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Effects of Large-Scale Solar Energy on Land and Water Resources in the Southwest U.S.

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Chris FieldNoah Diffenbaugh, and David Lobell, Environmental Earth System Science

For the part of this study evaluating utility-scale photovoltaic plants’ effects on monsoonal precipitation, Noah Diffenbaugh has recruited Bereket Lebassi, who models the impacts of rooftop solar panels on urban climate. Diffenbaugh and Lebassi have begun to explore the consequences of utility-scale PV for a range of climate feedbacks. The initial focus is on the climate consequences of allocating land to large PV use versus irrigated agriculture, which could be used for bioenergy crops. The initial result is that, relative to irrigated agriculture, utility-scale PV tends to produce local cooling but warming farther away.

For David Lobell’s part of the project, (investigating synergistic opportunities for integrating bioenergy agriculture and large solar infrastructure in desert regions), postdoc Sujith Ravi is completing a life-cycle analysis of PV, agave, and mixed PV-agave uses. Agave can be grown in the absence of irrigation, with added water used to clean PV modules, or with irrigation to reach high yields of ethanol. The energy benefits of adding only the PV-cleaning water would be quite small, accounting for merely one-tenth of the total direct energy benefit of the cleaner PVs.

For the final thrust, we look at whether some sites may simply be too dusty for large-scale solar, especially given the expected effects of climate change and the projects’ disruption of local soil. Graduate student Rebecca Hernandez has developed a master database of planned and deployed solar energy projects in California. Projects were mapped by size in land that is publicly and privately held, and in different ecosystem types. Hernandez and Field found that California does not need to build solar arrays on pristine, undeveloped land to meet its energy needs. In fact, areas for both small and large solar energy development within the built environment could meet the state's energy demand three to five times over.

Publications and media

"Solar energy’s land-use impact"  Carnegie Science(October 19, 2015).

Solar could meet California energy demand three to five times over” Carnegie Institution for Science Press Release (March 16, 2015).

"Efficient use of land to meet sustainable energy needs" Nature Climate Change 5 (2015): 353–358.

"Environmental impacts of utility-scale solar energy" Renewable and Sustainable Energy Reviews 29 (2014): 766-779.

"Tradeoffs and synergies between biofuel production and large solar infrastructure in deserts" Environmental Science & Technology48 (2014): 3021–3030.

"Nonhydrostatic nested climate modeling: A case study of the 2010 summer season over the western United States" Journal of Geophysical Research: Atmospheres 118 (2013): 10944-10962.

Awarded 2011 as part of the TomKat's Large-Scale Solar project.

Funded by the TomKat Center with support from the Precourt Institute for Energy.