“biopower”)2 is the largest source, having produced 55,000 GWh in 2007. Wind power and geothermal supplied 32,000 GWh and 14,800 GWh, respectively, during that year. Except for wind power, none of these sources has grown much since 1990 in terms of either total electric power production or generation capacity.

The largest growth in the use of renewable resources for electricity generation is currently in wind power and, to a lesser extent, in solar power. Wind power technology, having matured over the last two decades, now accounts for an increasing fraction of total electricity generation in the United States. Though wind power in 2007 represented less than 1 percent, it grew at a 15.5 percent compounded annual rate over the 1990–2007 period and at a 25.6 percent compounded annual growth rate between 1997 and 2007. Wind power supplied almost 6,000 GWh more in 2007 than it had the year before. According to the American Wind Energy Association, an additional 8,300 MW of capacity was added in 2008 (AWEA, 2009a), representing an additional yearly generation of 25,000 GWh assuming a 35 percent capacity factor.3 By the end of 2008, the overall economic downturn had caused financing for new wind power projects and orders for turbine components to slow, and layoffs began in the wind turbine manufacturing industry (AWEA, 2009a). Thus new capacity in 2009 recently looked to be considerably smaller than in 2008. However, AWEA (2009b) recently reported that 2.8 GW of new wind power generation capacity was installed in the first quarter of 2009. Further, analysis of the American Recovery and Reinvestment Act (ARRA) of 2009 shows that by 2012 wind power generation will more than double what it would have been without the ARRA (Chu, 2009).

Central-utility electricity generation from concentrating solar power (CSP) and photovoltaics (PV) combined was 600 GWh in 2007, just 0.01 percent of the U.S. total—a fraction that has been approximately constant since 1990. However, this estimate does not include contributions from residential and other small PV installations, which now account for the strongest growth in solar-derived electricity. Installations of solar PV in the United States have grown at a compounded annual growth rate of more than 40 percent from 2000 to 2005, with a genera-


Biopower includes electricity generated from wood and wood wastes, municipal solid wastes, landfill gases, sludge wastes, and other biomass solids, liquids, and gases.


The capacity factor is defined as the ratio (expressed as a percent) of the energy output of a plant to the energy that could be produced if the plant operated at its nameplate capacity.

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