Student Abstracts: Biology at NREL

Renovation of the Photovoltaic-Diesel Generator Hybrid System at Natural Bridges National Monument. BRITTANY WALKER (University of Colorado, Boulder, CO 80309) OTTO VAN GEET (National Renewable Energy Laboratory, Golden, CO 89401) .
In 1979 a large 93 kW photovoltaic-diesel generator hybrid system was installed as the only source of power for Natural Bridges National Monument. As the components in the system have aged the performance of the system has declined by more than 50% despite its upgrade in 1992. Natural Bridges has enlisted the help of the Federal Energy Management Program (FEMP) to provide suggestions on how to upgrade the existing hybrid system. A software program called Hybrid Optimization Model for Electric Renewables (HOMER) was used in determining cost-effective measures of upgrading the existing hybrid system at Natural Bridges. Two primary simulations were modeled in HOMER: the existing hybrid system performance and the optimum upgraded system. The model of the existing hybrid system was found to closely match the performance of the actual system. The HOMER simulations determined the optimum upgraded system to have a 40 kW photovoltaic array, a 400 kWh battery bank, a 40 kW inverter, and the current 60 kW generator. Based on knowledge of the condition of the components within the system and HOMER simulations, FEMP made recommendations to maintain the existing 40 kW photovoltaic array as well as the 60 kW generator, replace the existing 500 kWh battery bank with a 400 kWh battery bank, and also to replace the existing 50 kW inverter and existing charge controllers with newer models. If Natural Bridges takes penalties for emissions from diesel fuel into account, then the photovoltaic array should be increased approximately 15 kW to an output of 55 kW.