Gusting winds and swelling rivers bless the U.S. Pacific Northwest with an abundance of renewable energy resources in the spring and early summer. So much, in fact, that at times in recent years the Bonneville Power Administration (BPA), a federal utility, has forced wind farm owners to curb their output to keep electricity generation in balance with the rise and fall of demand on the grid. (See related quiz: "What You Don't Know About Wind Energy.")