Power plants need to operate flexibly these days. Whereas a constant rate of electrical output was the norm in the past, production at today’s conventional plants needs to fluctuate due to the increasing use of energy from renewable sources. As early as 12 years ago, Erich Schmid (60) who works and lives in Erlangen, had developed a whole range of operating processes that quickly increase electricity production in combined cycle power plants and maintain this higher production level for a specific period of time.

The first indications that combined cycle power plants would have to be able to quickly step electrical output up or down on short notice became apparent after the electricity market shifted from a system of rigid rates to one that operated on the basis of power exchanges with fluctuating prices. “Electricity consumption in the U.S. is lower at night, for example, so plant operators get less money for the power they deliver during that time,” Schmid explains. “It therefore made economic sense for them to shut down their facilities at night and then start them up again in the morning.” The problem was that the plants weren’t really designed for such an approach. In response, new technologies were introduced that transformed many power plants around the world from sluggish giants into rapidly responsive and effective facilities. Such technologies included Schmid’s inventions — in particular, his technique for optimizing combined cycle plants to accommodate peak load times, which is becoming more and more important today. One of Schmid’s ideas was to transfer the heat stored in the heat recovery steam generator to the steam turbine via an overload valve. The reduction in pressure causes the temperature in the boiler to fall, and this cooling process then produces extra steam that can be used to provide additional power to the turbine, and thus increase the electrical output. “This effect is particularly useful for extremely short-term output adjustments, because the reaction in the boiler and the steam turbine can be called upon at very short notice,” says Schmid.

Another possibility involves allowing the pressure in the vaporizer of the medium-pressure system to increase to a higher level than necessary and then simply reducing the pressure again when the turbines need to turn faster. This method also generates additional steam in a very short time.

The resulting rapid increase in electricity production is especially important in what is known as the frequency stability mode, which balances out sudden differences between the required and the actual amount of electricity generated that lead to changes in the line frequency. In the worst case, such discrepancies can cause the grid to break down completely. For this reason, network operators purchase reserve output from electricity producers. Any power plant that is required to provide it must be able to deliver the contractually agreed-on output within just a few minutes, and sometimes even within seconds. Higher block output for the longer term is then ensured by additional firing in the boiler or by peak-load gas turbine capacity.

Several other inventions developed by Schmid have made it possible to rapidly step up combined cycle output without using too much energy or materials or emitting too much CO2. “You need to carry out a whole lot of measures in order to get this result ,” says Schmid. “For example, you can take steps to ensure that a gas turbine increases its output as smoothly as possible and without interruption, while simultaneously starting up the steam turbine at an early stage and quickly feeding it all the steam produced in the boiler before the gas turbine reaches its base load. All of that saves time.” This approach also requires a special design for the heat recovery steam generator.

Other Schmid inventions are used in industrial plants where steam is needed for production operations. For example, several years ago a Dutch company issued a call for tenders for a new type of power plant to be equipped with a process steam extraction system that would include a heat recovery steam generator and a reserve steam generator. “We thought about the fact that such a reserve steam generator would use energy unnecessarily because it would always have to be in standby mode,” Schmid recalls. He therefore proposed a new design that divided the boiler into two parts. One of them — the auxiliary burner — would have a constantly burning flame that could be turned up if the main boiler were to fail. Schmid explained to the Dutch company that his system would reduce energy costs by several million euros over a period of 20 years. The company responded by changing its tender specifications to include a divided boiler, which was subsequently built. “I recently visited the Netherlands again and took a look at the facility, which is now operating very successfully,” Schmid says. “It’s really a great feeling when you see one of your own inventions come to life.”

Even as a child in Bavaria, Schmid used to come up with various design concepts that he then built using materials he was able to obtain for free. “I can still remember an angular boat that I built and sealed up with roofing paper and tar. My friend and I actually sailed it on a river,” he says. While he was studying mechanical engineering at Regensburg University of Applied Sciences, Schmid began working at Kraftwerk Union AG in Erlangen, which was fully absorbed by Siemens in 1977. He began his career there as a development engineer in 1976. Aside from a brief stint in Orlando, Florida, Schmid has remained in Erlangen to this day, continuing to work on power plant development, a field that is now part of the Siemens Energy Sector. Schmid has 36 inventions to his credit, and his ideas have been incorporated into 138 individual patents and 33 patent families. ​