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investment point of view, the return period is 25 years, with 6 percent interest. Under these assumptions, and without including the heat and CO 2 recovery, we have calculated the OPEX and capital expenses (CAPEX), which, when summed up, yield the water cost. The OPEX takes into account electricity, gas, chemicals, labor, and maintenance costs. The CAPEX takes into account the cost of the MVC unit, gas engine, and the balance of plant (BoP). As can be seen in the comparison table (above), the operational expenses are reduced by more than 55 percent and the total water cost by 35 percent. With an integrated heat recovery, the costs reduction is even higher. The ROI is approximately one year, which makes this a rewarding proposal for both new and refurbished plants. Enumerating Value 1. Unit efficiency and heat rate improvement a. Waste heat can be recovered from the gas engine to decrease the specific cost of the MVC unit (by minimizing the heat transfer area). b. At the same time, the waste heat can be used for steam production, thus increasing the heat rate of the plant. c. CO 2 can be recovered to the post-treatment (remineralization) process, to decrease the OPEX of the plant. 2. Electric infrastructure minimization — No need for medium voltage transformer, switchgear, MCC, cables, and conduits. 3. Easy refurbishment of existing plants — As weight and dimensions are comparable in size, it is easy to replace the electric motor with a gas engine. As gas prices drop, it becomes evident that integrating a gas engine instead of an electric motor in an MVC unit, in order to drive the centrifugal compressor — the "heart" of the unit — eliminates the need for most of the electricity in the plant. While not inflicting higher costs, the gas engine variation is able to reduce operation costs by more than 55 percent, and the total water cost by a third, with an ROI of about one year. The use of heat recovery will further increase savings and improve the heat rate of the plant. This modification of installing a gas engine is possible in both new and refurbished plants, making it a promising solution for the desalination market. n References 1. Monthly Energy Review - Energy Information Administration. [Online].; 2016 [cited 2016 April 19. Available from: http://www.eia.gov/totalenergy/data/monthly/. 2. U.S. Natural Gas Total Consumption (Million Cubic Feet). [Online].; 2016 [cited 2016 April 19. Available from: https://www.eia.gov/dnav/ng/hist/n9140us2A.htm. 3. Kronenberg G, Lokiec F. Low-temperature distillation processes in single- and dual- purpose plants. Desalination. 2001 May: p. 189-197. 26 wateronline.com n Water Innovations DESALINATION About The Authors Hadar Goshen is the thermal desalination process team leader at IDE Technologies, and has been overseeing advancements in IDE's thermal desalination since 2015. He previously served as a process engineer for five years, where he participated in project process design and worked with external suppliers. Goshen holds two pat- ents for the water vapor deposition process and freeze desalination. Goshen has an M.Sc. in systems engineering from the Technion – the Israel Institute of Technology, and a B.Sc. in mechanical engineering from Tel Aviv University. Tomer Efrat is the process engineering manager at IDE Technologies, where he is responsible for the process design of IDE Technologies' seawater desalination and industrial water treatment plants. Tomer has more than a decade of experience in desalination and treatment of seawater and industrial water. He has been with IDE for more than 10 years, first as a process engineer, and later as deputy manager and manager in the thermal process department. In these positions, Tomer has been closely involved in the commercial activities related to the process design of seawater desalination, industrial water treatment, and ice plants. In addition, he leads a team of highly skilled process engineers in the execution and implementation of the company's R&D program and supports sales and marketing and business development activities. He holds several patents and pend- ing patents for water treatment technologies. Efrat has an MBA and a B.Sc. in mechanical engineering from Tel Aviv University. Parameter Unit MVC Electric MVC Gas Capacity m 3 /day (kgal/day) Electricity kW 450 55 Gas MMBtu/m 3 (MMBtu/kgal) - 0.085 (0.322) OPEX $/m 3 ($/kgal) 1.30 (4.9) 0.55 (2.1) CAPEX M$ 3.7 3.9 Estimated Water Cost $/m 3 ($/kgal) 2.15 (8.15) 1.40 (5.30) 1000 (264) MVC Electric vs. MVC Gas Comparison Chart