Implementation of Brackish Groundwater Desalination Using Wind-Generated Electricity as a Proxy for Energy Storage: A Case Study of the Energy-Water Nexus in Texas

Abstract

With a push toward renewable electricity generation, wind power has grown substantially in recent U.S. history and technologies continue to improve. However, the intermittency associated with wind-generated electricity without storage has limited the amounts sold on the grid. Furthermore, continental wind farms have a diurnal and seasonal variability that is mismatched with demand. To increase the broader use of wind power technologies, the development of systems that can operate intermittently during off-peak hours must be considered. Utilization of wind-generated electricity for desalination of brackish groundwater presents opportunities to increase use of a low-carbon energy source and supply alternative drinking water that is much needed in some areas. As existing water supplies dwindle and population grows, cities are looking for new water sources. Desalination of brackish groundwater provides one potential water source for inland cities. However, this process is energy-intensive, and therefore potentially incongruous with goals of reducing carbon emissions. Desalination using reverse osmosis is a high-value process that does not require continuous operation and therefore could utilize variable wind power. That is, performing desalination in an intermittent way to match wind supply can help mitigate the challenges of integrating wind into the grid while transforming a low-value product (brackish water and intermittent power) into a high-value product (treated drinking water). This option represents a potentially more economic form of mitigating wind variability than current electricity storage technologies. Also, clean energy and carbon policies under consideration by the U.S. Congress could help make this integration more economically feasible due to incentives for low-carbon energy sources. West Texas is well-suited for desalination of brackish groundwater using wind power, as both resources are abundant and co-located. Utility-scale wind resource potential is found in most of the region. Additionally, brackish groundwater is found at depths less than 150 m, making west Texas a useful geographic testbed to analyze for this work, with applicability for areas with similar climates and water supply scarcity. Implementation of a wind-powered desalination project requires both economic and geographic feasibility. Capital and operating cost data for wind turbines and desalination membranes were used to perform a thermoeconomic analysis to determine the economic feasibility. The availability of wind and brackish groundwater resources were modeled using geographic information systems tools to illustrate areas where implementation of a wind-powered desalination project is economically feasible. Areas with major populations were analyzed further in the context of existing and alternative water supplies. Utilization of wind-generated electricity for desalination presents a feasible alternative to energy storage methods. Efficiency, economics, and ease of development and operation of off-peak water treatment were compared to different energy storage technologies: pumped hydro, batteries, and compressed air energy storage. Further economics of compressed air energy storage and brackish groundwater desalination were examined with a levelized lifetime cost approach. Implementation of water desalination projects using wind-generated electricity might become essential in communities with wind and brackish groundwater resources that are facing water quality and quantity issues and as desires to implement low carbon energy sources increase. This analysis assesses the economic and geographic feasibility and tradeoffs of such projects for areas in Texas.