It doesn’t seem like a lot, but 4.24% is a big number for the U.S. renewable energy industry. That’s the percentage of domestic electric power supply generated from non-hydropower renewable energy resources in April of 2009, according to the Department of Energy’s most recent Electric Power Monthly report. Renewable resources like solar power, geothermal , biomass and wind energy are all becoming an increasingly important part of the national energy mix, despite declines in total electri