Pumped Storage Hydro

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

Assessing low-cost ways to increase hydropower’s services at Alqueva
(EDP’s Alqueva pumped storage hydropower plant in Portugal. Credit: EDP and XFLEX HYDRO project/EU Horizon 2020 grant No 857832/Photographer: Mathias Magg.)

The owner of the 520 MW 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 Energias de Portugal (EDP) plant, equipped with four reversible fixed-speed Francis pump-turbine units, is trialing 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.

“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, EDP’s corporate R&D center.

Alqueva is one of three EDP hydropower plants involved in the 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.

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

“We are investigating, using computational fluid dynamics modelling, how the machinery will perform and behave at different water flow conditions,” said Professor Dr.-Ing. Stefan Riedelbauch, Director of the Institute of Fluid Mechanics & Hydraulic Machinery at the university. “The results of the numerical simulations, coupled with extensive field measurements tests, will allow us to define the new possible operating range. This will optimize the turbines’ performance while guaranteeing the safety of the hydropower plant.”

In relation to implementing HSC, Pedro Soares, senior technical specialist at EDP, said: “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 optimization and wear and tear reduction); and

Implement HSC, to maximize 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 development of a new smart digital control, the advanced joint control (AJC), for the project. “This tool will integrate optimization 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 optimize. The selection of this criteria can be adjusted for each site with the plant owner, efficiency, wear and tear, maintenance plan, etc.,” he said.

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

Click here to 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 program.

Click here for more information about the project and to sign up for progress updates.