A technical evaluation of concentrating solar thermal power generation technologies for the Upington area of South Africa.

Abstract

Studies undertaken by Eskom in 2001 identified three sites near the Northern Cape town of Upington which are suitable for a 100 MW Concentrating Solar Power (CSP) generating plant. Of the CSP technologies investigated, the central receiver option was identified as best for the Northern Cape, however almost none of Eskom’s analysis was made public. The basis of the central receiver’s suitability versus other CSP options is not publicly known. Given recent advances in concentrating systems, an argument exists for reassessing the suitability of various solar thermal technologies for bulk power generation. This study first characterises the incident solar radiation (insolation) levels at Upington from six data sources and assesses their quality. The data are then used to model performance of the parabolic trough, compact linear Fresnel reflector, central receiver, and dish-engine technologies. A software modelling tool of the United States National Renewable Energy Laboratory (System Advisor Model) is used to facilitate the comparison. Simulation results are compared with data from similar studies to ensure consistency of the CSP model inputs and performance outputs. Constraining the results to the environmental conditions of Upington, it is found that while central receiver technology produces less electricity per square kilometre of collector area, it uses less water than parabolic trough technology to obtain a higher annual electric output. Dish-engine technology has the most favourable annual electricity production to water-usage ratio, however, its modest annual electricity output and lack of energy storage capability weaken the case for it to match South Africa’s national load profile substantively. Examining the modelled month-to-month electricity output characteristic, the central receiver technology delivers significantly more electricity during the lower insolation winter period of the year than the competing technologies. This results in the central receiver technology achieving the highest annual electric output of the four technologies compared under the same insolation levels, strengthening the case for its implementation. As a whole, this work characterises the insolation levels at Upington, provides an analysis of the technical performance of competing CSP technologies for the proposed Northern Cape site, and argues quantitatively in favour of the central receiver option.