Abstract
In seawater desalination, the energy efficiency of practical processes is expressed in kWh_electricity or low-grade-heat per m3 of water produced, omitting the embedded energy quality underlying their generation processes. To avoid thermodynamic misconceptions, it is important to recognize both quality and quantity of energy consumed. An unmerited quantitative apportionment can result in inferior deployment of desalination methods. This article clarifies misapprehensions regarding seeming parity between electricity and thermal sources that are sequentially cogenerated in power plants. These processes are represented by heat engines to yield the respective maximum (Carnot) work potentials. Equivalent work from these engines are normalized individually to give a corresponding standard primary energy (QSPE), defined via a common energy platform between the adiabatic flame temperature of fuel and the surroundings. Using the QSPE platform, the energy efficiency of 60 desalination plants of assorted types, available from literature, are compared retrospectively and with respect to Thermodynamic Limit.
Highlights
Recent reports of stark gaps between the demand and supply of potable water[1,2,3,4] could inhibit the aspiration for sustainable economic growth
We assumed the average efficiencies of the processes involved in the components of cycle gas turbine (CCGT), i.e., the turbines and heat exchange processes
The co-generation scheme is illustrated in Fig. 3 where electricity is generated by both gas and steam turbines cycles and potable water by seawater desalination processes
Summary
Recent reports of stark gaps between the demand and supply of potable water[1,2,3,4] could inhibit the aspiration for sustainable economic growth. Further to recent report on improvement to potable water flux in membrane seawater desalination processes[25], major improvements in future seawater desalination processes are likely due to innovative methods and processes being developed Such improvements in desalination processes can be achieved either (i) by overcoming material challenges through improved membranebased systems with novel nano-structures materials, better fouling control[26,27,28,29,30,31], and appropriate use of associated models[32,33] and / or (ii) via a better thermodynamic synergy from temperaturecascaded efficient concentrated solar power (CSP) integrated hybrid processes for green electricity generation and heat-driven regenerative multi-effect seawater desalination processes[34,35,36,37,38]. The scope of computations for each and every cycle, stretching from power plants to hybrid separation processes, have been perceived as difficult to follow by many utility planners, engineers and operators
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