Bigger, Cheaper Solar Cells

Phenombecile800 writes "First Solar, a start-up from Arizona, is making photovoltaic cells at a fraction of the usual cost. Their secret: increasing the light-catching area 'from postage-stamp to traffic-sign dimensions,' reducing the manufacturing time to 1/10th of the competition's, and thinning the active element to 1/100th the usual thickness over a glass substrate, which enables the production of large panels. IEEE Spectrum provides some technical details about the production process. 'Glass is placed on rollers and fed into the first chamber, where it is heated to 600 C. Then it is transferred into the second chamber, which is full of cadmium sulfide vapor, formed by heating solid CdS to 700 C. The vapor forms a submicrometer deposit on the glass as it moves through this cloud, after which a similar process in a third chamber adds a layer of micrometers-thick CdTe in about 40 seconds. Then a gust of nitrogen gas rapidly cools the panels to 300 C in a fourth chamber, strengthening the material so that it can withstand hail and high winds.'"

Comments

Re:Great big solar cells?

[UnknowingFool]

The story doesn't say larger is better per se. The story says that these cells are cheaper because they can be manufactured on a different scale. The most efficient solar cells are unfortunately only in labs at the moment and may not make it to consumers because of cost. Such it is with a lot of technology. The efficiency/cost ratio is important for more widespread adoption of solar technology.

their tech

[opencity]

Cadmium Telluride is also a direct bandgap semiconductor which yields more watts per kg than the indirect bandgap semiconductor materials. Solar cells become less efficient at converting solar energy into electricity as their temperatures increase but Cadmium Telluride is less susceptible to cell temperature increases than traditional semiconductors generating relatively more electricity under high ambient temperatures. It's also more efficent at converting low and diffuse light to electricity more efficiently than conventional cells under cloudy weather and dawn and dusk conditions.

They also have a recycling plan in place for the lifetime of the product - somewhat at odds with the traditional landfill methods of yore. But, no retail. They don't sell to individuals and only deal with utility companies. Finance trivia: Their stock has grown spectacularly since the IPO and there is a large investment from the Walton family (insert TV joke here)

Re:The old green question

[Animats]

The head of Applied Materials solar division said in a talk at Stanford last year that their solar panels took two years of their own output in energy to make. They hope to get the energy breakeven point down to six months. He said the sputtering process they use in coating is energy-inefficient, and they're trying to develop something better.

Total installed energy cost is probably higher. Home solar installations are about 50% installation cost. The big open-field installations are cheaper; they have economies of scale.

Forbes mentions that Mojave Desert real estate is becoming more valuable because many companies want to build solar facilities there. There's plenty of space in California, Nevada, and Arizona for solar panels.

Mike Splinter of Applied Materials (the largest maker of semiconductor fab gear) likes to say "Everybody else's costs (in the energy business) are going up, and ours are going down. We're nowhere near market saturation. This is a great business for us."

Re:Article in two sentances:

[D. Taylor]

Maybe you should have spent two hours reading the article - you might summarize it correctly then.

The article states that current silicon photocells sell for around $3-$4 per watt.

The new CdS/CdTe cells cost $1.14/W to produce and sell for $2.45/W.

To reach "grid parity" they need to reduce the manufacturing costs to $0.60-$0.75/W and increase efficiency from "over 10 percent" to over 12 percent. The maximum theoretical efficiency for CdTe cells is over 20% and cells with an efficiency of 16.5% have already been made.

Re:The old green question

[rah1420]

What everyone seems to be waiting for is a cost-per-watt that is low enough so that ordinary people will decide to start buying them in large quantities without government subsidization.

You won't see it from FSLR, unfortunately. Their output is currently (no pun intended) earmarked for commercial ventures only, no retail/residential sales. Pity. Hope that changes.

Re:The old green question

[djarum72]

Article gives the size of the glass, and some temps, so it may just be answerable. Googling for: how much energy does it take to manufacture glass, 5 hit (no direct link since its a f***in word doc)

The Recipe For 1 Ton Of Glass (Resources)
                      1300 Pounds Sand

                          400 Pound Soda Ash

                          400 Pounds Limestone

                          150 Pounds Feldspar

                  24000 Gallons Water

                      4400 KWH of Energy

So, 4400 KWH per ton.

How much do the panels weigh?

(.6 m) * (1.1 m) * (.5 cm) * (2 500 (kg / (m^3))) = 8.25 kilograms

(8.25 kilograms) * 4 400 (KWh / ton) = 144 Mj

Apart from making the glass, there is heating the glass, heating the cadmium sulfur and telluride, mining all those chemicals, etc.

Glass specific heat is .84 J/g K.

(.84 (J / g)) * 8.25 kg * 580 = 4 019 400 joules

So I've calculated 148Mj for the glass manufacture and heating.
Ignoring the cadmium, sulpher, telluride chemical mining, what do you get out of it?

(85 watts) * 25 years = 6.7 Ã-- 10^10 joules

How much coal is that? http://www.newton.dep.anl.gov/askasci/eng99/eng99187.htm

6.7E10 joules) / (4.11E6 (joules / pound)) = 7 400 kg

Remember how I ignored the energy of mining those chemicals?
How does the energy compare for mining the GRAMS it would take to deposit a film of telluride compares to the energy for mining TONS of coal.

The answer to what you did ask, at least for the glass + heating, is pretty easy to answer:
(148E6 / 85) * s = 480 hours. Less than a month.

Re:The old green question

[bcrowell]

What everyone seems to be waiting for is a cost-per-watt that is low enough so that ordinary people will decide to start buying them in large quantities without government subsidization. Suppose you're having a new house built: if you could install a ten or fifteen kilowatt solar plant and inverter for ten grand, you might figure it's worth it to borrow a little more money from the bank.

A couple of things to keep in mind here:

1. The cost per watt is already low enough that it makes sense for a lot of people, like me, to buy photovoltaics. It depends on what latitude you live at, how much sunny weather you get, which way your roof faces, how much shade there is on your roof, what the local price of electricity is, and what you expect the local price of electricity to be over the 25-year life of a photovoltaic system.
2. When you talk about government subsidies, you should do an apples-to-apples comparison with the alternative, which is typically electricity that comes from burning fossil fuels. Fossil fuels enjoy massive government subsidies here in the U.S. We've fought three extremely expensive wars recently in the middle east, and I don't think we would have been involved in any of those wars if there hadn't been oil there; my grandkids will be paying for my generation's deficit-funded oil wars. There's also a huge amount of environmental damage done by burning fossil fuels, and that damage affects both this generation and future generations. If people paid the real costs of that environmental damage up front, then gas would be a lot more expensive. In places like Europe that don't subsidize fossil fuels as much, gas costs about twice what it does in the U.S.