Energy 36 (2011) 4950-4958

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    the cost-effectiveness is also expected to improve by making betteruse of a common infrastructure and the economy of scale of thesteam turbine [3]. Finally, considerable additional savings ofgreenhouse gas emissions come from the production of fresh water,since the majority of desalination plants are currently fed by powerproduced by fossil fuels.

    be separated from the coast. To solve all of these issues, specicscientic research, techno-economic analysis and demonstrationplants are needed to dene the best concepts and schemes of theintegration of a desalination plant into a CSP plant.

    More specically, a techno-economic analysis has been per-formed for the combination of parabolic-trough (PT) power plantsfor electricity production with MED and ultraltration/RO plants intwo sites in Israel (Ashdod) and Jordan (Aqaba) [11]. An analysiswas carried out taking into account the same fresh water

    * Corresponding author. Tel.: 34 950387941; fax: 34 950365015.

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    Energy 36 (2011) 4950e4958E-mail address: guillermo.zaragoza@psa.es (G. Zaragoza).make possible large concentrating solar power (CSP) plantsdevelopments in arid regions, such as the Desertec initiative [1].These regions suffer from a serious lack of fresh water availability,which could jeopardize the deployment of the CSP plants. Theintegration of desalination technology into CSP plants to producewater and electricity at the same time, could solve the water andenergy problems in many of the worlds arid areas [2]. CombiningCSP and Desalination facilities (concentrating solar power anddesalination (CSPD)) benets the identication of technologicalsynergies that could reduce the cost of combined power anddesalination production against independent plants. In addition,

    of CSP plants coupled with desalination systems (reverse osmosis(RO) and multi-effect distillation (MED)) has been shown for theMiddle East and North Africa (MENA) region [9,10]. Besides all thepotential benets of combining power and water productionshown, the integration of desalination processes and technologiesinto CSP plants is not yet a straightforward issue and many tech-nological aspects remain to be discussed. The CSPD conceptneeds, obviously, facilities to be located near the sea, where landcost and availability could be a signicant problem. Moreover, thesolar direct normal irradiance (DNI) is normally lower on areasclose to the sea, which makes CSP plants most optimal locations toKeywords:Solar energyConcentrating solar power (CSP)System integrationThermodynamic simulationSteam cyclesDesalination

    1. Introduction

    Many projects are currently under0360-5442/$ e see front matter 2011 Elsevier Ltd.doi:10.1016/j.energy.2011.05.039for coupling parabolic-trough (PT) solar power plants and desalination facilities in a dry location rep-resenting the Middle East and North Africa (MENA) region. The integration of a low-temperature multi-effect distillation (LT-MED) plant fed by the steam at the outlet of the turbine replacing the condenser ofthe power cycle has been simulated and compared with the combination of CSP with a reverse osmosis(RO) plant. Furthermore, an additional novel concept of concentrating solar power and desalination(CSPD) has been evaluated: a LT-MED powered by the steam obtained from a thermal vapourcompressor (TVC) using the exhaust steam of the CSP plant as entrained vapour and steam extractedfrom the turbine as the motive vapour of the ejector. This new concept (LT-MED-TVC) has been analyzedand compared with the others, evaluating its optimization for the integration into a CSP plant byconsidering different extractions of the turbine.

    2011 Elsevier Ltd. All rights reserved.

    sion and preparation to

    Several studies on different basic integrated power and desali-nation plants (IPDP) congurations have been published [4e8].However, not so many deal with solar power plants. The potential9 May 2011Accepted 20 May 2011a thermal desalination unit. This paper presents a thermodynamic evaluation of different congurationsReceived in revised formconsidered for the planned installation of CSP plants in arid regions. There are interesting synergiesbetween the two technologies, like the possibility of substituting the condenser of the power cycle forAssessment of different congurations fpower and desalination plants in arid re

    Patricia Palenzuela, Guillermo Zaragoza*, Diego C.Julin BlancoCIEMAT-Plataforma Solar de Almera, Ctra. de Sens s/n, 04200 Tabernas, Almera, Spai

    a r t i c l e i n f o

    Article history:Received 1 March 2011

    a b s t r a c t

    The combination of desali

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    journal homepage: www.All rights reserved.combined parabolic-trough (PT) solarions

    rcn-Padilla, Elena Guilln, Mercedes Ibarra,

    ion technology into concentrating solar power (CSP) plants needs to be

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    evier .com/locate/energy

  • production and electrical power generation capacity. The resultsshowed that the CSPRO setup has economic benets in compar-ison to the CSPMED conguration using a wet cooling system forthe power block. Another technical and economic study for waterdesalination and CSP power plants in different MENA countries hasbeen presented but this time considering a dry cooling system forthe turbine [12]. For each location, four congurations wereanalyzed, combining two types of solar technologies (PT and linearFresnel reector) and two types of desalination processes (low-temperature multi-effect distillation (LT-MED) and RO). The mainresult was that in most cases studied the solar eld required for theCSPRO was larger than for the CSPLT-MED, due to the higherelectrical consumption of the RO overcompensating the lowerthermal efciency of the turbine of the MED case.

    This paper presents a thermodynamic evaluation of differentcongurations for coupling PT solar power plants and desalinationfacilities in aMENA location (Abu Dhabi). The typical congurationsof combining CSP with a RO desalination plant and a LT-MED plantfed by the steam at the outlet of the turbine have been studied.However, an additional concept of CSPD has been evaluated forthe rst time in this kind of analysis: a LT-MED powered by thesteam obtained from a thermal vapour compressor (TVC). In thiscase, unlike in the typical thermal vapour compression MEDprocess (TVC-MED), the entrained vapour to be used in the steam

    working uid. The solar plant consists of PT (LS-3 type) collectorsaligned on a northesouth orientation and a thermal storage tank toprovide additional operation when solar radiation is not available.The collectors track the sun from east to west during the day toensure it is continuously focused on the linear receiver. Differentdesalination systems have been considered for combination withthis CSP plant. A dry cooling system is considered for condensingthe exhaust steam form the turbine in the power block, which is theusual means in arid areas, since the typical wet cooling towersconsume between 2 and 3 metric tons per MWh [13].

    The PT-CSP technology is the same in all the congurationsassessed. Steam at point A is generated from the thermal energycollected by the solar eld. It is subsequently sent to a HP turbinewhere, after suffering an expansion process is extracted at B inorder to reheat it. The reheated steam is left to its expansionthrough a LP turbine to obtain the required power. The expansion isup to state point D in all cases except that of Fig. 2, where theexpansion is only up to state point E.

    Conguration #1 corresponds to the basic combination of a ROdesalination plant with a PT-CSP plant. In this case (Fig. 1) thedesalination process is driven by the power output from the CSPplant. This conguration has the advantage that the desalinationprocess is completely independent from the power generation andcan be even separated geographically.

    P. Palenzuela et al. / Energy 36 (2011) 4950e4958 4951ejector comes from the exhaust steam of the CSP plant instead of anintermediate effect of the desalination plant. Within this concept(LT-MED-TVC), different schemes must be studied: a system thatuses the high exergy steam from the high pressure (HP) turbineoutlet as motive steam in the TVC, and others that use steamextracted at different pressures from the low pressure (LP) turbineas the motive steam in the ejector.

    2. Methodology

    2.1. Description of the systems

    The systems under consideration are described in Figs. 1e4.They each consist of a parabolic-trough concentrating solar power(PT-CSP) plant based on a reheat Rankine cycle with water as theFig 1. Diagram of Conguration #1 (RO uConguration #2 corresponds to a LT-MED integrated into a PT-CSP by replacing the conventional cooling unit of the steam cycle. Inthis case (Fig. 2), the desalination plant is fed by the LT steam fromthe turbine outlet (at state point F) after being reheated to obtainsaturated steam without increasing the temperature. In this casethe exhaust steam is considered at a slightly higher pressure than inthe previous case, as it must feed the LT-MED desalination plant at70 C.

    Congurations #3 and #4 consider LT-MED powered bya thermal vapour compressor (LT-MED-TVC) (Figs. 3 and 4). Theintegration of a LT-MED-TVC unit has a huge interest, since it isuseful for the coupling of any thermal desalination process toa power plant and not only for a MED process. In this case, unlikethe conventional thermal vapour compression process (TVC-MED),the entrained vapour to be used in the ejector comes from thenit combined with a PT-CSP plant).

  • MED

    P. Palenzuela et al. / Energy 36 (2011) 4950e49584952exhaust steam from the LP turbine instead of an effect of the MEDunit. As for the motive steam, two scenarios have been co