PROJECTION OF CALIFORNIA'S FUTURE FRESHWATER REQUIREMENTS FOR POWER GENERATION

Water and energy are inextricably linked. Water is needed for energy production, and energy is needed for the extraction, conveyance, treatment, and distribution of water. Water requirements for electricity generation vary significantly, depending on the primary energy source, conversion technologies, and cooling technologies. Therefore, to meet future demands, integrated planning between both the energy and water sectors is essential. This analysis provides a tool that supports integrated planning by quantifying the water requirements for electricity generation from both renewable and non-renewable sources. Using California as a case study, we assessed the freshwater requirements for current and future electricity generation under several different energy portfolios. Our analysis demonstrated the potentially positive effects of investment in certain renewable resources such as solar photovoltaics, wind power, and waste-based bioenergy. Similarly, dry cooling technologies, if employed in thermoelectric power plants, can greatly diminish the electricity sector's impact on freshwater resources. Conversely, increased reliance on dedicated energy crops may have extraordinary impacts on freshwater resources. Thus, meeting a "renewable energy portfolio" goal or standard requires careful analysis of the freshwater implications of various primary energy sources and their associated conversion processes. A portfolio with reduced water use and carbon emissions could produce a number of environmental benefits. The corresponding increase in electricity costs may result in increasing energy efficiency, potentially with some trade-off with regards to consumer well-being. Converting California's coastal power plants from seawater-cooled to wet recirculating or dry cooled could actually result in a very minor increase in overall freshwater withdrawals. If reclaimed water is used for cooling these plants, this may actually reduce pressure for freshwater withdrawals overall. While the analysis focused on California, the trends are valid for freshwater limited or stressed regions around the world, and may serve to make better decisions when planning energy and water infrastructure.