The energy water nexus : increasing water supply by desalination integrated with renewable power and reducing water demand by corporate water footprinting



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Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. Consequently, it would be valuable to manage both supply and demand of water to fully address water sustainability. Additionally, the inextricable link of water and energy -- energy is required to pump, treat, and distribute water and water is often used in the production of energy -- creates the need to study the use of these resources together. In response to water stress, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment and causes significant carbon emissions with conventional approaches. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Both wind and brackish groundwater resources are plentiful in the Panhandle region of West Texas, making an integrated wind-powered desalination facility an option for meeting increasing water demands. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from two low-value resources (saline water and wind power without storage). This thesis presents a thermoeconomic, geographic, and operational analysis of an integrated wind-powered reverse osmosis facility treating brackish groundwater in West Texas. The results demonstrate the favorability of the integrated facility under certain economic, geographic, and operating conditions. Also in response to water stress, corporations are becoming increasingly interested in identifying water vulnerabilities in their operational portfolios to minimize physical, reputational, regulatory, and financial risks associated with potential water shortages. The water footprint is one tool available to assess water use, identify vulnerabilities, and guide mitigation strategies. This thesis provides an accounting methodology for water reporting that includes direct water uses and indirect (embedded in energy, services, and products) water uses in the operations. Further, a case study is considered to illustrate the methodology by assessing the water impact of a mixed-use facility in Palo Alto, California. The results demonstrate the importance of considering the indirect water uses, which requires a more exhaustive analysis.