Mengesha Mamo (PhD)Soder Lennart (Prof.)Kena Likassa2024-07-312024-07-312024-06https://etd.aau.edu.et/handle/123456789/3374Energy has been a crucial factor for the survival of mankind since early primitive societies began to make fire from timber wood. Since then, there have been significant revolutions in using energy sources from fossil fuels such as coal and gasoline and the development of energy conversion technologies such as electric energy generators up to the more recent use of renewable energy sources (REs). The uneven distribution of fossil fuels in the world, the growing economic and social need for energy, the difficulty of tackling climate change, advances in energy technology, rising oil prices and the emergence of low-carbon societies have all contributed to the recent revolution towards renewable energy sources. However, REs especially variable renewable energies (VREs) such as wind and solar energy, pose an additional challenge for electric grid operators due to their inherent variability and unpredictability nature. Because of these characteristics of VREs, the grid integration of VREs can potentially jeopardize the reliability of the power grid. Countries need to conduct grid integration studies to overcome the challenges of integrating VREs. In this regard, utilities are increasingly relying on the traditional grid integration model, which ignores the various operational characteristics of VREs. Accordingly, it is important for the grid integration study to either develop new models or modify existing models to study the characteristics of VREs in the power sector. In developing countries, especially in Ethiopia, there is currently little research of this kind due to the slow development of VREs. Thus, this dissertation deals with the study of grid integration of VREs into the power system of Ethiopia according to local as well as global needs. The specific objectives are to assess the variability of existing VREs, simulate wind energy production for grid integration studies, estimate the maximum integration of VREs, and assess the difficulty of integrating them into the grid. To achieve these goals, the following four specific objectives are defined and briefed: To assess the variability of existing wind power in the grid of Ethiopia. This objective is pursued to evaluate and assess the magnitude and frequency of variability of individual and aggregate wind power in the Ethiopian power grid. A step-change and correlation are used to examine the variability of wind power generation. The results indicates that variability of Ethiopian wind power is significant. This huge variability is due to the small installed capacity. However, this variability does not have much influence on system operation because of the smaller magnitude of the wind compared with system size. Modeling Ethiopian wind power production for grid integration study using ERA5 reanalysis data is the second specific objective. The objective of this particular purpose is to produce wind power time series considering the various factors affecting wind power production including wake effect, diurnal and seasonal bias, and the loss in upcoming wind speed. The modeling was performed using wind speed data from ERA5 of the European Center for Medium-Range Weather Forecasts (ECMWF) and wind farm data from Ethiopian Electric Power (EEP). Moreover, the model has used spatial statistical down-scaling and interpolation to obtain the required result. The outcomes show that the model result and the measurements agree well, with a low root mean square error. This means that this model can be extended to other regions of the country to predict future wind power generation and to show the potential areas for simulating wind power generation for planning and operating wind turbines using ERA5 data. The third specific aim is to estimate a maximum variable renewable energy integration with a goal of 100% renewable energy and a high share of hydropower under different scenarios . This particular objective aims to determine the maximum integration of wind and solar PV into the power grid of Ethiopia. The current national VRE integration plan for the year 2030 is analyzed using the model along with eight alternative scenarios that consider dry years and annual variations in VRE for minimum load shedding and VRE curtailment. GenX, a modified version of capacity expansion planning, has been used for this work. The findings showed that Ethiopia could integrate more VRE into the grid than EEP had anticipated. The fourth specific objective is to study the challenges of system balancing and curtailment of wind power in Ethiopia grid under different scenarios. In addition to analyzing the challenge of system operation with wind, developing an hourly dispatch model and simulation of the Ethiopia power grid is the specific aim of this work. This model will be useful in analyzing future wind power curtailment and system balancing issues. The developed model was used to analyze the grid for the year 2030 under different scenarios and verified using historical data. With an annual wind energy share of 14.5%, 17.8%, and 25.2%, the study analyzed the impact of transmission capacity, regulation reserve needed, and daily minimum hydropower production. The result showed that the curtailment was less than 0.2%, 1.1%, and 9.8% for each wind share respectively. The cost of wind energy is also directly related to the extent of curtailment and the capacity of transmission lines. A better balance between production and consumption and fewer wind power curtailments is the result of a reduction in the minimum electricity production from hydropower and full utilization of transmission lines to neighboring countries.en-USBalancingCurtailmentEthiopiaGrid integration studyModelPVUncertaintyWindVREVariabilityDissertation