Hydropower Energy Recovery Systems: Development of Design Methodologies for Pumps As Turbines in Water Networks

Abstract

Given the urgency of tackling the challenges offered by climate change and natural resource depletion, it is a priority to increase the sustainability of the water industry by reducing its energy demand and associated pollutant emissions. One of the possible ways to achieve this goal is to implement on a vast scale hydropower energy recovery from pressurized pipelines, in order to generate clean renewable energy at sites where currently an excess of pressure is being dissipated by means of a throttling valve. A type of hydro converter which has the potential to meet the technical challenges of in-pipe small scale hydropower at a reduced cost are Pumps As Turbines (PAT), consisting of regular water pumps utilized in reverse as turbines. Despite this, their adoption worldwide as energy recovery devices has been sporadic and the technology has remained extremely marginal as for the number of applications. The present PhD dissertation focused on developing a comprehensive and robust PAT selection strategy under the format of a software application, able to assist designers during the selection of the most appropriate turbine for any given site. At the same time, in order to demonstrate the potential of the technology to a wide audience, the same software was used to design a laboratory test rig and two full scale pilot plants later built and commissioned in Ireland and Wales. The feedback obtained from the experimental campaign and the demonstration sites confirmed the validity of the PAT selection software, with all units performing according to the expectations. In particular, the two pilot plants showed an attractive return on investment (8.5 and 5 years) and a competitive cost of generated electricity (0.148 and 0.079 €/kWh) which would have not been possible with the adoption of a conventional and more expensive hydro turbine.