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Seawater desalination driven by renewable energies: a review
DESALINATION Desalination 143 (2002) 103-l 13
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Seawater desalination driven by renewable energies: a review Lourdes Garcia-Rodriguez Departamento Fisica Fundamental y Experimental, Universidad de La Laguna, 38205 La Laguna (Tenerifs), CanaT Islands, Spain Tel. +34-922-318303. Fax: +34-922- 318228; email: [email protected] Received 21 June 2001; accepted 17 December 200 1
Abstract This paper deals with seawater desalination systems driven by renewable energies. A review of pilot plants and perspectives of development is presented. There are many reasons why the use of renewable energies in seawater desalination is suitable, especially for remote areas where conventional energy supply and skilled workers are not usually available. Nevertheless, desalination systems driven by renewable energies are scarce and they tend to have a limited capacity. Keyword:
Seawater desalination; Renewable energies; Wind power; Solar energy
1. Introduction
The increasing use of desalination due to demographic and industrial growth makes necessary a parallel increasing of energy sources. Desalination systems driven by renewable energies are scarce, and they usually have a limited capacity. They only represent about 0.02% of total desalination capacity [l]. However, many reasons make the use of renewable energies suitable for seawater desalination: l Plant location. Many arid regions are coastal areas and renewable energy sources are available. l Seasonal changes. Often freshwater demand 001 l-9164/02/$-
increases due to tourism, which is normally concentrated at times when the renewable energy availability is high, especially in the case of solar energy. Energy availability. Conventional energy supply is not always possible in remote areas or little islands: on the one hand because of difficulties in fossil fuel supply, and on the other because the grid does not exist or the available power is not enough to drive a desalination plant. In such cases, the use of renewable energies permits sustainable socioeconomic development by using local resources.
See front matter 8 2002 Elsevier Science B.V. All rights reserved
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Self-sufficiency. Renewable energies allow energetic diversification and avoid external dependence on energy supply. These aspects are important, especially in the least developed countries, which moreover have unstable governments. Technology. The development and commercialisation of desalination systems driven by renewable energies make possible technology exportation and cooperation among countries with low development. Environmental impact. Seawater desalination processes are strongly energy consuming. Therefore, the environmental effects of the fossil fuels consumed are important. Note that total world-wide capacity of desalted water is about 23 x 1O6m3/d [2]. Economics. On several Mediterranean islands, fresh water requirements make necessary the transport of fresh water by ship, with high costs and improper hygienic conditions. Operation and maintenance. The operation and maintenance of renewable energy systems are normally easier than conventional energy ones. Therefore, they are suitable for remote areas. Promising commercial perspectives. The cost reduction of renewable energy systems has been significant during the last decades. Therefore, future reductions as well as the rise of fossil fuel prices could make possible the competitiveness of seawater desalination driven by renewable energies. Renewable energies are found in nature: solar radiation, wind, energy of life beings, of the sea, or the thermal energy of the earth. Since ancient times humans have used some of these energy sources, but the main development of renewable energy systems was due to the petroleum crisis of 1973. Besides that, the increasing preoccupation about the environment has increased the use of renewable energies. Nevertheless, their main limitations are their space and temporal changes,
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the high land requirements and investment costs of renewable energy facilities, in spite of their low operation costs. To avoid the fluctuations inherent in renewable energies, different energy storage systems may be used (see [3]). Nowadays, several renewable energy technologies are mature enough and may be competitive with conventional energies. Some others are still under development or research. With regard to coupling seawater desalination technologies to renewable energy systems, it is important to take into account different aspects: thermodynamic considerations (see [4,5]), specific characteristics of the system location and economic evaluations. If the desalination system is going to be installed in a remote area, the technology selection may be done according to the criteria given by Abdul-Fattah [6]: simplicity, easy handling, availability, maturity of the technology, guarantee of fresh water production, suitability of the system to the characteristics of the location, possibility of future increase of the system capacity, efftciency, among others.
2. Thermal solar energy Solar energy is one of the most promising applications of renewable energies to seawater desalination, Several reviews of solar desalination have been published [ 1,7-l 01; an interesting comparison of such systems is given in [ 1l-141, and finally references [ 15-201 deal with the present status and economics of solar desalination. A solar distillation system may consist of two separate devices, the solar collector and the distiller - indirect solar desalination - or of one integrated system - direct solar desalination. Small production systems such as solar stills may be used wherever fresh water demand is low and land is inexpensive. High fresh water demands require industrial-capacity systems. These systems consist in a conventional seawater
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distillation plant coupled to a thermal solar system. Many small systems of direct solar desalination and several pilot plants of indirect solar desalination have been designed and implemented [8,21-231. Table 1 shows indirect solar desalination pilots. A multi-stage flash (MSF) or a multi-effect distillation (MED) plant may be selected for solar thermal desalination. MSF is the most mature technology. Nevertheless, Massarani and Fusetti [24] proposed technological improvements and Sommariva et al. [25] analysed an innovative configuration for MSF desalination. Nevertheless, MED has greater potential than MSF for designs with high performance ratio [26] and, moreover, MED processes appear to be less sensitive to corrosion and scaling than the MSF process [27]. Several
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authors discussed the costs of solar MED [28-3 l] and MSF [ 18,321 desalination. A few parabolic trough collector desalination plants have been implemented and tested [8]. At the Plataforma Solar de Almeria (PSA), Spain [22], a parabolic trough solar field was connected to a MED plant. At the second phase of the project, a double-effect absorption heat pump was coupled to the solar desalination plant. Several authors have studied the coupling of heat pumps and the design of new solar heat pumps: Slesarenko [33], Gunzbourg et al. [34] and Hulin et al. [35]. Solar flat-plate collectors had been used in a few solar desalination pilot plants [8, 211. With regard to evacuated tube collectors, El-Nashar [44] and Madam [36] reported solar desalination experiences using the MED process.
Table 1 Solar distillation plants m3/d
Solar collectors
ME, 14 effects
40
Evacuated tube
ME, 18 effects
120 25 20
Evacuated tube
Plant location
Desalination process
La Desired Island, French Caribbean [36] Abu Dhabi, UAE [21] Kuwait [S]
MSF RO
Kuwait [8,23] La Paz, Mexico [8,23]
MSF auto-regulated MSF, 10 stages
Arabian Gulf [S]
ME
Al-Ain, UAE [37]
ME, 55 stages; MSF, 75 stages
Takami Island, Japan [S]
ME, 16 effects MSF
Margarita de Savoya, Italy [S] El Paso, Texas [23] Berken, Germany [38] Lampedusa Island, Italy [39] Islands of Cape Verde [40] University of Ancona, Italy [41] PSA, Almeria, Spain [23,42] Gran Canaria, Spain [43] Area of Hzag, Tunisia [23] Safat, Kuwait [23] Near Dead Sea [23]
MSF MSF MSF Atlantis “Autoflash” ME, TC ME, heat pump MSF Distillation MSF MED
100 10
Solar electricity generation system Parabolic trough Flat plate + parabolic trough
6000
Parabolic trough
500
Parabolic trough
16 50-60 19 20 0.3 300 30 72 10 0.1-0.35 10
Flat plate Solar pond Solar pond Low concentration Solar pond Solar pond Parabolic trough Low concentration Solar collector Solar collector Solar pond
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On the other hand, different plants have been implemented coupling a solar pond to a MSF [40] or a MED plant [41]. In solar distillation plants, the seawater or brine preheated by the distillation plant absorbs the thermal energy delivered by the heat storage zone of the solar pond. In addition, the thermal energy delivered by a salinity-gradient solar pond has been used, not only in seawater distillation plants, but also in seawater and brackish water reverse osmosis (RO) desalination [45]. Lu et al. [46] described a solar-pond- powered desalination plant at El Paso (USA). The solar pond drives both a thermal desalination and RO plants. Since the standard MSF process is not able to operate coupled to any variable heat source, the Atlantis Company developed an adapted MSF system called “Autoflash”. It can be connected to a solar pond [40]. Tleimat and Howe [47] analysed a MED plant driven by thermal energy delivered by a solar pond. Safi and Korchani [48] analysed the cost of dual plants connected to a solar pond. In addition, several authors [49,50] have selected solar-pond-powered desalination as one of the most cost-effective systems. Finally, Rajvanshi [5 l] has designed a special solar collector to be connected to a MSF distillation plant. Hermann et al. [52] reported the design and test of a corrosion-free solar collector for driving ME humidification. The pilot plant was installed at Pozo Izquierdo (Gran Canaria, Spain) [53]. With regard to direct solar desalination Fath [54] gives a valuable review. In most cases, such systems consist of a solar still or a compact desalination collector (CDC). Le Goff et al. [55] give different designs for a CDC, and Boeher [56] presented a “high-efficiency water distillation of humid air with heat recovery” with a capacity range of 2-20 m3/d. On the other hand, the distillation temperature in a solar still may be increased by the connection of a flat-plate collector field [57-591. Other interesting designs
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of direct solar desalination systems are given in references [60-65]. Solar electricity generation may be also used for seawater desalination. A solar-assisted freezing plant was installed at Yanbu, Saudi Arabia, as part of the SOLERAS project [66]. The solar collector field consists in 380 point-focusing collectors with two axes for sun tracking [66]. Furthermore, the shaft power from thermal solar energy may drive a RO process or mechanic vapour compression. A prototype of a RO plant was implemented with flat-plate collectors with freon as the working fluid [5]. Childs et al. [67] presented a system designed for the connection of a thermal solar collector to a RO plant.
3. Solar photovoltaic
energy
Solar energy may be directly converted into electricity by photovoltaic conversion. Photovoltaic cells usually consist of silicon though other semiconductors may be used. There are technologies for thin and thick film. In industrial production, efficiencies of 13-15% may be reached on monocrystalline silicon cells and 1O11% on polycrystalline silicon cells. The latter are less expensive than the former. There are also amorphous silicon cells, which are thin-film cells. Efficiencies between 18% and 24% have been reached with monocrystalline and polycrystalline silicon technologies. In cells of GaAs and its alloys, as GaInP,, efficiencies higher than 30% (ultrahigh-efficiency) have been reached
[W. The main points in research of photovoltaic cells are the increase in efficiency, the reduction of manufacturing costs and the search for other materials as GaAs, CdS, CdTe and CuInSe, (CIS). CIS is sensible to the part of the red and infrared spectrum that the amorphous silicon does not absorb. On the other hand, CIS offers other interesting possibilities [69].
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Solar photovoltaic energy is a mature technology, whose main problem is its high cost. This technology has been developed largely using stand-alone systems. The connection of photovoltaic cells to membrane processes in desalination could be an interesting alternative in remote areas. Nevertheless, RO presents significant requirements for chemicals, spare parts and skilled workers. In remote areas, the eletrodialysis process is most suitable for brackish water desalination because it is more robust and its operation and maintenance are simpler than in the case of RO. Photovoltaic technology connected to a RO system is currently commercial. The distance at which the photovoltaic energy is competitive with conventional energy depends on the plant capacity, the distance to the electric grid and the
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salt concentration of the feed. With regard to solar desalination facilities, Table 2 shows the values for RO-photovoltaic plants. Several pilot plants using electrodialysis systems connected to photovoltaic cells by means of batteries have been implemented. One of them was installed at the Spencer Valley, near Gallup (New Mexico). It was developed by the US Bureau of Reclamation [23,70]. Some others were installed at [23]: l Thar desert, India (1 m3/d, brackish water); l Ohsima Island, Nagasaki (10 m3/d, sea water); Fukue city, Nagasaki (8.33 m3/h, brackish water); l Spencer Valley, New Mexico, USA (2.8 m3/d, brackish water) The use of a hybrid wind-solar system to drive a desalination unit is a promising alternative
Table 2 Reverse osmosis plants driven by photovoltaic cells Plant location
Salt concentration
Plant capacity
Photovoltaic system
Jeddah, Saudi Arabia [8,23]
42800 ppm
3.2 m’ld
Conception de1 Oro, Mexico [8] North of Jawa [8]
Brackish water Brackish water
1.5 m’/d 12 m3/d
8 kW peak 2.5 kW peak
Red Sea, Egypt [23,70]
Brackish water
50 m’/d
Has&Khebi,
(4.4 g/l) Brackish water
0.95 m’/h
25.5 kW peak 19.84 kW peak (pump), 0.64 kW peak (control equipment) 2.59 kWp
Argelie [23,72]
Cituis West, Jawa, Indonesia [23]
(3.2 g/l) Brackish water
1.5 m’/h
25 kWp
OS-O.1 m’/h -
1.2 kWp 6 kWp
Seawater
0.5-l m’/d 5.7 m’ld
4.8 kWp 11.2 kWp
Thar desert, India [23] North west of Sicily, Italy [23]
Brackish water Seawater
1 m’/d -
0.45 kWp
St. Lucie Inlet State Park, FL, USA [23] Lipari Island, Italy [23] Lampedusa Island, Italy [23] University of Almerla, Spain [23,71]
Seawater Seawater Seawater Brackish water
2x0.3 m’/d 2 m’/h 3+2 m’ih 2.5 m3/h
Perth, Australia [23] Wan00 Roadhouse, Australia [23] Vancouver, Canada [23] Doha, Qatar [23]
Brackish water Brackish water Seawater
9.8 kWp + 30 kW diesel generator 2.7 kWp + diesel generator 63 kWp 100 kWp 23.5 kWp
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because of the complementary characteristics of both energy sources and because many coastal areas have suitable wind and solar resources. One of such systems was designed in the frame of the SOLERAS project. Moreover, the Cadarache Centre (France) designed another unit that was installed in 1980 at Borj-Cedria, Tunisia [70]. The system consists of a 0.1 m3/d compact solar distiller, with a 0.25 m3/h RO plant and an electrodialysis plant for 4 g/l brackish water. The energetic system consists of a photovoltaic field of 4 kW peak and a wind turbine of 4 kW. Other systems have been designed and implemented [23,74] (see also [75]).
4. Wind power Wind turbines may be classified depending on their nominal power (Pn) as very low power (Pn < 10 kW), low power (Pn < 100 kW), medium power (100 kW < Pn < 0.5 MW) and high power (Pn> 0.5 MW) [76] turbines. All are mature technologies and they are commercially available except for the high power systems, which still require several adjustments. In spite of such maturity, new control strategies may increase the output of the wind turbine [77]. Coastal areas have a high availability of wind power resources, and wind power is the most competitive renewable energy technology in power generation. Therefore, wind powereddesalination is a promising alternative. RO is the desalination process with the lowest energy requirements. Conventional systems are designed for their connection to the grid. Otherwise, shaft power may be directly used for driving a desalination plant. The fluctuations of wind power would ruin the RO system. Therefore, an intermediate energy storage system would be necessary, but it would reduce the available energy and would increase the cost of the plant. The main drawback of RO in remote areas is the complex pre-treatment, the require-
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ment of skilled workers, chemicals and membrane replacement. A preliminary cost evaluation of wind-powered RO is presented in [78]. Desalination systems driven by wind power are the most frequent renewable energy desalination plants. Some are described below. In 1984 a wind turbine was installed at Los Moriscos (Gran Canaria, Spain) for driving a brackish water desalination plant. It is a 200 m3/d RO system. The plant is connected to the grid as auxiliary energy when the wind power is not enough for plant operation. Energy consumption is 5 kWh/m3 [79]. In 1993 a wind driven seawater desalination system began operation at Pajara (Fuerteventura Island, Spain). It is a RO plant with a capacity of 56 m3/d driven by a hybrid diesel-wind system. It consists of two diesel engines and a wind turbine of 225 kW [80]. This hybrid system provides the energy requirements for a village of 300 people. The design and implementation of the systems were possible due to the Valoren program, the Council of Pajara, the Consorcio de Abastecimiento de Agua of Fuerteventura and the Instituto de Energias Renovables belonging to CIEMAT (Madrid). The Gobierno Autonomo de Canarias, as an initiative of the Consejeria de Industria y Energia, created the Centro de Investigaciones de Energia y Agua in Pozo Izquierdo (Gran Canaria). Its main purpose is the study of renewable energy-driven desalination. The first project developed consists of a RO system with a variable load [81]. They planned to study other desalination systems such as vapour compression and electrodialysis [23, 821. In 1986 the installation of a RO osmosis plant in the Middle East began. It is a 25 m3/d plant connected to a hybrid wind-diesel system [83]. In Drepanon, Achaia, near Patras (Greece), in 1995 the operation of another wind-powered RO system began [84]. Finally, [23] presents other facilities at: l Island of Suderoog (North Sea) with 6-9 m3/d;
L. Garcia-Rodriguez / Desalination 143 (2002) 103-l I3 l
l l
l
Ile du Planier, France Pacific Islands, with 0.5 m3/h; Island of Helgoland, Germany (2x480 m3/h); Island of St. Nicolas, West France (hybrid wind-diesel); Island of Drenec, France (10 kW wind energy converter).
Although mechanic vapour compression (MVC) consumes more energy than RO, it presents fewer problems due to the fluctuations of the energy resource than RO. MVC systems are more suitable for remote areas since they are more robust, they need fewer skilled workers and fewer chemicals than RO systems. In addition, they need no membrane replacement and offer a better quality product than RO. On the other hand, in case of contaminated waters, the distillation ensures the absence of microorganisms in the product. In Borkum Island in the North Sea, one such plant was implemented with fresh water production of about 0.3-2 m3/h [23, 851. In Ruegen Island (Germany) another one with a 300 kW wind energy converter and 120-300 m3/d of fresh water production was installed [23]. In addition, there is a commercial 300 m3/d plant [5]. Finally, the electrodialysis process is interesting for brackish water desalination; such desalination systems driven by wind power are more suitable for remote areas than RO plants.
5. Biomass Biomass is any type of organic matter whose origin is a biologic process. It may be used by direct combustion or by transformation on biofuels (e.g., methanol, ethanol, hydrogen, oils). Nowadays, the direct combustion of biomass is commercial. Where many biomass residues are available, it is possible to drive a distillation process or to drive other desalination processes by using thermo-mechanic conversion or elec-
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tricity generation. The use of biomass on desalination is not, in general, a promising alternative since organic residues are not normally available in arid regions. On the other hand, the growth of biomass for use in desalination is not an alternative since it needs more fresh water than expected in a desalination plant.
6. Geothermal
energy
There are different geothermal energy sources. They may be classified in terms of the measured temperature as low, medium and high. The corresponding thresholds are lower than 1OO”C,between 100°C and 15O”C, and up to 150°C, respectively. The thermal gradient in the earth varies between 15°C and 75°C per km depth. Nevertheless, heat flux is anomalous in different continental areas. Moreover, there are local centres of heat between 6 and 10 km deep due to disintegration of radioactive elements. The use of magma and of geo-pressurised energy is under research. In addition, the geothermal energy of hot rocks requires several adjustments. Nevertheless, the binary hydrogeothermal cycles are more developed than the ones mentioned above. It has to be said that electricity generation by geothermal energy is a mature and competitive technology. The main advantage of geothermal energy is that the thermal storage is unnecessary in such systems. In 1996,7 173.5 MW, were generated by geothermal energy, and in 1994,8664 MW, were consumed on other applications [86]. Between these applications the space heating is important, especially in Iceland where the 99% of the buildings in its capital are heated in this way [87]. For instance, in Italy, direct uses of geothermal heat consist of space- and districtheating, greenhouse heating, fish farming and some industrial applications. Excluding bathing and swimming, the total installed capacity is about 340 MW, [88].
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Geothermal waters in the upper 100 m may be a reasonable alternative to desalination [5] (see also [89]). Karytsas [90] developed a technical and economic analysis for the use of geothermal sources between 75OC and 90°C on MED. One such plant will be installed in Cyclades Islands (Greece). Besides that, El Amali et al. [91] proposed an application to membrane distillation. On the other hand, a high-pressure source allows the direct use of shaft power on desalination. Moreover, thermal energy conversions on shaft power or electricity would permit the connection with other desalination systems.
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the status of development reached by such technology. A variety of systems was described and their very different maturities were pointed out.
Acknowledgements
This study was supported financially by the Canary Autonomous Government (project PI2000/13 6) and La Laguna University.
References
7. Ocean energy
VI E. Delyannis and V.A. Belessiotis, Mediterranean
Ocean energy is expressed in many ways, e.g.,
waves energy, tides and thermal gradient of the sea. The nominal power is 0.5,240 and 40 MW,, respectively [75]. Nowadays, there are very few facilities of wave and tide energy conversion to electricity (see [ 11). The use of ocean energy for seawater desalination in not currently practical because wave energy is not yet commercial, tide energy is expensive, and the energy of the oceanic thermal gradient is still under research. Rabas and Panchal [92] described an MSF desalination system coupled to thermal ocean energy. The studies of Crear and Pritchard [93] showed that desalination using wave energy would be economically viable for capacities of lo6 m3/d. In addition, Heath [94] proposed a wind-wave hybrid system connected to a distiller. The advantages of such a system would be the availability of a more regular energy source than wind power.
8. Conclusions
The brief review of desalination powered by renewable energies presented in this paper shows
PI
[31
141
PI
PI 171
PI PI
Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES; EDS. Santorini, Greece, 1996, pp. 3-19. H.T. El-Dessouky, H.M. Ettouney and F. Mandani, International Workshop for small and medium size plants with limited environmental impact, Rome, 1998, Academia Nazionale delle Scienze detta Dei XL, 1999, pp. 281-312. D. Le Gourier&s, EnerglaE6lica. TeorIa, Concepci6n y C&lculo Pm&co de las Instalaciones, Masson, Barcelona, 1983. P. Baltas and K. Perrakis, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EUROREDNetwork, CRES; EDS. Santorini, Greece, 1996, pp. 31-35. M. Rodriguez-Girones, M. Rodrfguez, J. Perez and J. Veza, Proc. Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES; EDS. Santorini, Greece, 1996, pp. 20-25. A.F. Abdul-Fattah, Desalination, 60 (1986) 165-l 89. K. Wangnick, International Workshop for small and medium size plants with limited environmental impact, Rome, 1998. Academia Nazionale delle Scienze detta Dei XL, 1999, pp. 41-57. E.E. Delyannis, Desalination, 67 (1987) 3-19. J.I. Ajona, Desalination with thermal solar systems: Technology assessment and perspectives. Instituto de Energias Renovables, CIEMAT, 1991.
L. Garcia-Rodriguez / Desalination I43 (2002) 103-l 13 [lo] L. Garcia Rodriguez and C. Gomez Camacho, Desalination, 136 (2001) 213-218. [l l] S. Kalogirou, Renewable Energy, 12(4) (1997) 351367. [12] S. Kalogirou, Applied Energy, 60 (1998) 65-88. [13] A.M. El-Nashar, Solar Energy, 48 (1992) 207-213. [14] L. Garcia Rodriguez and C. Gdmez Camacho, Solar thermal technologies comparison for applications to seawater desalination. Desalination, 142 (2002) 135142. [15] M.S. Mohsen and O.R. Al-Jayyousi, Desalination, 124 (1999) 163-174. [16] M. Al-Shamiri and M. Safer, Desalination, 136 (1999) 45-59. [17] M. Rognoni and A. Trezzi, International Workshop on Desalination Technologies for Small and Medium Size Plants with Low Environmental Impact. Accademia Nazionale delle Scienze Delta dei XL, Rome, 1999, pp. 437-444. [18] A.C.Gangadharan,T.V.Narayanan,R.W.Bryersand E.W. Sommer, Colloques intemationaux du CNRS. Systemes Solaires Thermodynamiques, 306, 1980, pp. 205-211. [19] M.F.A. Goosen, S.S. Sablani, W.H. Shayya, C. Paton and H. Al.Hinai, Desalination, 129 (2000) 63-89. [20] M.R. Kamal, J. Simandl and J. Ayoub, International Desalination and Water Reuse, 9/2 (1999) 74-75. [21] A.M. El Nashar, Desalination, 52 (1985) 217-234. [22] E. Zarza Moya, Solar thermal desalination project, Phase II results and final project report. CIEMAT, Madrid, 1995. [23] European Commission, Desalination Guide Using Renewable Energies, 1998. [24] A. Massarani and F. Fusetti, Desalination, 92 (1993) 377-388. [25] D. Sommariva, D. Pinciroli, E. Sciubba and N. Lior, International Desalination and Water Reuse, 9(4) (2000) 51-52. [26] N.M. Wade, Desalination, 93 (1993) 343-363. [27] F.M. Mubeen, International Desalination and Water Reuse, 1 l(2) (2001) 15-19. [28] A.M. El-Nashar, Desalination, 93 (1993) 597-614. [29] S. Kalogirou, Renewable Energy, 12(4) (1997) 351367. [30] Y.G. Caouris, E.T. Kantsos and N.G. Zagouras, Desalination, 7 1 (1989) 177-20 1. [31] B.W. Tleimat, Desalination, 44 (1983) 153-165.
111
[32] D. Singh and S.K. Sharma, Desalination, 73 (1989) 191-195. [33] V.V. Slesarenko, Desalination, 126 (1999) 281-285. [34] J. Gunzbourg and D. Larger, Desalination, 125 (1999) 203-208. [35] H. Hulin, G. Xinshi and S. Yuehong, Int. J. ofEnergy Res., 23 (1999) l-6. [36] A.A. Madam, Desalination, 78 (1990) 187-200. [37] A. HanaIl, Desalination, 82 (1991) 175-185. [38] S. Krystsis, European Commission, EURORED Network, CRES; EDS, Santorini, Greece, 1996, pp. 265-270. [39] F. Palma, Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. [40] T. Szacsvay, P. Hofer-Noser and M. Posnansky, Desalination, 122 (1999) 185-193. [41] G. Caruso and A. Naviglio, Desalination, 122 (1999) 225-234. [42] E. Zarza Moya, Solar thermal desalination project: First phase and results & second hhase description, CIEMAT, Madrid, 1991. [43] V. Valverde Muela, Centro de Estudios de la Energia, Planta DesaIadora con energia Solar de Arinaga, Las Palmas de Gran Canaria, Departamento de Investigation y Nuevas Fuentes, 1982. [44] A.M. El-Nashar, IDA Magazine, l(4) (1987) 17-30. [45] D.D. Engdahl, Technical information record on the salt-gradient solar pond system at the Los Btios Demonstration Desalting Facility, 1987. [46] H. Lu, J.C. Walton and A.H.P. Swift, International Desalination and Water Reuse, IO(3) (2000) 35-43. [47] M.C. Tleimat and E.D. Howe, Solar Energy, 42(4) (1989) 339-349. [48] M.J. Safi and A. Korchani, Desalination, 125 (1999) 223-229. [49] R.K. Suri, A.M.R. Al-Marafe, A.A. Al-Homoud and G.P. Maheshwari, Desalination, 7 1 ( 1999) 165-175. [50] W. Bucher, ASRE 89, Intemat. Conf. on Applications of Solar & Renewable Energy, Cairo, 1988. [5 l] A.K. Rajvanshi, Solar Energy, 24 (1980) 551-560. [52] M. Hermann, J. Koschikowski and M. Rommel, Corrosion-free solar collectors for thermally driven seawater desalination. Proc. EuroSun 2000, Copenhagen, 2000.
112
L. Garcia-Rodriguez
/Desalination
[53] M. Rommel, M. Hermamr and J. Koschikowski, The
[54] [55] [56]
[57]
[58]
[59]
[60]
[al]
[62] [63] [64] [65] [66] [671 [68] [69]
[70]
SODESA project: development of solar collectors with corrosion-t& ansorbers and first results of the desalination pilot plant. Mediterranean Conference on Policies and Strategies for Desalination and Renewable Energies, Santorini, Greece, 2000. E.S.H. Fath, Desalination, 116 (1998) 45-55. P. LeGoff, J. LeGoff and M.R. Jeday, Desalination, 82 (1991) 153-163. A. Boeher, Solar desalination with a high efficiency multi-effect process offers new facilities, Desalination, 73 (1989) 197-203. Y.P. Yadav, Transient performance of a high temperature distillation system, Desalination and Water Re-use, Proc. Twelfth International Symposium, Vol. 2, Malta, 1991, p. 244. A.S. Lawrence and G.N. Tiwari, Theoretical evaluation of solar distillation under natural circulation with heat exchanger, Energy Conversion and Management, 30(3) (1990) 205-213. M.S. Sodha and R.S. Adhikari, Techno-economic model of solar still coupled with a solar flat-plate collector. Int. J. Energy Res., 14(5) (1990) 533-552. J.H.W. Graef, Solar desalination planta contra CO, emission, Desalination and Water Reuse, Proc. Twelfth International Symposium, Vol. 2, Malta, 1991, pp. 187-196. K.P. Thanvi and P.C. Pande, Renewable Energy and Enviroment. Himanshu Publications, Udaipur, 1990, pp. 271-275. R. Betaque and L.C.A. Naegel, Sunworld, 23 (1999) 18-20. A.N. Baytorun, Cordula Dumke and J. Meyer, Gartenbauwissenschaft, 54(2) (1989) 62-65. H. Miiller-Hoist, M. Engelhardt and M. Herve, Renewable Energy, 14( 1) (1998) 3 1 l-3 18. R. Bettaque and C.A. Naegel, SunWorld, 23(l) (1999) 18-19. W. Lufi, Int. J. Solar Energy, 1 (1982) 21-32. W.D. Childs, A.E. Daibiri, H.A. Al-Hinai and H.A. Abdullah, Desalination, 125 (1999) 155-166. K.D. Satyen, RenewableEnergy, 15 (1998) 467-472. S. Roberts, Solar Electricity: A Practical Guide to Designing and Installing Small Photovoltaic Systems, Prentice Hall International, UK, 1991, pp.12-19. A. Maurel, Desalination by reverse osmosis using renewable energies (solar-wind) Cadarche Centre
[71]
[72]
[73]
[74] [75]
[76]
[771
[78] [79]
143 (2002) 103-l I3
experiment. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 199 1. J.M. Andujar Peral, A. Contreras Gomez and J.M. Trujillo, IDM project: Results of one year of operation. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities, DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. S. Kehal, Reverse osmosis unit of 0.85 m3/h capacity driven by photovoltaic generator in South Algeria. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. M. Lichtwardt and H. Remmers, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 88-92. D. Weiner, D. Fisher, E.J. Moses, B. Katz and G. Meron, Desalination, 137 (2001) 7-13. P. Metzelopoulos and D. Bougas, Autonomous wind energy-photovoltaic water desalination unit in Thisassia Island. Presented at the conference on Policies and Strategies for Desalination and Renewable Energies, sponsored by the Renewable Energy Sources Unit of the National Technical University of Athens in cooperation with the Organization for European Development, Support and Research-TIFIN and Heliotopos S.A., Santorini, Greece, 2000. C. Gomez &macho, Uso de la Energla E6lica para la Desahnizacion. Course: Tratamiento de Aguas Mediante EnergIas Renovables, CIEMAT, Madrid, 1993 (in Spanish). A. Rjeb, Analisis de t&nicas de control con determinacion y ajuste de par-metros de una mquina de induction con estimation de velocidad, aplicada a un sistema e6lico mediante la teoria de camp0 orientado. PhD Thesis, Universidad de Valladolid, Spain, 200 1. L. Garcia-Rodriguez, Romero-Temero and C. G6mezCamacho, Desalination, 137 (2001) 259-265. J.M. Veza and A. Gomez-Gotor, Status of desalination in Canary Islands. Energy Related Aspects.
L. Garcia-Rodriguez / Desalination 143 (2002) 103-I 13
[SO]
[81]
[82] [83]
[84]
[85]
[86]
Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. A. Gonzalez, Proyecto de Desalinization por Energia Eolica en Fuerteventura. Curso: Tratamiento de Aguas Mediante Energhrs Renovables, CIEMAT, Madrid, 1993. H. Ehmann and M. Cendagorta, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 84-87. J.A. Cartaand R. Calero, Era Solar, 60 (1995) 5-10. M. Stahl, Small wind powered RO seawater desalination plant design, erection and operation experience. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. C. Kostopoulos, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 20-25. R. Coutelle, Sea-water desalination by wind-powered mechanical vapour compression plants. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. E. Barbier, Renewable and Sustainable Energy Review, 1(1/2) (1997) l-69.
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[87] F. Lopez Vera, Aprovechamiento de Energia Geotermica, en Conversion y Acumulacion de Energia, J. Gonzalez Velasco, ed., Editorial Centro de Estudios Ramon Areces, 1991, pp. 274-282. [88] A. Baldacci, P.D. Burgassi, M.H. Dickson and M. Fanelli, Non-electric utilization of geothermal energy in Italy, World Renewable Energy Congress V, Part I, A.A.M. Sayigh, ed., Pergamon Press, Florence, Italy, 1998, pp. 27-95. [89] K. Bourouni, R. Martin, L. Tadrist and H. Tadrist, Desalination, 114 (1997) 111-128. [90] C. Karytsas, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EUROREDNetwork, CRES, Santorini, Greece, 1996, pp. 128-131. [91] A. El Amali, S. Bouguecha and M. Maalej, Experimental study of air gap membrane distillation: Application to geothermal water desalination, Presented at the conference on Desalination Strategies in South mediterranean Countries, sponsored by the European Desalination Society and Ecole Nationale d’hrgenieurs de Tunis, Jerba, Tunisia, 2000. [92] T. Rabas and C. Panchal, Oceans (New York) 1 (1991) 38-45. [93] A.J. Crerar and C.L. Pritchard, Desalination and Water Re-use. Proc. Twelfth International Symposium, Miriam Balaban, ed., Institution of Chemical Engineers, 1991, pp. 391-398. [94] T. Heath, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 112-l 16.
ELSEVIER
www.elsevier.com/locate/desal
Seawater desalination driven by renewable energies: a review Lourdes Garcia-Rodriguez Departamento Fisica Fundamental y Experimental, Universidad de La Laguna, 38205 La Laguna (Tenerifs), CanaT Islands, Spain Tel. +34-922-318303. Fax: +34-922- 318228; email: [email protected] Received 21 June 2001; accepted 17 December 200 1
Abstract This paper deals with seawater desalination systems driven by renewable energies. A review of pilot plants and perspectives of development is presented. There are many reasons why the use of renewable energies in seawater desalination is suitable, especially for remote areas where conventional energy supply and skilled workers are not usually available. Nevertheless, desalination systems driven by renewable energies are scarce and they tend to have a limited capacity. Keyword:
Seawater desalination; Renewable energies; Wind power; Solar energy
1. Introduction
The increasing use of desalination due to demographic and industrial growth makes necessary a parallel increasing of energy sources. Desalination systems driven by renewable energies are scarce, and they usually have a limited capacity. They only represent about 0.02% of total desalination capacity [l]. However, many reasons make the use of renewable energies suitable for seawater desalination: l Plant location. Many arid regions are coastal areas and renewable energy sources are available. l Seasonal changes. Often freshwater demand 001 l-9164/02/$-
increases due to tourism, which is normally concentrated at times when the renewable energy availability is high, especially in the case of solar energy. Energy availability. Conventional energy supply is not always possible in remote areas or little islands: on the one hand because of difficulties in fossil fuel supply, and on the other because the grid does not exist or the available power is not enough to drive a desalination plant. In such cases, the use of renewable energies permits sustainable socioeconomic development by using local resources.
See front matter 8 2002 Elsevier Science B.V. All rights reserved
PII:SOOll-9164(02)00232-l
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Self-sufficiency. Renewable energies allow energetic diversification and avoid external dependence on energy supply. These aspects are important, especially in the least developed countries, which moreover have unstable governments. Technology. The development and commercialisation of desalination systems driven by renewable energies make possible technology exportation and cooperation among countries with low development. Environmental impact. Seawater desalination processes are strongly energy consuming. Therefore, the environmental effects of the fossil fuels consumed are important. Note that total world-wide capacity of desalted water is about 23 x 1O6m3/d [2]. Economics. On several Mediterranean islands, fresh water requirements make necessary the transport of fresh water by ship, with high costs and improper hygienic conditions. Operation and maintenance. The operation and maintenance of renewable energy systems are normally easier than conventional energy ones. Therefore, they are suitable for remote areas. Promising commercial perspectives. The cost reduction of renewable energy systems has been significant during the last decades. Therefore, future reductions as well as the rise of fossil fuel prices could make possible the competitiveness of seawater desalination driven by renewable energies. Renewable energies are found in nature: solar radiation, wind, energy of life beings, of the sea, or the thermal energy of the earth. Since ancient times humans have used some of these energy sources, but the main development of renewable energy systems was due to the petroleum crisis of 1973. Besides that, the increasing preoccupation about the environment has increased the use of renewable energies. Nevertheless, their main limitations are their space and temporal changes,
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the high land requirements and investment costs of renewable energy facilities, in spite of their low operation costs. To avoid the fluctuations inherent in renewable energies, different energy storage systems may be used (see [3]). Nowadays, several renewable energy technologies are mature enough and may be competitive with conventional energies. Some others are still under development or research. With regard to coupling seawater desalination technologies to renewable energy systems, it is important to take into account different aspects: thermodynamic considerations (see [4,5]), specific characteristics of the system location and economic evaluations. If the desalination system is going to be installed in a remote area, the technology selection may be done according to the criteria given by Abdul-Fattah [6]: simplicity, easy handling, availability, maturity of the technology, guarantee of fresh water production, suitability of the system to the characteristics of the location, possibility of future increase of the system capacity, efftciency, among others.
2. Thermal solar energy Solar energy is one of the most promising applications of renewable energies to seawater desalination, Several reviews of solar desalination have been published [ 1,7-l 01; an interesting comparison of such systems is given in [ 1l-141, and finally references [ 15-201 deal with the present status and economics of solar desalination. A solar distillation system may consist of two separate devices, the solar collector and the distiller - indirect solar desalination - or of one integrated system - direct solar desalination. Small production systems such as solar stills may be used wherever fresh water demand is low and land is inexpensive. High fresh water demands require industrial-capacity systems. These systems consist in a conventional seawater
L. Garcia-Rodriguez /Desalination
distillation plant coupled to a thermal solar system. Many small systems of direct solar desalination and several pilot plants of indirect solar desalination have been designed and implemented [8,21-231. Table 1 shows indirect solar desalination pilots. A multi-stage flash (MSF) or a multi-effect distillation (MED) plant may be selected for solar thermal desalination. MSF is the most mature technology. Nevertheless, Massarani and Fusetti [24] proposed technological improvements and Sommariva et al. [25] analysed an innovative configuration for MSF desalination. Nevertheless, MED has greater potential than MSF for designs with high performance ratio [26] and, moreover, MED processes appear to be less sensitive to corrosion and scaling than the MSF process [27]. Several
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105
authors discussed the costs of solar MED [28-3 l] and MSF [ 18,321 desalination. A few parabolic trough collector desalination plants have been implemented and tested [8]. At the Plataforma Solar de Almeria (PSA), Spain [22], a parabolic trough solar field was connected to a MED plant. At the second phase of the project, a double-effect absorption heat pump was coupled to the solar desalination plant. Several authors have studied the coupling of heat pumps and the design of new solar heat pumps: Slesarenko [33], Gunzbourg et al. [34] and Hulin et al. [35]. Solar flat-plate collectors had been used in a few solar desalination pilot plants [8, 211. With regard to evacuated tube collectors, El-Nashar [44] and Madam [36] reported solar desalination experiences using the MED process.
Table 1 Solar distillation plants m3/d
Solar collectors
ME, 14 effects
40
Evacuated tube
ME, 18 effects
120 25 20
Evacuated tube
Plant location
Desalination process
La Desired Island, French Caribbean [36] Abu Dhabi, UAE [21] Kuwait [S]
MSF RO
Kuwait [8,23] La Paz, Mexico [8,23]
MSF auto-regulated MSF, 10 stages
Arabian Gulf [S]
ME
Al-Ain, UAE [37]
ME, 55 stages; MSF, 75 stages
Takami Island, Japan [S]
ME, 16 effects MSF
Margarita de Savoya, Italy [S] El Paso, Texas [23] Berken, Germany [38] Lampedusa Island, Italy [39] Islands of Cape Verde [40] University of Ancona, Italy [41] PSA, Almeria, Spain [23,42] Gran Canaria, Spain [43] Area of Hzag, Tunisia [23] Safat, Kuwait [23] Near Dead Sea [23]
MSF MSF MSF Atlantis “Autoflash” ME, TC ME, heat pump MSF Distillation MSF MED
100 10
Solar electricity generation system Parabolic trough Flat plate + parabolic trough
6000
Parabolic trough
500
Parabolic trough
16 50-60 19 20 0.3 300 30 72 10 0.1-0.35 10
Flat plate Solar pond Solar pond Low concentration Solar pond Solar pond Parabolic trough Low concentration Solar collector Solar collector Solar pond
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On the other hand, different plants have been implemented coupling a solar pond to a MSF [40] or a MED plant [41]. In solar distillation plants, the seawater or brine preheated by the distillation plant absorbs the thermal energy delivered by the heat storage zone of the solar pond. In addition, the thermal energy delivered by a salinity-gradient solar pond has been used, not only in seawater distillation plants, but also in seawater and brackish water reverse osmosis (RO) desalination [45]. Lu et al. [46] described a solar-pond- powered desalination plant at El Paso (USA). The solar pond drives both a thermal desalination and RO plants. Since the standard MSF process is not able to operate coupled to any variable heat source, the Atlantis Company developed an adapted MSF system called “Autoflash”. It can be connected to a solar pond [40]. Tleimat and Howe [47] analysed a MED plant driven by thermal energy delivered by a solar pond. Safi and Korchani [48] analysed the cost of dual plants connected to a solar pond. In addition, several authors [49,50] have selected solar-pond-powered desalination as one of the most cost-effective systems. Finally, Rajvanshi [5 l] has designed a special solar collector to be connected to a MSF distillation plant. Hermann et al. [52] reported the design and test of a corrosion-free solar collector for driving ME humidification. The pilot plant was installed at Pozo Izquierdo (Gran Canaria, Spain) [53]. With regard to direct solar desalination Fath [54] gives a valuable review. In most cases, such systems consist of a solar still or a compact desalination collector (CDC). Le Goff et al. [55] give different designs for a CDC, and Boeher [56] presented a “high-efficiency water distillation of humid air with heat recovery” with a capacity range of 2-20 m3/d. On the other hand, the distillation temperature in a solar still may be increased by the connection of a flat-plate collector field [57-591. Other interesting designs
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of direct solar desalination systems are given in references [60-65]. Solar electricity generation may be also used for seawater desalination. A solar-assisted freezing plant was installed at Yanbu, Saudi Arabia, as part of the SOLERAS project [66]. The solar collector field consists in 380 point-focusing collectors with two axes for sun tracking [66]. Furthermore, the shaft power from thermal solar energy may drive a RO process or mechanic vapour compression. A prototype of a RO plant was implemented with flat-plate collectors with freon as the working fluid [5]. Childs et al. [67] presented a system designed for the connection of a thermal solar collector to a RO plant.
3. Solar photovoltaic
energy
Solar energy may be directly converted into electricity by photovoltaic conversion. Photovoltaic cells usually consist of silicon though other semiconductors may be used. There are technologies for thin and thick film. In industrial production, efficiencies of 13-15% may be reached on monocrystalline silicon cells and 1O11% on polycrystalline silicon cells. The latter are less expensive than the former. There are also amorphous silicon cells, which are thin-film cells. Efficiencies between 18% and 24% have been reached with monocrystalline and polycrystalline silicon technologies. In cells of GaAs and its alloys, as GaInP,, efficiencies higher than 30% (ultrahigh-efficiency) have been reached
[W. The main points in research of photovoltaic cells are the increase in efficiency, the reduction of manufacturing costs and the search for other materials as GaAs, CdS, CdTe and CuInSe, (CIS). CIS is sensible to the part of the red and infrared spectrum that the amorphous silicon does not absorb. On the other hand, CIS offers other interesting possibilities [69].
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Solar photovoltaic energy is a mature technology, whose main problem is its high cost. This technology has been developed largely using stand-alone systems. The connection of photovoltaic cells to membrane processes in desalination could be an interesting alternative in remote areas. Nevertheless, RO presents significant requirements for chemicals, spare parts and skilled workers. In remote areas, the eletrodialysis process is most suitable for brackish water desalination because it is more robust and its operation and maintenance are simpler than in the case of RO. Photovoltaic technology connected to a RO system is currently commercial. The distance at which the photovoltaic energy is competitive with conventional energy depends on the plant capacity, the distance to the electric grid and the
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salt concentration of the feed. With regard to solar desalination facilities, Table 2 shows the values for RO-photovoltaic plants. Several pilot plants using electrodialysis systems connected to photovoltaic cells by means of batteries have been implemented. One of them was installed at the Spencer Valley, near Gallup (New Mexico). It was developed by the US Bureau of Reclamation [23,70]. Some others were installed at [23]: l Thar desert, India (1 m3/d, brackish water); l Ohsima Island, Nagasaki (10 m3/d, sea water); Fukue city, Nagasaki (8.33 m3/h, brackish water); l Spencer Valley, New Mexico, USA (2.8 m3/d, brackish water) The use of a hybrid wind-solar system to drive a desalination unit is a promising alternative
Table 2 Reverse osmosis plants driven by photovoltaic cells Plant location
Salt concentration
Plant capacity
Photovoltaic system
Jeddah, Saudi Arabia [8,23]
42800 ppm
3.2 m’ld
Conception de1 Oro, Mexico [8] North of Jawa [8]
Brackish water Brackish water
1.5 m’/d 12 m3/d
8 kW peak 2.5 kW peak
Red Sea, Egypt [23,70]
Brackish water
50 m’/d
Has&Khebi,
(4.4 g/l) Brackish water
0.95 m’/h
25.5 kW peak 19.84 kW peak (pump), 0.64 kW peak (control equipment) 2.59 kWp
Argelie [23,72]
Cituis West, Jawa, Indonesia [23]
(3.2 g/l) Brackish water
1.5 m’/h
25 kWp
OS-O.1 m’/h -
1.2 kWp 6 kWp
Seawater
0.5-l m’/d 5.7 m’ld
4.8 kWp 11.2 kWp
Thar desert, India [23] North west of Sicily, Italy [23]
Brackish water Seawater
1 m’/d -
0.45 kWp
St. Lucie Inlet State Park, FL, USA [23] Lipari Island, Italy [23] Lampedusa Island, Italy [23] University of Almerla, Spain [23,71]
Seawater Seawater Seawater Brackish water
2x0.3 m’/d 2 m’/h 3+2 m’ih 2.5 m3/h
Perth, Australia [23] Wan00 Roadhouse, Australia [23] Vancouver, Canada [23] Doha, Qatar [23]
Brackish water Brackish water Seawater
9.8 kWp + 30 kW diesel generator 2.7 kWp + diesel generator 63 kWp 100 kWp 23.5 kWp
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because of the complementary characteristics of both energy sources and because many coastal areas have suitable wind and solar resources. One of such systems was designed in the frame of the SOLERAS project. Moreover, the Cadarache Centre (France) designed another unit that was installed in 1980 at Borj-Cedria, Tunisia [70]. The system consists of a 0.1 m3/d compact solar distiller, with a 0.25 m3/h RO plant and an electrodialysis plant for 4 g/l brackish water. The energetic system consists of a photovoltaic field of 4 kW peak and a wind turbine of 4 kW. Other systems have been designed and implemented [23,74] (see also [75]).
4. Wind power Wind turbines may be classified depending on their nominal power (Pn) as very low power (Pn < 10 kW), low power (Pn < 100 kW), medium power (100 kW < Pn < 0.5 MW) and high power (Pn> 0.5 MW) [76] turbines. All are mature technologies and they are commercially available except for the high power systems, which still require several adjustments. In spite of such maturity, new control strategies may increase the output of the wind turbine [77]. Coastal areas have a high availability of wind power resources, and wind power is the most competitive renewable energy technology in power generation. Therefore, wind powereddesalination is a promising alternative. RO is the desalination process with the lowest energy requirements. Conventional systems are designed for their connection to the grid. Otherwise, shaft power may be directly used for driving a desalination plant. The fluctuations of wind power would ruin the RO system. Therefore, an intermediate energy storage system would be necessary, but it would reduce the available energy and would increase the cost of the plant. The main drawback of RO in remote areas is the complex pre-treatment, the require-
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ment of skilled workers, chemicals and membrane replacement. A preliminary cost evaluation of wind-powered RO is presented in [78]. Desalination systems driven by wind power are the most frequent renewable energy desalination plants. Some are described below. In 1984 a wind turbine was installed at Los Moriscos (Gran Canaria, Spain) for driving a brackish water desalination plant. It is a 200 m3/d RO system. The plant is connected to the grid as auxiliary energy when the wind power is not enough for plant operation. Energy consumption is 5 kWh/m3 [79]. In 1993 a wind driven seawater desalination system began operation at Pajara (Fuerteventura Island, Spain). It is a RO plant with a capacity of 56 m3/d driven by a hybrid diesel-wind system. It consists of two diesel engines and a wind turbine of 225 kW [80]. This hybrid system provides the energy requirements for a village of 300 people. The design and implementation of the systems were possible due to the Valoren program, the Council of Pajara, the Consorcio de Abastecimiento de Agua of Fuerteventura and the Instituto de Energias Renovables belonging to CIEMAT (Madrid). The Gobierno Autonomo de Canarias, as an initiative of the Consejeria de Industria y Energia, created the Centro de Investigaciones de Energia y Agua in Pozo Izquierdo (Gran Canaria). Its main purpose is the study of renewable energy-driven desalination. The first project developed consists of a RO system with a variable load [81]. They planned to study other desalination systems such as vapour compression and electrodialysis [23, 821. In 1986 the installation of a RO osmosis plant in the Middle East began. It is a 25 m3/d plant connected to a hybrid wind-diesel system [83]. In Drepanon, Achaia, near Patras (Greece), in 1995 the operation of another wind-powered RO system began [84]. Finally, [23] presents other facilities at: l Island of Suderoog (North Sea) with 6-9 m3/d;
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l l
l
Ile du Planier, France Pacific Islands, with 0.5 m3/h; Island of Helgoland, Germany (2x480 m3/h); Island of St. Nicolas, West France (hybrid wind-diesel); Island of Drenec, France (10 kW wind energy converter).
Although mechanic vapour compression (MVC) consumes more energy than RO, it presents fewer problems due to the fluctuations of the energy resource than RO. MVC systems are more suitable for remote areas since they are more robust, they need fewer skilled workers and fewer chemicals than RO systems. In addition, they need no membrane replacement and offer a better quality product than RO. On the other hand, in case of contaminated waters, the distillation ensures the absence of microorganisms in the product. In Borkum Island in the North Sea, one such plant was implemented with fresh water production of about 0.3-2 m3/h [23, 851. In Ruegen Island (Germany) another one with a 300 kW wind energy converter and 120-300 m3/d of fresh water production was installed [23]. In addition, there is a commercial 300 m3/d plant [5]. Finally, the electrodialysis process is interesting for brackish water desalination; such desalination systems driven by wind power are more suitable for remote areas than RO plants.
5. Biomass Biomass is any type of organic matter whose origin is a biologic process. It may be used by direct combustion or by transformation on biofuels (e.g., methanol, ethanol, hydrogen, oils). Nowadays, the direct combustion of biomass is commercial. Where many biomass residues are available, it is possible to drive a distillation process or to drive other desalination processes by using thermo-mechanic conversion or elec-
109
tricity generation. The use of biomass on desalination is not, in general, a promising alternative since organic residues are not normally available in arid regions. On the other hand, the growth of biomass for use in desalination is not an alternative since it needs more fresh water than expected in a desalination plant.
6. Geothermal
energy
There are different geothermal energy sources. They may be classified in terms of the measured temperature as low, medium and high. The corresponding thresholds are lower than 1OO”C,between 100°C and 15O”C, and up to 150°C, respectively. The thermal gradient in the earth varies between 15°C and 75°C per km depth. Nevertheless, heat flux is anomalous in different continental areas. Moreover, there are local centres of heat between 6 and 10 km deep due to disintegration of radioactive elements. The use of magma and of geo-pressurised energy is under research. In addition, the geothermal energy of hot rocks requires several adjustments. Nevertheless, the binary hydrogeothermal cycles are more developed than the ones mentioned above. It has to be said that electricity generation by geothermal energy is a mature and competitive technology. The main advantage of geothermal energy is that the thermal storage is unnecessary in such systems. In 1996,7 173.5 MW, were generated by geothermal energy, and in 1994,8664 MW, were consumed on other applications [86]. Between these applications the space heating is important, especially in Iceland where the 99% of the buildings in its capital are heated in this way [87]. For instance, in Italy, direct uses of geothermal heat consist of space- and districtheating, greenhouse heating, fish farming and some industrial applications. Excluding bathing and swimming, the total installed capacity is about 340 MW, [88].
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Geothermal waters in the upper 100 m may be a reasonable alternative to desalination [5] (see also [89]). Karytsas [90] developed a technical and economic analysis for the use of geothermal sources between 75OC and 90°C on MED. One such plant will be installed in Cyclades Islands (Greece). Besides that, El Amali et al. [91] proposed an application to membrane distillation. On the other hand, a high-pressure source allows the direct use of shaft power on desalination. Moreover, thermal energy conversions on shaft power or electricity would permit the connection with other desalination systems.
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the status of development reached by such technology. A variety of systems was described and their very different maturities were pointed out.
Acknowledgements
This study was supported financially by the Canary Autonomous Government (project PI2000/13 6) and La Laguna University.
References
7. Ocean energy
VI E. Delyannis and V.A. Belessiotis, Mediterranean
Ocean energy is expressed in many ways, e.g.,
waves energy, tides and thermal gradient of the sea. The nominal power is 0.5,240 and 40 MW,, respectively [75]. Nowadays, there are very few facilities of wave and tide energy conversion to electricity (see [ 11). The use of ocean energy for seawater desalination in not currently practical because wave energy is not yet commercial, tide energy is expensive, and the energy of the oceanic thermal gradient is still under research. Rabas and Panchal [92] described an MSF desalination system coupled to thermal ocean energy. The studies of Crear and Pritchard [93] showed that desalination using wave energy would be economically viable for capacities of lo6 m3/d. In addition, Heath [94] proposed a wind-wave hybrid system connected to a distiller. The advantages of such a system would be the availability of a more regular energy source than wind power.
8. Conclusions
The brief review of desalination powered by renewable energies presented in this paper shows
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Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES; EDS. Santorini, Greece, 1996, pp. 3-19. H.T. El-Dessouky, H.M. Ettouney and F. Mandani, International Workshop for small and medium size plants with limited environmental impact, Rome, 1998, Academia Nazionale delle Scienze detta Dei XL, 1999, pp. 281-312. D. Le Gourier&s, EnerglaE6lica. TeorIa, Concepci6n y C&lculo Pm&co de las Instalaciones, Masson, Barcelona, 1983. P. Baltas and K. Perrakis, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EUROREDNetwork, CRES; EDS. Santorini, Greece, 1996, pp. 31-35. M. Rodriguez-Girones, M. Rodrfguez, J. Perez and J. Veza, Proc. Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES; EDS. Santorini, Greece, 1996, pp. 20-25. A.F. Abdul-Fattah, Desalination, 60 (1986) 165-l 89. K. Wangnick, International Workshop for small and medium size plants with limited environmental impact, Rome, 1998. Academia Nazionale delle Scienze detta Dei XL, 1999, pp. 41-57. E.E. Delyannis, Desalination, 67 (1987) 3-19. J.I. Ajona, Desalination with thermal solar systems: Technology assessment and perspectives. Instituto de Energias Renovables, CIEMAT, 1991.
L. Garcia-Rodriguez / Desalination I43 (2002) 103-l 13 [lo] L. Garcia Rodriguez and C. Gomez Camacho, Desalination, 136 (2001) 213-218. [l l] S. Kalogirou, Renewable Energy, 12(4) (1997) 351367. [12] S. Kalogirou, Applied Energy, 60 (1998) 65-88. [13] A.M. El-Nashar, Solar Energy, 48 (1992) 207-213. [14] L. Garcia Rodriguez and C. Gdmez Camacho, Solar thermal technologies comparison for applications to seawater desalination. Desalination, 142 (2002) 135142. [15] M.S. Mohsen and O.R. Al-Jayyousi, Desalination, 124 (1999) 163-174. [16] M. Al-Shamiri and M. Safer, Desalination, 136 (1999) 45-59. [17] M. Rognoni and A. Trezzi, International Workshop on Desalination Technologies for Small and Medium Size Plants with Low Environmental Impact. Accademia Nazionale delle Scienze Delta dei XL, Rome, 1999, pp. 437-444. [18] A.C.Gangadharan,T.V.Narayanan,R.W.Bryersand E.W. Sommer, Colloques intemationaux du CNRS. Systemes Solaires Thermodynamiques, 306, 1980, pp. 205-211. [19] M.F.A. Goosen, S.S. Sablani, W.H. Shayya, C. Paton and H. Al.Hinai, Desalination, 129 (2000) 63-89. [20] M.R. Kamal, J. Simandl and J. Ayoub, International Desalination and Water Reuse, 9/2 (1999) 74-75. [21] A.M. El Nashar, Desalination, 52 (1985) 217-234. [22] E. Zarza Moya, Solar thermal desalination project, Phase II results and final project report. CIEMAT, Madrid, 1995. [23] European Commission, Desalination Guide Using Renewable Energies, 1998. [24] A. Massarani and F. Fusetti, Desalination, 92 (1993) 377-388. [25] D. Sommariva, D. Pinciroli, E. Sciubba and N. Lior, International Desalination and Water Reuse, 9(4) (2000) 51-52. [26] N.M. Wade, Desalination, 93 (1993) 343-363. [27] F.M. Mubeen, International Desalination and Water Reuse, 1 l(2) (2001) 15-19. [28] A.M. El-Nashar, Desalination, 93 (1993) 597-614. [29] S. Kalogirou, Renewable Energy, 12(4) (1997) 351367. [30] Y.G. Caouris, E.T. Kantsos and N.G. Zagouras, Desalination, 7 1 (1989) 177-20 1. [31] B.W. Tleimat, Desalination, 44 (1983) 153-165.
111
[32] D. Singh and S.K. Sharma, Desalination, 73 (1989) 191-195. [33] V.V. Slesarenko, Desalination, 126 (1999) 281-285. [34] J. Gunzbourg and D. Larger, Desalination, 125 (1999) 203-208. [35] H. Hulin, G. Xinshi and S. Yuehong, Int. J. ofEnergy Res., 23 (1999) l-6. [36] A.A. Madam, Desalination, 78 (1990) 187-200. [37] A. HanaIl, Desalination, 82 (1991) 175-185. [38] S. Krystsis, European Commission, EURORED Network, CRES; EDS, Santorini, Greece, 1996, pp. 265-270. [39] F. Palma, Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. [40] T. Szacsvay, P. Hofer-Noser and M. Posnansky, Desalination, 122 (1999) 185-193. [41] G. Caruso and A. Naviglio, Desalination, 122 (1999) 225-234. [42] E. Zarza Moya, Solar thermal desalination project: First phase and results & second hhase description, CIEMAT, Madrid, 1991. [43] V. Valverde Muela, Centro de Estudios de la Energia, Planta DesaIadora con energia Solar de Arinaga, Las Palmas de Gran Canaria, Departamento de Investigation y Nuevas Fuentes, 1982. [44] A.M. El-Nashar, IDA Magazine, l(4) (1987) 17-30. [45] D.D. Engdahl, Technical information record on the salt-gradient solar pond system at the Los Btios Demonstration Desalting Facility, 1987. [46] H. Lu, J.C. Walton and A.H.P. Swift, International Desalination and Water Reuse, IO(3) (2000) 35-43. [47] M.C. Tleimat and E.D. Howe, Solar Energy, 42(4) (1989) 339-349. [48] M.J. Safi and A. Korchani, Desalination, 125 (1999) 223-229. [49] R.K. Suri, A.M.R. Al-Marafe, A.A. Al-Homoud and G.P. Maheshwari, Desalination, 7 1 ( 1999) 165-175. [50] W. Bucher, ASRE 89, Intemat. Conf. on Applications of Solar & Renewable Energy, Cairo, 1988. [5 l] A.K. Rajvanshi, Solar Energy, 24 (1980) 551-560. [52] M. Hermann, J. Koschikowski and M. Rommel, Corrosion-free solar collectors for thermally driven seawater desalination. Proc. EuroSun 2000, Copenhagen, 2000.
112
L. Garcia-Rodriguez
/Desalination
[53] M. Rommel, M. Hermamr and J. Koschikowski, The
[54] [55] [56]
[57]
[58]
[59]
[60]
[al]
[62] [63] [64] [65] [66] [671 [68] [69]
[70]
SODESA project: development of solar collectors with corrosion-t& ansorbers and first results of the desalination pilot plant. Mediterranean Conference on Policies and Strategies for Desalination and Renewable Energies, Santorini, Greece, 2000. E.S.H. Fath, Desalination, 116 (1998) 45-55. P. LeGoff, J. LeGoff and M.R. Jeday, Desalination, 82 (1991) 153-163. A. Boeher, Solar desalination with a high efficiency multi-effect process offers new facilities, Desalination, 73 (1989) 197-203. Y.P. Yadav, Transient performance of a high temperature distillation system, Desalination and Water Re-use, Proc. Twelfth International Symposium, Vol. 2, Malta, 1991, p. 244. A.S. Lawrence and G.N. Tiwari, Theoretical evaluation of solar distillation under natural circulation with heat exchanger, Energy Conversion and Management, 30(3) (1990) 205-213. M.S. Sodha and R.S. Adhikari, Techno-economic model of solar still coupled with a solar flat-plate collector. Int. J. Energy Res., 14(5) (1990) 533-552. J.H.W. Graef, Solar desalination planta contra CO, emission, Desalination and Water Reuse, Proc. Twelfth International Symposium, Vol. 2, Malta, 1991, pp. 187-196. K.P. Thanvi and P.C. Pande, Renewable Energy and Enviroment. Himanshu Publications, Udaipur, 1990, pp. 271-275. R. Betaque and L.C.A. Naegel, Sunworld, 23 (1999) 18-20. A.N. Baytorun, Cordula Dumke and J. Meyer, Gartenbauwissenschaft, 54(2) (1989) 62-65. H. Miiller-Hoist, M. Engelhardt and M. Herve, Renewable Energy, 14( 1) (1998) 3 1 l-3 18. R. Bettaque and C.A. Naegel, SunWorld, 23(l) (1999) 18-19. W. Lufi, Int. J. Solar Energy, 1 (1982) 21-32. W.D. Childs, A.E. Daibiri, H.A. Al-Hinai and H.A. Abdullah, Desalination, 125 (1999) 155-166. K.D. Satyen, RenewableEnergy, 15 (1998) 467-472. S. Roberts, Solar Electricity: A Practical Guide to Designing and Installing Small Photovoltaic Systems, Prentice Hall International, UK, 1991, pp.12-19. A. Maurel, Desalination by reverse osmosis using renewable energies (solar-wind) Cadarche Centre
[71]
[72]
[73]
[74] [75]
[76]
[771
[78] [79]
143 (2002) 103-l I3
experiment. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 199 1. J.M. Andujar Peral, A. Contreras Gomez and J.M. Trujillo, IDM project: Results of one year of operation. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities, DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. S. Kehal, Reverse osmosis unit of 0.85 m3/h capacity driven by photovoltaic generator in South Algeria. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. M. Lichtwardt and H. Remmers, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 88-92. D. Weiner, D. Fisher, E.J. Moses, B. Katz and G. Meron, Desalination, 137 (2001) 7-13. P. Metzelopoulos and D. Bougas, Autonomous wind energy-photovoltaic water desalination unit in Thisassia Island. Presented at the conference on Policies and Strategies for Desalination and Renewable Energies, sponsored by the Renewable Energy Sources Unit of the National Technical University of Athens in cooperation with the Organization for European Development, Support and Research-TIFIN and Heliotopos S.A., Santorini, Greece, 2000. C. Gomez &macho, Uso de la Energla E6lica para la Desahnizacion. Course: Tratamiento de Aguas Mediante EnergIas Renovables, CIEMAT, Madrid, 1993 (in Spanish). A. Rjeb, Analisis de t&nicas de control con determinacion y ajuste de par-metros de una mquina de induction con estimation de velocidad, aplicada a un sistema e6lico mediante la teoria de camp0 orientado. PhD Thesis, Universidad de Valladolid, Spain, 200 1. L. Garcia-Rodriguez, Romero-Temero and C. G6mezCamacho, Desalination, 137 (2001) 259-265. J.M. Veza and A. Gomez-Gotor, Status of desalination in Canary Islands. Energy Related Aspects.
L. Garcia-Rodriguez / Desalination 143 (2002) 103-I 13
[SO]
[81]
[82] [83]
[84]
[85]
[86]
Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. A. Gonzalez, Proyecto de Desalinization por Energia Eolica en Fuerteventura. Curso: Tratamiento de Aguas Mediante Energhrs Renovables, CIEMAT, Madrid, 1993. H. Ehmann and M. Cendagorta, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 84-87. J.A. Cartaand R. Calero, Era Solar, 60 (1995) 5-10. M. Stahl, Small wind powered RO seawater desalination plant design, erection and operation experience. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. C. Kostopoulos, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 20-25. R. Coutelle, Sea-water desalination by wind-powered mechanical vapour compression plants. Seminar on New Technologies for the Use of Renewable Energies in Water Desalination. Commission of the European Communities. DG XVII for Energy, Centre for Renewable Energy Sources, Athens, 1991. E. Barbier, Renewable and Sustainable Energy Review, 1(1/2) (1997) l-69.
113
[87] F. Lopez Vera, Aprovechamiento de Energia Geotermica, en Conversion y Acumulacion de Energia, J. Gonzalez Velasco, ed., Editorial Centro de Estudios Ramon Areces, 1991, pp. 274-282. [88] A. Baldacci, P.D. Burgassi, M.H. Dickson and M. Fanelli, Non-electric utilization of geothermal energy in Italy, World Renewable Energy Congress V, Part I, A.A.M. Sayigh, ed., Pergamon Press, Florence, Italy, 1998, pp. 27-95. [89] K. Bourouni, R. Martin, L. Tadrist and H. Tadrist, Desalination, 114 (1997) 111-128. [90] C. Karytsas, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EUROREDNetwork, CRES, Santorini, Greece, 1996, pp. 128-131. [91] A. El Amali, S. Bouguecha and M. Maalej, Experimental study of air gap membrane distillation: Application to geothermal water desalination, Presented at the conference on Desalination Strategies in South mediterranean Countries, sponsored by the European Desalination Society and Ecole Nationale d’hrgenieurs de Tunis, Jerba, Tunisia, 2000. [92] T. Rabas and C. Panchal, Oceans (New York) 1 (1991) 38-45. [93] A.J. Crerar and C.L. Pritchard, Desalination and Water Re-use. Proc. Twelfth International Symposium, Miriam Balaban, ed., Institution of Chemical Engineers, 1991, pp. 391-398. [94] T. Heath, Mediterranean Conference on Renewable Energy Sources for Water Production. European Commission, EURORED Network, CRES, Santorini, Greece, 1996, pp. 112-l 16.