Techno-economic analysis of an off-grid micro-hydrokinetic river system as a remote rural electrification option

Abstract

Remote rural electrification via grid-extension is a challenging solution due to high connection costs and low electricity consumption rate. As a result, it is difficult to recover the initial investment costs. Therefore, electrification is made possible by means of the commonly used off-grid approaches such as solar, wind, diesel generator and conventional micro-hydro. However, owing to non-continuous availability of sunlight and wind, high cost of diesel fuel, and requirements for construction of diversion weirs, these off-grid approaches might not offer a cost-effective and reliable solution to low income rural residents. There are many rural communities throughout the world without access to grid electricity and with access to flowing water. An off-grid micro-hydrokinetic river (MHR) system is one of the promising technologies to be used in remote rural areas with flowing water. It can bring sustainable improvement to their quality of life due to its high energy density and minimal environmental impact. This technology is still in the development stage and there is a lack of application, especially in rural areas. Hence, this study investigates the current status of MHR technology in rural applications. To demonstrate the economic feasibility of an off-grid MHR system, a rural site with multiple energy sources within South Africa has been used. The economic benefit offered by this proposed system at the selected site is compared to the economic benefits offered by other commonly used standalone systems such a solar, wind and diesel generator (DG). This economic comparison has been performed by making use of a Hybrid Optimization Model for Electric Renewable (HOMER) simulation tool. Grid extension has also been used as a comparison method for obtaining an economical distance between grid lines and the remote rural site. The results highlighted the acceptable economic performance of the MHR system. v Finally, most of the available modelling and simulation tools for mechanical and electrical systems are not equipped with hydrokinetic modules. Hence, an MHR system model has been developed in MATLAB/Simulink in order to study its dynamic performance as submitted to variable water resource. Its performance has then been compared to the performance of a wind system counterpart for generating the same amount of electrical power. This proved/verified that the proposed system can generate electricity markedly cheaper than a wind system even in areas with adequate wind resource within South Africa.