Thursday, February 14, 2013

2011 U.S. Electrical Power Generation by Fuel

Last week when the Environmental Protection Agency, EPA released the second year of reported greenhouse gas emissions data from large sources they stated in their press release that “Power plants remain the largest stationary source of GHG emissions, with 2,221 million metric tons carbon dioxide equivalent (mmtCO2e), roughly one-third of total U.S. emissions. In 2011 emissions from this source were approximately 4.6 % below 2010 emissions, reflecting an ongoing increase in power generation from natural gas and renewable sources.”

 Many news sources published the press release verbatim. If the increase in renewables was due to the recent surge in construction of wind and solar power generation installations this could be just the beginning in the shrinking of the CO2e footprint of the U.S. electrical grid. A fuel change from coal to natural gas would also significantly reduce the CO2e footprint of electrical power.  I decide to take a hard look at the Electrical Generation Data available from theU.S. Energy Information Administration. The major uses of energy in the United States are heating of residential and commercial buildings (11%), industry (20%), transportation including cars, trucks, trains, planes and ships (27.4%), and electric power generation (40%). Clearly, changes in the makeup of the generating sectors would have a profound effect on the CO2e generation of the nation.
From the U.S. EIA Data

 Overall from 2010 to 2011 electrical power generated in the U.S. fell fractionally less than half a percentage point- 19.40 billion Kilowatt hours to 4,105.7 billion Kilowatt hours of power generated in 2011. Power generated from coal fell 113 billion Kilowatt hours to 1,743.3 billion Kilowatt hours. Power generated from natural gas rose 28.9 billion Kilowatt hours to 1016.6 billion Kilowatt hours. Nuclear power generation fell 16.8 billion Kilowatt hours to 790 billion Kilowatt hours. Hydroelectric power generation rose 64.9 billion Kilowatt hours. Wind generation rose 25 billion Kilowatt hours and solar generation rose 0.6 billion Kilowatt hours.

The big reduction in greenhouse gas emissions appears to be from the overall reduction in fossil fuel based power generation of 93.4 billion Kilowatt hours which also included a reduction in coal generation and an increase in natural gas generation that generates only 56% of the CO2e per Kilowatt hour of power as coal and the significant increase in hydroelectric power. Power generated from renewable sources increased 92.7 billion Kilowatt hours in 2011 over 2010 the largest portion of which is attributed to an increase in hydroelectric power generation.

Since it has been two generations since the U.S. has built large damns, it seems most likely that the increase in hydroelectric generation was due to the heavy rains in that year increasing hydroelectric generation. Unfortunately in the drought year of 2012 the amount of power generated by hydroelectric will fall and fossil fuel generation will have to make up the difference. There has been a permanent  increase in wind power generation capacity as newly built wind farms have been tied into the power grid. This is likely to continue to increase in the short run as long as building the wind farms are subsidized by the government and the expense of connecting the wind generation to the power grid is carried by the rate payers. 

The drop in fossil fuel generation from 2010 to 2011 is almost exactly equal to the increase in renewable power generation- primarily hydroelectric and wind. The U.S. use of electricity is fairly stable at this time. The overall reduction in fossil fuel generation accounts for half the reduction in CO2e the other half of the reduction of CO2e appears to be coming from the migration to natural gas.  A slight reduction in overall generation would account for the difference. While this is exciting news, I was surprised how big hydroelectric generation was overall. Also, we have not built any damns in over two generations so that the hydroelectric capacity is very dependent on how wet a year it is. In the past40 years hydroelectric power generation has fluctuated from a high of around 325-350 billion Kilowatt hours a year during the wet years of the mid 1980’s and 1990’s to the lows of 220-250 billion Kilowatt hours during the early 2000’s. Since, 2012 was a drought year, the CO2e of electrical generation in the U.S. will increase despite the growing importance of wind power generation from 1.34% of power generated in 2008 to 2.92% of power generated in 2011. 
Hydroelectric Generation vs total Electrical Generation 1949-2011

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