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

Thesis (M. Tech. (Electrical Engineering )) - Central University of Technology, Free State, 2014Remote 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. 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

Exploration of renewable sources for isolated systems

Providing universal access to electricity is a priority worldwide. Renewable Energy Sources (RES) play an important role in the supply of energy to rural and remote areas, where grid electricity is not available, or the cost of the grid extension is excessively. Isolated communities in the Amazon region of Ecuador are frequently far away from each other, formed by scattered housing, exhibit very low population density, and are surrounded by dense vegetation. Supplying such communities is typically done through small paths, fluvial access, and in few cases through small planes. Therefore, implementing transmission and distribution lines for supplying energy is costly and harmful to the environment. Hence, the use of RES represents a crucial opportunity for power generation purposes. Photovoltaic Home Systems (PVHS) are typically used to provide electricity to the dwellings in off-grid rural communities. However, Centralized Photovoltaic Systems (CPVS) with their own low voltage distribution network (LVDN) is also being considered as an alternative for rural electrification. This thesis presents a comprehensive review on the use of RES for electricity, by providing the main features of this technology, classification, and schematic diagrams of hybrid systems (HS) in order to satisfy the energy demand for a single or an entire group of households in rural areas. This research also evaluates the electrical supply through PVHS and through a CPVS to provide energy to the rural community of Yuwints in the Ecuadorian Amazon. The most suitable system is selected after a comparison of the Net Present Cost (NPC) of various renewables system e.g. PV-Battery systems, Wind-battery systems, PV-Wind-battery systems, etc. The techno economic analysis is carried out through the microgrid optimization software Homer Energy. The result of the present study proposes the CPVS as the best option for the electrical supply of the community, allowing a full coverage of the load and guaranteeing a safe operation of the syste

Innovation in Energy Systems

It has been a little over a century since the inception of interconnected networks and little has changed in the way that they are operated. Demand-supply balance methods, protection schemes, business models for electric power companies, and future development considerations have remained the same until very recently. Distributed generators, storage devices, and electric vehicles have become widespread and disrupted century-old bulk generation - bulk transmission operation. Distribution networks are no longer passive networks and now contribute to power generation. Old billing and energy trading schemes cannot accommodate this change and need revision. Furthermore, bidirectional power flow is an unprecedented phenomenon in distribution networks and traditional protection schemes require a thorough fix for proper operation. This book aims to cover new technologies, methods, and approaches developed to meet the needs of this changing field

Modeling and Optimization of Renewable Energy Systems

This book includes solar energy, wind energy, hybrid systems, biofuels, energy management and efficiency, optimization of renewable energy systems and much more. Subsequently, the book presents the physical and technical principles of promising ways of utilizing renewable energies. The authors provide the important data and parameter sets for the major possibilities of renewable energies utilization which allow an economic and environmental assessment. Such an assessment enables us to judge the chances and limits of the multiple options utilizing renewable energy sources. It will provide useful insights in the modeling and optimization of different renewable systems. The primary target audience for the book includes students, researchers, and people working on renewable energy systems

Design and implementation of rural microgrids : Laguna Grande case study

In 2015 the United Nations established the 17 Sustainable Development Goals: a set of interrelated objectives and a guide to reach a more sustainable and higher quality future for all humanity. The goals were set with a timeline for 2030, the seventh goal refers specifically to the universal access to “affordable and clean energy”. Taking account the considerable fraction of world population that do not have access to electricity, especially in rural areas, this goal still requires a great effort and investment. Rural hybrid microgrids, that integrate and manage solar and wind energy resources to provide electric service to remote locations, are a promising solution to reach this “last mile” scenario. However, as is reported in the literature, there is still scarce information about the performance of these systems based on measured data obtained in real working field conditions. This work aims to contribute to this aspect mainly by analyzing the data obtained in the 9 kW Laguna Grande community hybrid microgrid, which is cooperative since 2016 in the coast of Perú, and has been equipped with sensors and data acquisition systems that measure and register solar radiation, wind speed, temperatures, and all the relevant electric parameters. As a preliminary study, the rural electrification gap and costs are assessed, as well as the availability of solar and wind resources in the area of interest. A literature and state of the art review is undertaken followed by the definition of the microgrid concept and the different ways in which a rural microgrid can be configured. The particular way in which the Laguna Grande microgrid is configured and instrumented is described. Measured meteorological conditions as solar radiation, wind speed and temperature are analyzed and related to the power generated by the photovoltaic arrays and wind turbine. This in turn leads to a balance with respect to the power delivered to the community and consequently to the voltage levels of the battery bank. Battery dynamics concepts are used to determine the depth of discharge (DOD) of the batteries in a real time regime. The statistics of the DOD values allows for the duration of the battery to be estimated which is a key factor to the microgrid economics and reliability. A parametric study is done to assess the effect of varying battery size on the technical and economic performance of the microgrid; similarly, with generating capacity in both photovoltaic arrays and wind turbines. Complementarily, a commercial software is used to optimize the microgrid, introducing state of the art components as lithium-ion batteries, power electronics and photovoltaic modules for a future upgrade. Finally, this study would not be complete without emphasizing the importance and adequate consideration of the human factor for the success and long-term sustainability of rural electrification projects.En el año 2015 las Naciones Unidas estableció los 17 Objetivos de Desarrollo Sostenible: un conjunto de objetivos interrelacionados y una guía para alcanzar un futuro más sostenible y de mayor calidad para toda la humanidad. Las metas se establecieron con una línea de tiempo para el 2030, la séptima meta se refiere específicamente al acceso universal a “energía limpia y asequible”. Teniendo en cuenta la fracción considerable de la población mundial que no tiene acceso a la electricidad, especialmente en las zonas rurales, este objetivo aún requiere un gran esfuerzo e inversión. Las microrredes híbridas rurales, que integran y gestionan los recursos de energía solar y eólica para proporcionar servicio eléctrico a lugares remotos, son una solución prometedora para llegar a este escenario de “última milla”. Sin embargo, como se reporta en la literatura, aún existe poca información sobre el desempeño de estos sistemas basada en datos medidos y obtenidos en condiciones operativas, reales de campo. Este trabajo busca contribuir en este aspecto principalmente mediante el análisis de los datos obtenidos en la microrred híbrida comunitaria de 9 kW en Laguna Grande, que está operativa desde 2016 en la costa de Perú. Esta microrred ha sido equipada con sensores y sistemas de adquisición de datos que miden y registran la energía solar, radiación, velocidad del viento, temperaturas y todos los parámetros eléctricos relevantes. Como estudio preliminar se evalúa la brecha y costos de electrificación rural, así como la disponibilidad de recurso solar y eólico en la zona de interés. Se realiza una revisión bibliográfica y del estado del arte, seguida de la definición del concepto de microrred y las diferentes formas en que se puede configurar una microrred rural. Se describe la forma particular en que se configura e instrumenta la microrred de Laguna Grande. Las condiciones meteorológicas medidas como la radiación solar, la velocidad del viento y la temperatura se analizan y relacionan con la energía generada por los arreglos fotovoltaicos y la turbina eólica. Esto a su vez conduce a realizar un balance con respecto a la potencia entregada a la comunidad y consecuentemente a los niveles de voltaje del banco de baterías. Los conceptos de dinámica de batería se utilizan para determinar la profundidad de descarga (DOD) de las baterías en un régimen a tiempo real. Las estadísticas de los valores DOD permiten estimar la duración de la batería, lo cual es un factor clave para la economía y confiabilidad de la microrred. Se realiza un estudio paramétrico para evaluar el efecto de variar el tamaño de la batería en el desempeño técnico y económico de la microrred; de igual forma, con la capacidad de generación tanto en arreglos fotovoltaicos como turbinas eólicas. Complementariamente, se utiliza un software comercial para optimizar la microrred, introduciendo componentes de última generación como baterías de iones de litio, electrónica de potencia y módulos fotovoltaicos para una futura actualización. Finalmente, este estudio no estaría completo sin enfatizar la importancia y la adecuada consideración del factor humano para el éxito y la sostenibilidad a largo plazo de los proyectos de electrificación rural.Postprint (published version

Innovation in Energy Systems

It has been a little over a century since the inception of interconnected networks and little has changed in the way that they are operated. Demand-supply balance methods, protection schemes, business models for electric power companies, and future development considerations have remained the same until very recently. Distributed generators, storage devices, and electric vehicles have become widespread and disrupted century-old bulk generation - bulk transmission operation. Distribution networks are no longer passive networks and now contribute to power generation. Old billing and energy trading schemes cannot accommodate this change and need revision. Furthermore, bidirectional power flow is an unprecedented phenomenon in distribution networks and traditional protection schemes require a thorough fix for proper operation. This book aims to cover new technologies, methods, and approaches developed to meet the needs of this changing field

Utilization of small conduit hydropower generation for domestic loads

Thesis (Master of Engineering in Electrical Engineering) -- Central University of Technology, Free State, 2019The growth in the world’s population has led to an increased energy demand. Today and in the near future, renewable energy should be widely implemented, to meet the growing demand for energy. In all various renewable energy technologies, hydropower generation is the most established. A portion of small hydropower generation can be obtained by recovering the energy within water supply systems. Investing in water energy recovery is of utmost importance, considering the unsustainable use of water on the world level. Therefore, the process of energy recovery should be part of the water cycle. Many countries have begun with the development of this technology, although not much is exploited. The exploitation may contribute to the cost reduction of water supply systems, increasing feasibility. The current study focused on developing a simulation tool that may be used for conduit hydropower generation. This will assist the conduit hydropower developers to quantify the available energy and evaluate the viability of the conduit hydropower projects. The main findings revealed that the developed model responded effectively under variable pressure. The system was solely active when excess pressure was available. This was due to the pressure difference between PRV pre-set pressure and the system pressure. When the inlet pressure was greater than that of the pressure setting at PRV, the energy recovery turbine utilized the pressure drop to drive the PMSG. Various output voltages and currents were obtained; the generator did not generate when the pressure drop was zero. Further research is required to address the factors not covered by this work. This include: evaluation of various turbine and generator technology to validate the model as a universal conduit hydropower model, application of various configurations of the pipeline system and incorporating it to the simulation model and a thorough analysis of the physical losses in the pipeline, in order to accurately match the measured and simulated outputs

Decision aiding in off-grid electrification projects: the role of uncertainty acknowledgement and objectives alignment

Most completed South African off-grid electrification projects have failed to contribute significantly to the sustainable development of the communities they supply. The hypothesis of this research is that the root causes of these failures can often be found in the pre-implementation decision making (planning) processes, specifically in three areas: 1. Decision aiding approaches and tools, aimed at supporting the decision making process, are either not used or do not support high quality decisions. 2. Uncertainties that can impact the project negatively are often not acknowledged (identified) initially, and can therefore not be addressed proactively. 3. The primary project objectives often do not align with sustainable development objectives, which mean that even if all the project objectives are achieved (i.e. a successful project) the project still does not contribute to sustainable development. The process of validating this hypothesis results in several outputs aimed at improving the contribution of future off-grid electrification projects to sustainable development: A framework of primary energisation objectives for sustainable development is developed, which defines what the outcomes of a successful off-grid electrification project should be. High quality decision making is defined, and a framework of decision aiding characteristics that support high quality decision making is developed against which decision aiding approaches and tools can be evaluated. The concept of soft and hard uncertainties is introduced, and it is shown that most of the social and institutional unacknowledged uncertainties in South African off-grid projects are hard. Hard uncertainties are impossible to represent probabilistically, and are difficult to include in traditional single-dimensional (mostly cost-based) decision aiding approaches and tools. A degree of surprise tool, based on Shackle's measure of a decision maker's degree of surprise at a future outcome becoming reality, is developed to act as an example of how hard uncertainty can be acknowledged in the decision making process. p14 - Abstract Soft uncertainty in the decision process is quantified for two examples: renewable energy system sizing, where an adequacy confidence index is proposed, and renewable energy resource estimation, where the accuracy and applicability of RETScreen and Homer within a South African climatic context are analysed. Finally, the above outputs are integrated into an existing decision aiding process and applied in order to demonstrate the value of decision aiding which includes uncertainty acknowledgement and objectives alignment. The applicability of the results of this research is not limited to off-grid electrification, and can be of value within any developmental project aligned with sustainable development, especially where social and institutional uncertainties are prevalent

FLATNESS BASED CONTROL OF MICRO-HYDROKINETIC RIVER ELECTRIFICATION SYSTEM

Published ThesisIn areas where adequate water resource is available, hydrokinetic energy conversion systems are currently gaining recognition, as opposed to other renewable energy sources such as solar or wind energy. The operational principle of hydrokinetic energy is not similar to traditional hydropower generation that explores use of the potential energy of falling water, which has drawbacks such as the expensive construction of dams and the disturbance of aquatic ecosystems. Hence, hydrokinetic energy generates electricity by making use of underwater turbines to extract the kinetic energy of flowing water, with no construction of dams or diversions. A hydrokinetic turbine uses flowing water, which varies with climatic conditions throughout the year, to power the shaft of a generator, hence, generating an unstable energy output. The aim of this dissertation is to develop a controller that will be used to stabilize the output voltage and frequency generated in a hydrokinetic energy system. An overview of various methods used to minimize the fluctuating impacts of power generated from renewable energy sources is included in the current conducted research. Several renewable energy sources such as biomass, wind, solar, hydro and geothermal have been discussed in the literature review. Different control methods and topologies have been cited. Hence, the study elaborates on the adoptive control principles, which include the load ballast control, dummy load control, proportional integral and derivative (PID) controller system, proportional integral (PI) controller system, pulse-width modulation (PWM) control, pitch angle control, valve control, the rate of river flow at the turbine, bidirectional diffuser-augmented control and differential flatness based controller. These control operations in renewable energy power generation are mainly based on a linear control approach. In the case whereby a PI power controller system has been developed for a variable speed hydrokinetic turbine system, a DC-DC boost converter is used to keep constant DC link voltage. The input DC current is regulated to follow the optimized current reference for maximum power point operation of the turbine system. The DC link voltage is controlled to feed the current in the grid through the line side PWM inverter. The active power is regulated by q-axis current while the reactive power is regulated by d-axis current. The phase angle of utility voltage is detected using PLL (phased locked loop) in a d-q synchronous reference frame. The proposed scheme is modelled and simulated using MATLAB/ Simulink, and the results give a high quality power conversion solution for a variable speed hydrokinetic system. In the second case, whereby the differential flatness concept is applied to a controller, the idea of this concept is to generate an imaginary trajectory that will take the system from an initial condition to a desired output generating power. This control concept has the ability to resolve complex control problems such as output voltage and frequency fluctuations of renewable energy systems, while exploiting their linear properties. The results show that the generated outputs are dynamically adjusted during the voltage regulation process. The advantage of the proposed differential flatness based controller over the traditional PI control resides in the fact that decoupling is not necessary and the system is much more robust as demonstrated by the modelling and simulation studies under different operating conditions, such as changes in water flow rate