An abundance of fossil fuels combined with advances in technology to harness wind and solar power has sent energy prices crashing around the world. WSJ explains how it all happened at once. Photo illustration: Carlos Waters/WSJ Utilities across the country are seizing a fast-expiring green energy subsidy to boost the efficiency of aging wind farms as they set ambitious goals to reduce their carbon emissions. Xcel Energy Inc., a Minneapolis-based utility company serving customers in eight states in the West and Midwest, recently announced plans to invest as much as $1.4 billion to refurbish some of its older wind farms as it pushes to provide carbon-free electricity by 2050. The projects, which will qualify for a gradually diminishing federal tax credit set to expire this year, involve retrofitting outdated turbines with bigger blades and new technology to boost efficiency. Analysts say the subsidy could be extended, but some companies […]