Assessing low-cost ways to increase hydropower’s services at Alqueva

The Alqueva pumped storage hydropower plant in Portugal is exploring three low capital expenditure opportunities to increase the plant’s services to the electricity grid. More flexibility in delivering electricity to the grid helps to support power system security and stability. This is increasingly important as more variable renewables – such as wind and solar power – come onto the grid.

The 520MW plant, equipped with four reversible fixed-speed Francis pump-turbine units, is trialling the extension of the operating range of the units, smart digital controls, and Hydraulic Short Circuit (HSC) – which allows for the simultaneous operation of pumping mode and generating mode by the units.

Alqueva is one of three EDP hydropower plants involved in the European Union (EU)-funded XFLEX HYDRO initiative, which is demonstrating how smart hydropower technologies can deliver a low-carbon, reliable and resilient power system. There are 19 project partners taking part, across six demonstrations in Portugal, France and Switzerland.

“The objective of this [the Alqueva] demonstration is to evaluate three low capital expenditure opportunities to extend the plant’s services and boost its flexibility,” says Joao Delgado, Senior R&D Engineer at EDP NEW.

In the first phase of the project, a series of initial tests using digital modelling and computer simulations have been performed by researchers from the University of Stuttgart. The researchers are assessing how to safely extend the operating range of the units.

Professor Dr.-Ing. Stefan Riedelbauch, Director of the Institute of Fluid Mechanics & Hydraulic Machinery at the University says: “We are investigating, using computational fluid dynamics modelling, how the machinery will perform and behave at different water flow conditions.

“The results of the numerical simulations, coupled with extensive field measurements tests, will allow us to define the new possible operating range. This will optimise the turbines performance while guaranteeing the safety of the hydropower plant.”

EDP’s Alqueva pumped storage hydropower plant in Portugal. Credit: EDP and XFLEX HYDRO project / EU Horizon 2020 grant No 857832 / Photographer: Mathias Magg.

In relation to implementing HSC, Pedro Soares, Senior Technical Specialist at EDP says: “The main challenge of hydraulic short circuit is that the pumped storage hydropower plants were not originally designed to operate the units simultaneously in turbine and pump mode.

“Therefore, firstly, we have developed a series of technical studies to demonstrate the safety compliance of the hydraulic, mechanical and electric components of the power plant in this mode of operation.

“Secondly, we are combining a mix of computational fluid dynamic simulations with a field test measurement campaign specifically to validate the HSC mode of operation.”

The Alqueva XFLEX HYDRO project team are aiming to:

  • Extend the operating range of the units to increase the power band currently offered by each unit,
  • Integrate advanced digital controls, to improve the power dispatch of the units (targeting the efficiency optimisation and wear & tear reduction),
  • Implement HSC, to maximise performance and increase flexibility by extending the plant operating range, from -100% in pumping mode continuously up to 100% in generating mode.

Guillaume Rudelle, Hydro Senior Product Manager at GE Renewable Energy in France, is leading on the development of a new smart digital control, the Advanced Joint Control (AJC) for the project. Commenting on the AJC, he says: “This tool will integrate optimisation algorithms to enable the optimum scheduling of power dispatch between units, depending on the current market conditions and according to a set of criteria to optimise.

The selection of this criteria can be adjusted for each site with the plant owner, efficiency, wear and tear, maintenance plan etc.”

Swiss research institute and university EPFL, Portuguese research and development institute INESC TEC, and French research and innovation centre SuperGrid Institute, are also involved in the demonstration.

View a short video about the Alqueva demonstration.

XFLEX HYDRO is a four-year project running until 2023 and has been funded by the EU’s Horizon 2020 research and innovation programme.

For more information about the project and to sign-up for progress updates, visit