Potential energy exploitation in collective irrigation systems using pumps as turbines: A case study in Calabria (Southern Italy)

The development of efficient energy, water and environment systems is considered a fundamental key to satisfy the principles of cleaner production, energy security and circular economy. The present study aims at investigating the possible energy exploitation of the untapped hydraulic potential in collective irrigation systems by adopting pumps as turbines. These machines are not extensively used to produce electricity due to the lack of information in reverse operation mode and the low efficiency outside the best efficiency point. This study proposes new correlation rules to obtain more accurate performance of the pumps as turbines and introduces a novel methodology to select the proper hydraulic machines and define the optimal hydropower configuration. The proposed procedure based on a multi-variable optimisation has been applied to the whole collective irrigation networks of Calabria (Southern Italy). Specifically, the energy production, greenhouse gas emissions and investment costs of 114 potential small hydropower plants have been estimated. The results show that the adoption of pumps as turbines in small-scale hydropower plants is a viable, clean and cheap solution for an extensive use in collective irrigation systems. These machines lead to a noticeable decrease in the electro-mechanical costs (−74%) with only a slight reduction (−19%) in the total electric power compared to specific-site designed turbines. Furthermore, the proposed hydropower systems guarantee a significant fall in greenhouse gas emissions (larger than 8800 tons/year) with respect to the conventional Italian electric production. The generated electricity could be used to satisfy a larger share of electric demand coming from collective irrigation agencies and/or agricultural farms with significant improvements in their economic and environmental impact. Overall, the proposed methodology may represent a valid design tool for an extensive exploitation of hydropower sources in rural water systems, in an effort to enhance cleaner energy productions and integrated systems of energy, water and environment.