This study provides an evaluation of Concentrating Solar Power (CSP) technologiesudand investigates the feasibility of distributed power generation in urban areas ofudJohannesburg. The University of the Witwatersrand (Wits) is used as a case studyudwith energy security and climate change mitigation being the main motivators.udThe objective of the study was to investigate the potential of CSP integration inudurban areas, specifically investigating Johannesburg’s solar resource. This is done byudassessing the performance and financial characteristics of a variety of technologiesudin order to identify certain systems that may have the potential for deployment.udTo aid the comparison of the technologies, CSP performance and cost data whichudwere taken from multiple sources, were adjusted giving it local, present dayudassumptions. A technology screening process resulted in the conception of twelveudalternative design configurations, each with a reference capacity of 120 kW(e).udHourly energy modelling was undertaken for Wits University’s West Campus forudeach of the twelve alternatives. Three configurations were further investigated andudare listed below; each with a design capacity of 480 kW(e).ud1. Compound Linear Fresnel Receiver (CLFR) field with an Organic RankineudCycle (ORC).ud2. Compound Linear Fresnel Receiver field with an Organic Rankine Cycle thatudintegrates storage for timed dispatch.ud3. Compound Linear Fresnel Receiver field with an Organic Rankine Cycle thatudintegrates hybridisation with natural gas.udLevelised electricity costs (LEC) of the systems were used as the basis for financialudcomparison. Real LECs, for the three configurations above, range betweenudR4.31/kWh(e) (CLFR, ORC) and R3.18/kWh(e) (CLFR, ORC with hybridisation).udvudWith the energy modelling of the hourly direct normal irradiation (DNI) input intoudthe CSP systems, Wits University’s West Campus Electricity bill was recalculated.udThe addition of the solar energy input resulted in certain savings and a new LEC thatudis Wits-specific. These LECs ranged between R3.98/kWh(e) (CLFR, ORC) andudR2.77/kWh(e) (CLFR, ORC with hybridisation). A third LEC was calculated thatudintegrates a CSP feed-in tariff (REFIT) of R2.05/kWh. At the time of writing, a CSPudREFIT of R2.10/kWh was released which favours the analysis.udThe analysis of the 480 kW(e) systems resulted in total plant areas of betweenud10350 m2 (CLFR, ORC,) and 15270 m2 (CLFR, ORC, with storage). With plantudmodulation, these plants can be placed on vacant land, above parking lots or on topudof buildings which would also provide shading.udThe values obtained for the average yearly insolation was 1781 kWh/m2 based onudTMY2 data. Johannesburg has a very intermittent source of DNI solar energy. Theudsummer months in Johannesburg yield a higher peak DNI, whereas the winterudmonths provide a more consistent average. This is due to the high amount of cloududcover experienced in summer. With this insolation, CSP electric generation isudpossible however, compared to the other locations, it is not ideal. Also, because of itsudintermittency is has been advised that certain applications such as HVAC andudprocess heat and steam requirements be pursued.udFrom the results, it can be concluded that power production costs through smalludscale CSP systems are still higher than with conventional fossil fuel options,udhowever several options that may favour implementation were recognised. Throughudthe analysis it was found that if the CSP generated electricity is valued at the marketudprice ( CSP REFIT), the payback time of such systems can be decreased from 73 toud12 years (CLFR, ORC with storage). Further, due to the scale of the plants analysed,udthe exploitation of high efficiencies and economies-of-scale of plants with powerudlevels above 50 MW(e), is not possible. With the introduction of these technologiesudviudat lower power levels, cost savings through the incorporation of other designudoptions (such as waste heat utilisation) should be pursued.udIt was recognised that South Africa in general has one of the greatest solar resourcesudin the world and should therefore be technology leaders and pioneers in CSPudtechnology. With greater emphasis being placed on the need for renewable energyudsystems, it is imperative that South Africa develops its skills and a knowledge baseudthat will work at making the implementation of renewable energy, and in particularudCSP generation, a reality. Technologies identified that should be pursued foruddistributed generation include Linear Fresnel collectors that are easy toudmanufacture and don’t involve complicated receiver systems. There is also scope foruddeveloping thermal storage technologies in order to make generation more reliable.
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