Investigations on pump running in turbine mode: A review of the state-of-the-art

In remote communities where it is not economical and practically possible to take the grid connection, stand-alone small hydro systems can be used to fulfill the energy requirement. Small-scale hydroelectric power systems are emerging as a promising source of renewable energy generation, but they require low cost hydraulic and electric equipments to make them economically feasible. In such plants, pumps can be used in turbine mode considering various advantages associated with pump e.g. ease of availability, proven technology, low initial and maintenance cost, availability for a wide range of heads and flows, etc. The efficiency of pump as turbine (PAT) is usually lower than that of conventional hydro turbines. However, efficiency is not the primary selection criterion for such machines and it is recommended to operate such machines around maximum efficiency point. In the present study, different turbines suitable for micro-hydropower plants are discussed. The historical development of PAT is described. The review of the state-of-the-art of pump running in turbine mode is presented. Different pumps suitable to run in turbine mode for low capacity power generation in micro-hydropower plants as well as in water supply piping systems are discussed. Theoretical, experimental and numerical investigations carried out by different researchers on PAT are reviewed. The research work on PAT including criteria for selection of pump running as turbine, cavitation analysis, force analysis, loss distribution, various methods of performance enhancement, cost analysis of hydropower plant with conventional hydro turbine and PAT, applications of PAT in water supply pipelines, etc is discussed. The worldwide implementation of PAT and different manufacturers of PAT are described. The limitations in implementation of PAT as well as the recommendations to improve the performance of PAT are described. The current trends and future scope for the further improvement and implementation of PAT are also discussed. (C) 2013 Elsevier Ltd. All rights reserved.