Techno-Economic Optimization Of Coupling A Cascaded Med System To A Csp-Sco(2) Power Plant

Integrating a multi-effect distillation (MED) process with a concentrated solar power (CSP) plant can enable a sustainable solution to meet our global society's increasing energy and freshwater demands. This integration makes possible the 'free' reuse of waste heat from an advanced power block, albeit at slightly reduced thermal efficiency. As such, this study can be considered a pioneering analysis of the potential of integrating a cascaded MED system with a supercritical CO2 (sCO(2)) cycle, which provides two main innovations: (a) a highly efficient sCO(2) cycle is proposed to mitigate the energy efficiency penalty of the more traditional (Rankine Cycle) in CSP-Desalination (CSP-D) coupling, and (b) a cascaded MED system is proposed to recover much more of the rejected waste heat than a single MED configuration. These two innovations were explored in detail by employing an inhouse thermo-economic numerical model, which was validated using literature data. It was found that 4-MED systems maximized the distillate production, with 57% waste heat energy recovery compared to 26% energy recovery using a single-MED system. Encouraged by this positive performance boost, an economic feasibility analysis was conducted by considering the installation site (i.e., pipeline distance from the coastline and the direct normal irradiance (DNI) resource) and the potential revenue from a power purchasing agreement (PPA) and a water purchasing agreement (WPA). It was found that the desalination process has a negligible effect on the payback due to the limited water production (i.e., similar to 1 million m(3)/yr) compared to the high electricity generation (i.e., similar to 190 GWh/yr). Thus, reducing the power block's investment cost and installing the plant in high PPA markets (i.e., above 20 UScents/kWh) represent the two most significant factors for improving the plant's feasibility. It was also found that a 0.6 kWh/m(2) day of additional DNI is required to offset each 100 km of pumping energy consumption (for a PPA of 20 UScents/kWh and WPA of 1.5 USD/m(3)) for a payback period of less than 20 years. Furthermore, a non-linear regression model was applied to develop a correlation that researchers can use to explore any potential sites that could benefit from this technology. This correlation was tested on water-stressed countries with access to the sea and high solar resources. It was found that countries with high electricity prices (i.e., above 20 UScents/kWh), such as Australia, Chile, Jordan, Somalia, Spain, and the Southwest region of the USA, could benefit most from using this cogeneration plant, but (unfortunately) the gulf states, where fossil-fuel desalination is dominant, are unlikely to see an immediate economic benefit from the proposed plant. Thus, this study provides deeper insights on how CSP-sCO(2)-MED cogeneration plants can help 'green-terraform' arid lands and help water-stressed countries.