Impact of Dual Variable Speed and Inlet Valve Control on the Efficiency and Operating Range of Low-Head Contra-Rotating Pump-Turbines
Artikel i vetenskaplig tidskrift, 2024

In an effort to make pumped hydropower storage (PHS) technology feasible for regions with a flat topography, recent research shows promising results using a contra-rotating reversible pump-turbine at low-head. In this study, the impact of dual variable speed and inlet valve control is analyzed to evaluate the effect of these three degrees of freedom (DOFs) on the system efficiency and operating range. To this end, analytical models are described to assess pump-turbine performance, conduit losses and electromechanical losses. Methodologically, optimal efficiency maps are computed for every combination of the three DOFs to evaluate individual and combined effects on the overall efficiency. Furthermore, three energy storage cycles are analyzed to further study the performance in realistic use-cases. Key conclusions include an increase in round-trip efficiency by combining variable speed ratio and inlet valve control of 5.6% and 2.0% compared with only variable speed ratio control and variable inlet valve control, respectively. Furthermore, it is shown that using only 1 DOF significantly limits the operating range, with the addition of a variable inlet valve granting a higher impact than a variable speed ratio. Combining inlet valve and speed ratio control leads not only to the highest efficiency, but also the largest operating range, with a maximum round-trip efficiency of 67.5% and an energy storage capacity of 58.6 Wh/m2. The results confirm that exploiting both dual variable speed operation and inlet valve control yields the maximum efficiency and operating range, and is thus the preferred topology for contra-rotating reversible pump-turbines in low-head operation.

Energy efficiency

Computational modeling

Hydroelectric power generation

Numerical models


Mathematical models

Hydropower storage

MIMO system


dual rotor pump-turbine

energy efficiency

cycle efficiency


MIMO communication


Daan Truijen

Universiteit Gent

Justus Hoffstaedt

TU Delft

Jonathan Fahlbeck

Chalmers, Mekanik och maritima vetenskaper, Strömningslära

Antonio Laguna

TU Delft

Håkan Nilsson

Chalmers, Mekanik och maritima vetenskaper, Strömningslära

Kurt Stockman

Universiteit Gent

Jeroen De Kooning

Universiteit Gent

IEEE Access

2169-3536 (ISSN) 21693536 (eISSN)

Vol. 12 86854-86868

Augmenting grid stability through Low-head Pumped Hydro Energy Utilization & Storage (ALPHEUS)

Europeiska kommissionen (EU) (EC/H2020/883553), 2020-04-01 -- 2024-03-31.


Hållbar utveckling




Strömningsmekanik och akustik




C3SE (Chalmers Centre for Computational Science and Engineering)



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