Tapping The Sun

"MORE ENERGY—in the form of sunlight—strikes Earth in one hour than all of the energy consumed by humans in an entire year."

It's a staggering statistic and just one of the facts that Nathan S. Lewis lists when he makes the case for the importance of solar energy research. Ready with data and calculations to bolster his argument, Lewis, a chemistry professor at California Institute of Technology, runs down the list of alternatives to fossil fuels—nuclear, wind, hydroelectric, biomass, and geothermal—and argues that the sun is the only viable and renewable source capable of satisfying humanity's great thirst for energy. Currently, on a global scale, energy usage is on the order of 13 terawatts (13 trillion W or 13 trillion joules per second), of which roughly 85% is generated by burning fossil fuels.

Showering Earth with an energy flow of some 120,000 TW, the sun would appear to be a limitless non-carbon-emitting energy fountain capable of meeting worldwide energy demands. "There's no doubt that we have ample energy resource in the sun," Lewis stresses. The challenge, he says, is figuring out how to tap into it inexpensively.

That challenge has been driving researchers to develop new materials and strategies for designing photovoltaic systems that convert sunlight into electricity. In addition to exploring new methods for reducing the cost of solar cells based on silicon, the traditional photovoltaic material, scientists have been experimenting with other semiconductors, inorganic nanocrystals, organic polymers, and a host of other light-sensitive materials.
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