Integrating high penetration variable renewables in economically and operationally plausible ways is a current clean energy challenge facing many countries and regions, including California. Renewable energy deployment is a relevant pathway to decarbonize the electricity sector and reduce greenhouse gas emissions (GHGs) and mitigate the harmful effects of climate change. This paper highlights the key findings from a recently completed study, funded by the California Solar Initiative, to develop and investigate strategies to integrate high penetration renewable energy and solar photovoltaic (PV) systems using distributed energy resources (DER). We develop hypothetical operating strategies that utilize the DER present in campus microgrids, such as combined heat and power (CHP) systems and thermal energy storage, and evaluate these based on economic criteria.
Our host site is the University of California, San Diego (UCSD) microgrid, which has a rich DER base that includes a 2.8 MW fuel cell powered by directed biogas, 30 MW of onsite generation, steam and electric chillers, thermal storage and roughly 1.5 MW of onsite solar PV. We develop and evaluate three types of strategies for integrating renewable generation: peak load shifting, on-site PV firming, and grid support. We analyze these strategies with an hourly dispatch optimization model and one year of data. We define a successful renewable integration strategy as one that is operationally plausible and economically viable.
We find all three classes of strategies are technically feasible and can be cost-effective under certain conditions. However, we find that the value proposition to customers such as the UCSD campus, under current tariff structures and market prices, will need to be higher to motivate such customers to offer these services, given the risks associated with changing microgrid operations from regular practice. Our findings suggest alternative incentive mechanisms and engagement strategies beyond those pathways currently available are needed to leverage the potential of DER at campuses for renewables integration purposes. Such efforts are relevant not only to campus resources but to similar commercial and industrial loads across California, including the vast combined heat and power resources.