While electricity generation from the primary fuel sources decreased in 2008 (coal by 1.5%, natural gas by 1.5%, and nuclear by 0.03%), generation from all renewable sources increased, with the exception of wood and wood derived fuels.

For the first time, power generation from wind energy constituted a larger share of total electricity than from petroleum or from wood and wood-derived fuels, notes Electric Power Industry 2008: Year in Review released by the Department of Energy’s Energy Information Administration. Output from wood and wood-derived fuels dropped in 2008, as did generation from coal (down 1.5%), natural gas (-1.5%) and nuclear (-0.03%).

Twenty-four of the US states have Renewable Portfolio Standards in place, and five other states have non-binding goals for renewable energy. Several recent pieces of federal legislation also offer substantial financial incentives for generation of electricity from wind and other renewable energy technologies.

In 2008, generation was adversely affected by the weak economy in the United States, with annual net generation dropping for the first time since 2001, down 0.9% to 4,119 TWh in 2008.  Summer peak load fell by 3.8% while winter peak load increased by the same percentage to 643,557 MW.

Total net summer generating capacity increased 1.5% over 2007 to 15,283 MW, of which new wind capacity accounted for 53.2% with 8136 MW installed. Wind net summer capacity increased 49.3%.

The generation share of conventional hydroelectric power was up slightly in 2008, but the general trend is one of decline, the report notes. In 2008, generation from conventional hydroelectric plants accounted for 6.2% of total net generation, compared with 10.2% in 1997. Excluding conventional hydroelectric, renewable energy sources contributed 3.1% of total net electric generation in 2008, up from 2.5% in 2007.

“This marks the fifth consecutive year in which this (renewable energy) category’s share of total net generation has increased, and the first time it crossed the 3% threshold,” it notes. “The largest portion of this increase comes from wind generation, which increased from 0.8% to 1.3% of total net electric generation.”

Net generation from renewable energy sources (excluding conventional hydroelectric) increased 19.9% in 2008, following an increase of 9% in 2007. More new wind energy capacity came online in 2008 than in the prior two years combined.

The top five wind-generating states in 2008 were Texas, California, Minnesota, Iowa and Washington. Texas, where wind generation was up 80.2%, was the largest source of wind energy with three times the output of second-place California. Nationally, wind generation increased 60.7% from its 2007 level and 72.6% of the national increase was installed in Texas, Colorado, Minnesota, Illinois, Oregon and Iowa.

Wood and wood-derived fuels, representing 0.9% of total net generation, accounted for 37 TWh, down 4.4% from 2007. Geothermal power plants supplied 15m MWh while generation from solar thermal and solar electric sources was up 41.2% from 2007, at 864,000 MWh.

Nuclear and coal-fired plants have the highest average capacity factors at 91.1% and 72.2% respectively, while the composite capacity factor for wind and all other renewable energy resources (other than hydroelectric) had a 37.3% capacity factor in 2008, a “significant decrease” from the 59.1% achieved in 2000 when the category was dominated by biomass which is a dispatchable sources. “The continuous decline in the average capacity factor for all non-hydroelectric renewable resources is consistent with the significant growth of wind capacity relative to other forms of renewable electricity generation,” the report explains.