A rosy outlook for clean energy now takes on an air of uncertainty as renewables look to avoid becoming a casualty of an era of low oil prices.
Because utilities can't control when the sun shines or the wind blows, it has been hard to incorporate solar and wind power into the electricity grid. But new storage technologies could soon change that.
Natural gas is cleaner than coal, but only if the industry can control its methane releases. A new report says it's doing OK, but methane releases are underestimated.
The growth of the US solar energy industry is impressive, Calhoun and Morris write, but so-called 'soft costs' keep solar prices high in the US, compared to countries like Germany, a champion of solar development.
In the developing world, where land-intensive wind turbines are being rapidly constructed, wind power has often turned clean energy into dirty business.
The Department of Energy, aiming to boost US competitiveness, gives a $150m. loan guarantee to a Massachusetts firm that has found a way to dramatically reduce the cost of solar voltaic cells.
Rep. Michele Bachmann, (R) Minnesota, joined by husband Marcus, left, family and friends, announces that she will end her campaign for president Wednesday, Jan. 4, 2012, in West Des Moines, Iowa.