Restoring the natural flow regime of a large hydroelectric complex:Costs and considerations

摘要

Electricity generated from hydropower is considered a clean energy source because it is both renewable and non-carbon emitting. However, large hydroelectric complexes can generate a wide range of deleterious impacts on downstream ecosystems. The purpose of this article is to describe an approach for estimating the system-wide electricity costs of altering the operation, called reoperation, of a large hydroelectric complex for the purpose of partially restoring natural downstream ecosystems. We study the effect of reoperating the Akosombo hydroelectricity complex in Ghana because the Akosombo plays a critical role in regional electricity production and the construction of the Akosombo Dam substantially altered the natural flow of the Volta River. We do this by comparing the observed operations for a one-year period spanning 2004-2005 with reoperation scenarios that have the goal of making the dam outflow pattern closer to the inflow pattern. We quantify the impact of these reoperation strategies on regional electricity costs using a calibrated model of productivity at the Akosombo Dam and a model of regional electricity generation and trade. We find that if annual generation stays essentially the same with increased wet season generation offsetting decreased dry season generation, the increase in annual costs to the West African Power Pool is about $20 million. If dam operation is altered to be as close to run of river as possible, annual generation decreases due to water spillage, and system-wide costs increase $155 million.