Economic analysis of PV hybrid power system: Pinnacles National Monument

PV hybrid electric power systems can offer an economically competitive alternative to engine generator (genset) systems in many off-grid applications. Besides the obvious 'green' advantages of producing less noise and emissions, the PV hybrid can, in some cases, offer a lower life-cycle cost (LCC) than the genset. This paper evaluates the LCC of the 9.6 kWp PV hybrid power system installed by the National Park Service (NPS) at Pinnacles National Monument, CA. NPS motivation for installation of this hybrid was not based on economics, but rather the need to replace two aging diesel gensets with an alternative that would be quieter, fuel efficient, and more in keeping with new NPS emphasis on sustainable design and operations. In fact, economic analysis shows a lower 20-year LCC for the installed PV hybrid than for simple replacement of the two gensets. The analysis projects a net saving by the PV hybrid system of $83561 and over 162000 gallons of propane when compared with the genset-only system. This net saving is independent of the costs associated with environmental emissions. The effects of including emissions costs, according to NPS guidelines, is also discussed. Key to the favorable economics of this PV hybrid system was an integrated program of load management and load segmentation. Load segmentation kept initial costs down while load management ensured that, over time, the PV array would provide the large fraction of total site energy for which it was designed.