Improving the efficiency of hydropower stations

Hydroelectric power provides 16 per cent of Europe’s electricity, but most of the plants and their turbines were designed many years ago. By redesigning the runner – the propeller-like component that transfers energy from the water to the drive shaft in the turbine – EUREKA project FLINDT enables operators to harness more power from their turbines.

According to Professor François Avellan, Director of the Swiss main project partner, Laboratoire de Machines Hydrauliques de l’ EPFL, Ecole polytechnique fédérale de Lausanne, the project can also help hydropower stations store power and manage peak demands.

He says, “hydropower stations are managed too conservatively. Small adjustments, within safety parameters, to the runner of the hydraulic machine can dramatically improve the output from existing hydropower plants.”

The challenge the project faced was to understand and predict the complex fluid dynamics within the “draft tube” containing the runner. The draft tube is a key component in hydropower stations as it converts the kinetic energy of the water into pressure energy that can be utilised to drive turbines.

The partners spent thousands of hours investigating the flow in draft tubes using computer models and a scale model. This provided a better understanding of the physics of such flows, allowing the partners to build up an extensive experimental database and enabling the project to avoid undesirable phenomena such as “flow blockage” and other dangerous instabilities when redesigning runners. The knowledge gained can now be applied to improve the output of existing hydropower stations, adding significantly to the European power generation economy.

Water is returned to the river after use. Therefore, in addition to the direct environmental benefits of renewable energy, the project also has indirect benefits: a better understanding of the flow characteristics within the draft tube allows better control of the mixing process in this component, in particular the stresses and the air diffusion, which is of prime importance for the local river life.

The original FLINDT project ran from 1997 to 2000 but the partners agreed to extend the project by two years to carry out further research and are now looking to set up other research projects to investigate safety and reliability issues to push hydroplants to even greater efficiency.

According to Prof. Avellan the project had three major benefits – an increased knowledge about flow through draft tubes, development of the draft flow database and education of the PhD students involved with the project.

“EUREKA’s unique bottom-up approach brought together competitors in a very aggressive market to co-operate in research that benefits all,” he says.