Integration and optimization of hydrokinetic turbines in canals in South Africa

Abstract

Small-scale hydrokinetic (HK) energy systems is a renewable energy source which has never before been explored in South Africa, mainly due to former low-cost coal-powered electricity. This renewable energy option makes use of the kinetic energy from flowing water rather than potential energy, which is more often used in conventional hydropower. This allows installations into existing water infrastructure with very little civil works. Approximately 66% of South Africa’s water supply is used by the agricultural sector with canal systems running through many areas which are in dire need of alternative energy sources. The objective of this study was to install a HK turbine into an existing irrigation canal in South Africa and test the integration thereof. It was hypothesized that these small-scale HK systems could function as a practical renewable energy option in existing water infrastructure in the country, having minimal risk and environmental impact and an overall positive social influence. The selected installation site lies in the upper region of the Boegoeberg irrigation canal, in the Northern Cape province of South Africa, which lies in one of the poorer regions of South Africa. With a largely unemployed population, the !Kheis Local Municipality (LM) has very little income to provide basic electricity needs to its citizens. The canal system is seen as a possible untapped source of HK energy development. A series of steps were followed to identify a suitable site for implementation and testing of these devices. A canal section in close proximity to the Groblershoop water treatment works (WTW), which supplies water to a large majority of the Groblershoop Town citizens, was chosen for implementation. This could aid the LM in reducing high electricity costs which are a consequence of the WTW pump station. The HK turbine selected for implementation and testing developed by Smart Hydropower GmbH, was designed to function in canal systems. After initial site selection and preparation, the turbine was installed at various orientations and the outputs and a few influences were recorded. Once installed possible practical optimisation techniques were tried to test the functioning of these systems where the desired operating velocity range is not readily available, starting with altering the turbine itself and thereafter altering the canal section. The results were evaluated and aspects such as power output and upstream damming levels were compared to establish which optimisation measures prove most effective from a practical, financial and sustainable viewpoint. The data collected allowed analysis of the functioning of such a system within the South African environment and legislation. Although the single installation cannot be representative of the country, it does provide a clearer image of important factors to be considered during the design of future HK installations in South Africa. The outcome of the study proved that with certain alterations to the turbine design and adequate pre-feasibility studies of the site details, implementation of these units within existing canal infrastructure in South Africa could be a practical and sustainable renewable energy source.