Thoughts on Solar Materials - Thin Film - 6/3/09

I hear the arguments on future domination of the Solar Industry by Thin Film Technologies, but I would suggest that this is far from certain.

What particularly gets me is when people talk about how they're going to come up with solar paint or some such thing, and all of our problems will be solved, just like that; like a snap of the fingers. The argument goes that there's little point in spending all the time and effort on the massive industrialization of Silicon, because some futuristic technology will simply come along to make it obsolete.

Ok, so maybe it's true that some revolution will come along that will completely change how we see Solar Energy. Maybe one day you'll be wearing Solar Clothing to charge your remote devices, and cars and homes will wear coats of Solar Paint to provide for their Energy needs.

Even if this Solar future is to be the case, though, we know that it will have to meet certain requirements, particularly in terms of Scalability / Material Availability, and Cost Efficiency.

Remember that only 1000 Watts of Power strike the surface of the earth per Square Meter on average in the middle of a clear day. That's it. No matter the wonderful technology that you develop, you can't generate more energy than what's available. To generate the incredible amounts of Energy that will be required of the future Solar niche will require a mind-dizzyingly vast array of "panels" distributed around the Planet. That's miles upon miles of glass and aluminum frames housing some kind of protected PV material, whether Wafer-based or Thin Film; or else unhoused, or lightly-housed thin films of various types, even potentially including "painted" Solar surfaces.

The main point that I want to mention at this point is on the value of Cell Longevity.

Note that when you invest in a Solar Panel, you are actually paying upfront for the entire future energy production of that panel. Normally, Solar Panels are rated in Cost per Watt Peak, or Peak Power, which is an indication of the amount of Energy that the Panel would produce at an instantaneous moment of time in ideal midday conditions. Peak Power, however, is no indication of how much Energy that the Panel will actually produce over its lifetime. Two different kinds of panels may cost the same number of Dollars per Watt, but if one lasts only half as long as the other, then ultimately it is twice as costly in terms of its total Energy Production over its lifetime.

This is where the Levelized Cost of Energy (LCOE) comes in. When you Calculate the Levelized Cost of Energy of a Solar System, you are basically determining the overall cost of the System per unit Energy over the Entire expected Life of the System. I did a rough version of this kind of calculation here. Sunpower Corp provides this nice description of the factors involved.

There are a several reasons why a Solar Cell might stop working. One reason that a cell could fail would be from molecular damage to the PV material simply by the bombardment of Solar Energy (including various cosmic rays). This could slowly degrade any kind of Solar Cell. Other types of Solar Cell may be chemically susceptible to degradation, such as today's Organic and Plastic Cells. These materials degrade quickly under common exposed conditions, and at this stage of the game, a lifespan of five years or so seems to be the cutting edge. Finally, of course, smashing a Solar Cell by way of storm debris or a baseball can destroy a panel, and dirt and grime can cover the surface and degrade its performance.

Solidly encasing the PV material in an aluminum and glass (or possibly plastic) module will, in most cases, help to protect the cells from physical damage, but that housing will certainly add to the cost of manufacturing the module. For a thin film product aiming to compete on very low manufacturing cost, this added expense is going to be a killer. In fact, during First Solar's Q1 '09 Conference Call, Jesse Pichel of PJC suggested that Glass was actually FSLR's largest cost. First Solar didn't disagree, and nobody mentioned Tellurium.

Now, if glass is actually even a significant portion of the cost per watt for a thin film, then it sets a kind of a lower limit on the potential cost to manufacture Thin Film Cells housed in glass (adjustable by efficiency). So, to some extent, the decision is whether to go for extreme affordability (or flexibility) and avoid a robust enclosure, but lower the operating lifetime of the cells; or else go for a longer lifespan, but adding significantly to the total cost of the module. First Solar, for example, is targeting a production cost of $.65 per Watt.

Though I'm certain that nanotech of various sorts will be able to make headway in durable exposed thin film cells, I can't help but think that it's going to have its limits. For comparison's sake, a tarp is made of very tough stuff, yet I've seen my share of tarps shredded by fall winds, and a tarp doesn't depend on the same kind of exacting chemical structure that a PV cell does. You can beat the crap out of a tarp, and it will still keep the rain off of your stuff. I'll be very impressed if I see a thin film material that you can roll into a ball, peat with a stick, and still use to generate electricity. I can't wait to see the infomercial.

There are numerous conclusions that I could follow with, but for now, I'm going to leave this with a simple idea for the consumer. Don't just buy solely based on Cost per Watt, or one day you're going to be led astray. Know what you're buying, and make sure that it has a solid warrantee over a time period to assure your expected payback. If you're offered a deal too good to be true on a cost per watt basis, it could simply be that the product you're buying is going to crap out long before it pays itself off.

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