After hearing Dr. Richard Swanson give an expert talk at the Palo Alto Research Center regarding progress in cost and performance for single crystal silicon solar cells, I was both intrigued, better informed, and somewhat challenged for my own research interests.
Dr. Swanson is the president and CTO of solar cell and solar module manufacturer SunPower, based in San Jose, California. He gave a general briefing of single crystal silicon solar cell development in the PV industry from the late 1970s until now. The presentation was both a reality check and a highly optimistic outlook on silicon solar technology. Please take the time to listen to or watch the presentation (about 50 minutes) if you have interests in solar cell development for the masses (like solar cell integration into rooftop shingles in your house). What an interesting researcher, company, and technology overview.
My summary and thoughts:
Learning Curve
Single crystal solar cells are the most efficient photovoltaics in the silicon family, but had previously been regarded as too expensive for practical use. Not any longer, though, says Dr. Swanson. Improvements through production cost reductions and increases in solar energy conversion efficiency have progressed at a measurable rate (a learning curve) such that material energy costs were found to be $3/Watt in 2002 (to make a complete PV module for use)–as compared to around $30/Watt in the early 1970s. A large part of this cost reduction was due to the huge increase in silicon demand for the microchip industry, and presently the PV industry is about to overtake the microchip industry in total demand for the polycrystalline silicon.
Silicon Shortage and China
Also, there is a shortage of silicon purification plants right now, making the cost a little over $2/Watt. Silicon plants cost hundreds of millions to build and take three years just to turn them “on”. China is currently building three of these enormous plants to make up for the new demand from both PV and microelectronics, and Dr. Swanson expects China to quickly become the epicenter of PV in the world. “The interest in photovoltaics in China is nothing but phenomenal.” The leading Chinese solar cell company is called Suntech and is publicly traded on the NYSE (and the main owner is now the richest man in China). Given the emerging new silicon production plants, Dr. Swanson expects costs to be below $1/Watt by 2012. In his opinion, that is the point at which USA governmental financial subsidizing of solar cell module costs for residential applications will no longer be necessary. A light at the end of the tunnel!
Embedded Energy
Also, the “embedded energy”, or the energy costs needed to purify the silicon precursor, make a silicon solar cell, the glass in the module, etc. requires approximately three years to be recovered as an equivalent from the sun. Given his estimates, by 2012 that will be reduced to 1.5 years to recover the energy. Now, there’s a tidbit that I’m happy to have a number for in terms of environmental consequences. Consider, the initial energy required to make the complete solar cell did not come from the sun, but from fossil fuels. But for every Watt you gather from your own solar cell modules (after collecting the embedded energy), your own demands of a fossil fuel power plant is reduced.
Necessary Breakthrough
For me, the interesting and challenging factor stated was that a major technological breakthrough is necessary in the years following 2012 to lower costs to the expected value of less than $0.65/Watt twenty years from now. This would be a point at which solar cell power plants could conceivably be manufactured and put out in the desert to return a profit. His words were that the industry has no idea of how they will get to that point as of yet. So there’s the challenge for all of the up-and-coming scientists and engineers dealing in photovoltaic research for areas other than silicon. The gauntlet has been tossed, we all have less than twenty years to come up with a brilliant disruption in solar cell technology (silicon or otherwise).
Thin-Film Successes
At the last minute of questions following Dr. Swanson’s presentation, a member of the audience asked about thin-film technologies (and other new solar technologies) from established new companies such as Nanosolar, based in Palo Alto, California (the city site of the talk, in fact). Nanosolar uses a non-silicon thin-film assembly called CIGS (copper-indium-gallium-diselenide). Normally CIGS is deposited in high vacuum, and was viewed as too costly for commercial production. Nanosolar appear to have developed an “ink” containing nanoparticles of CIGS material which can be roll-to-roll printed without a high vacuum (much less expensive). Dr. Swanson’s response was that the industry such as Nanosolar will have to beat the learning curve rate of silicon wafers to become a new competitive market, but that companies like Nanosolar appear to have a lot of potential for the future.
Additional materials side notes:
When solar cells become incorporated into industrial power plants, new high performance power storage materials (batteries, capacitors, etc.) will be essential for PV success. So go out and build a better battery too, my materials research colleagues.
Inverter: the “part” in the solar cell system in your house that transforms the direct current (DC) power from your PV into alternating current (AC) that you can use and feed into the electricity grid. This is the single part most likely to break over the course of 5-10 years. Want to work on a side technology? Work on the materials for electrical inverters.
Thanks so much to Sarah W for pointing me to this link, and the Palo Alto Research Center (PARC) (a subsidiary of Xerox Corporation) for making this talk available on the web! A fascinating way to spend a sunday afternoon in the Parisian heat.
