The Economic comparison of reservoir type and run of the river type hydropower plants: a case study for upper Kotmale

Abstract

At present, greenhouse gas emissions are considered as a factor even for hydropower because of the identified gas emission possibilities. Thus when planning a large hydropower project at a selected location, it is important to take the decision on which type of power plant to construct (such as a reservoir type or run of the river type) based on an economic comparison including environmental considerations. Out of the implemented two large run of the river type hydropower projects in Sri Lanka, Upper Kotmale was selected as the case study for this research. The existing Talawakele run of the river project and an earlier suggested Caledonia reservoir project were selected for the comparison as competitive projects. Net greenhouse gas emissions from the both projects were estimated in this study. For the economic comparison, the levelized cost of electricity of both projects were calculated considering related costs, benefits under Clean Development Mechanism, and annual electricity generation. The results show that the unit cost of electricity generation from run of the river type project is substantially lower than that of reservoir type project. As Upper Kotmale is a peak serving plant in Sri Lanka, a separate comparison between the two projects was done considering their night peak operation. The results show a loss to the country by energy reduction due to not using the potential for reservoir type. Based on the results of the case study, it is concluded that for future large hydropower developments, a detailed study, including Clean Development Mechanism benefits, to be carried out case by case before taking the decision on reservoir construction. The research outcome will not only be important to any remaining hydropower potential development in Sri Lanka but also to other hydropower dominant countries in the world.