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Holographic Solar Collectors
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."
they just replace sections of PV cells with this hologram stuff-- the panel is the same size, just less silicon
Products like this decrease the amount solar panels needed. Many of the wonderful improvements are available, but at a very high cost. This development specifically reduces the cost needed to attain the same amount of power.
Funnypics
That's what grid-connected solar arrays are for. You use the grid as your battery. In California at least, with a grid-connected array, PG&E buys any surplus electricity you generate during the day (while you're at work and the sun is shining) for the more expensive daytime retail price and when youg et home and actually consume, you buy back from the grid for the cheaper, night time price.
Just for the record, those batteries _suck_ for solar energy collection.s cssid=KS9FNAJCUXGV9LBH81QUWL707VKN9LB0&Ntt=mining& N=0&Dx=mode+matchallany&part_number=4D-XHD&Nty=0&D =mining&Nu=Part+Number&Ntx=mode+matchallany&part_d esc=Workaholic+-+1000+CCA&Ns=product+Type%7C0%7C%7 CRank%7C1&Ntk=SearchGroup
Something more like this:
http://www.ibsa.com/estore/search.asp?details=1&m
Though that's with an ultra quick search.
-nB
whois gawk date unzip strip find touch finger mount join nice man top fsck grep eject more yes exit umount sleep dump
The problem with concentrating the light too much is it generates more heat. Like a computer heat causes problems it reduces the efficency of the solar cell. Also the heat increases the rate the cell degrades and will have to be replaced more oftain. 10x is a reasonable amount of concentration because it does not significantly reduce efficency and does not stress the chip.
The issue here is the holograms are a replacing the mirrors/lenses. The actual photo cells are still the same.
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.
Light side of the Moon? Hunh? The lunar "day" is somewhere around 28 Earth days...fixed installations will be in shadow approximately 2 weeks at a time, and at unfavorable angles for some of the other 2 weeks.
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 planning on fabbing the stuff at the Moon, and maybe even if you are (to save on launch costs) just put them in geostationary orbits.
From the article it is clear that this technology is specifically designed to address two of your concerns. Admittedly it helps to have a background in physics in order to understand some of the concepts (particularly the optics.) Firstly, the holographic lens and waveguide have been designed to direct certain ranges of wavelengths to the silicon and the other wavelengths away from it. This helps to prevent overheating of the silicon cells. Secondly, the lens system is there in order to collect more light per area of silicon used. This causes the $/Watt to increase, while the efficiency (Watts converted per Watt theoretically availlable) remains the same (well, in a perfect world, it sounds like this will work significantly better in their second generation.)
the article states that they are shooting for a price around $2.4/watt, which I can assume ytou is well below what we are currently paying. i was recently quoted a price of $8/watt from solarsave (http://www.solarsave.com/) for a pv installation, so having to pay a third of that price is extremely reasonable from a cost per watt perspective, even if you don't get any added efficiency due to heat losses.
This company is apparently the spawn of TerraSun. They acknowledge this in the PDF mentioned above (http://www.nrel.gov/technologytransfer/entreprene urs/pdfs/prism_solar.pdf), slide 3 gives the company timeline and lists TerraSun.
I actually asked a similar question to a PV install vendor here, since our desert temperatures are around 45 Celsius during the day. This reduces the output of panels (which are rated at 25 Celcius) significantly, and it would seem ideal to cool the panels with water and pre-heat your hot water system, spa, etc.
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 together in series resulting in very high (several hundred) DC voltages being sent to the inverters. You also have to comply with local and federal electrical codes plus whatever constraints your utility has (if you grid-tie).
I'm not saying it couldn't or shouldn't be done -- it seems like a great idea to extract even more energy in the form of heat while increasing efficiency. It's just that few are willing to attempt safely putting the two together for consumer applications. I mean, can you really see Joe sixpack being careful when one of the components dies, leaks, or otherwise needs service? "It's just solar panels and water, can't really be all that much juice!"
If Star Trek had the internet: Captain, we've received an IM from the romulans. "Surrender or be destroyed. LOL. o.O"
Concentration is highly overrated from a cost standpoint. A typical solar cell runs about $3/peak watt produced at 1 sun illumination. A 10 to 1 concentration ratio would reduce solar cell area to $0.30 if you could continue to use the same cell and it can handle the concentration. You have achieved 90% of the possible cost reduction for the solar cell. A 1000 to 1 concentration ratio only buys about you another 29.9 cents or so cost reduction of the cells and you have to pay for a much more complicated concentrator setup.
OK, it's not quite that simple. What actually happens is that to design cells that can make use of a 10 to 1 concentration ratio may cost a little more than a standard cell. And today, these are a somewhat special product, so lack of an economy of scale further increase the cost compared to the standard cell. Cells designed for a 100 to 1 or a 1000 to 1 concentration ratio are an extremely specialized product and cost a mint, although you need very little total area of the cells themselves. The balance of the concentrator becomes a key cost in the system.
The other thing that happens is that when you are going for a high concentration ratio, some of the cells inherently get more efficient (as long as you can keep them cool... more of the "other costs" to deal with). In addition, because you are using just a little bit of specialized solar cell, you can pay a bit more for fancy triple junction cells that are more efficient by as much as a factor of two (up to say 30% efficiency at converting light to electricity compared to the standard silicon cell). However, the losses in the optics and the need for active cooling will take their toll on the system efficiency.
What it all seems to boil down to is that you have to design and cost out the system as a whole before you can say what makes sense for the market.
If you read the article, it says that lens don't work because they have to be always facing the sun -> heavier/more expensive.
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
My first thought reading the headline was that this was just called a "hologram" to get some buzz, over what is a very generic, straightforward way of increasing the power delivered to the expensive part, the solar cell. But (for those too lazy to RTFA) this is different for three reasons:
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.
This idea has already been implemented several years ago where this kind of setup (solar panels and holographic gratings) was incorporated into office windows, directing the usable light frequencies towards the panels but still leaving enough normal light through so rooms don't get too dark. I think they even deflected the far infrared away so the heat stayed out of the building!
Can't remember the report too clearly but I think it was an office building in France...