In a swell of renewables, power plants upgrade for flexibility

For the operators of combined cycle plants in Germany, including the one at Hamm-Uentrop in the northwestern corner of the country, arriving late at the party can mean there is no party at all.

Due to regulatory preferences for renewables and their occasional oversupply, if the plant is not first in when the market opens, it may lose its chance to participate. This gives Trianel, the plant’s operator, incentive to be able to start up fast and be first, so it can participate and earn revenue longer. It’s also the main reason Trianel is in the middle of a multi-year series of upgrades that are making the plant more flexible.

According to Trianel’s managing director Martin Buschmeier, when the plant started operations in 2007, it fired up in the morning, ended most evenings and only occasionally ran overnight. “But that changed,” Buschmeier says. “Now we need to get into the market fast, get out of it fast and avoid operating at times that mean low income or even negative income. The most important thing is flexibility, and now we have that advantage through fast shutdown and hot start on the fly.” 

Trianel Gaskraftwerk Hamm GmbH & Co. KG is owned by a communal network of 27 shareholders. It operates two turnkey single shaft configurations from Siemens Energy, with SGT5-4000F gas turbines, SST5-3000 steam turbines and SGen5-2000H generators. Designed for 8,000 operating hours per year, the plant contributed about half of the full load hours it was capable of in 2013, due to changing market conditions. Its ability to provide ancillary services such as secondary frequency response and minute reserve (tertiary frequency response) was crucial to keeping the plant in business.

Since then, the market has only gotten tougher for Trianel. It faces low profit margins, frequent part-load operation, which means reduced efficiency and increased emissions, and fluctuating prices on the power trading exchange. It must also cope with more changes to the operating schedule, forced nighttime operations and a high number of load change requests for a short duration that come in on short notice.

Already in 2011, Trianel had asked for help to stay on the market longer and return earlier, and Siemens (as the parent company of the spin-off Siemens Energy, an independent company that was formed in September 2020) began to accelerate its development activities to steepen the gas turbine load gradient from 13 megawatts per minute to higher values. But, as Matthias Nickl, the Product Manager of Flex-Power Services at Siemens Energy, says, “The potential for improving the operational flexibility of a combined cycle plant is very much dependent on integrated solutions that take all components of the plant into account, especially the interaction of the gas turbine with the downstream steam cycle. Getting this right means operators can stay in the money.”

An early adopter of new technologies, in part due to its fast decision-making capabilities, Trianel began upgrading the Hamm-Uentrop plant in 2018. It started with the implementation of Hot Start on the Fly, a software-based upgrade that enables parallel start-up of the gas turbine and the steam turbine, reducing start times by up to 20 minutes. In 2021 Trianel halved plant warm-start and shut-down times by adding Warm Start on the Fly and Fast Plant Shut Down, two further logic-based upgrades.

As a next step, Trianel plans a hardware upgrade as part of the Advanced Turbine Efficiency Package (ATEP), which will not only improve plant performance but will also lead to lower emissions. With ATEP, new designs for hot gas path parts using new turbine technology will provide higher operational efficiency, significantly reducing carbon emissions. “Our experience is that this is a good way to increase the overall performance of a plant,” Buschmeier points out, looking back at the decision to do a series of upgrades. “We found the right balance between wear and tear on the plant and operational flexibility.”

Trianel’s upgrades are being managed as part of the long-term service agreement (LTSA) between Trianel and Siemens Energy. The contract provides Trianel with customized service designed to mitigate technical and operational risks and keep the plant generating revenue. For power plant manager Thomas Kleinwächter, the contract provides an extra layer of security. “We cannot write down every detail of daily business,” he declares. “The contract means we have a high level of trust that even unforeseen details are handled with care.”

The LTSA was customized to meet Trianel’s specific requirements and budget and helps the operator remain flexible in the face of changing market conditions. That’s because of the preferred access the contract provides to spare parts and Siemens Energy experts, among other things.

The LTSA also boosts innovation, says Martin Bucher, long-term project manager at Siemens Energy. “Since we have worked together so closely for so long, we have an ongoing dialogue about improvements, with some conversations initiated by Trianel and some by Siemens Energy. We’re both eager to identify new areas for improvement.” 

Germany is in the middle of its energy transition. It has nearly finished phasing out nuclear power plants, and it has started to phase out coal. That was followed in mid 2020 by the approval of a national strategy for clean hydrogen meant to support Germany’s industry in playing a leading role in the development and export of hydrogen technologies.

Operators of gas-fired plants, including Trianel, are now considering how to bring synthetic fuels made with clean hydrogen into the fuel mix. Buschmeier says the company is looking into operating the plant with 10 to 20 percent hydrogen in the co-firing mix. “Hydrogen is going to be the next big challenge,” he says. “And it’s one that can change the equation for gas-fired plants.”

Kleinwächter adds, “Soon we will have to convert this natural gas plant into one that operates on both natural gas and hydrogen. Siemens Energy will be a critical partner to help us retrofit for hydrogen co-firing.” 

February, 2022

Rhea Wessel is an award-winning, independent journalist based in Frankfurt, Germany. Her work has appeared in Time, the Wall Street Journal and the New York Times.

Combined picture and video credits: Frank Peterschröder