Experimental analysis of a constant blade to jet speed ratio control for a micro-Pelton wheel turbine for use with an offshore hydro-pneumatic energy storage system

Abstract

Hydro-Pneumatic Energy Storage is a type of mechanical energy storage system being investigated for providing long duration energy storage which is becoming essential for integrating renewables on a wide scale. Pelton turbines are often being considered for converting the stored energy into electricity. This is due to the low specific speed requirements, resulting from the high pressure and low flowrates that characterise hydro-pneumatic systems. As opposed to conventional applications in hydro power, where variations in the operating head are small, hydro-pneumatic energy storage presents a more complex environment due to the relatively large variations in the head across the discharging cycle. This study implements a control scheme on a physical setup to maintain a constant blade-to-jet speed ratio for a grid-connected Pelton turbine. The proposed scheme increased the turbine’s overall efficiency from 62 % to 65 %, representing a 4.9 % relative improvement in recovered energy compared with the constant-speed control scheme.