Grid‐support photovoltaics: Evaluation of criteria and methods to assess empirically the local and system benefits to electric utilities

In 1988, researchers at the Pacific Gas and Electric Company (PG&E) formulated the hypothesis that strategically sited photovoltaics (PV) could provide substantial local benefits to a utility's electrical transmission and distribution (T&D) system. Initial modelling of simulated data confirmed this hypothesis. These results indicated a need for empirical testing through operation of a commercial-scale grid-support PV plant within an appropriate utility T&D system. Towards this end, a comprehensive research plan was formulated to characterize and evaluate local and system benefits. Local benefits to be evaluated are: extended distribution transformer life, increased distribution planning area capacity, extended load tap changer life and maintenance intervals, reduced electrical line losses, improved system voltage, improved distribution system reliability and increased transmission system capacity. System benefits to be evaluated are: reduced system energy production costs, reduced requirements for additional generation capacity, reduced minimum load operation costs and reduced environmental impacts of fossil energy generation. A 500 kW PV plant serving PG&E's Kerman Substation near Fresno, California, was selected and built as part of the Photovoltaics for Utility Scale Applications project. the plant began operating in April 1993, 6 months after construction was initiated, and evaluation of the benefits was initiated. Confirmation of the original hypothesis-that strategically sited PV generation provides substantial benefits to selected T&D systems-will demonstrate that PG&E and other utilities may be able to serve customers in a more cost-effective and environmentally sensitive manner. In the process, utilities could provide new markets for PV and other modular generation technologies.