Not all solar power consorts with the toxic devil

A reader makes a good case for the relative safety (and cost per watt) of solar thermal.

Published January 16, 2009 11:30AM (EST)

I would be remiss in not acknowledging a very informed letter from reader tencentlife pointing out that my report on the environmental critique of solar power yesterday should not have grouped all solar power technologies under one umbrella. Since tencentlife appears considerably more erudite on this topic than I, I will give him or her the floor:

"Building largely on its longtime work monitoring the health and safety dangers associated with the semiconductor industry, the SVTC compellingly documents the dangers to both workers in the solar power industry and the environment at large from the use of a wide array of toxic chemicals currently employed to manufacture silicon and all forms of solar power."

Andrew, I know you know the difference between photovoltaic (PV) and solar thermal electric power generation, so you really must be more careful to review your copy. The phrase "all forms of solar power" implies that PV will be the sole source of direct solar electric power generation, but even today we in the business know that as the already-available technologies are implemented, saying nothing about ideas yet-to-come, PV will become more and more a niche application where its simplicity of application outweighs its very high cost-per-watt (such as for lighting signage, remote telemetry, and other small power users, especially in off-grid locations). PV is very useful (my home runs on it, also off the grid), and one can make too much of the chemical hazards associated with semiconductor manufacture as well, but nonetheless PV is not at all likely to become very competitive at the industrial scale of generation needed to have a meaningful impact on the world's electric power portfolio. Some concentrating solar power (CSP) designs are already well under $2/watt and falling, whereas even with massive investment in new silicon ingot production capacity, $2/watt PV is a long, long way off.

For several years now, solar thermal power generation, in particular CSP in forms such as dish stirling, heliostat/tower boilers (look at Solar One near Barstow, CA), and some other designs are already much cheaper per installed watt than PV, and the economies of scale for these types of systems have not yet begun to be realised.

A CSP demonstration plant operated in California for several years in the mid-'90's, based on a dish stirling design developed in a private/public partnership at Sandia Labs, at that time showed that the design was already nearly competitive with new gas or coal-fired steam generation in cost per installed capacity, and that was at a scale of only several hundred 20kw units. That was only comparing installed equipment cost; of course the solar plant's fuel is free. As we speak, a commercial-scale plant is being built in two phases in the southern CA desert, using tens of thousands of the same dish concentrators, and when built out will produce a peak output nearly equivalent to a fission steam plant, almost 1 gigawatt, but it got online in far less time and for less money.

These are heat-driven machines, which are manufactured with methods more akin to automobile production than semiconductor manufacture. Although some of the stirling designs involve advanced metallurgy, the use of hazardous chemicals and powerful greenhouse gases as cited in your story are not a great concern.

When talking about solar electric power, PV is what most people immediately think, because they've seen PV panels at work but are unaware of the other technologies designed for the same purpose. A few industrial scale PV plants are being built, but as CSP is implemented it is clear it will become more and more the preferred technology for commercial-scale solar electric generation.

And, as several posters mentioned, on-site solar thermal for hot water and air heating in homes, and for industrial heat processes is already very cost-effective and obviates the need to supply electric or fuel energy for these uses. In the overall energy picture, conservation is equivalent to new sources. A home solar domestic hot water system will typically pay for itself in avoided cost within about 5 years. After that, the fuel is free, maintenance is minimal, and system life is measured in decades. This is not, however, passive solar technology, as one poster said. Passive has to do with the design of buildings to capture and store direct infrared energy to augment space heating needs, not delivery of other services.

By Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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