Stormwater detention tanks for sustainable energy management in urban environment

The risk of flooding in urban environment has become more and more frequent due to the increased impervious surfaces and climate change. The most suitable solutions for mitigating the urban flooding risks are stormwater detention tanks which temporarily store the exceeded rainfall and gradually release it into the urban drainage system at the end of the rainfall events. The present study aims to evaluate the feasibility of stormwater detention tanks used also for producing hydroelectric power serving a small town, through the release of such volumes. The study is applied to an urban watershed in the city of Cosenza, Italy. After a preliminary design, a hydrologic/hydraulic model, SWMM, coupled with a numerical model implemented in MATLAB was used to predict the stormwater volumes reusable for the production of electricity and the overall response of the system on annual basis. The results obtained showed that a mini-hydro system in an urban area is technically feasible. From an economic point of view, the system is self-sustainable only if one considers the need to integrate the urban drainage network with the electric power grid using the stormwater volumes to store energy in hours of maximum electric energy production that otherwise would be lost.