October 2, 2006 4:00 AM PDT

Silicon vs. CIGS: With solar energy, the issue is material

Silicon or CIGS. In the solar world, them's fightin' words.

The booming solar industry is in the midst of an argument over which material will become dominant in the future for harvesting sunlight and turning it into electricity. Solar panels made from crystalline silicon currently account for more than 90 percent of the solar infrastructure today.

Unfortunately, silicon panels remain relatively expensive to make. Without subsidies, it's still cheaper to get electricity from the grid. A two-year shortage of polysilicon, which may not ease until 2008, has severely limited growth and sales.

Panels that harvest energy with CIGS (copper indium gallium selenide) cost far less to make and install, say backers. The material can be sprayed onto foil, plastic or glass or incorporated into cement and other building materials. Conceivably, the entire exterior of a house or building could become a solar generator.

CIGS also doesn't degrade in sunlight like other thin-film technologies.

"The smartest investors are going short on silicon and long on thin film, especially CIGS," said Martin Roscheisen, CEO of Nanosolar, a start-up that has received $100 million in venture funds to build a plant capable of producing 430 megawatts-worth of CIGS panels.

Silicon solar panels

"The semiconductor is 100 times thinner. We combine low-cost materials with low-cost processes. The expenses on silicon are extremely high."

A huge vote of confidence in CIGS came earlier this year when Shell, one of the largest solar companies in the world, sold its silicon solar business to focus on developing CIGS.

So if CIGS is so good, why isn't there more of it out there? Mind share.

Silicon has become one of the most studied materials ever discovered, and advances in reducing processing time and manufacturing that were discovered in the semiconductor world rebound directly to silicon solar-cell manufacturers. Other alternatives--solar thermal energy, photovoltaic dyes--have failed to undercut it in functionality and cost.

"Silicon has a reliability record which is unmatched by any other material," said T.J. Rodgers, CEO of Cypress Semiconductor, which is the primary stockholder in the fast-growing silicon panel maker SunPower.

"They could rename the company NanoDollar, because that's all they are going to be left with after we get done kicking their butt," Rodgers said referring to Nanosolar.

"The smartest investors are going short on silicon and long on thin film, especially CIGS."
--Martin Roscheisen, CEO of Nanosolar

He's got a point. Back in the early 1990s, CIGS was emerging as an alternative to silicon, but the declining price of silicon snuffed out the movement.

"The three most studied materials in history are steel, cement and silicon, so they have a leg up on us there," acknowledged B.J. Stanberry, CEO of CIGS developer HelioVolt. "I'd say you're a fool if you predicted the imminent death of silicon. But their inability to deliver is creating an opportunity for thin film, and CIGS will have a significant portion of the market within 10 years."

With demand cranking up to an all-time high for solar technology, the two types of panels will likely co-exist for years--especially considering the miniscule role solar plays now in generating electricity, according to various estimates, and that demand is expected to double by 2025. Solar accounts for less than 0.10 percent of the current total.

Nonetheless, growing momentum for one technology among researchers, equipment makers and, ultimately, customers could pave the way for one to become dominant over the other.

Similar debates weighing promise against pragmatism have occurred in chipmaking. Gallium, indium and germanium have also been used to produce superfast semiconductors, but the higher costs associated with these materials have kept them toward the margins in the market.

Silicon hits and misses

Silicon, even its adherents admit, is not ideal. Theoretically, silicon is capable of converting 29 percent of the sunlight that strikes it into electricity, according to Dick Swanson, a former Stanford professor who founded SunPower.

"That imagines a cell that is perfect in every possible way. That would be without any energy losses or leaks other than those demanded by the physics of silicon," Swanson said. "The practical limit, most say it is around 25 percent to 26 percent."

SunPower already sells panels that convert an average of 20 percent of the sunlight into electricity and will come out later this year with panels that will convert 22 percent. The high efficiency is due to the design of the company's panels. SunPower puts the electrical contacts at the back (or bottom) of the panel to increase surface area. The silicon also sits atop a reflective layer: Photos that would otherwise pass through the panel entirely are bounced back into it and effectively recycled.

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22 comments

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Solar panels/CIGS on rooftops sounds ideal
You'll get that double whammy:

- create electricity to power the air conditioning,
- less heat from the sun hitting the surface means less heat to aircondition away inside

Plus the fact that your
Posted by jpsalvesen (31 comments )
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Solar panels/CIGS on rooftops sounds ideal
You'll get that double whammy:

- create electricity to power the air conditioning,
- less heat from the sun hitting the surface means less heat to aircondition away inside

Do they take this into account when they calculate the estimated ROI?
Posted by jpsalvesen (31 comments )
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No electricity Needed fo Solar Cooling
the peak demand for electricity is created by air conditioning loads.

Remember the referigerator in your camper that ran on propaine? There are several absorption chillers that use hot water or engine exhaust as the energy input.

The most common application today is in cogeneration, the waste heat from gas turbine or diesel generators is used to air condition buildings.

Solar heated water can also be used. Of ocurse electricity is still needed to run fans and pumps, but using solar heat directly for cooling and heating bypasses the inefficiencies of converting to electricity and then converting to mechanical motion in an electric motor, and finally to cooling.

One advantage of solar input for air conditioning, the available solar energy tracks air conditioning demand.
Posted by disco-legend-zeke (448 comments )
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Sounds like Sterling
That sounds like a Sterling engine app. That kind of stuff makes a lot of sense. If you combine a lot of these different techs and get away from things like Incandesent bulbs that are wasteful, we could do away with much of the fossil fuel issue.
Posted by MrHandle (71 comments )
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Sounds like Sterling
Sounds like Sterling Engine apps, where you can use waste heat for cooling amoung other things. It's good to see that sort of efficiency. By using the energy from sunlight (especially in a solar-concentration/Sterling design) to offset heat waste, engines can be highly efficient.
Posted by MrHandle (71 comments )
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re: air conditioning, try white roofs, GSHP, and swamp coolers b4 u funk it up w/ anything hi-tech.
Posted by maxwellsagain (2 comments )
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False hopes for CIGS
Misguided hopes, investments and government funding appropriated to CIGS and other thin films is probably the main reason the US market share of PV module manufacturing has monotonically and precipitously fallen from a leadership position of 45% in 1995 to about 9% in 2005. The smart money is not in the US, but in Japan, Germany, and other countries that have realized silicon is "where its at" for PV.

So CIGS is 100 time thinner. So what? Our Planet's crust contains 27% silicon (outdone only by oxygen at 46%) What could be more plentiful and widely available than sand -- Si02? There is 0.007% copper, 0.00001% indium, 0.0015% gallium, and 0.000009% selenium in the crust. And these elements are not particularly easy to mine in quantities required for gigawatts of solar cells. Do the math. Just the recent upsurge in flat panel display applications threw the indium markets is a tizzy.

Silicon photovoltaic feedstock material manufacturing is merely at a mismatch in planned capacity vs actual demand. This situation will correct itself within two years and leave CIGS in the (SiO2) dust with a nano-sized market share of world PV sales.
Posted by Siliconsultant (1 comment )
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Silicon Shortage
lol. Yeah, I keep seeing about this "shortage" of Silicon, when it's the second most abundant material on Earth. I guess it requires very high heats to work with, but we'll never run out of the stuff. My guess is that they'll continue to find ways to refine the manufacture of it and improve efficiency a bit. I also think it will continue to dominate. CIGS may have a few niche apps, but that's about it in my view..
Posted by MrHandle (71 comments )
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Silicon under pressure...?!
One thing is clear based on the rather unusual statement from T.J. Rogers: The silicon-wafer solar guys appear rather scared and on the edge...otherwise the CEO of a publicly traded company like Rogers wouldn't be losing it like this in public...! I guess with more than a dozen CIGS startups after you and investors increasingly wondering whether silicon cell production is not a cashflow black hole, the open nerves are understandable...
Posted by steph111 (1 comment )
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Solar power is a joke
Solar power is a joke. There's very little energy in a square foot of sunlight. It's never going to matter. It's just an impractical dream of environmentalists who don't want wind power in their own backyards.
Posted by lingsun (482 comments )
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a 100 sq meter house = 100 KW insolation -- even at 10% is 10KW
and for air conditioning, efficiencies could be much better.

no, solar is real. actually, petrolium is simply stored solar, after all.
Posted by disco-legend-zeke (448 comments )
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Solar/Wind Power Hallucination
Both solar and wind power are a joke. Enter the friendly atom.

Either the Toshiba 4S or Mitsubishi APWR reactors provide more power per square foot than solar or wind power ever will.
Posted by Too Old For IT (351 comments )
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Is it?
My solar powered calculators work just fine (during the day of course lol). And, they have more processing power than Eniac (the huge power-sucking first digital computer) did. The point is that we still use stuff like Incandescent bulbs that are extremely wasteful. If we would use energy much more efficiently, we wouldn't need so much of it. Solar alone isn't enough, but if we combine it with other things like wind, Sterling Engine, and intellingent energy management, we could be alright.

Personally, I'd like to see more effort put into developing fussion, but until that time, it doesn't hurt to try and get all we can from all possible sources.
Posted by MrHandle (71 comments )
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Solar power no joke.
30 years ago the internet was a joke too. Currently solar has a 9 to 10 year payback period, not worth it at credit card rates if you are on the grid.

But wait, solar is expanding rapidly. Why? As it gets cheaper per watt more and more uses become economical. Those solar walk lights are everywhere, as solar calculators have been for years. Now warning signs and street signs are being lit with solar. Campers are buying solar panels that roll up. Hopefully, port-a-potties will get solar fans soon.

Got a cabin in the middle of nowhere? Why pay hundreds per pole to bring the grid to you? Just buy some panels, batteries, ... for less. Want to wi-fi a city? Just put a small solar panel, UPS, and an access point on every street corner. No need for wires or meter readers.

If solar ever gets cheap enough and durable enough (a big if), how much energy would be created if all roads were covered with spray-on solar panels?
Posted by galeso (283 comments )
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Wrong
If you cover about 10% of the state of Navada with solar panels. You would have enough energy to power the entire country. That is becouse enough energy from the sun hits the earth every hour that it takes us a year to match. Don't beleve me? Watch the Renewable Energy episode of Modern Marvels on the History Channel.
Posted by DJRWolf (6 comments )
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lingsun, you're name has no power either.
No offense, lingsun, but that's about the most scientifically uneducated BS I've read in a long time, thanks for the laugh though! :)
Posted by foremanjf (2 comments )
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Sans atmos, downward direct solar irrad is about 1.3kw/m2. W/ an atmos, max is roughly 900 watts on a clear day. Given clouds, fog, diurnal/seasonal sun arc, sub-optimal angle of inclination/placement, etc., typical temperate zone irradiance might be in the neighborhood of 300-400 watts/m2 for 8 hours/day or 2,4-3.2kwh/day/m2, but more in the U.S. sw sun belt. Figure typical home roof area of 100m2 and maybe 1/3 of that well-positioned for photovoltaic reception. Ergo, in the sun belt 1/3 of your roof might receive a solar irradiance of 100kwh/day. So, if you could powder it w/ 35% efficient photovoltaics, you'd have 35kwh/day, which is 1050kwh/month, more than the standard home needs. With a few items like switch to fluorescent bulbs, energy-star appliances and remote shut-off power strip switches for solid state home electronics to stop dark current, average U.S. home electrical use could fall below 500kwh/month, except for air conditioning. Minimizing the latter need with white elastomeric roof paint and a ground source heat pump, you'd then have enough spare juice to charge your back-up power/load leveler aka your plug-in hybrid electric vehicle.

So, conceivably, w/i 5-10 years you could pretty much go off-grid. What that would cost is right now anybody's guess, but if it drops below a loanable $20k net initial entry above standard setup, it'll get VERY tempting. Let's see...rebuild my deck w/a fancy barbecue or go off-grid? Hmmm....
Posted by maxwellsagain (2 comments )
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CPV, smaller expense
Perhaps fossil fuels will be cheaper and so abundant in the future that solar will never compete? However, in the mean time, CPV could make up the difference since only a small amount of expense is shared with such things as mass produced mirrors, sensors and motors.
Posted by fireofenergy (18 comments )
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Solar could be our saviour
Whichever one wins the Battle, solar is by far the best solution to all our energy problems. Nuclear is too dangerous (think terrorism) and fossil fuels will pollute us to extinction. The only good answer is solar. We just need to work together to automate the manufacturing processes so much that we can roll them out and install them by the terawatt. Cost will definitely beat out fossil fuels very soon with economies of scale. Let's all jump on the band wagon here. There is more than enough room for all of us here.
Posted by lmacmich (2 comments )
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Electroplating of solar cell conductors
Regardless of which method is used - Si or CIGS - electroplating of solar cell conductors will be used to boos solar cell efficiencies. -Rob Schetty
Posted by persimmons2 (1 comment )
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How does Dyesol's DSC technology rate against thin film and conventional silicon based solar? The market cap of Dyesol is still extremely low relative to alternative players across the field.
Posted by Impala1948 (1 comment )
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