Renewable energy microgrid for iron-ore rail freight shunting yards

Abstract

Global warming and climate change has purposely encouraged the use of environmentally friendly energy so as to reduce greenhouse gas emissions generated from the use of fossil fuels. As such, coal as it is a widely used non-renewable energy source is studied recently in-order to find ways of mitigating its causes in greenhouse effect. Coal is still one amongst the highest providers of electricity generated in South Africa, although it is a major cause of global warming and climate change with the accompanying CO2 emissions and high-water usage depending on cooling technology. It is of public knowledge to note that, in South Africa, the state’s power utility is experiencing many challenges on their power production and distribution network due to insufficient supply of coal, the significant growth in geographical distribution as well as the load changes. The growth in economic requirements and transformation in technology as well as environmental policy are constantly advancing in the market. However, the industries, organizations and society at large should take drastic actions in changing this situation. The engineers are focused in a mission of improving the technology and environment; and renewable energy-based microgrid (MG) applications is developing interest, globally because of its reliability and efficiency in supplying power for both grid-tied and off-grid modes. Although renewable energy (RE) microgrids are an increasingly adopted method used in supplying power to the residences, industries, hospitals etc., this system has not yet found its ground in railway industry, to assist in supplying the vast of railway equipment and railway facilities. Moreover, as new and advanced technologies are introduced into the railway environment, more energy costs saving technology should be a priority in order to reduce energy expenses. Thus, Transnet Freight Rail (TFR) as freight rail operator in South Africa should be irresistible on that initiative. In this research, the development of an economically and environmentally viable real-time hardware-in-theloop (HIL) model of MG for a railway-shunting yard is studied. The developed microgrid system consist of a PV solar system of 1.5MW and wind turbine of 3MW that act as distributed energy resources as well as 1MWh of lithium-ion batteries for energy storage system (ESS). The distributed energy resources (DER’s) will be used in supplying power to the railway yard equipment and facilities, efficiently. The use of renewable energy sources must continue in-order to drive the global energy transformation, so that society can benefit from a clean environment and collective future. The developed microgrid system as designed in this research acts as a back-up system that works in both off-grid and grid-tied modes. Nonetheless, the design and development of the energy management system (EMS) for the developed renewable energybased microgrid is incorporated in order to effectively maintain the supply of 5MVA load. Additionally, the main purpose of the suggested EMS working together with Li-ion batteries for the developed microgrid system was to improve the use of energy efficiency and manage the peak load demand by scheduling the generation according to the availability of wind and solar energy. Thus, the EMS was designed using fuzzy logic controller (FLC) which is the control method attainable on MATLAB/Simulink. Consequently, MATLAB/Simulink model was also used to design and develop the developed microgrid system with its energy management system and therefore, the OPAL-RT simulation model simulates, control and analyse the model in real-time. Furthermore, the simulated results in both MATLAB/Simulink model and OPALRT simulation show that, the amount of power demanded by the load will always be equal to the power generated by the developed system when operating in both modes.