By 2020, 25% of all electricity generated in Germany should come from combined heat and power (CHP) plants. The aim is to save energy and the environment and thus help with climate protection. CHP plants also generate electricity and not just thermal energy required in heating systems or production processes. This allows for the use of between 80 and 90 percent of possible fuel output. Combined heat and power legislation and the German Renewable Energy Act (EEG) have freed up funding to extend current capacities. The Grasbergbased Steinbeis Innovation Center for Optimization, Control and Adjustment Control and a company called enable energy solutions GmbH from Bad Rothenfelde have been using the very latest mathematical models to develop a universal modeling method and optimize CHP plants. It is all part of a project sponsored by the Federal Ministry of Economics and Technology (BMWi) called High-Precision Modeling, Simulation, and Optimization of CHP plants.
The new modeling method only requires existing measurements – or data that is easy to measure – to develop highly precise CHP plant models. These can be adapted during operation or even optimized automatically. For the first time, this principle makes it possible to flexibly adapt modeling to new plants or even existing plants built with different constructions. The industrial partner, enable energy solutions, provided the information required for the project plus processed data from CHP plants. It also provided support with the programing of a graphical user interface. This was created to make it easier for users to work with and make the newly developed methods easy to understand.
CHP plants comprise a variety of different components that also have to be wired and operated in different ways. There are many ways to control such plants, for example, by connecting them to heat reservoirs or adding load regulators to turbines. While this is happening, it is important to take internal and external factors into account such as the outdoor temperature, atmospheric pressure, or contamination levels. This complex array of factors makes it impossible for operators to work out the optimum operating conditions based on commercial and environmental factors. Until now, plant operations were based on experience and previous measurements, focusing on thermal and electrical output requirements. Conventional systems for carrying out general modeling on CHP plants or power stations previously mapped systems by using thermodynamic and physical models, but these either ignored or paid too little attention to small changes within a plant resulting from cleaning, replacement parts, or similar factors. As a result, such traditional models can often only reflect the exact situation encountered in reality, so it involved a major investment in terms of time and personnel to improve estimates.
It was this that inspired the Steinbeis experts from Grasberg to develop a suitable online optimization system. The new system helps operators control a plant by taking electricity and thermal energy requirements within the company into consideration, as well as commercial factors such energy prices and feed-in tariffs. The system draws on data generated during live operation and uses this as part of a model which updates itself automatically. The plant operators are no longer required to do modeling themselves. Instead, they merely need to select which data is required for the specific system component being modeled. The new data-centric modeling methods make calculations efficient and allow for quick updates via the internet. Such effortless updates are essential for automated optimization solutions, since these often require a huge number of model evaluations. The optimization solution used in this case is called WORHP (We Optimize Really Huge Problems, www.worhp. de) and this was also developed by the Steinbeis Innovation Center for Optimization, Control and Adjustment Control. WORHP is capable of efficiently solving optimization tasks involving hundreds of millions of degrees of freedom and constraints. An interface was created specially for CHP plants to connect WORHP to the tool developed for this project. This can be used to optimize different kinds of CHP plants.
Turning to environmental aspects, rising energy consumption, and the limited availability of fossil fuels, a great deal of discussion these days revolves around efficiency improvements and reducing carbon emissions. The innovative solution developed by Steinbeis and enable energy solutions is a shining example involving a real plant. It shows the tremendous potential there is for achieving savings with CHP systems. The experts showed how using data-centric modeling and making optimizations where necessary can provide a road map for reducing greenhouse gas emissions by around 7,200 tons per year, and natural gas consumption by about 34 GWh. In monetary terms, this is a saving of around €1.2 million.
Professor Dr. Christof Büskens
Steinbeis Innovation Center Optimization, Control and Adjustment Control (Grasberg)
su1328@stw.de