A sudden zeal to go fossil-free is fueling plenty of hype in renewable energy circles. That hype hits its shrillest notes in the promise of the least cost-effective of the major renewable options: photovoltaics that convert sunlight directly into electricity.

Consider the holiday season gush around silicon-valley PV startup Nanosolar. The firm was founded to demonstrate a truly novel nanotech-inspired design, but is now commercializing comparatively conventional CIGS thin-film PV. Nevertheless, after Popular Science crowned the company’s “Powersheet” as its innovation of the year, articles on this “game-changing technology” multiplied to fill the slow late-December news season.

Never mind that Nanosolar declined to disclose the most important spec on its product: the efficiency with which it converts sunlight to electricity. Without the efficiency, it is impossible to analyze the product’s economic potential.

The solar rot, however, goes deeper than venture capital-fueled startups. My latest feature for IEEE Spectrum — “Solar-Cell Squabble” — shows that some scientists may also be overstating their advances. And they may be doing so in peer-reviewed reports in top journals such as Science and Nature.

Don’t get me wrong. I’m a big fan of solar energy, in all of its myriad forms. I’m ecstatic to see research dollars once again pouring into solar energy. But let’s make sure those dollars don’t pour back out via the sink, or walk out the rear exit.

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