Performance Evaluation of Desalination Technologies at Common Energy Platform

A major fraction of secondary energy consumed for our daily activities, such as electricity and low-grade heat sources, emanates from the conversion of fossil fuels in power plants. In the seawater desalination processes, the energy efficiency is usuallyexpressed in kWh electricity or kWh of low-grade heat per unit volume of waterproduced. Although kWh energy unit provides a quantitative measure of inputenergy, it has subtly omitted the embedded quality of supplied energy to desalinationplants. In assuming the equivalency across dissimilar energy forms, it results in athermodynamic misconception that has eluded the desalination industry hitherto, i.e.,not all units of derived energy are created equal. An incomplete energy efficacyapproach may result in the inferior selection of desalination processes to be deployed;—a phenomenon observed in the trend of installed desalination capacity globally.Operating a less efficient desalination plant over its lifespan would create mucheconomic burdens including a higher unit cost of water, higher CO2 emissions andgreater brine discharge to the environment. This book chapter clarifies the key con-cept and a thermodynamic framework to rectify the misconception in energy con-sumption, permitting energy planners and designers to optimize deployment of futuredesalination plants for energy sustainability. We have derived conversion factors to convert assorted derived energies into standard primary energy for fair comparison.