretically more efficient methods of concentrating the energy onto PC cells, you still get a 10x improvement over the typical installation (on a roof, with no fancy mirrors at all). And then 10x is huge.
10x input != 10x output (Score:5, Insightful)
PV efficiency reduces significantly with increase in temperature (which is why you see solar racer folk pouring water on the PV panels). Thus just cranking up the sunlight by concentration does not give a linear increase in output. PV cells for concentration thus need to be made thicker and differently (to code with the extra current, heat sinking etc.) but hopefully the payback is still there.
Personally I think the PV quest is being approached incorrectly. There's too much emphasis on efficiency. Labs try to out % eachother and the big solar showcase is the solar race which is all about high efficiency cells.
What they should target is $ per Watt because that is the real hurdle to making PV viable. Who cares if it's only 5% efficient, so long as it is cheap? Tile your house with the stuff to get the area.
Re:10x input != 10x output (Score:5, Informative)
$ per Watt (Score:2)
"We built a solar cell made of ice," he recalled. "While it is not as efficient as a silicon solar cell, it costs a penny a square mile."
We can make super cheap photovoltaics, but you have to factor in usability. There's a very limited part of the world where you can use a solar cell made of ice.
Also, silicon solar cells aren't going to get any cheaper in the near future. The demand for polysilicon has been booming and (like oil) the r
cost per watt (Score:3, Informative)
Re:10x input != 10x output (Score:5, Insightful)
You are almost absolutely correct. Except for two things:
1. Low efficiency leads to higher indirect costs- specifically, the infrastructure that holds the cells and connects them to the grid. As you get down to lower efficiencies, these costs become significant.
2. Even at 10% efficiency, you need a huge area to produce a significant amount of juice. Sure, we could in theory generate all the energy we need in the U.S. by covering "only" around 1% of the U.S. land area with 10% efficiency PV (practical issues aside), but that still works out to be a huge area. Like, say, Maine. So even if we had a nice, cheap, low-efficiency solar technology, it's usefulness would ultimately be limited by land use constraints.
Re:10x input != 10x output (Score:2)
I'm sure the black tar roofs (houses) or flat commercial
Re:10x input != 10x output (Score:2)
1. Rooftops
2. Parking lots
3. Paved roads
I'd wager it's close to the area you need, and covering any of the above with solar panels would have little to no effect on anything, since the roads/roofs/lots are already nicely free of plant life that might want to use the sun.
No reason not to stick a little 400w wind turbine on every other streetlight pole, either.
The big limit is financial, and this solar
Re:10x input != 10x output (Score:2)
Rooftops
Substantial. People have actually looked at this, but I don't have the numbers at my fingertips. It's a big number, but I think that when you filter out for the ones that could realistically have panels on 'em, it is only a pretty big number.
Parking Lots
This is my personal favorite. However, you'd need to build the infrastructure to hold the panels off the ground, which adds not insignificant costs. So in this case, efficiency is a strong driver of overall costs.
Paved roads
There are lots of prac
Re:10x input != 10x output (Score:3, Interesting)
Covering over the freeways with a half tube grid of cheap material... put up solar cells in grid cells where they make the most sense, let light, air and weather filter through the rest... feed it into the loc
Re:(1(kW/(M^2))*.1)=100W/m^2 (Score:2)
But only tree hugging idiots think in terms of ALL solar.
It's a scaling exercise. I am not suggesting we cover a single state with PVs (I'd have to go with AZ or NM in that case), I just want to provide a sense of scale.
My point is that any significant use of solar energy (which I am a huge proponent of) will require a non-trivial use of land. Nogt a deal killer, but not something that can be ignored.
Re:10x input != 10x output (Score:2, Insightful)
I'm not sure why they don't combine PV Solar with absorption panels linked to a heat pump and the hot water system, or heat the pool.
Finding uses for heat, in most building isn't all that hard.
Deal with PV's problems by teaming with other technologies instead of trying to solve all the problems in isolation.
Re:Only 10x? That's huge! (Score:3)
As far as I understand it, it will not increase the maximal amount of energy you could produce on your roof. Actually, this would decrease. If you pack regular PV cells on your whole roof, this would generate the most energy. But at the highest cost.
Most installations do not cover the whole roof, only parts. With these new cells integrated in holographic lenses you can actually cover more of the roof area for almost the same price. And although the area of active silicon will not increase, the lenses will
Re:Only 10x? That's huge! (Score:2)
There are a l
Re:Only 10x? That's huge! (Score:5, Insightful)
Yep.
a one square yard panel of naked PV cells shouldn't get any more energy than one square yard with holographic cells... right?
A square yard of naked cells (or cells imbedded in a classic panel), a square yard of focusing concentrator onto a smaller area of cells, and a square yard of holographic panel containing some smaller area of cells, would all potentially collect the same power (neglecting concentrator inefficiencies).
The point is that:
- doing a square yard of collection with a square yard of cells costs.
- A normal focusing concentrator focuses not just the useful light, but the non-useful far-infrared, so you need serious cooling of the cells to run at a high degree of contentration, and the concentrator is bulky, heavy, and may need to track the sun.
- This thing is WAY cheap to make, doesn't focus useless infrared below the cells' bandgap frequency, and doesn't need to track. It loses some of the light, so you may need a little extra area to make up for that. But you use only 10% of the cells compared to a classic panel for a given amount of power.
As I read the drawings this is basically a glass plate with solar cells glued to 10% or so of the back and the remainder covered with a holographic coating.
The holographic coating diffracts the desired frequencies so they become trapped between the faces of the glass plate by total internal reflection (as light is trapped in a fiber optic light pipe) and it bounces back and forth between the surfaces until it hits a place where a cell is glued to the back. At that point the glue's index of refraction is high enough that the light can escape into the cell. So you just need enough cells that most of the light encounters one before it gets to an edge or leaks out where a dirt speck sits on the glass. (I'm not clear how they keep the holographic coating from diffracting it back out toward the sun but I presume they've got that covered.)
Far infrared doesn't bend enough to get trapped so it escapes out the front or back of the panel.
This is VERY nice. With maybe 90% of the infrared passing through the panel or bouncing out the front of it you don't get the massive greenhouse effect of a classic panel.
No space savings (Score:2, Informative)
That's not the point (Score:3, Insightful)
Holograms? (Score:5, Insightful)
Re:Holograms? (Score:5, Interesting)
Since you can create multiple refractions inside a hologram, you can create a much better lense than with diffraction gratings. So while both are basically flat lenses, the holographic version is much more efficient.
many diffraction gratings are holographic (Score:3, Interesting)
When it comes to making diffraction gratings, phase-delaying gratings beat out amplitude-reducing gratings (parallel opaque parts) for transmission. It's easy to make both phase and amplitude gratings with an interferometer (to make fringes) and some holographic film. For phase gratings, you just bleach the film/plates after you wash them in developer and before you use the stop bath.
Three dimensional g
Re:many diffraction gratings are holographic (Score:2)
You can have an amplitude or a phase or a phase-and-amplitude hologram in transmission or reflection.
Comment removed (Score:4, Funny)
Re:Holograms? (Score:3, Insightful)
Not sure whether that is a spin. Heating is a real problem for Solar concentrators.. A lens will concentrate light, but also IR. These are quite high temperatures we are talking about. If they can actually take out IR from the question, then this indeed is a good idea..
Also, I can see pratical applications on window sills etc. In our place, temp can go up to 110. Think of a cheap window which will let in only light (similar to th
Re:Holograms? (Score:2)
One man's disadvantage is another man's cooling system. Since the solar cells are also wavelength dependent, the goal is to collect all the usefull light and let the rest (mostly) pass harmlessly through the glass plate. Very clever.
Solar collecting is good. (Score:4, Insightful)
Re:Solar collecting is good. (Score:5, Insightful)
I can see solar as a potential option for some businesses, but for home use you still have the small problem of no power output during the night. And that's usually just when you want some lights, television, heat, and so forth.
If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a cost-effective way to store and reuse the energy collected during the day.
Re:Solar collecting is good. (Score:4, Funny)
Someone should invent that.
Re:Solar collecting is good. (Score:4, Informative)
Something more like this:
http://www.ibsa.com/estore/search.asp?details=1&m
Though that's with an ultra quick search.
-nB
Re:Solar collecting is good. (Score:3, Funny)
thats a good link, can you read it back for me over the phone ?
Re:Solar collecting is good. (Score:5, Funny)
Sure:
ache tee tee pee colon whack whack dub dub dub aw fuckit dot see oh em
Re:Solar collecting is good. (Score:2)
Or, if you're not reading over the phone, just click the bloody link. [tinyurl.com] TinyURL was MADE for that sort of monstrosity :)
Re:Solar collecting is good. (Score:5, Interesting)
-nB
* for example pump water up a mountain to a storage lake and let it run down durring the night for power
-nB
Re:Solar collecting is good. (Score:2)
Okay... just for what it's worth, have you ever been to the Hover Dam? Ever seen the amount of water that goes through the turbines each day? Assuming, or course, you're not in Kansas or Indiana or some place lacking in available mountains.
Or considered just how many flywheels you'd need, and how large they'd have to be, to power an entire city for a night.
Not saying your ideas aren't practical, but...
Re:Solar collecting is good. (Score:2)
"The relatively low energy density of pumped storage systems requires either a very large body of water or a large variation in height. For example, 1000 kilograms of water (1 cubic meter) at the top of a 100 meter tower has a potential energy of about 0.272 kWh. The only way to store a significant amount of energy is by having a large body of water located on a hill relatively near, but as high as possible above, a second body of water. In some places this occurs naturally, in others one or b
Re:Solar collecting is good. (Score:2, Insightful)
it is used to balance out extreme loads reacting quickly to smooth out demand so that more power stations are not kept idling
Re:Solar collecting is good. (Score:2)
FYI: For those that think that this is just a random idea that networkBoy made up, http://www.nypa.gov/facilities/blengil.htm [nypa.gov] and http://www.nypa.gov/facilities/niagara.htm [nypa.gov] are examples of where this has been done for years.
Re:Solar collecting is good. (Score:3, Insightful)
Dams are really large storage cells. (Batteries)
Re:Solar collecting is good. (Score:2)
So do I, which is whi I led off with this statement:
"Since plain ol solar will never meet our energy needs, just use the grid as a storage device. "
The point of charging the "gravity battery" was that should we really have an absurd ammount of solar power available, that we can feed the entire country's needs durring daylight hours, then storing the excess would not need to be that efficent, we'd be so far ahead of the game just by turning off
Re:Solar collecting is good. (Score:2, Interesting)
Have you ever seen http://www.homepower.com/ [homepower.com] magazine?
Re:Solar collecting is good. (Score:2)
Re:Solar collecting is good. (Score:2, Insightful)
Put a solar farm on several people's roofs, put a wind farm here and there, coastal cities get wave generators, and everything else can be nuclear. That is the future, not pure solar.
If this new system could be inmproved to focus the light to a small line I wonder if panels could be hid inbetween roof shingles? Removing the ugly factor entirly
Re:Solar collecting is good. (Score:2)
I agree, except you missed one major change in the energy usage: population decline. The rate of change from efficiency based on fossil to other sources may be too high. So, the populate is affected through a massive price shift for most goods and transportation. I believe most folks will eventually conclude that energy resources can only come up so far, the rest is bringing down need to match.
There's only so much "getting off the [old] grid" one can do, and when? Most folks agree that "not no
Re:Solar collecting is good. (Score:3, Informative)
Re:Solar collecting is good. (Score:2)
But it's not a battery. Yes, you may be able to sell some excess power to the "grid", but the "grid" doesn't store energy, it just distributes it. As such, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at night.
So at night solar has issues. In fact, it's not too great on cloudy, snowy, short winter days either.
Re:Solar collecting is good. (Score:3, Interesting)
It takes a few hours (at least) for most power stations to significantly alter their outpu
Re:Solar collecting is good. (Score:2)
The operative word in that sentence being "some". Given all of the electrical grids on the planet, it looks like about three-four dozen or so are pumped storage systems. I also liked the following quote: "In 2000 the United States had 19500 MWe capacity of pumped storage. This produced a net -5500 MWe of power because they consume more power filling their reservoirs than they generate by emptying them."
Re:Solar collecting is good. (Score:2)
Right, which is why they work as load-balancers and promote financial efficiency rather than actually promoting power efficiency. Thankfully the main generating systems have already tied financial efficiency to their, somewhat more fluctuating power efficiency, so it all works out.
Re:Solar collecting is good. (Score:2)
Re:Solar collecting is good. (Score:2)
In developed areas, at least, there is already an easy way to do that: use the power grid as your energy store, by selling power to the grid during the day and buying it back again at night.
It's the new millenium people! Get with it! (Score:2)
If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a cost-effective way to store and reuse the energy collected during the day.
This is a non-issue. The technology and legislation addressing this has existed for nea
Re:It's the new millenium people! Get with it! (Score:2)
Simplistic, you mean. Repeat after me: The grid is not a battery. Yes, you may be able to sell some excess power to the "grid", but the "grid" doesn't store energy, it just distributes it. You can't buy "your" power back again.
So to repeat, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at home on a cold night.
"Come on people, do you honestly
Re:It's the new millenium people! Get with it! (Score:2)
So to repeat, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at home on a cold night.
Fortunately, the amount of power needed at night is far lower than that needed during the day. Other power generation mechanisms are sufficient
Re:It's the new millenium people! Get with it! (Score:2)
Another source that works well only under limited conditions (when the wind is blowing) and only practical in specific locations (where there tends to be a lot of wind). Like solar, both can help, but neither can be depended upon to provide and maintain constant baseline loads.
Re:It's the new millenium people! Get with it! (Score:2)
The point remains that once generated it's either used or gone. The grid doesn't store it. Which was the point of the original post. If we had a cost effective way to do so solar would have the potential to make a larger impact, as opposed to only operating under limited and/or optimal conditions.
"Uh huh. So you can turn off some plants during the day. Wouldn't that be a not-awful idea?"
For a rocket scientist, you're... ah... never mind. Let's just say I'd suggest you
Re:It's the new millenium people! Get with it! (Score:2)
I think he what he meant was, you can get by with fewer power plants, period, because the peak loads during the day would be reduced.
Re:It's the new millenium people! Get with it! (Score:2)
I submit that, in the Southern United States (and much of the temperate world) energy costs to cool dwellings is substantial. Most of that energy is required in the daytime. Wha
Re:It's the new millenium people! Get with it! (Score:2)
Never said it didn't. In my original post, however, I made the statement that solar would have a larger impact if we could develop a safe, cost-effective mechanism for storing the power produced so we have can have power at night and during non-optimal periods (cloudy, rainy days).
Re:Solar collecting is good. (Score:2)
> cost-effective way to store and reuse the energy collected during the day.
Agreed. Flywheels seem like a nice solution to that problem. Of course, next thing we'll know they'll be writing about "torque pollution"
Re:Solar collecting is good. (Score:2)
Re:Solar collecting is good. (Score:3, Insightful)
Re:Solar cells aren't about storing energy. (Score:2)
When solar cells are used, they are feed directly into your houses power supply and any excess electricy produced goes back into the power grid. Not stored in batteries.
This seems rather odd, but when electricity goes back into the power grid, it spins your meter backwards. Anytime your meter goes backwards, you get cash back from your power company.
Soo... You are still depedant on your local power grid for nightime power, but perhaps that might change for people who want to not have anyt
So many stories but where are they? (Score:4, Insightful)
Over the last decade quite a few of these wonderful improvements have been announced yet the commercially available solar-cell still has an efficiency of less than 15% and the price hasn't changed that much either.
I wonder if these announcements are more motivated by an upcoming investment round...
God knows we could use them, but when do we get to see them?
Re:So many stories but where are they? (Score:4, Informative)
Just to be clear on wording (Score:2)
You still need the same number of *panels* with this new technology. They are not more efficient per area than normal panels built with the same type of silicon, and probably slightly less due to loss in the diffraction.
But you need less silicon per panel, since most of the panel is just a cheap holographic diffraction grating that directs light towards the small strips of silicon.
You'll still need your whole roof, or whatever-- but it
Alternative to each other? (Score:2, Interesting)
What's stopping me using a holographic collector in conjunction with a mirror/lens affair? Use mirrors/lens' to angle 100 - 1000 times more light energy on to the hologram
Re:Alternative to each other? (Score:3, Insightful)
That would be innovative... and they have this thing designed to stop that kind of stuff.
It is called a 'patent'.
Re:Alternative to each other? (Score:2)
Why use a mirror lens when you can replace it with ANOTHER holographic collector?
Re:Alternative to each other? (Score:2, Informative)
Re:Alternative to each other? (Score:3, Informative)
The idea here is the holograms could be made flat while mirrors you'll have to link up with motors to track the sun.
If you have mirrors already tracking the sun, then you don't need holograms to redirect the light to the photo cells.
Re:Alternative to each other? (Score:2, Informative)
Hologram, eh? (Score:5, Funny)
Re:Hologram, eh? (Score:3, Insightful)
If you didn't find that absolutely hilarious you really need to watch some Red Dwarf [imdb.com].
Re:Hologram, eh? (Score:5, Funny)
Rimmer Directive 271 states clearly, "No chance, you metal bastard."
Re:Hologram, eh? (Score:3, Funny)
-- Mr. Flibble
Promising... (Score:3, Interesting)
Re:Promising... (Score:3, Insightful)
The other possibility is that the price of the alternatives might go up. If that happens, then solar will look more attractive even at its current pricing.
What happend to that South African break through? (Score:2)
Solar Holograms! (Score:2)
PV efficiency & moon power generation (Score:2)
Re:PV efficiency & moon power generation (Score:2, Informative)
Or do you mean build rails all the way around the Moon and motorize the panels so they can stay on the "light side". Or maybe position at the poles (too lazy to google it...does anybody know the axial tilt of the Moon? shallow enough to stay out of shadow at the poles?)
Better yet, unless you're p
Re:PV efficiency & moon power generation (Score:2, Funny)
And then when Bush Jr. Jr. Jr. decides that he doesn't like [bad country here], he'll just tell the opperators to point the giant microwave systems at [bad country] country for a while.
We used a similar product in 2001 (Score:5, Interesting)
The panels they came from a company called TerraSun and the one I have on my desk left from the project looks remarkably like the one in the article.
Archive.org still has some pages from the site which is long defunct http://web.archive.org/web/20010807151516/www.sol
Google finds reference to the technology that TerraSun was developing http://www.wapa.gov/es/greennews/2001/may14'01.ht
Re:We used a similar product in 2001 (Score:3, Informative)
How about Fresnel lenses? (Score:5, Interesting)
Re:How about Fresnel lenses? (Score:2)
Re:How about Fresnel lenses? (Score:2, Informative)
The problem is, if you are grid-tied or have a certified installer work on your system, they are extremely reluctant to even talk about mixing liquids with electricity. Often they tie the panels
Re:How about Fresnel lenses? (Score:2)
Re:How about Fresnel lenses? (Score:3, Informative)
The hohlgraphic plates can redirect light coming in from any direction and cause it to eventually (after much bouncing around) fall on a photovoltaic cell. It also has the benefit of filtering out bad (unhelpful) IR light.
Cheers,
Ben
Pointless. (Score:3, Interesting)
Cost is the primary draw... (Score:2)
One of the other factors with this panel is that it brings down the net carbon impact of the devices. It takes less energy to produce these panels, so the breakeven time is much shorter than on a conventional PV panel.
However, the b
Aesthetics (Score:2)
One interesting aspect is that these things seem to be pleasant to look at.
Aesthetics are an important issue for solar collectors, because if we want to generate any significant amount of power from solar, we are going to be looking at a lot of them. On average, with 10% efficiency, you can generate about 150 kWh per year per square meters. US electric power generation in 2004 was about 4 trillion kWh [doe.gov], so if solar were to provide even 10% of that, we'd need to cover the better part of Rhode Island with ce
Re:Aesthetics (Score:2)
Start off with an insignificant amount per new home, say a 1000 watt inerty system and/or enough solar hot water for 4 people, and up the amount every decade or so until the thing becomes self sustaining.
After visiting Hawaii I am conv
Re:Aesthetics (Score:2)
Finally, a use for Nevada/NewMexico/Arizona/Or any of those old Nuclear test sites.
Pyron Solar Has Got This Company Beat... (Score:2, Interesting)
They float the entire assembly in water to cool it and to assist in rotation so that the apparatus can follow the sun.
Our energy problems are licked, I hope.
Skeptics: this is NOT just a glorified Fresnel lnz (Score:5, Informative)
1) It is almost omnidirectional - a Fresnel lens is a flat subsititue for a regular lens, with limited off-axis focusing ability. This seems to use the glass as a lightguide instead, with a broader angular reach (in exchange for limited scalibility - bigger the glass width to thickness ratio, the more light lost because of increased internal reflections & distance from entrance to cell)
2) It uses a hologram to selectively reject useless frequencies like infrared, which is 80% (IIRC) of the energy of sunlight, but generates no electricity from the cell. In fact, infrared is harmful to the cell, because it increases its temperature, which reduces its effeciency!
3) Because of the above features, it does not need a turning mechanism to follow the sun, the solar cell (which is the most expensive part) lasts much longer because it is not heated as much even though it is capturing much more useful light and converting that into electricity, it is flat and relatively easy to handle, unlike traditional solar cells with large, bulky, moving "capture" mechanisms placed in front of them....
In summary, it is cheaper per kilowatt-hr, AND more effecient, AND more practical for installation (no moving parts or seperated pieces). This is pretty neat.
Re:Sounds like a ST:TNG episode... (Score:3, Funny)
Re:Plain old plants anyone? (Score:2)
Re:Plain old plants anyone? (Score:2)
Actually, that is very important (Score:2)
This reminds me a lot of the wind generator debate. Some people really loathe them, while some people find them rather pleasant, actually. Me included, of course.
Re:Question I've had in my head for awhile... (Score:2)
"We are taking energy from nature"
You may want to brush up your basic physics knowledge. You can't take energy from nature, as we are an integral part of the system. What may occur is energy conversion.
And you might also want to learn about the technologies you don't believe in (Gallileo [wikipedia.org] all over again - sigh).
With any human act