| Summary: | The primary energy consumption of a spectrum of desalination systems is assessed using operating information for real plants configured for coproduction of electricity and water. The energy efficiency of desalination plants is often rated using metrics such as electrical energy consumption per unit of water produced (SEC), water produced per unit of thermal energy consumed (GOR), or exergy use relative to the limit set by the second law of thermodynamics (ηII). Comparisons of desalination technologies using these metrics can be inaccurate if energy inputs to the desalination plant are not distinguished between electrical work input and heat input using exergetic methods. Further, the cost of electrical exergy and thermal exergy at a given temperature may be quite different. When both the heat and work inputs are drawn from a common primary energy source, as in electricity-water coproduction systems, work and heat can be compared and combined by tracing them to primary energy use. In the present study, we use an exergetic framework to compare 48 different configurations of electricity production and desalination, including cases with pretreatment and hybridized systems, based on performance figures from real and quoted desalination systems operating in the GCC region. The results show that, while reverse osmosis is the most energy efficient desalination technology, the gap between work and thermally driven desalination technologies is reduced when considered on the basis of primary energy. The results also show that pretreatment with nanofiltration can help to reduce energy requirements. Further, the differences are affected by the thermodynamic efficiency of the power plant itself. Conclusions with regard to hybrid systems are more ambiguous.
|
|---|
