Process Selection

Solar Power Design Manual

Do It Yourself Solar Energy

Get Instant Access

During the design stage of a renewable energy-powered desalination system, the designer must select a process suitable for that particular application. The factors that should be considered for such a selection are the following (Kalogirou, 2005):

1. The suitability of the process for renewable energy application.

2. The effectiveness of the process with respect to energy consumption.

3. The amount of freshwater required in a particular application, in combination with the range of applicability of the various desalination processes.

4. The seawater treatment requirements.

5. The capital cost of the equipment.

6. The land area required or that could be made available for the installation of the equipment.

Before any process selection can start, a number of basic parameters should be investigated. The first is the evaluation of the overall water resources. This should be done in terms of both quality and quantity (for a brackish water resource). Should brackish water be available, then this may be more attractive, since the salinity is normally much lower (< 10,000 ppm); hence, the desalination of the brackish water should be the more attractive option. In inland sites, brackish water may be the only option. On a coastal site, seawater is normally available. The identification and evaluation of the renewable energy resources in the area complete the basic steps to be performed toward the design of a renewable energy system (RES) to drive the desalination system. Renewable energy-driven desalination technologies mainly fall into two categories. The first category includes distillation desalination technologies driven by heat produced by a RES; the second includes membrane and distillation desalination technologies driven by electricity or mechanical energy produced by a RES. Such systems should be characterized by robustness, simplicity of operation, low maintenance, compact size, easy transportation to the site, simple pre-treatment and intake systems to ensure proper operation, and endurance of a plant at the difficult conditions often encountered in remote areas. Concerning their combination, the existing experience has shown no significant technical problems (Tzen and Morris, 2003).

Water production costs generally include the following items (Fiorenza et al., 2003):

• Fixed charges, which depend on the capital cost and a depreciation factor (determined from both plant life and financial parameters and consequently varying for each country).

• Variable charges, which depend on the consumption and cost of energy (related to the source employed and location selected), operational (personnel), maintenance cost (varying for each country), consumption and cost of chemicals used for pre- and post-treatment of water (especially in RO plants), and the rate at which the membranes are to be replaced in RO plants (both factors are site related).

Generally, the percentage of TDS in seawater has practically no effect in thermal processes but a remarkable effect in reverse osmosis, where the energy demand increases linearly at a rate of more than 1 kWh/m3 per 10,000 ppm (Fiorenza et al., 2003). If, however, the input pressures are left unchanged, the percentage of salts in the water produced could be intolerably high. Normally, this value for the RO process is expected to be around 300 ppm. The value, though lying well within the limit of 500 ppm (fixed by the WHO for drinking water), still results in at least one order of magnitude higher than the salinity of water produced from thermal processes. Also, for high salinity concentration, the use of RO technology is very problematic.

Renewable energy sources can provide thermal energy (solar collectors, geothermal energy), electricity (photovoltaics, wind energy, solar thermal power systems), or mechanical energy (wind energy). All these forms of energy can be used to power desalination plants.

Solar energy can generally be converted into useful energy either as heat, with solar collectors and solar ponds, or as electricity, with photovoltaic cells and solar thermal power systems. As was seen in previous sections, both methods have been used to power desalination systems. The direct collection systems can utilize solar energy only when it is available, and their collection is inefficient. Alternatively, in the indirect collection systems, solar energy is collected by more efficient solar collectors, in the form of hot water or steam. It should be noted, however, that solar energy is available for only almost half the day. This implies that the process operates for only half the time available, unless some storage device is used. The storage device, which is usually expensive, can be replaced by a backup boiler or electricity from the grid in order to operate the system during low insolation and nighttime. When such a system operates without thermal buffering, the desalination subsystem must be able to follow a variable energy supply, without upset. In all solar energy desalination systems, an optimum PR has to be calculated based on the solar energy collectors' cost, storage devices' cost (if used), and the cost of the desalination plant (Kalogirou, 2005). Probably the only form of stable energy supply is the solar pond, which, due to its size, it does not charge or discharge easily, and thus is less sensitive to variations in the weather.

Wind energy is also a highly variable source of supply with respect to both wind speed and frequency. When wind energy is used for electricity generation, the variation of the wind source can be balanced by the addition of battery banks, which act in a way similar to a storage tank in solar thermal systems, i.e., the batteries charge when wind is available and discharge to the load (desalination plant) when required. In the case of mechanical energy production from wind, the desalination plant can operate only when there is wind. In this case, the desalination plant is usually oversized with respect to water demand, and instead of storing the energy, the water produced when wind is available is stored.

In the technology selection, another parameter to be considered is the type of connection of the two technologies. An RO renewable desalination plant can be designed to operate coupled to the grid or off-grid (stand-alone, autonomous system). When the system is grid connected, the desalination plant can operate continuously as a conventional plant, and the renewable energy source merely acts as a fuel substitute. Where no electricity grid is available, autonomous systems have to be developed that allow for the intermittent nature of the renewable energy source. Desalination systems have traditionally been designed to operate with a constant power input (Tzen et al., 1998). Unpredictable and lack of steady power input forces the desalination plant to operate under non-optimal conditions and may cause operational problems (Tzen and Morris, 2003). Each desalination system has specific problems when it is connected to a variable power system. For instance, the reverse osmosis system has to cope with the sensitivity of the membranes regarding fouling, scaling, and unpredictable phenomena due to start-stop cycles and partial load operation during periods of oscillating power supply. On the other hand, the vapor compression system has considerable thermal inertia and requires considerable energy to get to the nominal working point. Thus, for autonomous systems, a small energy storage system, batteries or thermal stores, should be added to offer stable power to the desalination unit. Any candidate option resulting from the previous parameters should be further screened through constraints such as site characteristics (accessibility, land formation, etc.) and financial requirements (Tzen and Morris, 2003).

The energy required for various desalination processes, as obtained from a survey of manufacturers' data, is shown in Table 8.3. It can be seen from Table 8.3 that the process with the smallest energy requirement is RO with energy recovery. However, this is viable for only very large systems due to the high cost of the energy recovery turbine. The next lowest is the RO without energy recovery and the MEB. A comparison of the desalination equipment cost and the

Table 8.3 Energy Consumption of Desalination Systems

Process

Heat input (kJ/kg of product)

Mechanical power input (kWh/m3 of product)

Prime energy consumption (kJ/kg of product)a

MSF

294

2.5-4 (3.7)b

338.4

MEB

123

2.2

149.4

VC

8-16 (16)

192

RO

5-13 (10)

120

ER-RO

4-6 (5)

60

ED

12

144

Solar still

2330

0.3

2333.6

Notes:

aAssumed conversion efficiency of electricity generation of 30%.

bFigure used for the prime energy consumption estimation shown in last column.

Table 8.4 Comparison of Desalination Plants

Item

MSF

MEB

VC

RO

Solar still

Scale of application

Medium-large

Small-medium

Small

Small-large

Small

Seawater treatment

Scale inhibitor, antifoam chemical

Scale Inhibitor

Scale inhibitor

Sterilizer Coagulant acid Deoxidizer

(Euro/m3)

950-1900

900-1700

1500-2500

900-2500, membrane replacement every 4-5 years

800-1000

Note: Low figures in equipment price refer to bigger size in the range indicated and vice versa.

seawater treatment requirement, as obtained from a survey of manufacturers' data, is shown in Table 8.4. The cheapest of the considered systems is the solar still. This is a direct collection system, which is very easy to construct and operate. The disadvantage of this process is the very low yield, which implies that large areas of flat ground are required. It is questionable whether such a process can be viable unless cheap, desert-like land is available near the sea. The MEB is the cheapest of all the indirect collection systems and also requires the simplest seawater treatment. RO, although requiring a smaller amount of energy, is expensive and requires a complex seawater treatment.

Due to the development of RO technology, the energy consumption values of more than 20 kWh/m3 during the year 1970 have been reduced today to about 5 kWh/m3 (Fiorenza et al., 2003). This is due to improvements made in RO membranes. Research in this sector is ongoing worldwide, and we may see further reductions in both energy requirements and costs in the coming years. It should be noted that nearly 3 kg of CO2 are generated for each cubic meter of water produced (at an energy consumption rate of 5 kWh/m3 with the best technology currently used on a large scale), which could be avoided if the conventional fuel is replaced by a renewable one.

An alternative usually considered for solar-powered desalination is to use an RO system powered by photovoltaic cells. This is more suitable for intermittent operation than conventional distillation processes and has higher yields per unit of energy collected. According to Zarza et al. (1991b), who compared RO with photovoltaic-generated electricity with an MEB plant coupled to parabolic trough collectors, the following apply:

• The total cost of freshwater produced by an MEB plant coupled to parabolic trough collectors is less than that of the RO plant with photovoltaic cells, due to the high cost of the photovoltaic-generated electricity.

• The highly reliable MEB plant operation makes its installation possible in countries with high insolation levels but lacking in experienced personnel. Because any serious mistake during the operation of an RO plant can ruin its membranes, these plants must be operated by skilled personnel.

Also, since renewable energy is expensive to collect and store, an energy recovery turbine is normally fitted to recover energy from the rejected brine stream, which increases the RO plant cost considerably. Additionally, in polluted areas, distillation processes are preferred for desalination because water is boiled, which ensures that the distilled water does not contain any micro-organisms (Kalogirou, 2005). In addition to the high salinity, specific water quality problems include manganese, fluoride, heavy metals, bacterial contamination, and pesticide-herbicide residues. In all these cases, thermal processes are preferred to membrane ones. Even the simple solar still can provide removal efficiencies on the order of 99% (Hanson et al., 2004).

If both RO and thermal processes are suitable for a given location, the renewable energy available and the electrical-mechanical-thermal energy required by the process limit the possible selection. Finally, the required plant capacity, the annual and daily distribution of the freshwater demand, the product cost, the technology maturity, and any problems related to the connection of the renewable energy and the desalination systems are factors that influence the selection.

If thermal energy is available, it can be used directly to drive a distillation process, such as MSF, MEB, or TVC. MEB plants are more flexible to operate at partial load, less sensible to scaling, cheaper, and more suitable for limited capacity than MSF plants. TVC has lower performance than MEB and MSF. In addition, the thermomechanical conversion permits the indirect use of thermal energy to drive RO, ED, or MVC processes.

If electricity or shaft power can be obtained from the available energy resources, RO, ED, or MVC can be selected. Fluctuations in the available energy would ruin the RO system. Therefore, an intermediate energy storage is required, but it would reduce the available energy and increase the costs. In remote areas, ED is most suitable for brackish water desalination, because it is more robust and its operation and maintenance are simpler than RO systems. In addition, the ED process can adapt to changes of available energy input. On the other hand, although MVC consumes more energy than RO, it presents fewer problems than RO due to the fluctuations of the energy resource. MVC systems are more suitable for remote areas, since they are more robust and need fewer skilled workers and fewer chemicals than RO systems (Garcia-Rodriguez, 2003). In addition, they need no membrane replacement and offer a better quality product than RO. Moreover, in case of polluted waters, the distillation ensures the absence of micro-organisms and other pollutants in the product.

It is believed that solar energy is best and most cheaply harnessed with thermal energy collection systems. Therefore, the two systems that could be used are the MSF and the MEB plants. As can be seen from previous sections, both systems have been used with solar energy collectors in various applications. According to Tables 8.3 and 8.4, the MEB process requires less specific energy, is cheaper, and requires only a very simple seawater treatment. In addition, the MEB process has advantages over other distillation processes. According to Porteous (1975), these are as follows:

1. Energy economy, because the brine is not heated above its boiling point, as is the case for the MSF process. The result is less irreversibility in the MEB process, since the vapor is used at the temperature at which it is generated.

2. The feed is at its lowest concentration at the highest plant temperature, so scale formation risks are minimized.

3. The feed flows through the plant in series, and the maximum concentration occurs only in the last effect; therefore, the worst boiling point elevation is confined to this effect.

4. The other processes have a high electrical demand because of the recirculation pump in the MSF or the vapor compressor in the VC systems.

5. MSF is prone to equilibrium problems, which are reflected by a reduction in PR. In MEB plants, the vapor generated in one effect is used in the next and PR is not subject to equilibrium problems.

6. Plant simplicity is promoted by the MEB process because fewer effects are required for a given PR.

Of the various types of MEB evaporators, the multiple-effect stack (MES) is the most appropriate for solar energy application. This has a number of advantages, the most important of which is stable operation between virtually 0 and 100% output, even when sudden changes are made, and the ability to follow a varying steam supply without upset (Kalogirou, 2005). For this purpose, collectors of proven technology such as the parabolic trough can be used to produce the input power to the MEB system in the form of low-pressure steam. The temperature required for the heating medium is between 70 and 100°C, which can be produced with such collectors with an efficiency of about 65% (Kalogirou, 2005).

EXERCISES

8.1 Estimate the mole and mass fractions for the salt and water of seawater, which has a salinity of 42,000 ppm.

8.2 Estimate the mole and mass fractions for the salt and water of brackish water, which has a salinity of 1500 ppm.

8.3 Find the enthalpy and entropy of seawater at 35°C.

8.4 A solar still has a water and glass temperature equal to 52.5°C and 41.3°C, respectively. The constants C and n are determined experimentally and are found to be C = 0.054 and n = 0.38. If the convective heat transfer coefficient from water surface to glass is 2.96 W/m2-K, estimate the hourly distillate output per square meter from the solar still.

8.5 An MSF plant has 32 stages. Estimate the Mf/Md ratio if the brine temperature in the first effect is 68°C and the temperature of the brine in the last effect is 34°C. The mean latent heat is 2300 kJ/kg and the mean specific heat is 4.20 kJ/kg-K.

REFERENCES

Adam, S., Cheng, R.C., Vuong, D.X., Wattier, K.L., 2003. Long Beach's dual-stage NF beats single-stage SWRO. Desalin. Water Reuse 13 (3), 18-21.

Adhikari, R.S., Kumar, A., Sodha, G.D., 1995. Simulation studies on a multi-stage stacked tray solar still. Sol. Energy 54 (5), 317-325.

Akinsete, V.A., Duru, C.U., 1979. A cheap method of improving the performance of roof type solar stills. Sol. Energy 23 (3), 271-272.

Al-Karaghouli, A.A., Alnaser, W.E., 2004a. Experimental comparative study of the performances of single and double basin solar-stills. Appl. Energy 77 (3), 317-325.

Al-Karaghouli, A.A., Alnaser, W.E., 2004b. Performances of single and double basin solar-stills. Appl. Energy 78 (3), 347-354.

Al-Madani, H.M.N., 2003. Water desalination by solar powered electrodialysis process. Renewable Energy 28 (12), 1915-1924.

Al-Suleimani, Z., Nair, N.R., 2000. Desalination by solar powered reverse osmosis in a remote area of Sultanate of Oman. Appl. Energy 65 (1-4), 367-380.

Awerbuch, L., Lindemuth, T.E., May, S.C., Rogers, A.N., 1976. Geothermal energy recovery process. Desalin. 19 (1-3), 325-336.

Baldacci, A., Burgassi, P.D., Dickson, M.H., Fanelli, M., 1998. Non-electric utilization of geothermal energy in Italy. In: Proceedings of World Renewable Energy Congress V. Part I, 20-25 September 1998, Florence, Italy, Pergamon, Oxford, UK, p. 2795.

Barbier, E., 1997. Nature and technology of geothermal energy. Renewable and Sustainable Energy Rev. 1 (1-2), 1-69.

Barbier, E., 2002. Geothermal energy technology and current status: an overview. Renewable and Sustainable Energy Rev. 6 (1-2), 3-65.

Bier, C., Coutelle, R., Gaiser, P., Kowalczyk, D., Plantikow, U., 1991. Sea-water desalination by wind-powered mechanical vapor compression plants. In: Seminar on New Technologies for the use of Renewable Energies in Water Desalination. 26-28 September 1991, Athens, Commission of the European Communities, DG XVII for Energy, CRES (Centre for Renewable Energy Sources), Session II, 1991, pp. 49-64.

Boegli, W.J., Suemoto, S.H., Trompeter, K.M., 1977. Geothermal-desalting at the East Mesa test site. Desalin. 22 (1-3), 77-90.

Boeher, A., 1989. Solar desalination with a high efficiency multi-effect process offers new facilities. Desalin. 73, 197-203.

Bouchekima, B., Gros, B., Ouahes, R., Diboun, M., 2001. Brackish water desalination with heat recovery. Desalin. 138 (1-3), 147-155.

Cengel, Y.A., Boles, M.A., 1998. Thermodynamics: An Engineering Approach, third ed. McGraw-Hill, New York.

Cengel, Y.A., Cerci, Y., Wood, B., 1999. Second law analysis of separation processes of mixtures. Proc. of ASME Advanced Energy Systems Division 39, 537-543.

Cerci, Y., 2002. Exergy analysis of a reverse osmosis desalination plant. Desalin. 142 (3), 257-266.

Chaibi, M.T., 2000. Analysis by simulation of a solar still integrated in a greenhouse roof. Desalin. 128 (2), 123-138.

Daniels, F., 1974. Direct Use of the Sun's Energy, sixth ed. Yale University Press, New Haven, CT, and London (Chapter 10).

Delyannis, A., 1960. Introduction to Chemical Technology. History of Chem. Technol. [in Greek], Athens, Chapter 1.

Delyannis, A.A., 1965. Solar stills provide an island's inhabitants with water. Sun at Work 10 (1), 6.

Delyannis, A.A., Delyannis, E.A., 1970. Solar desalting. J. Chem. Eng. 19, 136.

Delyannis, A., Delyannis, E., 1973. Solar distillation plant of high capacity. Proc. of Fourth Inter. Symp. on Fresh Water from Sea 4, 487.

Delyannis, A., Piperoglou, E., 1968. The Patmos solar distillation plant: technical note. Sol. Energy 12 (1), 113-114.

Delyannis, E., 2003. Historic background of desalination and renewable energies. Sol. Energy 75 (5), 357-366.

Delyannis, E., Belessiotis, V., 2000. The history of renewable energies for water desalination. Desalin. 128 (2), 147-159.

Delyannis, E.E., Delyannis, A., 1985. Economics of solar stills. Desalin. 52 (2), 167-176.

Doucet, G., 2001. Energy for tomorrow's world. Renewable Energy, 19-22.

Dresner, L., Johnson, J., 1980. Hyperfiltration (Revere Osmosis). In: Spiegler, K.S., Laird, A.D.K. (Eds.) Principles of Desalination, Part B, second ed. Academic Press, New York, pp. 401-560.

Dunkle, R.V., 1961. Solar water distillation; the roof type still and a multiple effect diffusion still, International Developments in Heat Transfer ASME. In: Proceedings of International Heat Transfer, Part V. University of Colorado, p. 895.

Eggers-Lura, A., 1979. Sol. energy in developing countries. Pergamon Press, Oxford, UK pp. 35-40.

Eibling, J.A., Talbert, S.G., Lof, G.O.G., 1971. Solar stills for community use—Digest of technology. Sol. Energy 13 (2), 263-276.

El-Bahi, A., Inan, D., 1999. A solar still with minimum inclination, coupling to an outside condenser. Desalin. 123 (1), 79-83.

El-Dessouky, H., Ettouney, H., 2000. MSF development may reduce desalination costs. Water and Wastewater Intern., 20-21.

El-Nashar, A.M., 1992. Optimizing the operating parameters of a solar desalination plant. Sol. Energy 48 (4), 207-213.

El-Nashar, A.M., Al-Baghdadi, A.A., 1998. Exergy losses in multiple-effect stack seawa-ter desalination plant. Desalin. 116 (1), 11-24.

El-Sayed, Y.M., Silver, R.S., 1980. Fundamentals of distillation. In: Spiegler, K.S.,

Laird, A.D.K. (Eds.) Principles of Desalination, Part A, second ed. Academic Press, New York, pp. 55-109.

Fiorenza, G., Sharma, V.K., Braccio, G., 2003. Techno-economic evaluation of a solar powered water desalination plant. Energy Convers. Manage. 44 (4), 2217-2240.

Florides, G., Kalogirou, S., 2004. Ground heat exchangers—A review. In: Proceedings of Third International Conference on Heat Power Cycles. Larnaca, Cyprus, on CD ROM.

Frick, G., von Sommerfeld, J., 1973. Solar stills of inclined evaporating cloth. Sol. Energy 14 (4), 427-431.

Garcia-Rodriguez, L., 2003. Renewable energy applications in desalination: State of the art. Sol. Energy 75 (5), 381-393.

Garcia-Rodriguez, L., Romero, T., Gomez-Camacho, C., 2001. Economic analysis of wind-powered desalination. Desalin. 137 (1-3), 259-265.

Garg, H.P., Mann, H.S., 1976. Effect of climatic, operational and design parameters on the year round performance of single sloped and double sloped solar still under Indian and arid zone condition. Sol. Energy 18 (2), 159-163.

Gomkale, S.D., 1988. Solar distillation as a means to provide Indian villages with drinking water. Desalin. 69 (2), 171-176.

Goosen, M.F.A., Sablani, S.S., Shayya, W.H., Paton, C., Al-Hinai, H., 2000.

Thermodynamic and economic considerations in solar desalination. Desalin. 129 (1), 63-89.

Grutcher, J., 1983. Desalination a PV oasis. Photovoltaics Intern. (June/July), 24.

Hamed, O.A., Zamamiri, A.M., Aly, S., Lior, N., 1996. Thermal performance and exergy analysis of a thermal vapor compression desalination system. Energy Convers. Manage. 37 (4), 379-387.

Hanson, A., Zachritz, W., Stevens, K., Mimbella, L., Polka, R., Cisneros, L., 2004.

Distillate water quality of a single-basin solar still: laboratory and field studies. Sol. Energy 76 (5), 635-645.

Hermann, M., Koschikowski, J., Rommel, M., 2000. Corrosion-free solar collectors for thermally driven seawater desalination. In: Proceedings of the EuroSun 2000 Conference on CD ROM, 19-22 June 2000, Copenhagen, Denmark.

Houcine, I., Benjemaa, F., Chahbani, M.H., Maalej, M., 1999. Renewable energy sources for water desalting in Tunisia. Desalin. 125 (1-3), 123-132.

Howe, E.D., Tleimat, B.W., 1974. Twenty years of work on solar distillation at the University of California. Sol. Energy 16 (2), 97-105.

Hussain, N., Rahim, A., 2001. Utilization of new technique to improve the efficiency of horizontal solar desalination still. Desalin. 138 (1-3), 121-128.

ITC (Canary Islands Technological Institute), 2001. Memoria de gestion [in Spanish].

Kalogirou, S.A., 1997a. Solar distillation systems: a review. In: Proceedings of First International Conference on Energy and the Environment, vol. 2. Limassol, Cyprus, pp. 832-838.

Kalogirou, S., 1997b. Survey of solar desalination systems and system selection. Energy— The Intern. J. 22 (1), 69-81.

Kalogirou, S.A., 2001. Effect of fuel cost on the price of desalination water: A case for renewables. Desalin. 138 (1-3), 137-144.

Kalogirou, S., 2005. Seawater desalination using renewable energy sources. Prog. in Energy Combus. Sci. 31 (3), 242-281.

Karameldin, A., Lotfy, A., Mekhemar, S., 2003. The Red Sea area wind-driven mechanical vapor compression desalination system. Desalin. 153 (1-3), 47-53.

Kiatsiriroat, T., 1989. Review of research and development on vertical solar stills. ASEAN J. Sci. Technol. Dev. 6 (1), 15.

Klotz, I.M., Rosenberg, R.M., 1994. Chemical Thermodynamics: Basic Theory and Methods, fifth ed., Wiley, New York.

Kreider, J.F., Kreith, F., 1981. Sol. Energy Handbook. McGraw-Hill, New York.

Kudish, A.I., Gale, J., 1986. Solar desalination in conjunction with controlled environment agriculture in arid zone. Energy Convers. Manage. 26 (2), 201-207.

Kumar, S., Tiwari, G.N., 1996. Estimation of convective mass transfer in solar distillation systems. Sol. Energy 57 (6), 459-464.

Kumar, S., Tiwari, G.N., 1998. Optimization of collector and basin areas for a higher yield active solar still. Desalin. 116 (1), 1-9.

Kvajic, G., 1981. Solar power desalination, PV-ED system. Desalin. 39, 175.

Lobo, P.C., Araujo, S.R., 1978. A Simple multi-effect basin type solar still. In: SUN, Proceedings of the International Solar Energy Society, Vol. 3. New Delhi, India, Pergamon, Oxford, UK, pp. 2026-2030.

Luft, W., 1982. Five solar energy desalination systems. Int. J. Sol. Energy 1 (21).

Lui, C.C.K., Park, J.W., Migita, R., Qin, G., 2002. Experiments of a prototype wind-driven reverse osmosis desalination system with feedback control. Desalin. 150 (3), 277-287.

Major, J.K., 1990. Water wind and animal power. In: McNeil, J. (Ed.), An Encyclopedia of the History of Technology. Rutledge, R. Clay Ltd, Great Britain, Bungay, pp. 229-270.

Malik, M.A.S., Tiwari, G.N., Kumar, A., Sodha, M.S., 1982. Solar Distillation. Pergamon Press, Oxford, UK.

Matz, R., Feist, E.M., 1967. The application of solar energy to the solution of some problems of electrodialysis. Desalin. 2 (1), 116-124.

Maurel, A., 1991. Desalination by reverse osmosis using renewable energies

(solar-wind) Cadarche Centre Experiment. In: Seminar on New Technologies for the Use of Renewable Energies in Water Desalination, 26-28 September 1991, Athens. Commission of the European Communities, DG XVII for Energy, CRES (Centre for Renewable Energy Sources), Session II, pp. 17-26.

Morris, R.M., Hanbury, W.T., 1991. Renewable energy and desalination—A review. In: Proceedings of the New Technologies for the Use of Renewable Energy Sources in Water Desalination, Sec. I, Athens, Greece, pp. 30-50.

Moustafa, S.M.A., Jarrar, D.I., Mansy, H.I., 1985. Performance of a self-regulating solar multistage flush desalination system. Sol. Energy 35 (4), 333-340.

Mukherjee, K., Tiwari, G.N., 1986. Economic analysis of various designs of conventional solar stills. Energy Convers. Manage. 26 (2), 155-157.

Mustacchi, C., Cena, V., 1978. Solar water distillation, technology for solar energy utilization. United Nations, New York, pp. 119-124.

Ophir, A., 1982. Desalination plant using low-grade geothermal heat. Desalin. 40 (1-2), 125-132.

Parekh, S., Farid, M.M., Selman, R.R., Al-Hallaj, S., 2003. Solar desalination with humidification-dehumidification technique—A comprehensive technical review. Desalin. 160 (2), 167-186.

Plantikow, U., 1999. Wind-powered MVC seawater desalination-operational results. Desalin. 122 (2-3), 291-299.

Popiel, C., Wojtkowiak, J., Biernacka, B., 2001. Measurements of temperature distribution in ground. Exp. Therm Fluid Sci. 25, 301-309.

Porteous, A., 1975. Saline Water Distillation Processes. Longman, Essex, UK.

Rajvanshi, A.K., 1980. A scheme for large-scale desalination of seawater by solar energy. Sol. Energy 24 (6), 551-560.

Rajvanshi, A.K., 1981. Effects of various dyes on solar distillation. Sol. Energy 27 (1), 51-65.

Rodriguez, G., Rodriguez, M., Perez, J., Veza, J. 1996. A systematic approach to desalination powered by solar, wind and geothermal energy sources. In: Proceedings of the Mediterranean Conference on Renewable Energy Sources for Water Production, European Commission, EURORED Network, CRES, EDS, Santorini, Greece, 10-12 June 1996, pp. 20-25.

Rommel, M., Hermann, M., Koschikowski, J., 2000. The SODESA project: Development of solar collectors with corrosion-free absorbers and first results of the desalination pilot plant. In: Mediterranean Conference on Policies and Strategies for Desalination and Renewable Energies, 21-23 June 2000, Santorini, Greece.

Satcunanathan, S., Hanses, H.P., 1973. An investigation of some of the parameters involved in solar distillation. Sol. Energy 14 (3), 353-363.

Shaffer, L.H., Mintz, M.S., 1980. Electrodialysis. In: Spiegler, K.S., Laird, A.D.K. (Eds.) Principles of Desalination, Part A, second ed. Academic Press, New York, pp. 257-357.

Sodha, M.S., Adhikari, R.S., 1990. Techno-economic model of solar still coupled with a solar flat-plate collector. Int. J. Energy Res. 14 (5), 533-552.

Sodha, M.S., Kumar, A., Tiwari, G.N., Tyagi, R.C., 1981. Simple multiple-wick solar still: analysis and performance. Sol. Energy 26 (2), 127-131.

Suneja, S., Tiwari, G.N., 1999. Optimization of number of effects for higher yield from an inverted absorber solar still using the Runge-Kutta method. Desalin. 120 (3), 197-209.

Tabor, H., 1990. Solar energy technologies for the alleviation of fresh-water shortages in the Mediterranean basin, Euro-Med solar. In: Proceedings of the Mediterranean Business Seminar on Solar Energy Technologies, Nicosia, Cyprus, pp. 152-158.

Talbert, S.G., Eibling, J.A., Lof, G.O.G. 1970. Manual on solar distillation of saline water, R&D Progress Report No. 546, U.S. Department of the Interior, Battelle Memorial Institute, Columbus, OH.

Tanaka, H., Nosoko, T., Nagata, T., 2000a. A highly productive basin-type-multiple-effect coupled solar still. Desalin. 130 (3), 279-293.

Tanaka, H., Nosoko, T., Nagata, T., 2000b. Parametric investigation of a basin-type-multiple-effect coupled solar still. Desalin. 130 (3), 295-304.

THERMIE Program, 1998. Desalination Guide Using Renewable Energies. CRES, Athens, Greece.

Thomson, M., Infield, D., 2003. A photovoltaic-powered seawater reverse-osmosis system without batteries. Desalin. 153 (1-3), 1-8.

Tiwari, G.N., 1984. Demonstration plant of multi-wick solar still. Energy Convers. Manage. 24 (4), 313-316.

Tiwari, G.N., 1992. Contemporary physics-solar energy and energy conservation, Chapter 2. In: Recent Advances in Solar Distillation. Wiley Eastern Ltd, New Delhi, India.

Tiwari, G.N., 2002. Solar Energy. Narosa Publishing House, New Delhi, India.

Tiwari, G.N., Noor, M.A., 1996. Characterization of solar still. Int. J. Sol. Energy 18, 147.

Tiwari, G.N., Singh, H.N., Tripathi, R., 2003. Present status of solar distillation. Sol. Energy 75 (5), 367-373.

Tiwari, G.N., Yadav, Y.P., 1985. Economic analysis of large-scale solar distillation plant. Energy Convers. Manage. 25 (14), 423-425.

Tleimat, B.W., 1978. Solar distillation: The state of the art, Technology for solar energy utilization. United Nations, New York, pp. 113-118.

Tleimat, M.W., 1980. Freezing methods. In: Spiegler, K.S., Laird, A.D.K. (Eds.) Principles of Desalination, Part B, second ed. Academic Press, New York, pp. 359-400.

Tleimat, B.W., Howe, E.D., 1967. Comparison of plastic and glass condensing covers for solar distillers. In: Proceedings of Solar Energy Society, annual conference, Arizona.

Tzen, E., Morris, R., 2003. Renewable energy sources for desalination. Sol. Energy 75 (5), 375-379.

Tzen, E., Perrakis, K., Baltas, P., 1998. Design of a stand-alone PV-desalination system for rural areas. Desalin. 119 (1-3), 327-333.

Veza, J., Penate, B., Castellano, F., 2001. Electrodialysis desalination designed for wind energy (on-grid test). Desalin. 141 (1), 53-61.

Voropoulos, K., Mathioulakis, E., Belessiotis, V., 2001. Experimental investigation of a solar still coupled with solar collectors. Desalin. 138 (1-3), 103-110.

Zarza, E., Ajona, J.I., Leon, J., Genthner, K., Gregorzewski, A., 1991a. Solar thermal desalination project at the Plataforma Solar De Almeria. In: Proceedings of the Biennial Congress of the International Solar Energy Society, 1, Part II, Denver, Colorado, pp. 2270-2275.

Zarza, E., Ajona, J.I., Leon, J., Genthner, K., Gregorzewski, A., Alefeld, G., Kahn, R., Haberle, A., Gunzbourg, J., Scharfe, J., Cord'homme, C., 1991b. Solar thermal desalination project at the Plataforma solar de Almeria. In: Proceedings of the New Technologies for the Use of Renewable Energy Sources in Water Desalination, Athens, Greece, Sec. III, pp. 62-81.

Zein, M., Al-Dallal, S., 1984. Solar desalination correlation with meteorological parameters. In: Proceedings of the Second Arab International Conference, p. 288.

conventional sources is impractical or costly. For grid connected distributed systems, the actual value of photovoltaic electricity can be high because this electricity is produced during periods of peak demand, thereby reducing the need for costly extra conventional capacity to cover the peak demand. Additionally, PV electricity is close to the sites where it is consumed, thereby reducing transmission and distribution losses and thus increasing system reliability.

A PV cell consists of two or more thin layers of semiconducting material, most commonly silicon. When the silicon is exposed to light, electrical charges are generated; and this can be conducted away by metal contacts as direct current. The electrical output from a single cell is small, so multiple cells are connected and encapsulated (usually glass covered) to form a module (also called a panel).

The PV panel is the main building block of a PV system, and any number of panels can be connected together to give the desired electrical output. This modular structure is a considerable advantage of the PV system, where further panels can be added to an existing system as required.

Photovoltaic devices, or cells, are used to convert solar radiation directly into electricity. A review of possible materials that can be used for PV cells is given in Chapter 1, Section 1.5.1. Photovoltaic cells are made of various semiconductors, which are materials that are only moderately good conductors of electricity. The materials most commonly used are silicon (Si) and compounds of cadmium sulphide (CdS), cuprous sulphide (Cu2S), and gallium arsenide (GaAs). These cells are packed into modules that produce a specific voltage and current when illuminated. A comprehensive review of cell and module technologies is given by Kazmerski (1997). PV modules can be connected in series or parallel to produce larger voltages or currents. PV systems rely on sunlight, have no moving parts, are modular to match power requirements on any scale, are reliable, and have a long life. Photovoltaic systems can be used independently or in conjunction with other electrical power sources. Applications powered by PV systems include communications (both on earth and in space), remote power, remote monitoring, lighting, water pumping, and battery charging. Some of these applications are analyzed in Section 9.5. The global installed capacity of photovolta-ics at the end of 2002 was near 2 GWp (Lysen, 2003).

Was this article helpful?

0 0
Living Off The Grid

Living Off The Grid

Get All The Support And Guidance You Need To Be A Success At Living Off The Grid. This Book Is One Of The Most Valuable Resources In The World When It Comes To When Living Within The Grid Is Not Making Sense Anymore.

Get My Free Ebook


Post a comment