Sustainable future CSP fleet deployment in South Africa: A hydrological approach to strategic management

Duvenhage, Dries Frank (2019-12)

Thesis (PhD)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The global growth in renewable energy, as a means to mitigate climate change, has seen the large-scale deployment of solar photovoltaics (PV) and wind in the electricity generation mix. However, this presents several challenges; primarily that both wind and PV are unpredictable and therefore cannot supply reliable electricity. This necessitates energy storage or the other, more flexible electricity generators to meet the shortfall. Concentrating solar power (CSP) can supply this shortfall in electricity through the concentration of solar irradiation and thermal storage of this heat. This thermal process requires cooling, best achieved with a finite resource, namely water. Paradoxically, CSP is ideally suited to areas of high solar irradiation that are characteristically arid with low and variable water availability. However, the need for water, mainly as a source of cooling, is often neglected in the planning and development of CSP at a national scale, with few studies that explicitly assess and quantify these hydrological constraints. This study aims to fill this research gap by improving our understanding of the constraints imposed by water resources on CSP development in arid regions, using South Africa as a case study. A systematic approach was used to model the hydrological constraints to CSP plants’ operation and its wide-spread deployment. To determine to what extent CSP might play a role in supplying electricity to the South African grid, a review of future energy mix plans was performed. Although the theoretical potential of CSP based on the solar resource and suitable land is around 12,000 TWh (for the most efficient commercial CSP technologies), the current plans limit this potential considerably to between only 1.87 TWh and 142 TWh. Furthermore, these allocated capacities to CSP in the South African electricity supply are well below the limitations imposed by water resources, especially if dry-cooled plants are used. CSP performance varies according to design and location, since meteorological conditions vary spatially and temporally. A high-level efficiency model (HLEM) was developed to quantify this variability in South Africa. It uses validated equations and assumptions from literature with CSP energy transfer efficiencies to determine monthly performance in terms of net electricity generation, water consumption factor and total volume of water consumption. Parabolic Trough and Central Receiver CSP plants were modelled with either wet or dry cooling and the CSP performance analysed at thousands of suitable locations in South Africa. To assess water availability for CSP deployment at these locations, publicly available hydrological data for river flows, dam storage levels and groundwater reserves were used. The water demand from the four CSP-cooling configurations was then measured against the monthly available water per quaternary catchment area. The hydrological limitations were calculated for each configuration, and it was found that, depending on the CSP-cooling configuration, water availability will reduce the theoretical potential for CSP deployment to between 1 - 5% thereof (from 12,000 TWh to 120 – 566 TWh). These results provide guidelines for policy and planning of CSP deployment in South Africa, to ensure the sustainable management of water resources.

AFRIKAANSE OPSOMMING: Die wêreldwye groei in hernubare energie, as 'n wyse om klimaatsverandering te beveg, het die grootskaalse ontplooiing van fotovoltaïese sonkrag (PV) en windkrag in die elektrisiteit opwekkings netwerk meegebring. Dit bied egter verskeie uitdagings; hoofsaaklik dat wind en PV onvoorspelbaar is en dus nie betroubare elektrisiteit kan lewer nie. Dit noodsaak energie berging of ander, buigsamer kragopwekkers om aan die tekort te voldoen. Gekonsentreerde sonkrag (GSK) kan hierdie tekort aan elektrisiteit voorsien deur die konsentrasie van sonbestraling en termiese berging van hierdie hitte. Hierdie termiese proses vereis egter verkoeling, wat die beste bereik word met 'n beperkte hulpbron, naamlik water. GSK is, teenstrydig hiermee, ideaal geskik vir gebiede met hoë sonbestraling wat kenmerkend droog is met 'n lae en veranderlike water beskikbaarheid. Die behoefte aan water, hoofsaaklik as verkoelings bron, word egter gereeld verwaarloos tydens die beplanning en ontwikkeling van GSK op nasionale skaal, met min studies wat hierdie hidrologiese beperking eksplisiet analiseer en kwantifiseer. Hierdie studie het ten doel om hierdie leemte in die navorsing te vul deur ons begrip van die beperkinge wat deur waterbronne op GSK-ontwikkeling in droë streke plaas, te verbeter en Suid-Afrika as 'n gevallestudie te gebruik. 'n Stelselmatige benadering is gebruik om die hidrologiese beperkings op die werking van GSK-aanlegte en die wydverspreide implementering daarvan te modelleer. Om vas te stel in watter mate GSK 'n rol kan speel in die verskaffing van elektrisiteit aan die Suid-Afrikaanse krag voorsieningsnetwerk, is 'n oorsig van toekomstige energie-mengsel-planne uitgevoer. Alhoewel die teoretiese potensiaal van GSK, gebaseer op die sonbestraling en geskikte grond ongeveer 12,000 TWh is (vir die doeltreffendste kommersiële GSK-tegnologie), beperk die huidige planne hierdie potensiaal aansienlik. Vanaf ses-en-twintig scenario's met betrekking tot die Geïntegreerde Hulpbron Plan (IRP), kan die aandeel van GSK in die toekomstige jaarlikse elektrisiteit opwekking mengsel teen 2030 wissel van 1,87 TWh tot 142 TWh; afhangend van Suid-Afrika se beleid, groei en ekonomiese klimaat. GSK -werkverrigting wissel volgens ontwerp en ligging, aangesien meteorologiese toestande ruimtelik en tydelik verskil. 'n Hoëvlak-doeltreffendheid model (HLEM) is ontwikkel om hierdie veranderlikheid in Suid-Afrika te kwantifiseer. Dit maak gebruik van gevalideerde vergelykings en aannames uit literatuur met GSK-energie-oordragdoeltreffendhede om die maandelikse prestasie te bepaal ten opsigte van netto elektrisiteit opwekking, water verbruiksfaktor en totale volume waterverbruik. Paraboliese trog- en sentrale ontvanger- GSK -aanlegte is met nat of droë verkoeling gemodelleer en die GSK-prestasie is op duisende geskikte plekke in Suid-Afrika geanaliseer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107028
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