An investigation of integrated reservoir and power system operation, an optimal dispatch of the Ethiopian Electric Power System
Creators: name: Ashenafi, Alemu
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2015

description: Ethiopian Electric Utility (which is born from EEPCo) has been running a Load Dispatch Center (LDC), which is tasked with the responsibility of an optimal power dispatch from an operational point of view. However, to date most operational decisions (including reservoir management) are done manually. Under such circumstance, integrated reservoir management and power system dispatch become more challenging as more and more plants with different technologies are to be added in coming years. Thus, it is very important to perform high resolution system dispatch to identify short term challenges, opportunities and potential solutions. This study was performed using two parallel, linear optimization, models that have been developed using MATLAB optimization toolbox. The first one, which is termed as energy model, deals with year round reservoir operations subject to the energy requirement of the power grid. This model has 73 time steps, with each time step representing a block of successive five days. The second one uses the output of the former model to test the hourly power balance and hourly reserve needs subject to the requirements of hourly water balance in reservoir and power systems operation over the selected days. The second model has 120 time steps, with each time step representing an hour. The result for the reference scenario shows that hydropower contributes significant amount of energy (approximately 90%) to meet 2017's annual demand at least cost. It also indicates that this could be achieved while maintaining steady state reservoir level and fulfilling the power reserve requirement. However, vulnerability related to heavy reliance on hydropower puts the power grid at significant risk that would lead to high cost of electricity due to shortage of water during dry year and high demand conditions. It was also shown that 3 GW capacity of GERD power plant should be available at the beginning of 2017 in order to avoid high cost of electricity generation and unserved energy that could occur if the construction is delayed. The result shows that depending on scenarios' the increase in cost of electricity, including cost of unserved energy, was approximately 6.3 to 8.75 fold the cost at the reference scenario. The major causes of this cost increase are the direct cost related to the use of more expensive electricity generators, and the indirect cost due to unserved energy (lost GDP per kWh). In short, it is concluded that integrated reservoir and power system operation leads to efficient resource utilization (Especially water and power system infrastructure), which should be given due attention during hydropower power resources development and operation. Future mitigation of the observed vulnerability should look into the following four solutions. These are: (i) implementing an optimal integrated operation; (ii) emphasizing the use of diverse generation resources; (iii) implementing strategies that enhance water inflows to reservoirs; (iv) designing power plants with higher capacity factors.