Integrating desalination with concentrating solar power: large scale cogeneration of water and electricity.

Dall, Ernest Peter (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The demand for fresh water is a growing concern that is shared globally. Finite fresh water resources, accompanied by an exponential population growth will demand the need for additional installed desalination plants worldwide. However, desalination is extremely energy intensive with the costs thereof depending on the availability of local energy resources (coal, oil, gas, etc.). Fortunately, most arid regions generally also have high solar energy resources that could be utilized instead of conventional fossil fuel resources. Concentrating solar power (CSP) is steadily gaining more market acceptance as the cost of electricity from CSP power plants progressively declines. Cogeneration is an attractive prospect for future CSP developments as the simultaneous production of power and potable water can have positive economic implications towards increasing the feasibility of CSP plant developments. This is a theoretical case study, within the context of Namibia, in Southern Africa, investigating the possible benefits and concerns of integrating a multiple-effect desalination (MED) plant with a 100MWe concentrating solar power (CSP) tower plant for the large scale cogeneration of electricity and potable water (CSP+D). The focus of this study is set on the analytical modelling of a MED plant which captures the sensitivities of the parameters required for cogeneration analysis. A simplified CSP and Rankine cycle is modelled in terms of the optical-to-thermal conversion of energy. The high capital costs of thermal desalination heat exchangers as well as the pumping of seawater far inland is the most significant barrier in making this approach competitive against more conventional desalination methods such as reverse osmosis. The compromise between the lowest levelized cost of electricity and potable water depends on the sizing and the top brine temperature of the desalination plant. Additionally, the feasibility and final sizing of a CSP+MED plant would ultimately depend on the Namibian CSP tariffs and structures as well as the tariff for desalination.

AFRIKAANSE OPSOMMING: Die aanvraag vir vars water is ʼn groeiende kwessie wat wêreldwyd ervaar word. Beperkte vars water bronne gekombineer met ʼn eksponensiële groei in bevolking sal aandring op die addisionele konstruksie van ontsoutings aanlegte wêreldwyd. Die probleem is dat ontsoutingsprosesse ongelooflik energie intensief is en dat die koste daarvan afhanklik is van die lokale beskikbaarheid van energiebronne, byvoorbeeld steenkool, gas en olie. Gelukkig het die meerderheid van woestyn areas ook die meeste sonkrag potensiaal wat gebruik kan word in plaas van fossiel brandstowwe. Die mark vir gekonsentreerde sonkrag (CSP) is stadig maar seker besig om te groei soos wat die elektrisiteitskostes daarvan jaarliks daal. Die mede-generasie van elektrisiteit en ontsoute seewater is ʼn aantreklike vooruitsig vir die toekomstige ontwikkeling van CSP kragstasies. Die gelyke produksie van elektrisiteit en water kan positiewe ekonomiese implikasies hê en dus die haalbaarheid van CSP projekte verder motiveer. Hierdie is ʼn teoretiese gevallestudie, binne die konteks van Namibië, wat die moontlike voordele en kwessies aangaande die integrasie van ʼn meervoudige-effek distillasie (MED) prosesse binne-in ʼn CSP toring aanleg bespreek. Die netto-elektriese kapasiteit van die CSP aanleg is ʼn 100 MWe. Die fokus van hierdie studie is gemik op die analitiese modellering van ʼn MED aanleg wat die sensitiwiteitseienskappe van parameters vasvang wat benodig is vir die analise van ʼn mede-generasie aanleg. ʼn Vereenvoudigde CSP en Rankine siklus word gemodelleer in terme van die optiese tot termiese omskakeling van energie. Die hoe kapitale kostes van korrosiebestande hitteruilers as ook die pompkostes om seewater na die binneland te vervoer is die hoof struikelblok wat hierdie benadering minder kompeterend maak in vergelyking met “tru-osmose”. Die kompromie tussen die koste van elektrisiteit en water hang af van die grootte en boonste pekel temperatuur van die MED aanleg. Verder sal die haalbaarheid en gekose grootte van die CSP+MED aanleg afhanklik wees van die tariewe wat toegeken sal word vir CSP en ontsoute water in Namibië.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101238
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