Scenario modelling for short to long term rollout of Concentrating Solar Power (CSP) in South Africa

Auret, Christina (2015-03)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: South Africa is currently in the process of greatly expanding its electricity generating infrastructure. A significant portion of the new capacity will be made up out of renewable energy systems. The aim of this study was to investigate potential benefits and pitfalls of introducing concentrating solar power (CSP) into the South African electricity generating system, by making use of spatio-temporal modelling. Government policy for the expansion of the generating fleet is defined in the Integrated Resource Plan for electricity (IRP). A draft update of the IRP that describes a number of possible scenarios for the composition of the generating fleet was released in 2013. Three of these were selected and modelled for the 2030 and 2050 fleet composition and projected demand for the purpose of this study. The effect of implementing a two tier tariff designed to incentivise electricity production during evening peak by CSP plants was also investigated. All modelling was done on an hourly basis. Spatio-temporal modelling was used to model wind, photovoltaic and CSP electricity production. The balance of the generating system was modelled using a behavioural model. The system performance was compared across scenarios by using the following system adequacy measures: electricity shortfall, open cycle gas turbine capacity factor and coal plant capacity factor. Comparing CSP plants that were optimised to be remunerated under a two tier tariff with plants that were optimised to minimise levelized cost of electricity showed that imposing the tariff had a significant impact on plant configuration and electricity production. Using CSP plants that were under a rigid two tier tariff was also found to have a negative impact on system adequacy measures in a system with a high renewable energy uptake. The results were reasonable for a system with a moderate uptake in renewable energy and good for a system with a low uptake. For example: acceptable levels of electricity shortfall in a projected system would be equal to 20 GWh per year. With the two tier tariff in place the low uptake scenario averaged 32.9 GWh, the moderate uptake scenario 99.6 GWh and the high uptake scenario 5059.7 GWh for 2050. Results for the two higher uptake scenarios were improved significantly by redeploying a large portion of the CSP plants as base load units that were responsive to system needs. The results for a system with a high uptake of renewable generating capacity was still not at acceptable levels (e.g. 844.52 GWh shortfall), but the moderate uptake system performed well. This may indicate that the higher the uptake is of renewable energy, the more flexible the electricity output of the CSP will have to be for optimal overall system performance. While this flexibility is technically feasible, according to this study a rigid remuneration structure will not incentivise the CSP plants to act on this capability.

AFRIKAANSE OPSOMMING: Suid Afrika is in die begin fase van ʼn grootskaalse uitbreiding in kragopwekking infrastruktuur. Hernubare energie, insluitend sonpanele, windkrag en gekonsentreerde sonkrag, gaan ʼn beduidende porsie van die uitbreiding wees. Die doelwit van hierdie studie was om die potensiële voordele en nadele van die byvoeging van gekonsentreerde sonkrag tot die kragopwekkings stelsel te bestudeer met behulp van tydruimtelike modellering. Die regering se beleid vir die uitbreiding van kragopwekking infrastruktuur is saamgevat in die Geïntegreerde Hulpbronne Plan vir elektrisiteit. ʼn Voorgestelde opdatering van die dokument, wat ʼn aantal moontlike scenarios vir die tegnologie samestelling van die beoogde kragopwekking infrastruktuur bevat, is in 2013 uitgereik. Drie van die scenarios en die geprojekteerde kragaanvraag vir 2030 en 2050 was in hierdie studie gemodelleer. Die effek van ʼn twee vlak tarief, wat ontwerp is om gekonsentreerde sonkragstasies aan te moedig om krag gedurende die aand piek aanvraag periode op te wek, is ook ondersoek. Alle modellering was op ʼn uurlike basis uitgevoer. Tydruimtelike modellering was gebruik om sonpanele, windkrag en gekonsentreerde sonkrag se modelleer. Die res van die kragopwekking was met ʼn gedrag gebaseerde model gemodelleer. Die scenario was aan die hand van drie kriteria geëvalueer: totale elektrisiteit tekort, oop siklus gas turbine kapasiteitfaktor en steenkool kapasiteitfaktor. Daar was gevind dat ʼn twee vlak tarief ʼn beduidende inpak op die konfigurasie en elektrisiteit lewering van ʼn gekonsentreerde sonkragstasie het. Verder was gevind dat die gebruik van gekonsentreerde sonkragstasies wat onder so ʼn tarief ontwerp was ʼn negatiewe impak op die stelsel uitkomste gehad het, veral vir die scenario met ʼn hoë opname van hernubare energie. Die resultate was goed vir die scenario met ʼn lae opname en redelik vir die scenario met ʼn matige opname van hernubare energie. Ter illustrasie: 20 GWh per jaar word as ʼn aanvaarbare vlak van elektrisiteit tekort gereken in ʼn gegewe scenario. Met ʼn twee vlak tarief vir gekonsentreerde sonkrag lewer die scenario met ʼn lae opname in hernubare energie ʼn tekort van 32.9 GWh, die scenario met ʼn matige opname lewer 99.6 GWh en die scenario met ʼn hoë opname lewer 5059.7 GWh in 2050. Resultate vir die twee scenarios met hoër opnames in hernubare energie kan aansienlik verbeter word deur ʼn groot porsie van die gekonsentreerde sonkragstasies te loop as stasies wat vrag aanpas na gelang die stelsel aanvraag. Die resultate vir die scenario met ʼn hoë opname in hernubare energie bereik nog steeds nie aanvaarbare vlakke nie (bv. 844.52 GWh elektrisiteit tekort), maar die matige opname scenario bereik dit wel. Hierdie resultate toon moontlik dat hoe hoër die opname in hernubare energie is, hoe meer aanpasbaar gekonsentreerde sonkrag se beheer deur die stelsel sal moet wees om optimale uitkomste moontlik te maak. Volgens hierdie studie is die aanpasbaarheid tegnies moontlik maar dit sal nie deur gekonsentreerde sonkragstasies ten toongestel word onder ʼn onbuigbare tariefstruktuur nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96941
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