Development of a design and implementation process for the integration of hydrokinetic devices into existing infrastructure in South Africa

Abstract

In South Africa there is currently no notable use of modern small-scale hydrokinetic (HK) energy systems, mainly due to formerly 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. Updated refined versions of this technology are now being investigated and manufactured due to the global drive towards reducing carbon emissions and increasing energy efficiency. These modular units allow for installation of HK turbines into existing water infrastructure with very little civil works. The study’s objective was to develop a simplified design and implementation process for HK devices within the South African legislative and regulatory environment. Approximately 66% of South Africa’s water supply is used by the agricultural sector with more than 6 500 km of canal systems running through many areas which could benefit from alternative energy sources. The recent electricity crisis in the country allowed for problem resolution through funding opportunities and thereby an introduction of an innovative and sustainable technology to provide renewable electricity where otherwise not feasible. A pilot HK project was implemented in an applicable section on the Boegoeberg irrigation canal in the Northern Cape Province and tested for optimum functionality and correct application. This process allowed evolution of a development process for the implementation of HK devices in existing water infrastructure.

Development of a Hydrokinetic Turbine Backwater Prediction Model for Inland Flow through Validated CFD Models

“…In a study on a pilot HK installation in an irrigation canal, the backwater effect from the presence of the turbine extended up to 2.7 km upstream, due to the flat slope and subcritical flow present in the channel [1] (Figure 3). The clearance coefficient for this installation had not yet been defined.…”

“…Additionally, two three-bladed turbine models with experimental results found in the literature [41] and tested on site [1] were modelled as specified in [40], for further measurements and validation of the backwater calculation methods. Where possible, BEM-VD (virtual disk) models were used to reduce the computational expense required.…”

“…Where possible, BEM-VD (virtual disk) models were used to reduce the computational expense required. However, for the turbines which customized NACA profiles (Smart Hydropower turbine used in [1]) the full rotor geometry was modelled using a sliding mesh.…”

“…Operational condition boundaries were set to within the typical canal operating conditions, where deployment of HK devices would be considered. Scenarios outside of these boundaries were not considered, as it was assumed that the use of such a model would not be necessary outside of these conditions (e.g., at supercritical flow conditions) [1,14,53].…”

“…Research and development of hydrokinetic (HK) devices in canal systems is increasing in popularity due to increasing electricity costs and the drive towards finding renewable energy sources with unconventional applications [1][2][3]. Although most development has focussed on tidal applications, multiple opportunities exist for the deployment of HK systems within inland water infrastructure (e.g., canal systems) [1]. However, the placement of such a device can have significant water level and hydrodynamic energy loss effects [4].…”