How to repower a plant for the hydrogen future

Over the years, the 800-megawatt thermal power plant in Theiss, Austria, has seen its role in the energy market radically change as renewables became the country’s dominant source of power. Built in 1976, between a picturesque stretch of the Danube and nearby vineyards dotting the hills, the plant is one of Austria’s largest, generating enough power to light up half a million households. But squeezed by a dwindling market for fossil fuels, it no longer runs as a baseload but instead fills the power gap on windless and overcast days.

Maintaining grid stability means the Theiss plant needs to ramp output up and down quickly and be able to operate at a low minimum load with minimal emissions. So when the plant’s main gas turbine was nearing the end of its lifetime, operator and Austrian energy provider EVN decided to replace it with a more efficient and eco-friendly one that can use up to 10 percent hydrogen – securing the plant’s position in a greener future.

In spring 2020, as part of a Siemens Energy Brownfield Exchange (BEX) program designed to minimize on-site disruption and extend the facility’s lifetime, the Theiss plant became the first in the country to commission a hydrogen-capable gas turbine, a key fuel in decarbonization. “Without a doubt,” says Jürgen Wilhelm, EVN engineer and project manager of the turbine renewal, “to meet the EU’s climate targets we have to invest in hydrogen technologies. We’re taking a step in the right direction.”

Already now, Austria is one of the world’s leading countries for renewable energy use, with more than 75 percent of its electricity being produced by water, wind, photovoltaic, and biomass systems, and the country is committed to becoming carbon-neutral by 2040 – ten years before the rest of the EU. However, since renewables inevitably go hand in hand with fluctuations of supply, fossil energy systems are still required as a backup.

This is where gas-fired plants like the one at Theiss often come into play: In the last few years, whenever there had been a lack of supply in the grid, the plant’s gas turbine was fired up to ensure security of supply. But as it neared the end of its expected operating life and lifetime extension measures were required, “we were facing a very serious question,” says Wilhelm: “Should we carry out a major overhaul of the old gas turbine?” 

EVN opted instead to invest in a more modern Siemens Energy gas turbine that offers the plant the flexibility to run on a mixture of hydrogen in the future. “The new turbine has an efficiency that’s nearly 2 percent higher,” says Wilhelm, “and we now have a larger load volume that offers us a higher degree of flexibility. We can operate at a maximum load of 240 megawatts and a partial load of as low as 120 megawatts. We also have significantly better emission levels over the year and so we’re making a positive contribution to the environment, too.”

With higher fluctuations in the power grid, long-term planning is becoming increasingly difficult for energy providers, Wilhelm points out. “Thanks to the new turbine, we’re able to react immediately and start up the turbine even faster and more efficiently than we could in the past.” Another major plus, adds Wilhelm, “is the turbine’s capability to run reliably when the temperature outside is higher than 35 degrees,” which previously wasn’t the case.

All in all, the new turbine is 40 megawatts more powerful than its predecessor, powers up faster, holds a significantly extended maintenance interval and has cut emissions by 50 percent, from 30 to 15 nitrogen oxide (NO_X) parts per million. “With our advanced technology and know-how,” says Christian Niederle, the project manager at Siemens Energy in charge of the Theiss BEX program, “we’re helping power plants to get ready for the future.”

Of course, Siemens Energy has already had years of experience in renewing and modernizing gas turbines, but an exchange of this size, conducted at such a pace, was nevertheless a first, says Niederle. “Projects with more than 250 people involved require a tremendous amount of planning. All it takes is just one miscalculation, one part not fitting or even the smallest detail being overlooked, and the whole project can come to a standstill for days.”

Originally planned for 75 days, which was already considered “ambitious” for a turbine exchange, the project was completed in 68 days – a week ahead of schedule. This is especially noteworthy as the work at Theiss coincided with the first wave of the Covid-19 pandemic. “Like everyone else, we weren’t prepared for a situation like this,” says Wilhelm.

Together with Siemens Energy, EVN quickly came up with security measures such as daily fever checks, safety distances, special accommodations, and rental car concepts for the entire 80-person team on the ground. “We also managed to organize masks for all our staff,” adds Niederle, “even though at the time finding masks was anything but easy.” Both Wilhelm and Niederle are happy to report that not a single infection occurred during the work on site. 

It goes without saying that the natural gas Theiss burns isn’t entirely free from pollution, but it is by far the most environmentally friendly of all fossil fuels and will play a large role in maintaining grid stability until energy systems can transition to carbon-neutral fuels like clean hydrogen. Today, using hydrogen for energy production isn’t only becoming a topic on the political agenda, it’s also becoming more and more feasible for power providers.

“We’re constantly analyzing how to optimize our power plants to make them more environmentally friendly and profitable. With the new turbine both aspects are considerably improved,” says Wilhelm. He believes that hydrogen has enormous potential for the future, which is why EVN has been researching ways to produce, store and use hydrogen for more than ten years now. “Burning hydrogen is 100 percent possible and definitely makes sense,” says Wilhelm. “We’re confident we made the right decision with this investment.”

July 14, 2021

Florian Bayer is a freelance journalist based in Vienna, Austria, where he has written for Die Zeit Online, Der Standard, and the Wiener Zeitung.

Combined picture and video credits: Anna Stöcher and EVN