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The Desert Research Institute (DRI) in Nevada has recently installed eight solar PV systems with a cumulative nameplate capacity of 2.4 MW that scale from 3 kW to 1145 kW. These systems supply approximately 40% of the total electricity used at DRI’s Reno and Las Vegas campuses. This work explored greenhouse gas (GHG) impacts and economic performance of these PV systems by developing and applying comprehensive life cycle analysis (LCA) combined with economic analysis. The LCA model was built using data appropriate for each type of panel used in the DRI systems. Power output was estimated using the National Renewable Energy Laboratory (NREL) model, called PVWatts (R). The performance of PVWatts (R) was verified by comparison with actual measurements from one of DRI’s PV systems over an entire year. Lifecycle metrics quantified for the DRI systems include GHG intensity, energy payback time, cost payback time, and cost of avoided CO2.

Manufacturing of PV modules is the major contributor to total lifecycle impacts of a solar PV system. The main benefits are solar electricity’s lower GHG intensity and lifecycle energy use compared with typical grid electricity. Model results showed the 25-year GHG intensity of DRI’s PV systems to be 35-58 g CO(2)e/kW h, and the lifecycle energy use to be 0.586-0.898 MJ/kW h. The cost payback times and return on investment (ROI) varied with system size. For the six systems larger than 50 kW, the cost payback times ranged from 14.4 to 26.7 years, and the 25-year ROI ranged from 0.95 to 2.0. The cost per tonne CO2e avoided by displacing grid electricity was between $100 and $180, which is 2-3 times as high as estimated costs for carbon capture from pulverized coal power plants.

The modeled benefits of the PV systems are dependent upon the power mix of the grid electricity that is being displaced. As the grid becomes "cleaner" by elimination of coal and greater use of renewables, the CO2 reduction benefits are diminished. Changing from a "business as usual" scenario to cleaner grid scenarios was shown to reduce the GHG benefits of installed PV systems by up to 40%. (C) 2015 Elsevier Ltd. All rights reserved.