Optimal planning of waste-to-energy-based combined heat and power plant on a power distribution network.
Alao, Moshood
Alao, Moshood
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Abstract
Increase in population, urbanisation and industrialisation are major proponents to energy demand growth as well as municipal solid waste (MSW) generation. Wasteto-energy (WtE) has evolved as a promising solution for sustainable energy generation as well as waste management. One critical issue of concern to distribution companies (DISCOs) is electric distribution system expansion planning (EDSEP) due to load growth as well as demand variability. Conventionally, EDSEP is done by building new substations or reinforcing the existing ones with new
transformers and upgrading the network feeders. This additional cost may impose significant financial burdens on the DISCOs. The integration of distributed generator(DG) to the electric distribution networks (EDNs) has the capability of addressing the EDSEP problem. The energy carriers of a WtE technology can be fed into a DG such as combined heat and power (CHP). Therefore, optimal planning of a WtECHP on a power distribution network is deemed to address the fundamental issues of waste management and EDSEP with the view to ensuring environmental sustainability and improved network performance. However, there is limited studies on holistic approach for optimal planning of WtE-CHP and its integration to the distribution network in the open literature. In a bid to close this research gap, this study is aimed at developing comprehensive approaches for optimal planning of WtE-CHP on a power distribution network involving upstream and downstream planning strategies. In the upstream planning, selection of appropriate WtE technology and suitable prime mover (CHP equipment) was implemented. As a result of conflicting multi-criteria nature of WtE technologies as well as CHP equipment, selecting an appropriate alternative among them is a complex problem. To address this challenge, novel hybrid fuzzy multi-criteria decision making (MCDM) methods incorporating unification of objective and subjective weighting approaches were developed and applied using the City of Johannesburg and City of Cape Town, South Africa as case studies. In the downstream planning strategy, the optimal allocation of the WtE-CHP equipment to a power distribution network was executed. Due to load growth, voltage dependency of various consumers and seasonal demand variability, it is imperative to include all of these in the optimal allocation of WtE-CHP for technoeconomic and environmental benefits of EDSEP, hence a multi-objective optimisation problem. This was addressed by developing and applying an improved multi-objective particle swarm optimisation (IPSO) algorithm based on weighted randomised acceleration coefficient and adaptive inertia weight with a dynamic approach for economic and environmental assessments using standard IEEE 69 and 33 bus distribution systems and Soweto, Johannesburg as the case study. It is deduced that the application of the developed novel hybrid fuzzy MCDMs indicated anaerobic digestion (AD) technology as the most suitable WtE technology for South African cities while fuel cell (FC) and internal combustion engine (ICE) are best CHP-DGs that utilise the energy carrier (i.e., biogas) of AD. When connected to the distribution network, it is inferred that ICE based CHP-DGs modelled to operate at optimal power factor improves the network performance parameters such as total active power loss, voltage deviation and voltage stability index better than FCs based CHP-DGs modelled to operate at unity power factor in all cases and scenarios considered. It is also shown that yearly load growth causes an increase in the size of the CHP-DGs but not on their locations on the distribution network. Based on seasonal mixed voltage dependent load models including daytime and night-time of the season, it is concluded that lower DG capacities are needed in the night-time compared to the daytime hence, allowing the distribution companies (DISCOs) to disengage some DG units in the night-time thereby reducing the cost of fuel, enabling maintenance of any ailing equipment and elongating the life span of the DGs while ensuring optimal economic dispatch of the DGs. It is also inferred that FCs based CHP-DG is more economically viable than ICE based DGs when operated in CHP mode. On the other hand, it is deduced that ICE-based DG is more economically viable when operating in power-only mode. It is shown that FCs-CHP are more environmentally friendly than ICE since FCs are non-combustion-based equipment in which the main emission during their operation is water vapour which has no health or harmful effect on humans and the environment. The developed IPSO is able to minimise the objective functions while improving the network performance parameters better than the standard PSO in terms of solution quality, convergence speed and statistical analysis. The developed IPSO is also perceived to be better than most of the state-of-the arts optimisation algorithms found in literature. Even though South African cities and townships are taken as case studies in this research, the models developed can be applied for any cosmopolitan city with similar waste composition and economic status to South Africa around the world.
Description
Submitted in partial fulfilment of the requirements for the degree of Doctor of Engineering: Electrical Engineering In the Department of Electrical Engineering
in the Faculty of Engineering and the Built Environment at the Tshwane University of Technology.
Date
2024-03-29
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Tshwane University of Technology
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Keywords
Waste-to-Energy, Optimal planning, Anaerobic digestion, Distribution network, Distributed generation, Waste-to-energy-based combined heat and power