Photovoltaics Grows Up (and Leaves Home?)

Conceived at Bell Labs in the ‘50s, a child during the ‘70s, this technology put on a growth spurt during the ‘90s. Insiders predict it will come of age in the 21st century. But is America neglecting its progeny?

- by Dan Drollette, Senior Editor

The ranger station at Cape Range National Park lies on one of the most remote and isolated parts of the coast of Western Australia. It’s an hour’s drive from the nearest village, six hours from the more substantial town of Useless Loop, and two days from the city of Perth. In Aussie slang, this region is “beyond the black stump,” where the most prominent feature of the landscape is bushfire-scorched eucalyptus trees. More wild animals live here than humans, and the ranger-biologist must chase kangaroos off the porch during the heat of the day.

So when I saw a photovoltaic (PV) array at the park entrance, the six-meter square panel of shiny blue cells looked as alien as a space ship. Manufactured by BP Solarex, a division of British Petroleum, the system converted the outback’s glare into electricity for lights and emergency telephones. Its crystal silicon cells contained two 300-μ thick layers of light-sensitive materials sandwiched together; one layer easily lost electrons while the other easily gained them. When a photon struck this sandwich, it dislodged electrons from one layer into the other, creating an electric potential.

Long dismissed by some pundits as expensive and impractical, PV cells, also known as solar cells, are a popular way to generate electricity in remote areas. John Benner, a researcher at the National Renewable Energy Laboratory (NREL) in Golden, Colo., said the main reason is cost: stringing up wires from existing power lines to outlying areas averages between $10,000 and $30,000 per kilometer. Grant Behrendorff, manager of the Far North Queensland Electrical Corporation in Cairns, Australia, concurred: “Out here, there can be 100 kilometers between you and your nearest neighbor. If you can get hooked up to the grid for a quarter of a million dollars, I’d say you’re getting a bargain.” Under these conditions, the $20,000-$30,000 average price of a freestanding household PV system — able to generate and store electricity — is competitive, especially if this one-time cost is spread out over the system’s estimated 20-year lifespan. In contrast, conventional power sources such as diesel generators require constant attention, seldom lasting beyond a few years of constant use. And locating and transporting generator replacement parts and diesel fuel is difficult in the outback.

Industry experts predict that by mid-21st century, photovoltaics will expand beyond such established niches into the energy mainstream. The cells will no long just power satellites, calculators and emergency telephones but become an intimate part of the utility grid. PV cell prices will continue to go down and efficiencies to go up, mirroring advances in the closely related semiconductor industry. (80 to 90 percent of the cell’s silicon comes from rejected semiconductor wafers.) “PV’s no longer a technical curiosity,” said Bill Rever, a physicist and marketing manager at BP.

Photovoltaic cells have come a long way since they were first popularized during the energy crisis of the ‘70s, just as music has progressed from 8-tracks to CDs. Large energy companies are now getting into the game. Cor Herkstroter, chairman of Royal Dutch/Shell said, “In 50 years, Shell could be 50/50 oil and renewables.” Or, as Dan Kammen of the University of California at Berkeley’s Renewable and Appropriate Energy Laboratory put it: “Photovoltaics will no longer be installed and maintained by Birkenstock-wearing, bearded guys running around in the woods. They might start it, but it’s going to be managed by the fat cats.”

However, Kammen cautioned that he doesn’t expect the $1 billion PV industry to replace fossil fuels entirely. Instead, he envisioned PV taking a larger slice of the $250 billion worldwide energy pie. This view was reiterated by Terry Peterson, spokesman for the utility-funded Electric Power Research Institute: “We have a firmly established energy distribution system already. PV is here now, but not as a competitor to coal-fired plants.”

Kammen said that a big question in photovoltaics is the future role of the US. America’s investment in PV research and development has dropped 30 percent, while Germany and Japan increased their research budgets. Japan has changed from a small PV market five years ago to the world’s largest. Partly because Japan lacks its own coal and oil supplies, Japan’s government subsidizes half the installation cost of rooftop PV systems, and plans for PV to provide 3 percent of the country’s electrical consumption. In contrast, Benner said, only .02 percent of America’s energy comes from PV, and the playing field here is tilted in favor of oil and gas.

America’s share of PV chip-manufacturing has also shrunk. Rever said the industry is afraid of a reprise of what he called “the VCR effect,” in which American companies conducted basic research on a technology but the commercialization and exploitation was done by overseas competitors – who reaped the benefit.

One reason this may happen in the PV industry is because of differences in local economics and social policies here and abroad. Freestanding PV systems are popular in developing countries such as Kenya and Indonesia, where the power grid is inadequate or nonexistent. “Kenya has the biggest PV market per capita in the world, with more people paying for PV systems than paying to join the grid,” he said. “Anyone who can sell to those decentralized markets can make a killing.”

In developed countries, social concerns play a larger role. Rever said, “People are now turning to solar for a different set of reasons that in the ‘70s. Then, it was because of fears that we were running out of oil; now, it’s because of concerns over rising CO2 emissions.” Kammen said that when the external costs of fossil fuels are factored in – such as increased cases of lung cancer and the high price of environmental cleanup – PV looks more attractive. As European countries have stronger environmental movements (and higher fossil fuel prices), their policymakers are willing to pay more for this lean, clean alternative. As a result, countries such as Holland have ambitious PV programs. The Dutch just finished building a 5000-home suburb that meets all its 1 MW energy needs with photovoltaic cells. In comparison, the US has cheap fossil fuel and a weaker environmental movement.

Due to these factors, PV cells must produce electricity at a cost two to five times cheaper than presently to be accepted here. Rever said, “Cost and efficiency are subtly linked. Most of the cost is in the glass in front of the cell proper and the connectors. If that cost remains the same, but the electricity you get out of it goes up, then cost per watt has gone down.”

Benner said the cost of PV-generated electricity now ranges from 25 to 50 cents per kwh, in comparison to 7 to 20 cents per kwh for conventional fossil fuels. (Energy prices vary according to region and peak demand. During spring run-off in the hydropower-rich rural northwest, prices plummet, whereas they skyrocket during a heat wave in New York city, when air-conditioners run full-blast.)

The cell’s efficiencies have climbed from an average of 10 percent for the first crystal silicon chips to nearly 34 percent for the latest gallium-arsenide laboratory prototypes. With these improvements, the PV industry has grown 25 percent per year for the last ten years.

Industry boosters said the technology could improve even more, by using thinner (3 μ) films of light-sensitive materials and incorporating them into the roofing materials and siding of residences and office. Some California utilities encourage the development of such products by offering “net metering,” where any excess power generated by a home or office is sold back to the power company. In theory, electric meters could run back backward, and homeowners could receive checks from the utility instead of bills. “The grid acts as your storage system,” commented James Wilkie, a materials scientist with Shell Solar.

Eventually, power companies could no longer be selling physical products such as oil and gas but instead providing a service: energy at lowest cost. Kammen said, “People just want lights and television. They don’t care about how it gets to them.” He sees parallels to the internet, where money is made providing services instead of products. Also like the internet, energy would come from decentralized, multiple sources, instead of the present hierarchical system where energy is generated in one place and distributed elsewhere. He said this fundamental shift would have to take place over a long time period. “Don’t forget, it took 50 to 100 years for the world to switch from wood to coal, and another 50 to 100 years to switch from coal to oil.”

To get to this “PV heaven,” the cells must reach new levels of competitiveness. Accordingly, researchers in Switzerland are studying cheap, dye-solar cells that mimic the effects of photosynthesis. Shell’s Wilkie said that these organically based cells consist of a glass plate with a conductor and a coating of a dye such as titanium dioxide – the pigment in toothpaste. The dye absorbs sunlight, becomes excited and emits an electron. “Then you just steal the electron away from the dye and carry on,” Wilkie said. He added, “You can think of it as a solar cell made out of toothpaste.”

In the lab, these dye-sensitive solar cells had efficiencies of 11 percent. Wilkie said, “Those cells the Swiss are working on have the potential to be produced really, really cheap. And if you can manufacture solar cells cheaply enough, it doesn’t matter how efficient they are.”

Wilkie commented “I always tell people that a PV cell is just a photo detector. We’ve just got to make it cheap.”

Photonics Spectra

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