- Email: [email protected]
Nuclear seawater desalination — IAEA activities and economic evaluation for southern Europe
DESALINATION ELSEVIER
Desalination 126 (1999) 301-307 www.elsevier.com/locate/desal
Nuclear seawater desalination IAEA activities and economic evaluation for southern Europe Peter J. Gowin*, Toshio Konishi lnternational Atomic Energy Agency, PO Box 100, A-1400 Vienna, Austria Tel. +43 (1) 2600-22863; Fax +43 (1) 2600-29598; email: [email protected]
Abstract
The International Atomic Energy Agency (IAEA) has addressed the issue of seawater desalination for potable water production with renewed intensity since 1989. It has been found that there are no technical impediments to the use of nuclear reactors as an energy source for seawater desalination. Highlights of projects regarding nuclear desalination in several of the IAEA Member States are described, such as a feasibility study in Morocco using a Chinese heating reactor and facilities in India. The role of nuclear energy in the next century is discussed; economics, security of supply and the overall goal of a sound energy mix in national energy plans have been considerations in the choice of nuclear power along with an awareness of its environmental benefits. The IAEA has developed a computer software package, Desalination Economic Evaluation Programme (DEEP), used for the economic comparison of different seawater desalination options. Its economic evaluation methodology is described. In 1998, the IAEA initiated the most comprehensive comparative study to date on nuclear seawater desalination of its kind. The DEEP software was used for the economic comparison of different seawater desalination options after a validation of the software by international experts. The study was conducted for three different regions of the world, being described by different labour costs, interest rates, and seawater conditions; in each region two economic scenarios were calculated, favouring nuclear and fossil options, respectively. Reverse osmosis, multi-effect distillation and multi-stage flash were chosen as desalination technologies to be coupled to ten selected power options, including pressurized water reactors and pressurized heavy water reactors, as well as to fossil-fueled plants (coal and combined cycle). Results are presented for the region of southern Europe. Without considering all input data in detail, and also taking into account results from previous studies, it was found that nuclear and fossil desalination yield water costs in the same range. More specific results and findings regarding a comparison between nuclear and fossil options are given in the paper. The desalination of seawater using nuclear energy is a cost competitive and feasible option for potable water production. Keywords: Nuclear desalination; IAEA; southern Europe
*Corresponding author. Presented at the Conference on Desalination and the Environment, Las Palmas, Gran Canaria, November 9-12, 1999. European Desalination Society and the International Water Services Association. 0011-9164/99/$- See front matter © 1999 Elsevier Science B.V. All rights reserved PII: S0011-9164(99)00186-1
302
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
1. Introduction For human life a sufficient amount of water of adequate quality is essential. The scarcity of freshwater and especially potable water is jeopardizing many regions of the world [1]. By 2025, about two-thirds of the world's population may suffer from high or moderate water shortages. Seawater desalination offers one of the most promising alternatives for the supply of potable water. In order to contribute to the solution of this problem, the International Atomic Energy Agency (IAEA) has assessed the option to produce water using nuclear energy. A total of 434 nuclear power plants were operating around the world in 1998, based on data reported to the IAEA. During 1998, four nuclear power plants representing 2958 MWel net electric capacity were connected to the grid, three in the Republic of Korea and one in the Slovak Republic. Additionally, construction of four new nuclear reactors started in 1998 - - two in China (plus one in Taiwan, China) and one in Japan, bringing the total number of nuclear reactors reported as being under construction to 36. Overall nuclear power plants provided approximately 16% of the world's electricity production in 1998. Cumulative worldwide operating experience from civil nuclear power reactors at the end of 1998 exceeded 9000 reactoryears. The interest in the deployment of nuclear energy has started to gradually shift from industrialized states to developing countries. This trend is expected to continue in the short- and mid-term future. Forecasts predict that much of future energy demand will be in developing countries, and nuclear energy can contribute to meet that demand while helping to keep CO 2 emissions at a sustainable level [2]. 2. Seawater desalination using nuclear energy Seawater desalination is the processing of seawater to obtain fresh water with low salinity
adequate for drinking. It has been found that there are no technical impediments to the use of nuclear reactors as an energy source for seawater desalination. Nuclear reactors could provide electricity or heat, or both, as required by the desalination processes. Regarding nuclear safety, the same principles, criteria, and measures would apply as to any other nuclear power plant. An additional requirement is that the product water has to be adequately protected against possible contamination. A broad spectrum of nuclear reactors is available today. In principle, all nuclear power reactors are capable of providing energy for desalination processes. Due to their typically low working temperatures, dedicated heating reactors can be combined with distillation processes. Furthermore, as nuclear reactors show their highest efficiency in base load operation and desalination basically is a base load process, nuclear desalination seems to have inherent advantages over other energy options. Depending on the availability and size of an electric grid, nuclear power plants can be integrated into the grid to supply the electricity market. The maximum size of the power plant will then depend on the grid capacity. In areas without a suitable grid, the reactors would have to be dedicated exclusively to supplying energy to the desalination plant and for local use leading to small nuclear units. Such small reactors could be installed on shore as land-based units supplying adjacent desalination plants or as barge-mounted self-sufficient floating plants.
3. International highlights Combining the use of nuclear energy with the industrial process of seawater desalination has been considered as far back as in the 1960s. The total worldwide operating experience with nuclear seawater desalination adds up to about 100 reactor-years. In addition to that, experience
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
with nuclear district heating, where a similar technology for heat extraction is used, yields another 600 reactor-years of worldwide operating experience. Nuclear seawater desalination is now worldwide in a decisive phase. Two countries, Morocco and India, have already started their own national demonstration projects; others are preparing such projects. The IAEA has assisted these countries in providing the only comprehensive and regular worldwide forum for information exchange and cooperation in this field. This included coordinating research activities to issue technical and economic documents and to provide evaluation software and training to Member States. The most comprehensive overview of activities in nuclear desalination to-date is given in [3]. In Morocco, a first step in the direction of nuclear seawater desalination was made in a governmental agreement between Morocco and China in September 1996. This agreement provides for a pre-project study on using a 10MWth heating reactor from China for the production of potable water in Morocco using MED technology. The complex would produce about 8000 m3/d of potable water; two suitable sites at Tan-Tan have been selected. The estimated water cost of this demonstration plant can then be extrapolated for a commercial nuclear desalination plant of the same type (one option is potable water production of 140,000m3/d using a 200MW~ heating reactor). The pre-project study was finished in 1998; in 1999, a decision was made to continue the project. India has operated a small experimental desalination facility at the nuclear complex in Mumbai since 1984. The MSF plant uses intake and outfall of a 100 MWth research heavy water reactor (Cirus type) and produces 425 m3/d of potable water using MSF technology. Its product water is sent to the research reactor as and when there is need for process water. A 30 m3/d low-temperature vacuum evaporation (LTE) unit is now being coupled with the research reactor, which will use the moderator
303
waste heat as energy source and will provide the makeup water for the reactor. A desalination unit is intended to be coupled to an existing Pressurized Heavy Water Reactor at Kalpakkam (Madras Atomic Power Station site) with 170 MWe,. The desalination unit will combine multi-stage flash and reverse osmosis elements and form a hybrid plant producing 6300 m3/d of water (4500 by MSF and 1800 by RO). Civil work for the project is already under way, and commissioning for the plant is expected in 2001.
4. Economic evaluation software and input data
In 1998, the IAEA initiated the most comprehensive comparative study to date on nuclear seawater desalination, using the IAEA software Desalination Economic Evaluation Programme (DEEP 1.1). The software DEEP was validated in 1998 both against plant data of operating plants and against other computer codes used for desalination plant planning and evaluation and is available as a trial version DEEP 1.1, working with MS EXCEL 7.0 and Windows 95 or higher from the IAEA. The software, its purpose and structure are described in detail in Section 4.1. In December 1998, a group of international experts deten ,ined the calculation scheme and the input data to be fed into the software. The input data for the calculation are given in Section 4.2. 4.1. Desalination Economic Evaluation Programme (DEEP)
The purpose of DEEP 1.1 is outlined in the Manual [4] as follows: "The Spreadsheet Methodology for Cogeneration/Desalination Economic Evaluation [now: DEEP 1.1] is suitable for economic evaluations and screening analyses of various desalination and energy source options. The spreadsheet includes simplified models of several types of nuclear/fossil power plants, nuclear/fossil heat
304
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
sources, and both distillation and membrane desalination plants. Current cost and performance data have already been incorporated so that the spreadsheet can be quickly adapted to analyze a large variety of options with very little new input data required .... The spreadsheet output includes the levelized cost of water and power, breakdowns of cost components, energy consumption and net salable power for each selected option. Specific power plants can be modeled by adjustment of input data including design power, power cycle parameters and costs. The spreadsheet serves three important goals: • It enables side-by-side comparison of a large number of design alternatives on a consistent basis with common assumptions. • It enables quick identification of the lowest cost options for providing specified quantities of desalinated water and/or power at a given location. • It gives an approximate cost of desalinated water and power as a function of quantity and site specific parameters including temperatures and salinity. However, the user is cautioned that the spreadsheet is based on simplified models. For planning an actual project, final assessment of project costs should be assessed more accurately based on more substantive information including project design and specific vendor data." DEEP comprises modules for several desalination and energy generation options: multieffect distillation (MED), multi-stage flash (MSF), reverse osmosis (RO), including all possible hybrid combinations. DEEP contains I 1 energy modules: five nuclear reactors, three of which are nuclear steam power plants; superheated steam boilers for coal, oil or gas; an open cycle gas turbine; a combined cycle gas turbine; a diesel, used as poweronly plant and a boiler (steam or hot water), used as
heat-only plant. Steam extraction/condensing turbine models are assumed both for the nuclear and the fossil energy options. DEEP can combine the above-mentioned technologies for all plant sizes, with a focus on plants of 10,000 m3/d or larger. For each plant option, DEEP calculates power and water production performance and resulting costs for distillation (MED or MSF), for both stand-alone and contiguous (located at the same site as the power plant) RO systems, and for a hybrid plant. DEEP first calculates an unmodified power plant. Then, DEEP calculates the modified system performance for coupling with a distillation system, if relevant, when heat is extracted. Next, the distillation plant calculations are performed, if relevant. A gain output ratio (GOR) for both MED and MSF plants is calculated from the number of stages/effects which in turn is calculated from the available working temperature difference of the distillation plant. The total water production is then calculated. After the distillation plant calculations, calculations are performed for the stand-alone and the contiguous membrane plants, if relevant. For all calculations, WHO drinking water standards are assumed. DEEP then calculates the base power plant power cost, the distillation system water cost and the RO system water cost by summing the annual capital, fuel (or energy) and O&M costs and dividing by the annual product output. The electricity cost is calculated as "lifetime levelized electricity cost", i.e., by dividing the discounted sum of all expenditures associated with the generation by the discounted value of the product. For the distribution of costs to the two products in a co-generation plant, i.e., power and water, DEEP uses the "power credit method", i.e., the loss of electricity generation is charged to the water costs. In effect, the water is credited with all economic benefits resulting from the plant being a co-production plant. The application of this method is justified for large energy plants, where electricity generation dominates. For hybrid cases, the water
8.5
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aPressurized water reactor; bpressurized heavy water reactor; cPulverized coal; aCombined cycle, eGas turbine; fHeating reactor.
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Reference power plant unit net output, MWeL Reference condensing temperature, °C Main steam temperature, °C Reference net thermal efficiency, % Overnight cost = specific construction cost DEEP, $/kWet Construction lead time, m Specific O&M cost, $/MWh Fuel (cycle) cost,
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Table 1 Cost input data for all power options
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P.£ Gowin, T. Konishi / Desalination 126 (1999) 301-307
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Fig. 1. Region 1. Water cost for selected power options for RO and MED technology and for two economic scenarios, favouring nuclear (up) and fossil (down) as a function of the water plant size. The water plant sizes chosen were 120,000 m3/d, 240,000 m3/d and 480,000 m3/d from left to right.
cost is equal to the blend of the distillation and RO cost according to the amounts of distillation water and RO water produced.
4.2. Economic evaluation scheme: input data Studies were performed for three broad regions: • Region 1, corresponding to southern Europe (south of France, Italy, Greece, Turkey and Spain) • Region 2, corresponding to southeast Asia, the Red Sea region and the North African region • Region 3, corresponding to the Arabian Gulf region (average seawater salinity and temperature) The regions were chosen on the basis of the DuPont world map for desalination. The water conditions for Regions 1, 2 and 3 were: total dissolved solids (TDS) of 38,000 ppm and a seawater temperature of
20 oC in Region 1; 41,000 ppm and 25 oC in Region 2 and 45,000ppm and 30°C in Region 3. Labour costs were fixed to be $160,000/a in Region 1 and $60,000/a in Regions 2 and 3. A baseline for cost input data for all power options was defined and is given in Table 1. Within each region, two economic scenarios were defined: "up" (favouring nuclear) and "down" (favouring fossil). The two economic scenarios used the cost input data given in Table 1 with variations of ±15% for up and down, respectively, but also assumed different values for interest/discount rate (Region 1: 5% and 8%, Regions 2 and 3: 8% and 10%) and fossil fuel cost ($20/bbl and $30/bbl for oil/gas ($50/t and $70/t for coal) in all regions, with a real escalation rate set to zero, thus assuming average values over the lifetime of 40 years. (This means that with an initial fuel price (in 1999) of$12 and $18/bbl and a real escalation rate of 2%, the
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
prices of $20 and $30/bbl will be reached after 25 years.) Apart from input data specified for the study, the default input data in DEEP version 1.1 was used. The economic lifetime was generally to be set to 40 years, with minor exceptions not repeated here. All cost data are given in 1998 US dollars. In addition to the region-by-region studies, a sensitivity analysis, with variations of all important parameters, was carried out to permit evaluation and understanding of possible trends. Three power options with 600MWel were chosen, PWR-600, PHWR-600 and CC-600. Results of the sensitivity analysis cannot be presented in the frame of this paper. In all regional studies, RO and MED were chosen as desalination processes, and multi-stage flash (MSF) was included only for Regions 2 and 3. The base unit cost for MED was determined to be $900/(m3/d) installed capacity, for MSF $1800/ (m3/d) and for RO $800/(m3/d) for all calculations. The DEEP default value of 70°C was taken as the "maximum brine temperature" (unless the DEEP item "minimum required maximum brine temperature" is higher; in that case, DEEP automatically takes the higher value. This was the case if the desired water production could not be achieved with 70°C). The projected needs were based on historical records of installed seawater desalination capacity, known orders for new capacity to be installed over the next several years, population projections and expert judgments. The following water plant sizes were selected: 480,000m3/d, 240,000m3/d, 120,000m3/d, and 60,000 m3/d.
307
5. Economic evaluation results for southern Europe Fig, 1 gives the results of the calculations for Region 1, corresponding to southern Europe. It shows the water cost in S/ms for all power options as a function of the water plant size. Different symbols reflect different water desalination technologies.
References [1] WorldWater Forum, Marrakech,Morocco, 1997. [2] Intemational Atomic Energy Agency, Sustainable developmentand nuclear power, Vienna, 1997. [3] International Atomic Energy Agency, Nuclear desalination of sea water, Proc., Series STI/PUB/ 1025, Vienna, 1997. [4] InternationalAtomic Energy Agency, Methodology for the economic evaluation of cogeneration/desalination options: a user's manual, Computer Manual Series No. 12, Vienna, 1997. [5] InternationalAtomic Energy Agency, Use of nuclear reactors for seawater desalination, TECDOC-574, Vienna, 1990. [6] InternationalAtomic Energy Agency, Technical and economic evaluation of potable water production through desalination of seawater by using nuclear energy and other means, TECDOC-666, Vienna, 1992. [7] International Atomic Energy Agency, Potential for nuclear desalination as a source of low-cost potable water in North Africa,TECDOC-917, Vienna, 1996.
Desalination 126 (1999) 301-307 www.elsevier.com/locate/desal
Nuclear seawater desalination IAEA activities and economic evaluation for southern Europe Peter J. Gowin*, Toshio Konishi lnternational Atomic Energy Agency, PO Box 100, A-1400 Vienna, Austria Tel. +43 (1) 2600-22863; Fax +43 (1) 2600-29598; email: [email protected]
Abstract
The International Atomic Energy Agency (IAEA) has addressed the issue of seawater desalination for potable water production with renewed intensity since 1989. It has been found that there are no technical impediments to the use of nuclear reactors as an energy source for seawater desalination. Highlights of projects regarding nuclear desalination in several of the IAEA Member States are described, such as a feasibility study in Morocco using a Chinese heating reactor and facilities in India. The role of nuclear energy in the next century is discussed; economics, security of supply and the overall goal of a sound energy mix in national energy plans have been considerations in the choice of nuclear power along with an awareness of its environmental benefits. The IAEA has developed a computer software package, Desalination Economic Evaluation Programme (DEEP), used for the economic comparison of different seawater desalination options. Its economic evaluation methodology is described. In 1998, the IAEA initiated the most comprehensive comparative study to date on nuclear seawater desalination of its kind. The DEEP software was used for the economic comparison of different seawater desalination options after a validation of the software by international experts. The study was conducted for three different regions of the world, being described by different labour costs, interest rates, and seawater conditions; in each region two economic scenarios were calculated, favouring nuclear and fossil options, respectively. Reverse osmosis, multi-effect distillation and multi-stage flash were chosen as desalination technologies to be coupled to ten selected power options, including pressurized water reactors and pressurized heavy water reactors, as well as to fossil-fueled plants (coal and combined cycle). Results are presented for the region of southern Europe. Without considering all input data in detail, and also taking into account results from previous studies, it was found that nuclear and fossil desalination yield water costs in the same range. More specific results and findings regarding a comparison between nuclear and fossil options are given in the paper. The desalination of seawater using nuclear energy is a cost competitive and feasible option for potable water production. Keywords: Nuclear desalination; IAEA; southern Europe
*Corresponding author. Presented at the Conference on Desalination and the Environment, Las Palmas, Gran Canaria, November 9-12, 1999. European Desalination Society and the International Water Services Association. 0011-9164/99/$- See front matter © 1999 Elsevier Science B.V. All rights reserved PII: S0011-9164(99)00186-1
302
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
1. Introduction For human life a sufficient amount of water of adequate quality is essential. The scarcity of freshwater and especially potable water is jeopardizing many regions of the world [1]. By 2025, about two-thirds of the world's population may suffer from high or moderate water shortages. Seawater desalination offers one of the most promising alternatives for the supply of potable water. In order to contribute to the solution of this problem, the International Atomic Energy Agency (IAEA) has assessed the option to produce water using nuclear energy. A total of 434 nuclear power plants were operating around the world in 1998, based on data reported to the IAEA. During 1998, four nuclear power plants representing 2958 MWel net electric capacity were connected to the grid, three in the Republic of Korea and one in the Slovak Republic. Additionally, construction of four new nuclear reactors started in 1998 - - two in China (plus one in Taiwan, China) and one in Japan, bringing the total number of nuclear reactors reported as being under construction to 36. Overall nuclear power plants provided approximately 16% of the world's electricity production in 1998. Cumulative worldwide operating experience from civil nuclear power reactors at the end of 1998 exceeded 9000 reactoryears. The interest in the deployment of nuclear energy has started to gradually shift from industrialized states to developing countries. This trend is expected to continue in the short- and mid-term future. Forecasts predict that much of future energy demand will be in developing countries, and nuclear energy can contribute to meet that demand while helping to keep CO 2 emissions at a sustainable level [2]. 2. Seawater desalination using nuclear energy Seawater desalination is the processing of seawater to obtain fresh water with low salinity
adequate for drinking. It has been found that there are no technical impediments to the use of nuclear reactors as an energy source for seawater desalination. Nuclear reactors could provide electricity or heat, or both, as required by the desalination processes. Regarding nuclear safety, the same principles, criteria, and measures would apply as to any other nuclear power plant. An additional requirement is that the product water has to be adequately protected against possible contamination. A broad spectrum of nuclear reactors is available today. In principle, all nuclear power reactors are capable of providing energy for desalination processes. Due to their typically low working temperatures, dedicated heating reactors can be combined with distillation processes. Furthermore, as nuclear reactors show their highest efficiency in base load operation and desalination basically is a base load process, nuclear desalination seems to have inherent advantages over other energy options. Depending on the availability and size of an electric grid, nuclear power plants can be integrated into the grid to supply the electricity market. The maximum size of the power plant will then depend on the grid capacity. In areas without a suitable grid, the reactors would have to be dedicated exclusively to supplying energy to the desalination plant and for local use leading to small nuclear units. Such small reactors could be installed on shore as land-based units supplying adjacent desalination plants or as barge-mounted self-sufficient floating plants.
3. International highlights Combining the use of nuclear energy with the industrial process of seawater desalination has been considered as far back as in the 1960s. The total worldwide operating experience with nuclear seawater desalination adds up to about 100 reactor-years. In addition to that, experience
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
with nuclear district heating, where a similar technology for heat extraction is used, yields another 600 reactor-years of worldwide operating experience. Nuclear seawater desalination is now worldwide in a decisive phase. Two countries, Morocco and India, have already started their own national demonstration projects; others are preparing such projects. The IAEA has assisted these countries in providing the only comprehensive and regular worldwide forum for information exchange and cooperation in this field. This included coordinating research activities to issue technical and economic documents and to provide evaluation software and training to Member States. The most comprehensive overview of activities in nuclear desalination to-date is given in [3]. In Morocco, a first step in the direction of nuclear seawater desalination was made in a governmental agreement between Morocco and China in September 1996. This agreement provides for a pre-project study on using a 10MWth heating reactor from China for the production of potable water in Morocco using MED technology. The complex would produce about 8000 m3/d of potable water; two suitable sites at Tan-Tan have been selected. The estimated water cost of this demonstration plant can then be extrapolated for a commercial nuclear desalination plant of the same type (one option is potable water production of 140,000m3/d using a 200MW~ heating reactor). The pre-project study was finished in 1998; in 1999, a decision was made to continue the project. India has operated a small experimental desalination facility at the nuclear complex in Mumbai since 1984. The MSF plant uses intake and outfall of a 100 MWth research heavy water reactor (Cirus type) and produces 425 m3/d of potable water using MSF technology. Its product water is sent to the research reactor as and when there is need for process water. A 30 m3/d low-temperature vacuum evaporation (LTE) unit is now being coupled with the research reactor, which will use the moderator
303
waste heat as energy source and will provide the makeup water for the reactor. A desalination unit is intended to be coupled to an existing Pressurized Heavy Water Reactor at Kalpakkam (Madras Atomic Power Station site) with 170 MWe,. The desalination unit will combine multi-stage flash and reverse osmosis elements and form a hybrid plant producing 6300 m3/d of water (4500 by MSF and 1800 by RO). Civil work for the project is already under way, and commissioning for the plant is expected in 2001.
4. Economic evaluation software and input data
In 1998, the IAEA initiated the most comprehensive comparative study to date on nuclear seawater desalination, using the IAEA software Desalination Economic Evaluation Programme (DEEP 1.1). The software DEEP was validated in 1998 both against plant data of operating plants and against other computer codes used for desalination plant planning and evaluation and is available as a trial version DEEP 1.1, working with MS EXCEL 7.0 and Windows 95 or higher from the IAEA. The software, its purpose and structure are described in detail in Section 4.1. In December 1998, a group of international experts deten ,ined the calculation scheme and the input data to be fed into the software. The input data for the calculation are given in Section 4.2. 4.1. Desalination Economic Evaluation Programme (DEEP)
The purpose of DEEP 1.1 is outlined in the Manual [4] as follows: "The Spreadsheet Methodology for Cogeneration/Desalination Economic Evaluation [now: DEEP 1.1] is suitable for economic evaluations and screening analyses of various desalination and energy source options. The spreadsheet includes simplified models of several types of nuclear/fossil power plants, nuclear/fossil heat
304
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
sources, and both distillation and membrane desalination plants. Current cost and performance data have already been incorporated so that the spreadsheet can be quickly adapted to analyze a large variety of options with very little new input data required .... The spreadsheet output includes the levelized cost of water and power, breakdowns of cost components, energy consumption and net salable power for each selected option. Specific power plants can be modeled by adjustment of input data including design power, power cycle parameters and costs. The spreadsheet serves three important goals: • It enables side-by-side comparison of a large number of design alternatives on a consistent basis with common assumptions. • It enables quick identification of the lowest cost options for providing specified quantities of desalinated water and/or power at a given location. • It gives an approximate cost of desalinated water and power as a function of quantity and site specific parameters including temperatures and salinity. However, the user is cautioned that the spreadsheet is based on simplified models. For planning an actual project, final assessment of project costs should be assessed more accurately based on more substantive information including project design and specific vendor data." DEEP comprises modules for several desalination and energy generation options: multieffect distillation (MED), multi-stage flash (MSF), reverse osmosis (RO), including all possible hybrid combinations. DEEP contains I 1 energy modules: five nuclear reactors, three of which are nuclear steam power plants; superheated steam boilers for coal, oil or gas; an open cycle gas turbine; a combined cycle gas turbine; a diesel, used as poweronly plant and a boiler (steam or hot water), used as
heat-only plant. Steam extraction/condensing turbine models are assumed both for the nuclear and the fossil energy options. DEEP can combine the above-mentioned technologies for all plant sizes, with a focus on plants of 10,000 m3/d or larger. For each plant option, DEEP calculates power and water production performance and resulting costs for distillation (MED or MSF), for both stand-alone and contiguous (located at the same site as the power plant) RO systems, and for a hybrid plant. DEEP first calculates an unmodified power plant. Then, DEEP calculates the modified system performance for coupling with a distillation system, if relevant, when heat is extracted. Next, the distillation plant calculations are performed, if relevant. A gain output ratio (GOR) for both MED and MSF plants is calculated from the number of stages/effects which in turn is calculated from the available working temperature difference of the distillation plant. The total water production is then calculated. After the distillation plant calculations, calculations are performed for the stand-alone and the contiguous membrane plants, if relevant. For all calculations, WHO drinking water standards are assumed. DEEP then calculates the base power plant power cost, the distillation system water cost and the RO system water cost by summing the annual capital, fuel (or energy) and O&M costs and dividing by the annual product output. The electricity cost is calculated as "lifetime levelized electricity cost", i.e., by dividing the discounted sum of all expenditures associated with the generation by the discounted value of the product. For the distribution of costs to the two products in a co-generation plant, i.e., power and water, DEEP uses the "power credit method", i.e., the loss of electricity generation is charged to the water costs. In effect, the water is credited with all economic benefits resulting from the plant being a co-production plant. The application of this method is justified for large energy plants, where electricity generation dominates. For hybrid cases, the water
8.5
5
40
253
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52 6.8
1677
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676
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60
236
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1552
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875
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N/A
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42
42 1842
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600
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60 6.2
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DEEP default DEEP default 40
600
GT ' , 600
aPressurized water reactor; bpressurized heavy water reactor; cPulverized coal; aCombined cycle, eGas turbine; fHeating reactor.
40
72 9
60 11
40
1600
1937
200
DEEP default 33
DEEP default 31.5
200
42
42
$/MWelh Specific decommissioning cost, $/kWot Economic and technical lifetime, y
900
600
Reference power plant unit net output, MWeL Reference condensing temperature, °C Main steam temperature, °C Reference net thermal efficiency, % Overnight cost = specific construction cost DEEP, $/kWet Construction lead time, m Specific O&M cost, $/MWh Fuel (cycle) cost,
PWR, 900
PWR ~, 600
DEEP item
Table 1 Cost input data for all power options
40
67
2.6
40 2.2
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486
DEEP default DEEP default N/A
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P.£ Gowin, T. Konishi / Desalination 126 (1999) 301-307
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W a t e r Plant Size(m3/d)
Fig. 1. Region 1. Water cost for selected power options for RO and MED technology and for two economic scenarios, favouring nuclear (up) and fossil (down) as a function of the water plant size. The water plant sizes chosen were 120,000 m3/d, 240,000 m3/d and 480,000 m3/d from left to right.
cost is equal to the blend of the distillation and RO cost according to the amounts of distillation water and RO water produced.
4.2. Economic evaluation scheme: input data Studies were performed for three broad regions: • Region 1, corresponding to southern Europe (south of France, Italy, Greece, Turkey and Spain) • Region 2, corresponding to southeast Asia, the Red Sea region and the North African region • Region 3, corresponding to the Arabian Gulf region (average seawater salinity and temperature) The regions were chosen on the basis of the DuPont world map for desalination. The water conditions for Regions 1, 2 and 3 were: total dissolved solids (TDS) of 38,000 ppm and a seawater temperature of
20 oC in Region 1; 41,000 ppm and 25 oC in Region 2 and 45,000ppm and 30°C in Region 3. Labour costs were fixed to be $160,000/a in Region 1 and $60,000/a in Regions 2 and 3. A baseline for cost input data for all power options was defined and is given in Table 1. Within each region, two economic scenarios were defined: "up" (favouring nuclear) and "down" (favouring fossil). The two economic scenarios used the cost input data given in Table 1 with variations of ±15% for up and down, respectively, but also assumed different values for interest/discount rate (Region 1: 5% and 8%, Regions 2 and 3: 8% and 10%) and fossil fuel cost ($20/bbl and $30/bbl for oil/gas ($50/t and $70/t for coal) in all regions, with a real escalation rate set to zero, thus assuming average values over the lifetime of 40 years. (This means that with an initial fuel price (in 1999) of$12 and $18/bbl and a real escalation rate of 2%, the
P.J. Gowin, T. Konishi / Desalination 126 (1999) 301-307
prices of $20 and $30/bbl will be reached after 25 years.) Apart from input data specified for the study, the default input data in DEEP version 1.1 was used. The economic lifetime was generally to be set to 40 years, with minor exceptions not repeated here. All cost data are given in 1998 US dollars. In addition to the region-by-region studies, a sensitivity analysis, with variations of all important parameters, was carried out to permit evaluation and understanding of possible trends. Three power options with 600MWel were chosen, PWR-600, PHWR-600 and CC-600. Results of the sensitivity analysis cannot be presented in the frame of this paper. In all regional studies, RO and MED were chosen as desalination processes, and multi-stage flash (MSF) was included only for Regions 2 and 3. The base unit cost for MED was determined to be $900/(m3/d) installed capacity, for MSF $1800/ (m3/d) and for RO $800/(m3/d) for all calculations. The DEEP default value of 70°C was taken as the "maximum brine temperature" (unless the DEEP item "minimum required maximum brine temperature" is higher; in that case, DEEP automatically takes the higher value. This was the case if the desired water production could not be achieved with 70°C). The projected needs were based on historical records of installed seawater desalination capacity, known orders for new capacity to be installed over the next several years, population projections and expert judgments. The following water plant sizes were selected: 480,000m3/d, 240,000m3/d, 120,000m3/d, and 60,000 m3/d.
307
5. Economic evaluation results for southern Europe Fig, 1 gives the results of the calculations for Region 1, corresponding to southern Europe. It shows the water cost in S/ms for all power options as a function of the water plant size. Different symbols reflect different water desalination technologies.
References [1] WorldWater Forum, Marrakech,Morocco, 1997. [2] Intemational Atomic Energy Agency, Sustainable developmentand nuclear power, Vienna, 1997. [3] International Atomic Energy Agency, Nuclear desalination of sea water, Proc., Series STI/PUB/ 1025, Vienna, 1997. [4] InternationalAtomic Energy Agency, Methodology for the economic evaluation of cogeneration/desalination options: a user's manual, Computer Manual Series No. 12, Vienna, 1997. [5] InternationalAtomic Energy Agency, Use of nuclear reactors for seawater desalination, TECDOC-574, Vienna, 1990. [6] InternationalAtomic Energy Agency, Technical and economic evaluation of potable water production through desalination of seawater by using nuclear energy and other means, TECDOC-666, Vienna, 1992. [7] International Atomic Energy Agency, Potential for nuclear desalination as a source of low-cost potable water in North Africa,TECDOC-917, Vienna, 1996.