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A techno-economic feasibility study of a gridconnected hybrid solar pv-wind power generation system in Zimbabwe

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2019-1
Samu, Remember
The depletion of fossil fuel resources on a worldwide basis and an increase in greenhouse gas emissions and climate change as a whole have caused an urgent search for alternative sustainable energy sources to cater for the rising energy demands. The demand of energy is rapidly growing in both developing and developed nations thus making hybrid renewable energy power systems (RES), comprising Solar Photovoltaic (PV) and wind energy to be chosen as one of the best alternatives. However, on the downside, these resources are unpredictable and intermittent, even though to a certain extent they complement each other to fix this problem. Batteries, fuel cells or other storage systems could also be proposed but they increase the cost and some options may not be environmentally friendly. The renewable energy sources can partially or fully meet the deficit in Zimbabwe’s demand with minimal disturbance on the stability of the country. The main objective of this present study is to convert the solar and wind resources in different locations in Zimbabwe into electrical energy so as to meet the demand that is significantly growing. This kind of hybrid system ensures efficient utilization of the available renewable energy resources thus making them more efficient than their separate modes of generation. The system’s annual generated energy, annual excess energy and energy deficit, are amongst other energy parameters analyzed in this study. The goal of this thesis is to model a hybrid PV-Wind system using Microsoft Excel, so as to maximize the renewable energy sources (RES) fraction for Zimbabwe’s grid. An electricity demand forecast analysis was done up to 2030. An analysis of the levelized cost of electricity (LCOE) is also performed so as to examine the economic impact of this addition. In addition, Environmental costs were analyzed to point out the importance of this system to the environment. Four different scenarios were examined for in this study; (1-2) individual solar PV and wind resources were examined, (3) a hybrid solar PV/Wind with the energy storage system (ESS), (4) hybrid solar PV/Wind energy systems without energy storage systems. The obtained results show that there will be an increase in primary energy consumption from 0.17 quadrillion Btu to 0.183 quadrillion Btu by 2030 which then corresponds to an expected to increase in power consumption from 2200 MW to 2368.19 MW by 2030. Furthermore, the integration of ESSs to a hybrid PV/Wind system increases the capital cost of the system without significantly increasing the RES fraction. Only Gwanda location was studied for this scenario, by integrating Zinc Bromine and Lithium-Ion batteries and this system only had RES fraction of 60.47% compared to 60.42% where there was no ESS. The NPV of this system was US$39,130 and a capacity factor of 30.82% against a capacity factor of 30.58% for the system with no ESS. This system consisted of 157 kWh of Zinc Bromine batteries, a wind capacity of 2 MW and a PV capacity of 503 kW. The addition of ESSs, therefore, increased the system’s capital cost without significantly increasing the RES fraction. A grid connected hybrid system consisting of 4 MW wind capacity and 1328.76 kW PV capacity has the highest RES fraction of 74.03%, highest capacity factor of 30.84 %, the highest NPV of US$ 9.41 million and the highest yearly avoided carbon dioxide emissions of 19042.64 tons which gave a total yearly avoided cost of US$ 760000. This system was located at Victoria Falls and it is, therefore, considered the most favourable location for investment whilst the least favourable of the 16 locations under study is Harare. Overall the hybrid system gave rise in RES fraction, capacity factor and annual energy production compared to the individual PV only or wind only configurations.