Tuesday, June 25, 2013

Dr. Gay Canough: The Vast Majority of Solar Cells are Made of Silicon

Response by Dr. Canough about concerns of rare-earth metals in solar cells.

---------- Forwarded message ----------
From: Gay Canough
Date: Tue, Jun 25, 2013 at 12:15 PM
Subject: The Vast Majority of Solar Cells are Made of Silicon


The Vast Majority of Solar Cells are Made of Silicon, the same stuff as in Sand (which is silicon dioxide). If you are afraid of silicon, you will NOT be going to the beach this summer, will you?

My primary push for renewables involves solar electricity (photovoltaics/PV) and solar hot water heating(SHW). The first thing to understand is that almost ANYTHING that can be made ONCE (with all the mining and processing it requires) and then used for 20 or 30 years is going to be better, environmentally (the obvious thing being lower carbon emissions). While anything you have to keep extracting daily (fuel) is worse, environmentally speaking.

Both PV and SHW are in the make-once category and perhaps wind turbines (although they do require more regular maintenance). 

The MAJORITY of PV, by far, is made of silicon, the exact same material as used in nearly all integrated circuits and computer CPUs on Earth. By the way, "silica" is a fancy word for sand. And yes, very fine sand is hazardous if you breath it, which is true of nearly any very fine material.
A PV solar cell is the simplest semiconductor device, one p-n junction. So it is much simpler to make than a CPU (which has hundreds of millions of p-n junctions in them). 

A solar module has solar cells, copper, tin, ethylene vinyl acetate, Tedlar (plastics), glass and aluminum in it. These are all pretty benign materials. Electronics manufacture of all kinds used to involve lead-based solder, but many countries have banned this type of solder, so manufacturers are moving to lead-free solder. My hubby Larry has done a lot of research work and testing,  for various companies,  for new kinds of lead-free solder. 

Kim M. brings up thin-film PV. One of these, CIGS PV, is not made of silicon (a couple of factories are making this). There is also ONE PV factory making cadmium telluride PV (CdTe) and obviously cadmium is a hazardous material. However, both these technologies involve rare elements and so, as we go to more and more solar power, silicon is going to win, since it is, um, common as sand! Or perhaps a new kind of solar cell, made of organic material will win. Organic solar power (photosynthesis) is, after-all, what Mother Nature came up 500 million years ago!

A solar hot water collector is even simpler. It involves copper tubing, aluminum frame, glass cover and insulation (which is the same kind of stuff people put in their walls and roof). Lead-free plumbing solder has been the norm now for years (2 to 3 decades, I think).

What about the manufacture of these? Manufacturing of ANYTHING will never be completely hazard free. As soon as you get out of bed each day, you are taking a risk. We MUST get over this notion of "COMPLETELY SAFE". There is NO SUCH THING. We MUST begin to make things again in this country. What we are doing now is shuffling money  amongst ourselves through retail and services. This might be a downward spiral into lower income and standard of living. We need to MAKE THINGS. And if we make things here, we can monitor the safety of the workers and the pollution controls on the factories (which we can't do for things made in China).

How do you manufacture things without making a mess, being a health hazard or making your local community an unpleasant place to live? It seems to me that we are masters of this technique compared to the rest of the world (excepting Germany, which is better at it than us). In many other countries, they are just starting to admit to themselves that they have to regulate manufacturing to reduce pollution. 

One really good practice for factories is to be able to take back and recycle nearly everything they make, or make products from easily recyclable materials. First Solar, which makes CdTe,  takes back any panel they produce. 

What about batteries?
For many years, our primary storage was lead-acid batteries and these are still in wide use. All lead-acid batteries must be recycled in the USA (federal law). Now we have lithium ion batteries in wide use for cameras, phones and computers. Whatever rules we are putting in place for the re-cycle of these, will apply to the re-cycle of electric vehicle batteries. I do not know what all goes into manufacturing of lithium-ion batteries, but I bet it's not more hazardous than lead-acid! Again, we need to make things and do it as safely as possible, while remembering that  "completely safe" is mythological! 

Now here's some more food for thought... all of these technologies are relatively old. It would be money well spent to do research and develop BETTER kinds of solar cells and batteries (which they are doing at Binghamton U, with a pretty small budget). If we were to put the YEARLY billions of bucks worth of fossil fuel subsidies  into some serious research and development, pretty soon we would be making solar cells for 10 cents/Watt out of organic materials (spinach?) and everyone would be driving their electric vehicle, with its fancy battery, to work, plugging it in and selling power to NYSEG to shave the peak load!  AND then we would be exporting this technology. 

Any way of getting energy that we come up with will have its shortcomings. But I am pretty darn sure that having electricity and heat available is better than not having it. Unless we want to greatly reduce the human population, I am not sure we can do without these anymore. So every time you poo-poo some form of energy, I want you to think about how you will live without electricity and heat OR what is your fabulous alternative? 

We should always be on the lookout for problems and address them (rather than our usual response, which has been denial and hysteria). If there is one thing humans are really good at, it's technology. And if there is one energy resource that is far and away the largest, it's solar energy. If there's one main reason to stop burning fossil fuel, it's climate change. The flood last year is a nasty taste of things to come. It cost $500 MILLION dollars worth of damage in our area.

Silicon: The second most common element on Earth. 12000 square kilometers: the area of silicon solar cells it takes to generate 100% of the USA's electrical use. The solar resource: Can serve a world-wide energy need 1400 times greater than it is now for at least 5 billion more years! 
Wide-spread use of solar power: Inevitable. 

---Gay
Gay Canough
ETM Solar Works
Endicott NY
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May you, and all beings
be happy and free from suffering :)
-- ancient Buddhist Prayer (Metta)

2 comments:

Vic Furman said...

http://www.theatlantic.com/magazine/archive/2009/05/clean-energys-dirty-little-secret/307377/

http://www.realclearpolicy.com/articles/2013/04/22/the_dirty_little_secret_about_clean_energy_491.html

Bill Huston said...

What's your point, Vic?

Whatever the problems are with solar (made in China, rare earth metals, etc), we can fix with innovation, and public policy.

Whatever problems there are with fracking, nobody can fix. Fracking is inherently unsafe and deadly to living things.