Balancing the Grid: PhD Candidate Explores Reversible Pump Turbines

Renewable energy is becoming a greater part of the energy systems worldwide, with especially large contributions from wind and solar energy. As these technologies lack the ability to store energy, hydropower is provided with a huge challenge – and opportunity - to stabilize and balance the energy grid.

Pumped storage projects provide excellent prospect in this regard and has already been sought after for facing this challenge. Waterpower Laboratory at NTNU has focused its research on the reversible pump turbines, which are responsible for driving the pumped storage projects. As the first PhD candidate to start the work in the research centre RenewHydro, Amul Ghimire has started his work on Reversible pump turbines (RPTs). 

The Need for Reversible Pump Turbines 

With intermittent renewable energy sources like wind and solar expected to dominate the energy mix in the near future, grid stability is more important than ever. Hydropower is the only renewable energy source that can supply this. Variable-speed pump turbines offer a promising way to integrate these non-dispatchable power sources efficiently. However, RPTs come with their own set of challenges—one of the most significant being the required submergence level for higher head applications. 

Too much submergence can drive up project costs, while too little can lead to severe issues like cavitation and turbine vibrations, which can shorten the lifespan of the equipment and increase maintenance needs. Finding the optimal balance is a challenge that Ghimire aims to address in his PhD research. 

A New Approach to Estimate Submergence  

As part of Research Program 1.1 in RenewHydro, Ghimire's study will: 

• Design and optimize Reversible Pump-Turbine for a reference case. 
• Develop a new method to estimate the required submergence more precisely. 
• Assess the implications of inadequate submergence on turbine performance and maintenance/life. 
• Identify possible operation ranges with partly inadequate submergence, which could lower costs with minimal sacrificing of performance. 

By refining the criteria for submergence and exploring cost-effective solutions, this research could help make pumped storage power plants more cost-efficient and accessible.