Most rapidly expanding renewable resources are expected to be wind and solar. In the United States, wind is expected to grow from 31 TWh in 2008 (1.3% of total supply) to 1160 TWh by 2030 (wind energy target of 20% of total supply of 5800 TWh) [8]. The unpredictability of wind energy resources is indicated by their low capacity factors (typically 20% to 40% [9]) which are much lower than conventional generators. This creates chal- lenging problems in the control and reliability of the power grid. As shown in Fig. 2, the variability of wind energy has little cor- relation to the variability of the load and hence contributes only a little towards meeting ERCOT’s peak load despite the expected 18 GW of wind capacity.