Desalination Energy efficiency

The performance ratio of ME plants is just slightly lower than the number of effects, which is deterrnined as an optimized compromise between energy efficiency and capital cost. Six effects ate typical, although plants with as many as 18 effects have been built. Eurther detail about ME desalination can be found in (56,59). 

Membrane technology is already recognized as the best choice for water desalination since thermal options for desalting are about 10 times less energy efficient [1, 4]. 

VC plants are of small (<4,000 m /d) capacity and relatively high energy efficiency, the latter depending on the number of effects incorporated, eg, a two-effect plant had an energy use of 57 kj per 1 water produced. Further detail about VC desalination can be found in References 48, 55, 56, and 60. 

Reverse osmosis membrane is widely used in seawater and brackish water desalination processes. Compared to traditional distillation, there is no energy-intensive phase change involved in membrane processes. Therefore, desalination with RO membrane is more energy efficient. In addition to the traditional desalination processes, RO membranes have also found wide application in industrial and municipal wastewater treatment, in pure water production for the electronic and pharmaceutical industries, and in the food industries. 

While membrane processes have infiltrated many process schemes, prohahly the most extensive replacement has been in the area of water treatment. For example, reverse osmosis has largely replaced distillation/evaporation for the production of drinking water from seawater [41,42]. Clearly, with the right mix of material properties, efficient process designs, and economic drivers, energy-efficient membrane processes can replace conventional thermally driven separation processes. Later in this chapter, desalination will be a featured example. 

In recent years reverse osmosis membranes have become the most popular desalination technology because of their high energy efficiency. To improve the separation features of polyamide films, typically used as a selective layer, different fillers have been dispersed in the polymer phase. The in situ dispersion of the nanoparticles during the interfacial polymerization reaction of the polyamide layer is reported to be able to achieve a suitable dispersion. 

Sanchez Fernand ez E, Geerdink P and Goetheer E L V (2010), Thermo pervap the next step in energy efficient pervaporation . Desalination, 250,1053-1055... 

One of the most attractive features of electrodialysis is its energy efficiency. The electric current A needed to desalinate a solution is directly proportional to the quantity of ions transported through the membranes and is given by the equation... 

Farid Benyahia (immobilized nitrifiers in wastewater treatment membrane distillation desalination water quality and energy efficiency analysis airlift bioreactors low-grade heat in membrane distillation for freshwater production bioremediation of oil spills development, design and evaluation of advanced refinery wastewater treatment processes), College of Engineering, Department of Chemical Engineering, Qatar University (QU), Doha... 

Malhson, Ahssa, Study shows forward osmosis desalination not energy efficient, MIT Press, http //newsoffice.mit.edu/2014/study-shows-forward-osmosis-desalination-not-energy-efficient, July 33, 2014, accessed December 23,2014. 

S. Sarkar, A.K. SenGupta. A new hybrid ion exchange-nanofiltration (HIX-NF) separation process for energy-efficient desalination Process concept and laboratory evaluation, Journal of Membrane Science 324 (2008) 76-84. 

Solar cells, 22 220, 9 729, 23 32. See also Photovoltaic (PV) cells antimony compounds, 3 53-54 dye-sensitized, 26 878 degradation of, 22 139 economics of, 22 140 efficiency of, 23 15 for electricity generation, 23 26 hydrogenated amorphous silicon in, 22 135, 136, 138-139 materials for, 23 14-15 micromorph, 22 140 polymethine dyes in, 20 516-517 silicon for, 22 507-508 silicon purification for, 22 496 stacking, 23 38-39 vitreous silica in, 22 444 Solar collectors, 23 25 Solar constant, 23 2 Solar control coatings, 23 16 Solar desalination, 26 89-94 Solar electricity, 23 51, 52 Solar energy... 

Several schemes have been put forth in the past for desalinization by use of electrolysis. They had been discarded because of the large amounts of energy required. The idea was resurrected in anticipation of much more efficient recovery of energy through the use of fuel cells. 

Desalination processes may be characterized by their effluents emitted to the environment, the land and atmosphere nearby, and the sea. Desalination is highly dependent on energy, and generally uses fossil energy. All types of air pollution associated with energy production, namely, the emission of NOx, S02, volatile compounds, particulates and C02, also exist through the use of electricity produced by conventional power stations or by a dedicated power station. Using gas turbines may increase efficiency and therefore reduce pollutants. 

A 100-million-m3 RO-based seawater desalination plant requires an electrical energy supply of less than 50 MW. A dedicated power station can work at a much higher efficiency than a regular power station for this purpose since it is operated constantly without the known sine wave, representing day-night, summer-winter... 

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