Determining Power System Capacity Value of Steam-Constrained Cogeneration

Abstract

Combined heat and power (CHP) plants have received a resurgence of attention from power system planners and policy makers in an effort to fully realize the potential of the technology. CHP plants that are thermal-primary, however, do not always maximize the benefits provided to the power system. In this study, we examine how power system planning metrics can be applied to CHP plants to better understand the impact of steam-driven constraints. This application of these methods will allow CHP plant owners and grid operators to be better informed of the capacity value that these plants provide to the power system and identify opportunities to increase CHP contribution to resource adequacy. Using the University of Michigan’s Central Power Plant as a case study, we found the effective load carrying capability (ELCC) of the plant to be 56% of its rated capacity, with the steam constraints limiting that value. We also showed that if steam demand could be increased during peak power system demand, then the capacity value of the plant would increase linearly. Currently, local steam demand is greatest during winter months while regional daily electric peaks are greatest during summer months. Alleviation of this misalignment would be necessary to increase the ELCC of the plant.