Technical and Economic Assessment of Photovoltaic-Driven Desalination Systems

Home , Electrodialysis reversal, Solar desalination

Renewable Energy 35 (2010) 323–328

Contents lists available at ScienceDirect

Renewable Energy

journal homepage: www.elsevier.com/locate/renene

Review Technical and economic assessment of photovoltaic-driven desalination systems

Ali Al-Karaghouli*, David Renne, Lawrence L. Kazmerski

National Renewable Energy Laboratory, 1617 Cole Blvd. Golden, CO 80401, USA article info abstract

Article history: Solar desalination systems are approaching technical and cost viability for producing fresh-water, Received 11 February 2009 a commodity of equal importance to energy in many arid and coastal regions worldwide. Solar photo- Accepted 24 May 2009 voltaics (PV) represent an ideal, clean alternative to fossil fuels, especially for remote communities such Available online 28 June 2009 as grid-limited villages or isolated islands. These applications for water production in remote areas are the ﬁrst to be nearing cost-competitiveness due to decreasing PV prices and increasing fossil fuel prices Keywords: over the last ﬁve years. The electricity produced from PV systems for desalination applications can be Photovoltaic used for electro-mechanical devices such as pumps or in direct-current (DC) devices. Reverse osmosis Desalination Reverse-osmosis (RO) and electrodialysis (ED) desalination units are the most favorable alternatives to be coupled with PV Electrodialysis systems. RO usually operates on alternating current (AC) for the pumps, thus requiring a DC/AC inverter. Brackish-water In contrast, electrodialysis uses DC for the electrodes at the cell stack, and hence, it can use the energy Sea water supplied from the PV panels with some minor power conditioning. Energy storage is critical and batteries are required for sustained operation. In this paper, we discuss the operational features and system designs of typical PV-RO and PV-ED systems in terms of their suitability and optimization for PV operation. For PV-RO and PV-ED systems, we evaluate their electricity need, capital and operational costs, and fresh-water production costs. We cover ongoing and projected research and development activities, with estimates of their potential economics. We discuss the feasibility of future solar desalination based on expected (or predicted) improvements in technology of the desalination and PV systems. Examples are provided for Middle East and other parts of the World. Ó 2009 Published by Elsevier Ltd.

1. Introduction osmotic pressure is applied on salt water (feedwater) passing through the synthetic membrane pores separated from the salt. A Photovoltaic (PV) is a rapidly developing technology with concentrated salt solution is retained for disposal. The RO process is declining costs. And the study of coupling this technology with effective for removing total dissolved solid (TDS) concentrations of desalination methods has increased significantly in the last few up to 50,000 parts per million (ppm), which can be applied for decades. Moreover, the use of this technology is an excellent both brackish-water (1500–10,000 ppm) and seawater (33,000– choice for providing desalinated water for small communities in 45,000 ppm). It is currently the most widely used process for remote arid areas and isolated islands that have access to sea or seawater desalination. brackish-water. The reason includes the economic benefits and The ED process uses electromotive force applied to electrodes the solar system’s modularity, low maintenance, low noise level, adjacent to both sides of a membrane to separate dissolved long life, and non-emission of greenhouse gases [1]. Typical minerals in water. The separation of minerals occurs in an indi- desalination methods that require electricity and could be well vidual membrane called a cell pair, which consists of an anion suited to this technology are reverse osmosis (RO) and electrodi- transfer membrane, cation transfer membrane, and two spacers. alysis (ED). The coupling of these methods with solar PV systems The complete assembly of the cell pairs and electrode is called holds great promise for increasing water supplies in water-scarce a membrane stack. Electrodialysis reversal (EDR) is a similar regions [2]. process, except that the cations and anions reverse to routinely Reverse osmosis is a physical process that uses the osmosis alternate the current flow. In design applications, the polarity is phenomenon, i.e., the osmotic pressure difference between salt reversed four times per hour, which creates a cleaning mecha- water and pure water. In this process, a pressure greater than the nism and decreases the scaling and fouling potential of the membrane. ED and EDR are best used in treating brackish-water

* Corresponding author. Tel.: þ1 303 384 7699; fax: þ1 303 384 6481. with TDS of up to 5000 ppm and are not economical for higher E-mail address: [email protected] (A. Al-Karaghouli). concentrations.

0960-1481/$ – see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.renene.2009.05.018 324 A. Al-Karaghouli et al. / Renewable Energy 35 (2010) 323–328

In this work, we discuss the RO and ED technologies, their diacetate and triacetate blend or a thin-film composite usually performance, research and development (R&D) work, implemented made from polyamide, polysulphone, or polyurea polymers. projects, economics, and expected future applications. A typical industrial SW membrane is about 100–150 cm long and 20–30 cm in diameter. An HF membrane is made from both cellu- 2. Typical PV power system driving RO-ED units lose acetate blends and non-cellulose polymers such as polyamide. Millions of fibers are folded to produce bundles about 120 cm long Any photovoltaic system consists of a number of PV modules, and 10–20 cm in diameter. SW and HF membranes are used to which convert solar radiation into direct-current (DC) electricity. desalt both seawater and brackish-water. The choice between the The voltage and current of the system can be increased by con- two is based on factors such as cost, feedwater quality, and product- necting multiple cells in series and parallel, respectively. The other water capacity. The main membrane manufacturers are in the system equipment includes a charge controller, batteries, inverter, United States and Japan [6]. and other components needed to provide the output electric power The post-treatment system consists of sterilization, stabiliza- suitable to operate the systems coupled with the PV system. PV is tion, and mineral enrichment of the product water. Due to the RO a rapidly developing technology, with costs falling dramatically unit operating at ambient temperature, corrosion and scaling with time, and this will lead to its broad application in all types of problems are diminished compared to distillation processes. systems. Today, however, it is clear that PV-RO and PV-ED will However, effective pretreatment of the feedwater is required to initially be most cost-competitive for small-scale systems where minimize fouling, scaling, and membrane degradation. In general, other technologies are less competitive. the selection of proper pretreatment and proper membrane RO usually uses alternating current (AC) for the pumps, which maintenance are critical for the efficiency and life of the system. means that DC/AC inverters must be used. In contrast, ED uses DC for the electrodes at the cell stack, and hence, it can use the energy 3.2. RO technology deployment supply from the PV panels without major modifications. Energy storage is again a concern, and batteries are used for PV output RO units are available in a wide range of capacities due to their power to smooth or sustain system operation when solar radiation modular design. Large plants are made of hundreds of units that are is insufficient. accommodated in racks. A typical maximum plant capacity is 128,000 m3/day, and very small units (down to 0.1 m3/day) are also 3. PV-RO system used for marine purposes, houses, or hotels. PV power is used for small-size RO units due to initial cost benefits [6]. 3.1. RO technology description Numerous RO plants have been installed for both seawater and brackish-water applications. The process is also widely used in Reverse osmosis is a form of filtration in which the filter is manufacturing, agriculture, food processing, and pharmaceutical a semi-permeable membrane that allows water, but not salt, to pass industries. through. A typical RO system consists of four major subsystems: The total installed capacity of RO units in the United States is pretreatment system, high-pressure pump, membrane module, 32%, followed by 21% in Saudi Arabia, 8% in Japan, and 8.9% in and post-treatment system [3]. Fig. 1 is a schematic diagram of Europe. Some 23% of RO units are manufactured in United States, a PV-RO system. 18.3% in Japan, and 12.3% in Europe [7]. Feedwater pretreatment is a critical factor in operating an RO system because membranes are sensitive to fouling. Pretreatment commonly includes sterilizing feedwater, filtering, and adding 3.3. PV-RO systems applications chemicals to prevent scaling and bio-fouling. Using a high-pressure pump, the pretreated feedwater is forced PV-powered reverse osmosis is considered one of the most- to flow across the membrane surface. RO operating pressure ranges promising forms of renewable-energy-powered desalination, from 17 to 27 bars for brackish-water and from 55 to 82 bars for especially when it is used in remote areas. Therefore, small-scale seawater. Part of the feedwaterdthe product or permeate water- PV-RO has received much attention in recent years and numerous dpasses through the membrane, which removes the majority of demonstration systems have been built. Two types of PV-RO the dissolved solids [4]. The remainder, together with the rejected systems are available in the market: brackish-water (BWRO) and salts, emerges from the membrane modules at high-pressure as seawater (SWRO) PV-RO systems. Different membranes are used a concentrated reject stream (brine). The energy efficiency of for brackish-water and much higher recovery ratios are possible, seawater RO depends heavily on recovering the energy from the which makes energy recovery less critical [8]. pressurized brine. In large plants, the reject brine pressure energy is recovered by a turbine (Peloton-wheel turbines are commonly 3.3.1. Brackish-water PV-RO systems used), recovering 20% to 40% of the consumed energy. Brackish-water has a much lower osmotic pressure than The RO membrane is semi-permeable, possessing a high degree seawater; therefore, its desalination requires much less energy and of water permeability, but presents an impenetrable barrier to salts. a much smaller PV array in the case of PV-RO. Also, the lower It has a large surface area for maximum flow and is extremely thin pressures found in BWRO systems permit the use of low-cost plastic so that it offers minimal resistance to water flow; but it is also components. Thus, the total cost of water from brackish-water PV- sturdy enough to withstand the pressure of the feed stream [5]. RO is considerably less than that from seawater, and systems are Polymers currently used for manufacturing RO membranes are beginning to be offered commercially [9]. Table 1 presents infor- based on either cellulose acetates (cellulose diacetate, cellulose mation on installed brackish-water PV-RO systems [10–15]. triacetate, or combinations of the two) or polyamide polymers. Two Many of the early PV-RO demonstration systems were essen- types of RO membranes commonly used commercially are spiral- tially a standard RO system, which might have been designed for wound (SW) membranes and hollow-fiber (HF) membranes. Other diesel or mains power, but powered from batteries charged by PV. configurations, including tubular and plate-frame designs, are This approach generally requires a rather large PV array for a given sometimes used in the food and dairy industries. SW membrane flow of product because of poor efficiencies in the standard RO elements are most commonly manufactured from a cellulose systems and batteries. Large PV arrays and the regular replacement A. Al-Karaghouli et al. / Renewable Energy 35 (2010) 323–328 325

Fig. 1. A schematic diagram of a PV-RO system. of batteries typically make the cost of water from such systems between seawater and brackish-water desalination, the cost of the rather high. first is about 3–5 times the cost of the second for the same plant size. 3.3.2. Seawater PV-RO application systems As a general rule, a seawater RO unit has low capital cost and The osmotic pressure of seawater is much higher than that of significant maintenance cost due to the high cost of the membrane brackish-water; therefore, its desalination requires much more replacement. The cost of the energy used to drive the plant is also energy, and, unavoidably, a somewhat larger PV array. Also, the significant. The major energy requirement for RO desalination is for higher pressures found in seawater RO systems require mechan- pressurizing the feedwater. Energy requirements for SWRO have ically stronger components. Thus, the total cost of water from been reduced to about 5 kWh/m3 for large units with energy seawater PV-RO is likely to remain higher than that from recovery systems, whereas for small units (without energy- brackish-water, and systems have not yet passed the demon- recovery system), this may exceed 15 kWh/m3. For brackish-water stration stage. Table 2 shows some of the installed seawater desalination, the energy requirement is between 1 and 3 kWh/m3. PV-RO plants [10–15]. The product water quality ranges between 350 and 500 ppm for both seawater and brackish-water units. According to published 3.4. PV-RO system economics reports [10–15], the water cost of a PV seawater RO unit ranges from 7.98 to 29 US$/m3 for product-water capacity of 120–12 m3/day, Cost figures for desalination have always been difficult to obtain. respectively. Also for a PV-RO brackish-water desalination unit, The total cost of water produced includes the investment cost, as a water cost of about 7.25 US$/m3 for a product-water capacity of well as the operating and maintenance cost. In a comparison 250 m3/day has been reported in the literature [10–15].

Table 1 Brackish-water RO plants driven by PV power.

Location Feed water ppm Capacity m3/day PV kWp Batteries kWh Energy Consumption kWh/m3 Water Cost USS/m3 Year Sadous Riyadh, SA 5800 15 10.08 264 1994 Magan. Isrea; 4000 3 3.5 þ 0.6 wind 36 11.6 1997 Elhamarawien, Egypt 3500 53 19.8 þ 0.64 control 208 0.89 1986 Heelafar Rahab Oman 1000 5 3.25 9.6 6.25 1995 White Cliffs, Australia 3500 0.5 0.34 None 2–8 Solar ﬂow, Australia 5000 0.4 0.12 None 1.86 10–12 Hassi-Kheba, Algeria 3200 0.95 2.59 10 INETI, Lisbon, Portugal 5000 0.1–0.5 0.05–0.15 None 2000 Conception del Oro, Mexico 3000 0.71 2.5 None 6.9 1982 Thar desert, India 5000 1 0.45 1 kWh/kg salt 1986 Perth Australia BW 0.4–0.7 1.2 4–5.8 1989 Gillen Bore, Australia 1600 1.2 4.16 None 1996 Wano Road, Australia BW 6 Kasir Ghilen, Tunis 5700 50 7.25 2006 Coite-Pedreias, Brazil BW 0.25 1.1 9.6 3–4.7 14.9 Mesquire, Nevada 3500 1.5 0.4 1.38 3.6 2003 N. Jawa, Indonesia BW 12 25.5 Univ. of Almeria, Spain BW 2.5 23.5

Refs. [8–15]. 326 A. Al-Karaghouli et al. / Renewable Energy 35 (2010) 323–328

Table 2 Seawater RO plants driven by PV power.

Location Feed water ppm Capacity m3/day PV kWp Batteries kWh Energy Consumption kWh/m3 Water Cost USS/m3 Year Lampedusa, Italy SW 40 100 880 5.5 9.5 1990 Jeddah, S. Arabia 42,800 3.2 8 1981 St. Luice, FL 32,000 0.64 2.7 13 1995 Doha, Qatar 35,000 5.7 11.2 None 10.6 Cress, Laviro, Greece 36,000 <14þ 0.9 wind 44 33 2001 ITC Canaries Island, Spain SW 3 4.8 19 5.5 13 1998 Crest, UK SW 0.5 L/h 1.54 None 4.2 2003 Vancouver, Canada SW 0.5–1.0 0.48 Ponta Libeco, Italy SW 9.8 1993

Refs. [8–15].

4. PV-ED system membranes. This inhibits deposition of inorganic scales and colloidal substances on the membranes without the addition of 4.1. ED technology description chemicals to the feedwater. This development enhances the viability of this process considerably because the process is now ED is an electrochemical process and a low-cost method for self-cleaning. In general, EDR requires minimum feedwater the desalination of brackish-water. Due to the dependency of the pretreatment and minimum use of chemicals for membrane energy consumption on the feedwater salt concentration, the ED cleaning [18]. process is not economically attractive for desalinating seawater. In the ED process, ions are transported through a membrane by an 4.2. ED technology deployment electrical field applied across the membrane. An ED unit consists of the following basic components: pretreatment system, ED has been in commercial use since 1954, more than ten years membrane stack, low-pressure circulation pump, power supply before RO. Since then, this process has seen widespread applica- for direct-current (rectifier or PV system), and post-treatment tions, with the production of potable water as one of the most system. Fig. 2 shows a schematic diagram of a PV-powered ED important. Due to its modular structure, ED is available in system [16]. a wide range of sizes, from small (down to 2 m3/d) to large The principle of ED operation is as follows: electrodes (generally (145,000 m3/day) capacities. ED is widely used in the United States, constructed from niobium or titanium with platinum coating) are which has 31% of the total installed capacity. In Europe, the ED connected to an outside source of direct-current (such as a battery process accounts for 15% and the Middle East have 23% of the total or PV source) in a container of salt water. The electrical current is installed capacity. carried through the solution, with the ions tending to migrate to The EDR process was developed in the early 1970s. Today, the the electrode with the opposite charge. Positively charged ions process is used in 1100 installations worldwide. Typical industrial migrate to the cathode and negatively charged ions migrate to the users of EDR include power plants, semiconductor manufacturers, anode. Salinity of the water is removed as water passes through the pharmaceutical industry, and food processors. The installed ion- selective membranes positioned between the two electrodes PV-ED units are only of small capacity and are used in remote (see Fig. 3). areas. These membranes consist of flat-sheet polymers subjected to special treatment in which micro-sized cracks or crevices are 4.3. PV-ED applications produced in the plastic film surface. These crevices permit the transport of ions, while ion-exchange sites incorporated into the Currently, there are several installations of PV-ED technology membrane’s polymer matrix promote membrane selectivity. worldwide. All PV-RD applications are of a stand-alone type, and Anion-permissible membranes allow anions to pass through to the several interesting examples are discussed below. positively charged electrode, but reject cations. Conversely, cation- In the city of Tanote, in Rajasthan, India, a small plant was permissible membranes allow cations to pass through to the commissioned in 1986 that features a PV system capable of negatively charged electrode, but reject anions. providing 450 Wp in 42 cell pairs. The ED unit includes three stages, Between each pair of membranes, a spacer sheet is placed to producing 1 m3/d water from brackish-water (5000 ppm TDS). The permit water flow along the face of the membrane and to induce unit energy consumption is 1 kWh/kg of salt removed [16]. a degree of turbulence. One spacer provides a channel that carries A second project is a small experimental unit in Spencer Valley, feedwater (and product water), while the next spacer carries New Mexico (USA), where two separate PV arrays are used: two brine. By this arrangement, concentrated and diluted solutions are tracking flat-plate arrays (1000 Wp power, 120 V) with DC/AC created in the spaces between the alternating membranes. ED inverters for pumps, plus three fixed arrays (2.3 kWp, 50 V) for ED cells can be stacked either horizontally or vertically. In practice, supply. The ED design calls for 2.8 m3/d product water from a feed several membrane pairs are used between a single pair of elec- of about 1000 ppm TDS. This particular feedwater contains trodes, forming an ED stack. Feedwater passes simultaneously in uranium and radon, apart from alpha particles. Hence, an ion- parallel paths through all the cells, providing a continuous flow of exchange process is required prior to ED. Unit consumption is product water and brine out of the stack. Stacks on commercial ED 0.82 kWh/m3 and the reported cost is 16 US$/m3 [17]. A third plants contain a large number of cell pairs, usually several project is an unusual application in Japan, where PV technology is hundred [17]. used to drive an ED plant fed with seawater, instead of the usual A modification to the basic ED process is electrodialysis reversal. brackish-water of an ED system. The solar field consists of 390 PV An EDR unit operates on the same general principle as a standard panels with a peak power of 25 kWp, which can drive a 10 m3/d ED ED plant, except that the product and brine channels are both unit. The system, located on Oshima Island (Nagasaki), has been identical in construction. In this process, the polarity of the elec- operating since 1986. Product-water quality is reported to be below trodes changes periodically in time, reversing the flow through the 400 ppm TDS, and the ED stack is provided with 250 cell pairs. A. Al-Karaghouli et al. / Renewable Energy 35 (2010) 323–328 327

Fig. 2. A schematic diagram of a PV-ED system.

4.4. PV-ED economics 4 kWh/m3 for a feedwater of 1500–3500 ppm TDS, respectively. The water cost of a PV-operated ED unit ranges from 16 to In general, electrodialysis is an economically attractive process 5.8 US$/m3 [16,17]. The main advantage of PV desalination systems for low-salinity water. EDR has greater capital costs than ED is the ability to develop small-scale desalination plants. because it requires extra equipment (e.g., timing controllers, automatic valves), but it reduces or almost eliminates the need for 5. Recommendations for overcoming PV-(RO/ED) chemical pretreatment. In ED applications, the electricity from a PV deployment barriers system can power to electro-mechanical devices such as pumps or to DC devices such as electrodes. The total energy consumption of Research and development have shown that PV-RO and PV-ED an ED systemdunder ambient temperature conditions and systems are the most suitable solution for decentralized water assuming product water of 500 ppm TDSdwould be about 1.5 and desalination in rural regions. Numerous pilot plants are operating

Fig. 3. Ion exchange in an ED system. 328 A. Al-Karaghouli et al. / Renewable Energy 35 (2010) 323–328 today, and commercial-sized plants will follow soon once some from technical and economic perspectives. In particular, we need technical and non-technical barriers are overcome. When consid- much stronger R&D efforts, more installations, and close collabo- ering whether to use PV-powered desalination systems, the ration between R&D organizations and industry. This work will lead primary barrier is the cost of water production. This cost can be to reliable, compact renewable energy devices for the market at reduced by several methods, such as the following: a reasonable cost. Other non-technical barriers will be overcome by accelerating information dissemination, education, and installation Appropriate investment incentives to expand the PV market by and maintenance training. lowering PV system device prices. The high initial cost of PV equipment must be lowered while technology is close to maturity. References Improve the performance of PV system devices. Further d research is needed to increase efficiency, decrease price, and [1] Water desalination technologies in the ESCWA member countries economic and social commission for Western Asia, UN report, http://www.escwa.org.ib/ improve the already impressive lifetime of solar cells. Some information/publications/division/docs/tech-01-3-e. other measures to address PV system performance and to [2] ARMINES. Technical and economic analysis of the potential for water desali- lower the cost include the following: nation in the Mediterranean region, RENA-CT94–0063, France; 1996. [3] Maurel A. Desalination by reverse osmosis using renewable energies (Solar- - Use a DC positive-displacement pump and energy-recovery wind): cadarache central experiment. In: Proceedings of the new technologies device for water pumping. for the use of renewable energy sources in water desalination conference, - Use fluid systems for cooling PV panels and heating feed session II, Athens, Greece; 1991. p. 17–26. [4] Richards BS, Schafer IA. Design considerations for a solar-powered desalina- water to reduce the energy requirement and to improve PV tion system for remote communities in Australia. Desalination 2002;144: performancedand, hence, reduce the size of the PV system 193–9. and its initial cost. Preheat the feed water, results in increased [5] Avlonitis SA, Kouroumbas K, Vlachakis N. Energy consumption and membrane replacement cost for seawater RO desalination plants. Desalination permeate water output by about 20–30 percent. 2003;157:151–8. - Use a linear current booster to allow the system to function at [6] Avlonitis S, Sakellaropoulos GP, Hanbury WT. Optimal design of spiral wound low light conditions. This improves the energy output of the modules: an analytical method. Trans I ChemE 1995;73(Part A):575–80. system by 15% to 20%. [7] European Commission. Desalination guide using renewable energies, Thermie Programme, Directorate General for Energy (DG XVII), ISBN 960-90557-5-3; - Improve membrane performance and extend life expectancy. 1998. Increase the awareness of and expertise about installation, [8] Thomson M, Gwillim J, Rowbottom A, Draisey I, Miranda M. Batteryless operation, and maintenance through intense education and photovoltaic reverse osmosis desalination system, S/P2/00305/REP, ETSU, DT1, UK. training activities. [9] Fiorenza G, Sharma V, Braccio G. Technoeconomic evaluation of a solar powered water desalination plant. Energy Convers Manage 2003;44:2217–40. 3 6. Conclusions [10] Kehal S. Reverse osmosis unit of 0.85 m /h capacity driven by photovoltaic generator in South Algeria. In: Proceedings of the new technologies for the use of renewable energy sources in water desalination conference, session II, Desalination systems that incorporate renewable energy Athens, Greece; 1991. p. 8–16. resources are still far from achieving their full potential. But tech- [11] Tzen E, Perrakis K. Prefeasibility study for small Aegean islands, RENA-CT94– 0063, CRES, Greece; 1996. nological advancements will continue to improve these systems [12] Thomson M, Infield D. A photovoltaic powered seawater reverse-osmosis that benefit a growing market. Several studies [1,2,8,9,15] on system without batteries. Desalination 2002;153:1–8. a suitable technical match between renewable energy resources [13] Hafez A, El-Manharawy S. Economics of seawater RO desalination in the Red Sea region, Egypt. Part 1: a case study. Desalination 2003;153:335–47. and desalination processes propose that PV-RO and PV-ED tech- [14] Perrakis K, Tzen E, Baltas P. PV-RO desalination plant in Morocco, JOR3-CT95- nologies are very promising among the existing options. At present, 0066, CRES, Greece. small-scale PV/desalination systems appear to be especially suit- [15] Finken P, Korupp K. Water desalination plants powered by wind generators able in remote regions without access to the electric grid, where and photovoltaic systems. In: Proceedings of the new technologies for the use of renewable energy sources in water desalination conference, session II, water scarcity is a major problem, and solar radiation is high. The Athens, Greece; 1991. p. 65–98. large-scale implementation of these systems is still hindered by [16] Adiga MR, Adhikary SK, Narayanan PK, Harkare WP, Gomkale SD, Govindan KP. non-technical barriers. For example, the high investment cost of Performance analysis of photovoltaic electrodialysis desalination plant at Tanote in the Thar desert. Desalination 1987;67:59–66. renewable energy-based desalination plants could be overcome by [17] Kuroda O, Takahashi S, Kubota S, Kikuchi K, Eguchi Y, Ikenaga Y, et al. An appropriate investments to expand the market of such systems and electrodialysis seawater desalination system powered by photovoltaic cells. provide a competitive option. Although there is experience in PV- Desalination 1987;67:161–9. d [18] Lichtwardt M, Remmers H. Water treatment using solar powered electrodi- RO and PV-ED desalination systems and successful applications alysis reversal. In: Proceedings of the mediterranean conference on renewable do existdthere is still much room for improving these technologies energy sources for water production; 1996.