Solar Cheaper than Coal: First Solar's Cadmium Telluride Breakthrough
by Christine Lepisto, Berlin on 08.10.08
PHOTO: Gehrlicher Solar via IEEE Spectrum
The quest for inexpensive solar panels continues, with cadmium telluride generating enthusiasm among investors and hopeful followers of the advance of alternative energy technologies. Over at IEEE Spectrum, Richard Stevenson speculates that First Solar might beat over 80 competitors to achieve manufacturing costs low enough to market solar panels at less than $1 per Watt, the target considered necessary for solar to compete with coal-burning electricity on the grid. Tempe, Arizona, based First Solar's main market currently is Germany, where government policies promote solar power growth.
Cadmium Advantages in Solar Panels
With silicon supplies under pressure after rocketship market growth, alternative photovoltaic technologies can wedge into the competition. Cadmium has several advantages over traditional silicon technology. These include:
- The necessary electric field, which makes turning solar energy into electricity possible, stems from properties of two types of cadmium molecules, cadmium sulfide and cadmium telluride. This means a simple mixture of molecules achieves the required properties, simplifying manufacturing compared to the multi-step process of joining two different types of doped silicon in a silicon solar panel.
- Cadmium telluride absorbs sunlight at close to the ideal wavelength, capturing energy at shorter wavelengths than is possible with silicon panels
- Cadmium is abundant, produced as a by-product of other important industrial metals such as zinc.
Cadmium telluride drawbacks
Cadmium telluride solar panels currently achieve an efficiency of 10.6%, which is significantly lower than the typical efficiencies of silicon solar cells, quoted as 16% in Stevenson's article. This makes the necessity of lowering the cost per square foot critical.
Environmental Issues of Cadmium
Concerns that risks of cadmium telluride in solar photovoltaic film have been raised. TreeHugger Forums commenter green Wind Power Fan makes reference to an article noting that few manufacturers are producing cadmium telluride solar panels which pass the US EPA's leaching test, a process used to determine whether toxic metals, such as cadmium, might seep out into groundwater from improperly disposed waste.
But solar panels have relatively long lifespans, measured in decades. This means that laws like the European ban on cadmium in electronic gadgets are less necessary, because the benefits of a long lifespan outweigh the managed risks of using cadmium telluride. Furthermore, recycling at end of life will minimize risks. First Solar already plans for the take-back of solar panels they sell today, after a 25 year lifespan.
More on Cadmium Telluride Solar Panels
The Challenge And Opportunity Of Cadmium Telluride, Solar Photovoltaic Film
New Solar Panels Produced at Less Than $1 Per Watt
IEEE Spectrum
Update: If you are interested in solar power, also check out 15 Photovoltaics Solar Power Innovations You Must See.
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We all know that economics drives change, whether for better or no, so news like this is great to hear. One of my coauthors on GreenerTrends recently discussed the benefits of building green in terms of cost. A production level, cheap, solar system would increase these benefits significantly.
As an aside, it would be highly interesting to compare the evils of cadmium to that of, let's say, coal, to see which one provides the most harm per unit in the environment.
Thanks for the well done article, especially for the links. Maybe cost competitive photovoltaic is getting close. ..Dan B
First Solar is committed to recycling old panels because they can recover material from them then reform the recovered material into new panels.
There is a loss inherent to the recovery process as well as age and damage related degradation but it's to their benefit to harvest the materials.
A safety issue that I like about these panels is that they have been tested to 1100 °C heat for release of potentially fatal levels of toxic cadmium fumes. According to the article insignificant amounts were released.
And a nice little passage .... that should bring the cost of solar watts down for First Solar installations
Does anyone know what other chemicals could be used for this, possibly ones that won't pollute the environment when they are managed incorrectly?
Infrared (heat) and visible light are being researched for use in photovoltaics, but what about UV radiation or any of the other sorts? Would it be posible to collect energy from radiation in Uranium mines?
This is great news that I suppose we should be somewhat thankful for German regulators in helping to drive the R&D.
Can't wait till solar cells get more cost and energy efficient. Sad to still be waiting, but definitely an encouraging article for sure..
Hey TP,
Why 1100 deg C? That's almost the melting point of steel. It's what you get when you pour jet fuel all over everything and light it up. Did you mean 100 deg C (boiling pt of water)? or 110 deg F (a hot day in the desert)?
Melting point of steel is around 1500C. Max burn of jet fuel (though it depends on the grade of fuel) is about 980C. Avg burn is about 500C. I don't know what that has to do with this though. 1100C seems like a decent test -- more than the panel would ever reach from the sun.
Perhaps high-temperature tests were done in anticipation of concentrated solar applications?
Solar energy panels like those for the roofs of houses - this is the future!
Andreas
@j JSDryer
1100 C is correct -- it's a fire related burn poin --- ie a potential what could happen in when a large commercial building goes up with these panels installed on the roof -- just remember that safety testing is of the mindset that doesn't rule out the high side beyond normal circumstances such as a fire that reaches that temperature. Please note @ stradric is correct with the numbers -- it would take a very unusual set of circumstances for a commercial fire to reach and sustain 1100+ C
@ Anthony
Safety issues seem to be the concern for the heat testing rather than concentrated solar applications.
Cadmium's boiling point is 765 C but it's trapped in a thin layer of glass -- so heating the glass to 1100 C allows for a significant safety test because the cadmium can both turn into a vapour at that temperature and escape the heated glass layer.
Installation of the panels on commercial buildings requires a greater level of safety testing than installing them in large solar farms because cadmium fumes are potentially fatal.
Just a note on the "drawbacks" for Cadmium Telluride. The U.S. department of Energy has stated that Cadmium Telluride has an efficiency o6 16.5%. Even if this efficiency is calculated per cell made, the efficiency can in no way reach 10%.
Thanks TP. I was just wondering why that number was important. That makes sense.