Cleantech.

• Position: TRENDS IN TECH - Brief article

"You might use the headline, 'Renewables under threat," says Adam Rentschler, a Denver-based cleantech consultant and executive, judging chair in the Rocky Mountain Region of the Cleantech Open.

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"The economics of renewable energy are sensitive to the price of legacy fuels," Rentschler says, specifically citing the flat pricing projections for the U.S. gas market. "Natural gas prices are now decoupled from oil. That's all based on where this stuff comes from." Rentschler says hydrological fracturing, or "fracking," will potentially uncork a century or more of natural gas for the country, threatening the economics of utility-scale wind and solar.

Intermittency and storage are two complementary issues also holding up renewables, Rentschler adds. "Solar and wind are both intermittent. To overcome that, the renewables industry needs to come up with better storage solutions." Rentschler says it's unclear what technology will emerge from concepts as disparate as pumping water uphill to storage rooted in chemical energy. "It's very difficult to pick the winners right now," he says.

"The intermittency...