September 19, 2009
Inkjet Boosts Silicon Solar Cells Efficiency
Another step toward lower photovoltaic (PV) solar power prices.
A California company is using silicon ink patterned on top of silicon wafers to boost the efficiency of solar cells. The Sunnyvale, CA, firm Innovalight says that the inkjet process is a cheaper route to more-efficient solar power. Using this process, the company has made cells with an efficiency of 18 percent.
The efficiency increase was from a starting efficiency 16.5-17% up to 18%. So this additional layer captures an additional 1% of the sunlight falling on the silicon PV cells. This by itself isn't going to close the cost gap between silicon PV and cheaper thin film PV from the likes of First Solar, Solyndra, and Nanosolar. But it is another reason why PV prices are going to stay down even as demand surges in China and the United States.
This report reminds me of how 1366 Technologies is also going to sell an efficiency-boosting technique to silicon PV makers. The existing manufacturers are now so big that new entrants develop technology to sell to them rather than directly going into manufacturing themselves. The scale of existing manufacturers make the barriers to entry too big for most innovators. There are exceptions to this such as Nanosolar which looks like it is coming out with manufacturing technology so revolutionary that they might be entering the market as the new low cost leader. Impressive achievement if so. Sure looks that way given their order book.
No reason for continued gloom about high solar power prices. The market is turning up lots of innovators. Costs are falling.
You've posted a fair bit about the new solar technologies. Having researched these myself over the past year and a half for applications we have in mind, I will tell you what you should look for.
First, the process should be a "wet" process. That is, the PV materials can be deposited without the need for vacuum process. This is key because vacuum process is inherently expensive. Solar power will never make the cut as long as it requires vacuum processing to make it.
Second, the transparent upper electrode also has to be deposited by a "wet" non-vacuum process. If they are using ITO (which everyone is, but no one talks about) it can only be deposited by a vacuum process. It does little good to have a "wet" process for the PV material, but use a vacuum process for the ITO upper electrode. The other problem with ITO is that the Indium is a limited material. It is refined as a by-product of Zinc refining and is quite rare (and therefor expensive). Indeed, used ITO targets used for flat panal manufacturing are recycled to make more ITO available. My beef with the solar people is that none of the ones I contacted are working to develop a replacement for ITO. In fact, they all told me that they were looking for a "strategic partner" to develop this for them!
Third, the life times of the material. PV materials degrade over time due to the UV exposure. All the materials have this problem. Then, theres the problem with the more advanced materials such as the conductive polymers in that they react with the atmosphere (Oxygen IS reactive, you know) and that none of the people I talked to have dealt with this problem either (its really quite frustrating in dealing with these people once you realize how they have neglected some of these key issues).
Until these three technical issues get solved, solar will never be cost competitive with out government subsidies (a form of robbing Peter to pay Paul) no matter what the flowery rhetoric you see on the various solar websites or hear from the greens.
Sorry for the critical rant. But I have actually tried to deal with these people and have, so far, come up short.
It is my understanding that Nanosolar uses a wet chemistry process with no vacuum. Nanosolar looks like the best bet so far.
Nanosolar does use indium. But it is my impression that Nanosolar uses much less material than their competitors.
Lifetime: I do not know what Nanosolar's PV longevity is. But at least the (admittedly higher cost) silicon PV lasts a long time.
Nanosolar looks like a contender to me.
I'm still confused by the solar claims and how to compare them to traditional sources of electricity. I've seen claims of around 30 cents/kwh for solar now. Is that without subsidy? How much are the subsidies now per kwh?
Nanosolar talks about getting down to 10 cents/kwh. Again, is that before any subsidy?
And is that only during peak daylight hours? Coal can give us 5 cents/kwh 24/7 and be built pretty much anywhere in the country. Nuclear is also 24/7.
Is there some measure that takes availability into account? No matter how amazing Nanosolar turns out to be, it won't do much good at night.
Doesn't this mean a solar plants capital costs need to be a fraction of a coal or nuclear plant since it only operates 8-12 hrs/ day?
Most of the solar #s I find seem to be comparing apples to oranges.
Coal is 5 cents/kwh if you run the generator 24/7. Depreciation is the largest cost for coal generated electricity so power generated at 13:00 is not 5 cents. Solar is at that time at its peak generation so 10 cents/kwh is competitive with coal. It is also not true that coal (and any other steambased) plant can be placed anywhere in the country as it needs loads of water.
You need to keep in mind that demand for electric power varies by time of day (higher in the afternoon and lowest late at night), day of year (most when very hot outside), weekday vs weekend, and still other factors.Therefore the wholesale price of electricity varies greatly. Solar power happens during the daylight hours which puts it closer to when demand is higher and, most importantly, when wholesale prices are higher.
Due to different regulatory environments, different availability of coal, hydro, and other local power sources, and other factors local electric power prices differ by state and even area within a state. Whether solar competes where you live depends on the prices it has to beat.
Solar power peaks at noon. But demand peaks in the afternoon and early evening. Not a perfect match, but close enough to mean that solar electric power competes at a higher price point than the average price for electricity.
Also, solar power's cost depends on where you put it and how big the facility. Solar panels in Phoenix Arizona put out much more electricity than the same solar panels in Anchorage Alaska. See this chart of average insolation for each month of the year for a list of cities in the United States. You can see the differences as ratios are greatest in December.
So there's not a single answer to your question.
So when the latest news story comes out saying solar company Z can produce electricity at X cents/kwh. Is that peak? Avg during the day? Does that include any subsidy?
Right now I read it as peak -- that at high noon on a cloudless day in Phoenix they can produce at X cents/kwh. And for most other times and weather conditions and locales they produce at a significantly higher cost. Am I right?
I tend to think they are factoring in subsidies as well. I'm not trying to bash solar here, I'm just trying to get some straight info, and the solar companies seem to be kinda deliberately vague when it comes to this.
10 cents/kwh is the average production price. That is total kwh production / total cost which dependent on gas price makes them cheaper than gas.