Parametric Studies on Pump Running in Turbine Mode

Abstract

Hydropower is the top most renewable energy source and micro hydro power plant is one of the best solutions for energy crisis in remote, rural and hilly areas. The pump running in turbine mode is the excellent alternative of turbine for micro hydro power plants. Pump as turbine offers many advantages e.g. easily available, low installation and maintenance costs, available for large range of head and discharge etc. The efficiency of pump as turbine (PAT) is usually lower than the conventional turbines, but it can be compensated by the low initial cost. One of the reasons for lower efficiency at part load of PAT is absence of flow control mechanism which is present in conventional turbines. The efficiency of PAT can be increased by providing some low cost modifications like by impeller shroud rounding, trailing edge sharpening, suction eye enlargement etc. In the present study, introduction of micro hydropower and PAT is given. The literature review related to PAT is presented. The effects of some low cost modifications in the impeller viz. shroud rounding, trailing edge sharpening, suction eye enlargement were studied. The experiments were performed in the speed range of 1000-1400 rpm. It was found that, the shroud rounding led to improvement in the part load efficiency by 1-4.5% at different discharges; whereas, trailing edge sharpening and suction eye enlargement resulted in 2-3% increase in power and 2-8% rise in the maximum efficiency. After all these modifications (combined), the maximum efficiency was obtained as 74.83% at 1200 rpm which was 11.43% higher than that of original unrounded impeller.