Observed synergistic effects of wind and solar resource blending on capacity credit at increasing regional grid penetration levels

The wide-scale deployment of variable renewable energy technologies (VREs) offers a pathway to decarbonize the electric grid. The challenge of ensuring sufficient generating capacity to meet demand at all hours, provides motivation in this study to quantify the contribution of VRE to resource adequacy as a function of VRE penetration, across several regions, technologies, and resources. A computational model was built using the effective load carrying capability (ELCC) method to calculate capacity credit values for regions spanning the contiguous United States. As the deployment of VRE increases, results of the study show that its marginal contribution to meeting peak load decreases, which in turn requires additional generating capacity to maintain reliability. Capacity credit curves are produced to display the benefit of various onshore wind-solar blend mixes to the electric grid. When compared to a mean average capacity credit curve of 100% onshore wind and 100% solar, a 50%-50% wind-solar blend outperforms as grid penetration increases. This synergistic behavior presents rationale to account for future VRE deployment by gradual implementation of several resource types collectively rather than focusing on the implementation of singular resource types. Using context-specific values for capacity credit can improve long-term decision making in generation capacity expansion, cultivating more economical long-term resource planning for deep decarbonization.