Simulating better alloys

A German consortium is testing the endurance of high-strength nickel alloys for use in critical components for power plants. These would enable coal-fired plants to increase the steam temperature in their boilers and turbines to 700°C, so cutting carbon emissions and improving efficiency.

The consortium includes RWE Power, metallic alloy producer ThyssenKrupp VDM and the Fraunhofer Institute for Mechanics of Materials in Freiburg.

'We are developing computer simulation methods for critical power plant components based on expertise we developed for the automotive industry,' said Hermann Riedel, head of materials-based process and part simulation at Fraunhofer.

Riedel said computer simulation will produce more reliable results than laboratory testing because it can take into account different loading conditions over the 20-year life of the components.

New demands on power companies have made loading conditions more complex. 'Nowadays there are brokers who buy and sell electric current,' he said. 'They will call a power plant and tell them within half an hour they need a certain megawattage of power. So a power plant has to start up within a very short time, which means a lot of thermal stresses in the plant.'

Riedel said to conduct the computer simulations, researchers must first test the materials in the laboratory to extract the behavioural characteristics. 'We then put this into mathematical equations and implement these equations into computer codes,' he said. 'The computer codes transfer that to a turbine or a boiler. So then we are able to predict its behaviour over time.'

Ralf Mohrmann, from the power plant planning and approval unit of RWE Power, said the simulations will help it optimise the geometry and load conditions when designing critical parts. They will also help it define practical maintenance intervals and test locations. 'They allow us to determine which components need to be replaced ahead of schedule, depending on power plant operation,' he said.

Researchers will be able to identify possible weaknesses in the geometry of the parts and develop alternatives. Mohrmann said this will speed up the construction of more environmentally-friendly power plants.

Jutta Klöwer, head of research and development at ThyssenKrupp VDM, said the computer simulations will also save time in developing materials as they will determine quickly whether the material is suitable for long-term use in high, fluctuating temperatures.

'They allow material development times to be reduced from over 10 years to just a few months,' she said. 'They help us achieve greater power plant efficiency more quickly and thus make a positive contribution to protecting the environment.'

Siobhan Wagner