Feasibility of once-through cooling for 50MWe solar thermal power plant on / near the lower Orange River.

Thesis (MEng)--Stellenbosch University, 2019.ENGLISH ABSTRACT: The rapid increase in demand for solar energy and its contribution to the national grid has placed new emphasis on the performance of Concentrating Solar Power (CSP) Plant. Plant performance can be enhanced by using once-through watercooling instead of the conventional direct air-cooled systems. Water withdrawn from the Orange River for agricultural irrigation purposes near Upington, in the Northern Cape can accommodate once-through cooling. To achieve this, a detailed study of CSP plant and different types of the cooling systems that are available was undertaken. The different types of CSP plant were evaluated and the best CSP plant based on the technology advancement was identified. The use and management of the irrigation system, government policies and environmental legislation along the lower Orange River was studied to look for synergy between CSP and agricultural water use. Once-through cooling for CSP plant that is also known as open-cycle cooling was modelled and fully analysed. The components of the CSP plant were also modelled, with emphasis on condenser fouling. This includes heliostat field, receiver tower, thermal storage, steam generator and power block. The heliostat field model determined the heliostat field optical efficiency over the year. The power block model determined the thermal efficiency of CSP plant and the function of growth with the cooling water temperature in the cooling system. The model was also used to determine the impact of changing different CSP plant operating parameters on the cooling system and evaluate the plant output. All existing CSP plants, except Bokpoort, make use of direct air-cooled condensers. Hence, direct air-cooling was adopted as benchmark for this study. Compared to a direct air-cooled CSP plant, once-through cooling shows that there is an improvement in the thermal efficiency of 2.9 percentage points. The model is based on hourly fluctuations in cooling water temperature from the river that ranges from 20°C to 25 ℃.AFRIKAANSE OPSOMMING: Die snel toename in die vraag na son-termiese energie, en die bydrae daarvan tot die nasionale kragleweringsnetwerk, het die effektiwiteit van son-termiese kragstasies (STK) onder die vergrootglas geplaas. Direkte deurvloei water verkoeling is ‘n aantreklike opsie in die Noord Kaap, siende dat water vir vloedbesproeing uit die rivier onttrek word, vir verkoeling gebruik kan word. Die sinergie tussen verkoeling en landbou behoeftes van die hipotetiese STK is krities ondersoek. Om die mees geskikte aanleg konfigurasie te kies, is ‘n oorsig oor bestaande STK en verkoelingsisteme gedoen. ‘n Volledige model van ‘n deurvloei verkoelde STK, wat die heliostate, onvanger, termiese energie stoor, stoom-opwekker en Rankine kringloop insluit, is ontwikkel. Die model voorspel die aanleg se uitset oor ‘n volle kalender jaar, om veranderinge in son straling, water temperature en aanpakking van die kondenser buise op die aanleg se kraglewering insluit. Bestaande wetgewing rondom die ontrekking van water vanuit, en terugvoer na ekosisteme soos van toepassing op die landbou, eerder as industrie, is gevolg. Dit bied groot voordele om die voorgestelde stelsel te bedryf. Alle bestaande CSP-aanlegte, behalwe Bokpoort, maak gebruik van direkte lugverkoelde kondenseerders. Daarom is direkte lugverkoeling as maatstaf vir hierdie studie aangeneem. Vergeleke met 'n direkte lugverkoelde CSP-aanleg, wys eenmalige verkoeling dat die termiese doeltreffendheid van 2,9 persentasiepunte verbeter word. Die model is gebaseer op uurlikse skommelinge in koelwatertemperatuur vanaf die rivier wat wissel van 20 ° C tot 25 ℃.AFRIKAANSE OPSOMMING: Alle bestaande CSP-aanlegte, behalwe Bokpoort, maak gebruik van direkte lugverkoelde kondenseerders. Daarom is direkte lugverkoeling as maatstaf vir hierdie studie aangeneem. Vergeleke met 'n direkte lugverkoelde CSP-aanleg, wys eenmalige verkoeling dat die termiese doeltreffendheid van 2,9 persentasiepunte verbeter word. Die model is gebaseer op uurlikse skommelinge in koelwatertemperatuur vanaf die rivier wat wissel van 20 ° C tot 25 ℃.Master