LA Times reporter Ralph Vartabedian recently wrote about the use of natural gas generation to provide electricity when the wind is not blowing. He cites an afternoon in California when the wind power production was only 1% of the rated wind generation capacity.
In regions where peak demand is due to air-conditioning, wind will typically be producing far less than its rated capacity when the electrical demand is highest. For Texans, this is familiar: on those very hot, muggy days in August when the AC is running at full blast, we just don’t expect to be able to walk outside and feel a cooling zephyr on our faces.
ERCOT, the grid operator for most of Texas, “counts” on less than 10% of the rated wind generation capacity to be actually generating in these summer peak times. There are days when there is essentially no wind generation at the time of the peak electrical demand. On these days, other generators must be used to generate enough power to cover the peak demand.
There is a cost to keeping other sources of electricity available for when the wind does not blow. The cost of such reserves, or “ancillary services,” is likely to increase as the penetration of wind increases. My students at the University of Texas are trying to understand these issues in more detail in the context of anticipated wind expansion in Texas. We aim to predict more accurately the amount of reserves that we will need to have in Texas, and understand the costs of doing so.