CSP parabolic trough and power tower performance analysis through the Southern African universities radiometric network (SAURAN) data

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The objective of this paper is to analyse the performance of parabolic trough and power tower technologies by selecting two radiometric stations in different geographic locations, with approximately equal annual direct normal irradiance (DNI) values, but with different monthly DNI distributions. The two stations chosen for this study are situated at the University of Free State, Bloemfontein, Free State Province and in Vanrhynsdorp, Western Cape Province. The annual measured DNI values for both these locations in South Africa are in the range of 2500-2700 kWh/m2. The comparison between the different monthly DNI distributions of these selected sites includes an assessment of annual hourly data in order to study the performance analysis of the most mature concentrating solar power (CSP) technologies, namely parabolic trough and power tower plants. The weather data has been obtained from the Southern African Universities Radiometric Network (SAURAN). A comparison between the different monthly DNI distributions of these selected sites includes the assessment of hourly data. Selection of these radiometric stations has also been done on the basis that they have been operational for at least one year. The first year that most SAURAN stations have been online for at least one year is 2014, thus data from this year has been considered. The annual performance analysis shows that parabolic trough plants have a higher energy yield in Vanrhynsdorp while power tower plants seem to be more suitable for Bloemfontein. Power tower plants in both the locations have a higher annual energy yield when compared with parabolic trough plants. A parabolic trough power plant in Vanrhynsdorp in the Western Cape Province has very low monthly electricity generation in the winter months of May, June, July and August. This is partly due to the higher cosine losses in the parabolic trough ‘one–axis’ tracking systems and lower DNI values in the winter months. However, a power tower plant in Vanrhynsdorp performs better in these months. CSP plants are often regarded to have a potential to supply base load power in South Africa which has a morning and a more pronounced evening peak in both summers and winters. In such a situation, a parabolic trough plant in Vanrhynsdorp, with very low electricity generation in the winter months is not a suitable technology. A power tower must be considered instead in such a location. This gives us an indication that monthly DNI distribution might play an important role in CSP technology selection. Satellite derived data for these stations must be considered in the future in order to derive more accurate conclusions and recommendations for technology selection.