Intermittent Nature of Green Power Is Challenge for Utilities

The 21 turbines at the Kingdom Community Wind farm in Vermont soar above Lowell Mountain, a testament in steel and fiberglass to the state’s growing use of green energy.

Except when they aren’t allowed to spin at their fastest. That has been the case several times in the farm’s short existence, including during the record July heat wave when it could have produced enough much-needed energy to fuel a small town. Instead, the grid system operator held it at times to just one-third of what it could have produced.

“We were being told to turn on diesel-fired units that are very expensive and dirty and told to ramp down what is renewable, cost-effective energy for our customers,” said Mary Powell, chief executive of Green Mountain Power, the utility that owns and operates the wind plant. “We should go with the sources that can have the highest value, especially during peak times.”

It is not the first time the grid system operator, ISO New England, which operates in six states, has cut back energy from the farm since it began operating at the end of last year, or from others in the region, including some in Maine and New Hampshire. Other windy states and regions like Texas and the Midwest have experienced similar cutbacks, known as curtailments.

http://www.nytimes.com/2013/08/15/business/energy-environment/intermittent-nature-of-green-power-is-challenge-for-utilities.html?nl=todaysheadlines&emc=edit_th_20130815&_r=0