Mirroring a recent report out of the U.S., researchers in Spain are reporting that “cycling” – the ramping up and down of fossil-fuel-burning power plants to back up intermittent wind power – doesn’t much hinder wind power’s ability to trim greenhouse gas emissions.
Was there some impact from cycling? Yes, the researchers said – at high rates of wind penetration. But even then, the GHG reductions remained “significant.”
At low penetration levels, each wind megawatt-hour “introduced in the network allows us to avoid all the CO2 of each displaced thermal MWh,” the researchers said. “When penetration levels are as high as 50%, the wind effect is accumulative and reductions would reach just 80%.However, this reduction is still significant and there are no negative cases as mentioned by other reports.”
That fits with a study released last month by the National Renewable Energy Laboratory in Colorado.
The NREL reported that while there are some downsides to “cycling,” they are so tiny compared to the benefits gained by fueling electrical generation with free wind, that they barely rate as a footnote. “The negative impact of cycling on overall plant emissions is relatively small,” the researchers reported. “The increase in plant emissions from cycling to accommodate variable renewables are more than offset by the overall reduction in CO2, NOx, and SO2. In the high wind and solar scenario, net carbon emissions were reduced by one third.”
The idea that wind’s intermittency renders it a poor tool to reduce GHG emissions, in part because of cycling inefficiencies, is a favorite of wind power’s critics. Matt Ridley wrote last year that carbon savings from wind are tiny and “may even be a negative number.” And U.K. columnist Christopher Brook, citing the anti-wind Global Warming Policy Foundation, wrote that “ramping the back-up gas plants up and down would mean running them very inefficiently, and give off so much CO2 that we could end up increasing our overall emissions rather than reducing them.”