Browsing by Author "Poole, Ian Vincent"
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- ItemConcentrating solar power in South Africa - a comparison between parabolic trough and power tower technologies with molten salt as heat transfer fluid(Stellenbosch : Stellenbosch University, 2017-03) Poole, Ian Vincent; Dinter, Frank; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The most common type of concentrating solar power (CSP) plant in operation today is the parabolic trough plant. In recent years molten salt power tower plants have demonstrated the benefit of using molten salt as heat transfer fluid and a storage medium. New research has shown that molten salt can be used in parabolic trough technology in a similar manner. This thesis documents an investigation into both technologies in order to compare them on a qualitative and quantitative basis. South Africa has become a hotspot for the development of CSP thanks to the abundant solar resource and the implementation of the Renewable Energy Independent Power Producer Procurement Program (REIPPPP) in the country. South Africa therefore provides a realistic backdrop for the comparison of the two CSP technologies. Parabolic trough and a power tower simulation models are constructed for the comparison of the two technologies. Meteorological data for six selected sites in South Africa are used to simulate the performance of both of the technologies, while operating under a flat feed in tariff and a two-tiered feed in tariff. Results of plant simulations show that molten salt can be used effectively as heat transfer fluid in parabolic trough technology. Parabolic troughs are shown to have higher annual optical efficiency compared to power towers. The main drawback of the parabolic trough technology is the thermal losses experienced in the field during overnight recirculation of the hot molten salt. Parabolic trough solar fields show a large seasonal variation in efficiency while power tower plants are shown to benefit from relatively consistent solar field efficiency throughout the year. The seasonal variation in solar field efficiency results in substantially higher thermal energy being available in the summer than in the winter, thereby resulting in storages being filled and the subsequent dumping of solar energy in parabolic trough plants. A simple cost model is built to compare the financial performance of the two technologies and allow for the optimization of the plants according to levelized cost of electricity (LCOE). At a site near Springbok in the Northern Cape Province optimization of both plant types resulted in an estimated LCOE of 0.127 USD/kWhe and 0.129 USD/kWhe for parabolic trough and power tower plants respectively. This study demonstrates that both parabolic trough and power tower plants require careful consideration when selecting the most appropriate CSP technology for a given location. Depending on the available solar resource and the tariff structure under implementation, this thesis finds that both parabolic trough and power tower plants can offer competitive CSP solutions with their own set of strengths and weaknesses.