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The venerable Augustinerstrasse in the old city of Mainz, Germany.

Flex-Power Services

KMW’s hot start innovation

A combined cycle plant in Mainz, Germany, gains flexibility by reusing steam from waste combustion that helps to maintain its hot start capability, facilitating faster and more frequent starts.

IAlong the Rhine River in the industrial heart of Mainz, a combined cycle power plant is trying something new. While other plant operators struggle in the market for fossil fuel power – facing lower demand, lower margins, and a harsh competitive climate due to subsidies for renewable energy – this plant is meeting the challenges with decisive steps to make its plant operations more flexible.

As part of its efforts, German operator Kraftwerke Mainz-Wiesbaden AG (KMW) is developing a steam reuse concept that will maintain the hot start capability of its power plant at times when generation is not profitable, but a fast restart capability is desired. Specifically, KMW has tested a system that makes use of steam from a nearby waste burning facility to keep components in the power plant warm so that the plant can be started up faster and more frequently. The system will allow KMW operators to respond quickly when demand for power rises and prices are adequate.

Worldwide first: Warm component heat reuse concept

Like a few operators elsewhere in the world, KMW already makes use of residual steam to generate electricity. The plant was designed with a large steam turbine and heat recovery steam generator, so KMW could use 65 tonnes of additional steam from the waste burning facility. The steam is transported to the electricity plant in an overland line that is more than 100 meters long.

KMW’s pilot project using the steam to keep components warm is the first to test the idea for enabling a plant to maintain hot start conditions after longer standstills, according to plant operators. Together with Siemens, KMW has validated the concept and is using it actively for the heat recovery steam generator. The company is working on plans to expand the system permanently to the steam turbine, as well as to improve the initial idea.

KMW’s combined cycle power plant.

Midsized company, big-sized ideas

As a midsized company where employees often work their entire careers, KMW has a culture that is open to innovation, according to Olaf Thun, who leads KMW’s Generation division. Where larger companies might have entire departments working on different aspects of innovation and efficiency improvement – and hardly speaking with one another about their projects – KMW engineers frequently sit together in the lunchroom bouncing ideas off one another.

Indeed, the design of the newly built lunchroom gives employees a relaxing and aesthetic place to take their meals, away from the constant drone of rotating turbines. Over a meal, people talk informally about projects, without regard to hierarchy or protocol. It was in this type of setting in 2011 that Thomas Zimmerer, KMW’s Team Leader for I&C and Process Technologies, and colleagues first began discussing the idea of using steam to keep components warm and began thinking about how to stay in warm start mode for a longer time.

Heating up the start sequence

KMW is working to reduce the number of operating hours and starts per year significantly. “This situation motivated us to optimize warm and cold starts and to implement a faster start-up sequence," said Zimmerer. “We’re pioneering warm and cold starts to implement a faster start-up sequence. We are confident we can reach these targets by maintaining a fast  start-up capability for more than eight hours with our new heating concept,” explains Zimmerer.

We’re pioneering warm and cold starts to implement a faster start-up sequence.
Thomas Zimmerer, Team Leader for I&C and Process Technologies, KMW


Thun envisions more enhancements such as minimized on-site power through smaller pumps in the condensate system and the evacuation system, as well as savings from a faster plant shutdown capability. But the market in Germany is changing so quickly that much of the business is unpredictable. Says Thun: “Since I never know what will happen after the next election, I think flexible operations are the best way to go.”

Rhea Wessel, journalist based in Frankfurt.
Picture credits: Claudius Schulze