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  • The power of efficiency

Generating cleaner energy from water

With growing demand for electricity, rising fuel costs, and climate change concerns, GE believes renewable energy provided by hydro, wind, and solar technologies can make the difference. The company seeks to make renewable energy more affordable and, in turn, even more commonplace. ArcelorMittal Europe – Flat Products and GE Renewable Energy recently worked together to develop a new methodology to calculate losses in synchronous machines used to generate energy from hydroelectric installations. As low losses are critical to the high efficiency of hydro-generators, the findings will influence the design of future machines.

The generators used in hydroelectric plants have specific requirements that machine designers must address. As well as being large, the generators must be highly efficient and reliable. “Because of the special challenges hydroelectric power stations pose, the generators must be tailor-made, and robust,” notes Sigrid Jacobs, portfolio director for electrical steels at ArcelorMittal Global R&D. “When creating the stator for a hydroelectric generator, it makes sense to use the best quality electrical steel to optimise efficiency.”

Losses impact efficiency

“The efficiency of a GE hydro generator is closely related to the loss performance of the electrical steel used in its stator,” notes Olivier Basset, global commodity manager for GE Renewable Energy. “At GE we only use electrical steels with the best electromagnetic performance. ArcelorMittal has built-up a wide range of electrical steels which meet our specifications for the highest and thinnest quality.”

ArcelorMittal and GE recently worked together to develop a new methodology to calculate iron losses in large, synchronous hydro-generators as Sigrid Jacobs explains: “Today the overall efficiency of large generators for hydropower plants is above 99 percent. However, even a one-percent loss on a 300 megawatt (MW) machine corresponds to 3 MW of losses. To improve the modelling tools both GE and ArcelorMittal use, we looked at the effect of punching on iron losses. They can account for up to a quarter of the total losses in this type of generator.” 

Findings influence new stator designs

Working with Thomas Lugand and Alexander Schwery from GE Renewable Energy, Lode Vandenbossche and Sigrid Jacobs from ArcelorMittal Global R&D discovered that some manufacturing processes can impact a machine’s performance. “These include punching of the electrical steel’s laminations, and applying stresses on the lamination stacks during machine production,” notes Sigrid Jacobs. “These processes can impact the torque and efficiency of the machine.”

“Cooperating with a raw material supplier was a new approach for us,” says Olivier Basset. “With the assistance of ArcelorMittal Global R&D, we gained a comprehensive understanding of the origin of losses in the stators of our hydroelectric machines. It will help us enhance our design and ArcelorMittal has become a strategic partner as a result.”

As a strategic partner, GE Renewable Energy has high expectations from ArcelorMittal as Olivier Basset explains: “We are looking forward to 2018 and expect that we can continue to rely on ArcelorMittal’s quality offer and improved delivery performance.”

Full range of coatings including formaldehyde-free

All electrical steels require coatings to protect the steel from corrosion and to insulate them from magnetic interference. While ArcelorMittal supplies a full range of coatings, many generator makers are specifying that they are formaldehyde-free to minimise emissions of volatile organic compounds (VOCs). This is particularly important for generators which are often housed in closed spaces. Trapped VOCs can reach harmful levels for the maintenance technicians who will service the generators over their lifetime.

To meet this specification, ArcelorMittal uses special formaldehyde-free coatings. Corresponding to a C6 formaldehyde-free coating, the coatings typically use inorganic minerals and pigments and an organic synthetic resin. ArcelorMittal’s formaldehyde-free coatings have already been combined with some of our highest quality electrical steels to create safe solutions.

Images © General Electric