Solar-power sunrise
Posted: Monday, April 23, 2007 7:40 PM by Alan Boyle
Sun-generated electricity may not be America's salvation in the short term, but the public-TV documentary "Saved by the Sun," premiering Tuesday in the wake of Earth Day, shows how technology and savvy marketing tactics are brightening the outlook for solar power.
Solar cells generally come in at the bottom of the list of U.S. energy sources, producing less than 1 percent of the nation's electricity. The main reason is the bottom line: The cost for solar is currently pegged in the neighborhood of at least 20 cents per kilowatt hour, compared with the national average rate of 10 cents.
All is not lost, however. "Saved by the Sun," produced by the "Nova" documentary team, shows how the growing concern about carbon-dioxide emissions and the growing popularity of renewable energy are change the equation. And if you add in the effect of less expensive, more efficient photovoltaic technologies, you can begin to sense the solar winds of change:
- In Germany, solar-energy subsidies have brought the goal of generating 20 percent or more of that country's electricity through photovoltaics well within reach. The program tells the story of one farmer who has invested $5 million to put solar arrays in one of his fields - and is making around $60,000 a year selling the power back to the grid. There is a downside, in the form of higher electric rates for all Germans - and "Saved by the Sun" tells that side of the story as well.
- In California's Mojave Desert, a 310-megawatt network of electricity-generating facilities is on the rise, powered completely by arrays of more than 900,000 sunlight-collecting mirrors that set steam turbines spinning. It's the world's largest solar-energy site. Taken together, the 1,500-acre Kramer Junction mirror farms can put out enough power to supply more than 230,000 homes - and the setup is designed for optimal use during Southern California's power-draining peaks in the summertime. (PDF factsheet). But again, there's a downside: How many other places are suited for such facilities, and how many other places would be willing to host hundreds of thousands of mirrors?
- In Ridgewood, N.J., a Whole Foods store struck a deal with Sun Edison to have the store's roof outfitted with solar-electric panels. Sun Edison pays the cost of putting in the equipment; in return, Whole Foods agrees to buy the power from Sun Edison for 20 years. Sun Edison thus has a reliable market for its electricity, while Whole Foods comes out ahead as well - that is, if electric rates from other providers turn out to be more expensive over the long haul.
- Around the country, homeowners are coming up with their own systems to take advantage of the sun. The TV show profiles several solar converts - including power users in areas you wouldn't expect to be sun-drenched. Maine's Bill and Debbi Lord have been adding innovations to their Solar House for more than a decade. Colorado's Amory Lovins, co-founder of the Rocky Mountain Institute, raves about the power boost (and the bananas) produced at his solar-optimized home base. Yet another solar-centered family traces how they did it on the "Nova" Web site. The upfront cost can be high - potentially $50,000 or more - but the idea is that the money is earned back through lower utility bills (and, I suppose, higher house values).
To me, the most interesting aspect of the show was the research being conducted into cheaper, better solar cells. Right now, the typical solar cell achieves energy efficiencies of 12 to 20 percent - and the cells will have to become about twice as efficient to be competitive with coal-fired electricity.
"Saved by the Sun" focused on two technological paths: multijunction cells, which are setting fresh records every year for efficiency, even though they're relatively expensive; and dye-based cells, which aren't nearly as efficient but are likely to be cheaper. The dye-based technology could conceivably open the way to "paint-on" or plastic-film solar cells you could apply to the roof of your house (or your car, for that matter).
Despite their high cost, multijunction cells are already having their day in the sun. Such cells were used on NASA's Mars Exploration Rovers, which have lasted three years longer than their expected three-month operating life and are still going strong. And researchers say the cells are now ready for prime time on Earth as well as Mars.
"There's a sense that we have already reached the point where the multijunction cell makes commercial sense," said Sarah Kurtz, a researcher at the National Renewable Energy Laboratory who recently won a share of the $1 million Dan David Prize for future-oriented research.
The best multifunction cells have already achieved more than 40 percent efficiency, and Kurtz noted that the efficiency rates have been improving by 1 percentage point every year. "We have no reason to think that is going to stop now," she told me today.
It will take a while for the market to catch up with the leading edge of innovation, she said.
"The development of the concentrator systems take more time than most people would think, and therefore we need to allow time for the prototype to be tested in the field," she said. "You want to first make sure you've got a reliable product."
But the technology seems certain to take hold eventually. In fact, some companies are talking about solar-cell applications in the range of "tens of megawatts," she said.
Multijunction cells won't be the only products out there, she stressed. "Like the battery industry has many different technologies for different applications, there will also be many different solar-cell technologies for different applications," she said.
And that brings up another sore point for solar: Once you've generated that power, how do you store it? "Saved by the Sun" touches upon the point that power-storing technologies will have to keep pace with power-generating technologies - particularly when you're talking about a variable power source like sunlight.
To learn more about the state of the art in power storage, check out this report about a next-generation battery-ultracapacitor hybrid (which is already quite familiar to some Cosmic Log readers) and this discussion of Russia's "star batteries." Wikipedia and Gizmag have still more about ultracapacitors.
We haven't even gotten into way-out technologies such as space solar power, but if you can think of additional ways we can be "saved by the sun," feel free to add your comments below.
