Spatial-temporal model to evaluate the system potential of concentrating solar power towers in South Africa

Gauche, Paul (2016-12)

Thesis (PhD)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Concentrating solar power (CSP) is a relatively unknown power generation technology entering into the growth phase of its technology life-cycle. The value of CSP is relatively well understood from a state of the art point of view, but its value and potential in a power generation network is not as clear. South Africa potentially offers an accelerated market due to constrained electricity capacity and an excellent solar resource. The objective of this dissertation is to quantifiably evaluate CSP in the electricity system of South Africa and thereby aid national policy. The methodology required the development and validation of a model to predict the performance of central receiver CSP plants in an electricity system. The Integrated Resource Plan (IRP) of South Africa legislates the definition of the national electricity system with a twenty year horizon and intended updates every two years. The IRP initiated significant renewable energy adoption, but only 1 GW of CSP is officially allocated until 2030, despite several analysis updates recommending increased capacity for CSP in scenarios based on scarcity of resources for fossil or nuclear technologies. The spatial-temporal CSP model was developed and validated within available means to about 7 % accuracy within a standard deviation of known CSP tower settings. This model permits cascaded allocations of CSP capacity by location, plant configuration and size without being overly prescriptive to technology specification or advancements. The model is, therefore, able to comprehensively evaluate a distributed network of CSP towers within an energy system environment. A deterministic energy system model and a probabilistic economic model were developed to test the behavior of the CSP model in an energy system. The value of CSP towers was studied in various scenarios, including an emulation of the 2010 IRP, the 2013 proposed IRP Update and scenarios commissioned by the Worldwide Fund for Nature (WWF) in South Africa. The WWF scenario resulted in a renewable-centric proposal for 2030 that includes 8 GW of CSP with 12 storage hours on average. This scenario unexpectedly outperforms other scenarios in terms of cost regardless of resource scarcity. The analysis, however, correlates with other recent research, finding that CSP capacity needs to operate only serving the system to avoid unserved power. In this mode, CSP levelized cost of energy (LCOE) increases due to a drop in capacity factor, but the marginal value of electricity (MVOE) attributable to this operating mode is R 0.48 per kWh. MVOE is introduced as a method to inform tariff policy. The model successfully demonstrates the importance of technology, space and time within a constrained electricity system in order to fully evaluate the role of CSP towers. The evaluation itself provides initial quantified evidence that CSP has an important role for South Africa and should be pursued by investing more resources in research, planning and implementation.

AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag (GSK) is 'n relatief onbekende vorm van kragopwekking wat tans die groeifase bereik in sy tegnologie lewensiklus. Die status van GSK as baanbreker tegnologie word relatief goed verstaan, maar die waarde en potensiaal daarvan in 'n kragopwekking netwerk is onduidelik. Suid Afrika bied potensieel 'n versnelde mark aan as gevolg van beperkte elektrisiteit kapasiteit en 'n uitstekende son hulpbron. Die doel van hierdie proefskrif is om GSK binne die Suid-Afrikaanse elektrisiteitsnetwerk kwantifiseerbaar te evalueer ter ondersteuning van nasionale beleid. Die metodologie het die ontwikkeling en bevestiging van 'n model vereis om die prestasie van sentraal-ontvanger gekonsentreerde sonkragstasies in 'n elektrisiteit stelsel te voorspel. Suid-Afrika se Geïntegreerde Hulpbronplan (GHP) wet gee die definisie van die nasionale elektrisiteit stelsel met 'n 20 jaar horison en word elke 2 jaar opgedateer. Die GHP het 'n beduidende aanneming van hernubare energie geïnisieer, maar slegs 1 GW van GSK is amptelik toegeken tot 2030 ten spyte van verskeie opgedateerde analises wat groter kapasiteit vir GSK aanbeveel het in raamwerke gebaseer op skaarstes aan hulpbronne vir fossiel of kern tegnologieë. Die ruimtelike-temporale GSK model is ontwikkel en bewys binne beskikbare hulpbronne tot sowat 7 % akkuraatheid binne 'n standaardafwyking van bekende gekonsentreerde sonkragtoring instellings. Die model laat kaskade toekenning van GSK kapasiteit per ligging, aanleg opstelling en grootte toe sonder om buitensporig voorskriftelik te wees in terme van tegnologie spesifikasies of vooruitgang. Die model is dus in staat om 'n verspreide netwerk van gekonsentreerde sonkragtorings binne 'n energiestelsel omvattend te evalueer. 'n Deterministiese energiestelsel-model en 'n waarskynlikheids-gebaseerde ekonomiese model is ontwikkel om die GSK model gedrag binne 'n energiestelsel te toets. Die waarde van gekonsentreerde sonkragtorings is bestudeer in verskeie scenarios, insluitend 'n emulasie van die 2010 GHP 2010, die voorgestelde 2013 GHP verbetering en scenarios in opdrag van die Wêreldwye Fonds vir die Natuur in Suid-Afrika. Die WWF scenario het gelei tot 'n hernubaar-sentriese voorstel vir 2030 wat 8 GW van GSK insluit met 'n gemiddeld van 12 uur van stoorkapasiteit. Hierdie scenario presteer onverwags beter as ander scenarios in terme van koste, ongeag hulpbron skaarsheid. Die ontleding stem egter ooreen met ander onlangse navorsing wat bevind dat GSK kapasiteit slegs in diens van die stelsel moet werk ten einde ontoegediende krag te vermy. In hierdie modus, verhoog die vergelykbare elektrisiteitskoste van GSK as gevolg van 'n daling in kapasiteitsfaktor, maar die marginale waarde van elektrisiteit toegeskryf aan hierdie modus van operasie is R 0.48 per kWh. Die marginale waarde van elektrisiteit is ingestel as 'n metode om tariefbeleid in te lig. Die model slaag daarin om die belangrikheid van tegnologie, ruimte en tyd binne 'n beperkte elektrisiteit stelsel te illustreer ten einde die rol van gekonsentreerde sonkrag torings ten volle te evalueer. Die evaluering self bied aanvanklike gekwantifiseerde bewyse dat GSK 'n belangrike rol vir Suid-Afrika bied en dat dit deur belegging van meer hulpbronne in navorsing, beplanning en implementering nagestreef moet word.

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