There is a new study that points out that the addition of windmills to the electrical grid causes coal power plants to run less efficiently due to the intermittent nature of wind power. Via The Foundry:

Second, the intermittency of wind forces coal and gas-fired plants to operate inefficiently and actually increase emissions. Coal plants run most efficiently when continuously running, so the ramping up and down of conventional coal plants to make up for intermittent wind pumps out more carbon dioxide. Bryce likens it to the efficiency of an automobile: “An automobile that operates at a constant speed—say, 55 miles per hour—will have better fuel efficiency, and emit less pollution per mile traveled, than one that is stuck in stop-and-go traffic.”

This has proven to be the case in Colorado and Texas, two states that have adopted a renewable portfolio standard, which mandates that wind be included in the state’s electricity supply. A recent study commissioned by the Independent Petroleum Association of Mountain States looks at the power plant records from these two states and finds:

Coal-fired power plants are designed to run most efficiently at stable rates and are not well-suited to accommodate the load variability imposed by the integration with wind generation. Cycling causes coal-fired power plants to operate less efficiently, and reduces the effectiveness of their environmental control equipment, which together drive up emissions. Paradoxically, using wind energy in such a way that it forces utilities to cycle their coal generation often results in greater SO2, NOX and CO2 emissions than would have occurred if less wind energy were generated and coal generation was not cycled.

Remind me again why we are subsidizing wind power?