Modelling and Impact of Hydraulic Short Circuit Operation in Pumped Hydro Energy Storage

Abstract

This paper investigates the hydraulic short circuit (HSC)operation of pumped hydro energy storage systems,specifically how it can be modelled and its impact onenergy capacity, efficiency and operating range. Hydraulicshort circuit operation enables power modulation duringcharging for fixed-speed pumped hydro systems, therebyallowing them to operate more flexibly. In this work, apumped hydro storage system with 140.5 MW nominal chargingpower and 10 h nominal charging time is analysed. Thestorage is simulated via a dynamic, system-level modelcomposed of detailed physical component models toaccurately depict the HSC operating behaviour. HSC enablespart-load operation from 39 MW to 107 MW but withsignificantly lower overall system efficiencies. The HSCoperating limits are governed by the turbine's minimum flowand maximum power. The custom-built OpenModelica libraryemployed for this analysis can be downloaded fromhttps://github.com/ibeyers/pumped-storage-analysis.