2025 Theses Doctoral

Development of sustainable solar desalination modeling platforms and proposed application in climate change scenarios in the US

Zhang, Zhuoran

Water demand in the United States is projected to increase by up to 140% by 2050 and 220% by 2070 while climate change will reduce the availability of freshwater in large parts of the country. Climate change threatens existing freshwater supplies, increases drought severity, and destabilizes the water cycle. About 44 percent of the U.S. is experiencing some level of drought with almost 10 percent under “severe to extreme drought.” Desalination technologies offer the potential to substantially reduce water scarcity by converting the almost inexhaustible supply of seawater and the apparently vast quantities of brackish groundwater into new sources of freshwater, although for inland regions the desalination brine management is a big roadblock for such applications, making zero-liquid-discharge (ZLD) desalination an important topic.

This Thesis describes the development of desalination models and simulation platforms that integrate solar energy and water desalination technologies. Furthermore, the Thesis investigates the potential of desalination powered with renewable energy in alleviating projected water scarcity in specific regions. The modeling platform development uses solar generation techno-economic models from NREL’s SAM platform and desalination models from Plataforma Solar de Almeria (PSA) in Spain and Trevi Systems, enhancing the utility of these models by converting them in a Python open-access platform and verifying their results with comparisons with pilot plant and field data. Geographical information system (GIS) databases and tools were integrated with the process modeling platform and created a Solar Energy Desalination Analysis Tool (Sedat) for identifying and characterizing locations with strong prospects for solar-enabled desalination. In a subsequent stage of this research, desalination pretreatment models were integrated in the Water treatment Technoeconomic Assessment Platform (WaterTAP) in a joint project with the National Energy Laboratory (NREL) and New Mexico State University (NMSU). In addition, this research culminated to a new model of multi-effect crystallization for ZLD applications and a US supply-demand analysis which is informed by IPCC projections of water scarcity. an innovative multi-component crystallization approach is proposed for desalination brine management, to greatly reduce the volume of brine and recover marketable salts.

This approach incorporates a multi-effect crystallization system for sodium chloride (NaCl) recovery, and a reactive crystallization process that selectively recovers magnesium (Mg) and calcium (Ca) salts. The new model is used in conjunction with an enhanced reverse osmosis and a membrane distillation model operating in a batch mode, to investigate the potential of renewable-energy-driven desalination with ZLD in response to dry and hot climate IPCC scenarios. This analysis was informed with established brackish water and consumption data layers and showed that desalination using emerging technologies such as low-salt-rejection reverse osmosis (LSRRO), and batch membrane distillation (batch-MD), powered by mainly solar power, can sustainably satisfy projected, due to climate change, deficits in fresh-water supply and demand in the United States.