The scarcity of fossil fuels and increasing environmental pollution have led to a rethink in the field of energy production: according to the so-called “Erneuerbare-Energien-Gesetz” (Renewable Energy Sources Act), at least 35% of electrical energy should be provided by renewable sources, such as wind energy and photovoltaic systems, by 2020. By 2050, this value should be raised to 80%.
These energy sources are very volatile and subject to major fluctuations due to weather conditions, times of day and seasons. The handling and bridging of load peaks and supply gaps will be the most important challenge in future energy generation.
The research alliance "Dynamics of Energy Conversion" (German: Dynamik der Energiewandlung - DEW) represents an interdisciplinary research project with the aim of meeting these future challenges in energy conversion. The project includes five central research areas, which are introduced below:
I. Dynamics of chemical-to-thermal Energy Conversion
New challenges in the optimization of combustion processes are resulting from the importance of partial load operation, higher load gradients, increasing load cycles and new combustion technologies such as power-to-gas.
Under the leadership of Prof. Friedrich Dinkelacker, various aspects of the dynamics of chemical-to-thermal energy conversion are investigated and new innovations realised. These include:
- Gas combustion at low-load operation combined with high hydrogen content in gas turbines
- Gas engines as a technology for flexible and decentralized energy production
- Additional combustion in the steam cycle of thermal power plants to provide secondary reserve power
- Thermal inertia effects of power plant components
- Power-to-gas technologies as chemical energy storage
II. Dynamics of thermal-to-mechanical Energy Conversion
Away from the design point, large losses in efficiency are seen in gas turbines, steam turbines and gas pipeline compressors. However, future power plant requirements will demand high efficiency in the transient and partial load range.
The research field Dynamics of Thermal-Mechanical Energy Conversion deals specifically with these topics. Under the direction of Prof. Joerg R. Seume, solutions are developed for complex topics in the fields:
- Three-dimensional flow in turbomachinery at low load
- Increased ability of turbomachinery to work at partial load
- Transient aeroelasticity of turbomachinery
- Thermomechanical stresses and fatigue in transient operation
III. Dynamics of mechanical-electrical energy conversion
Electrical machines are converters that can work in two directions. When working as a motor, electrical energy is converted into mechanical energy. When working as a generator, mechanical energy is converted into electrical energy.
The mechanical-to-electrical and electrical-to-mechanical energy conversions show distinctive non-linear properties. Harmonic field effects and asymmetric behaviour of voltage and current, induced by differences to the ideal current behaviour or the spatial field progression lead to pulsation moments in electrical machines. For example, a coupling with to a thermal-to-mechanical energy converter, the variations in moment can be transferred to the machine and induce vibrations in turbine and compressor blades.
To prevent or reduce additional blade loads that can lead to their failure, solutions are designed and investigated in the research area Dynamics of mechanical-electrical energy conversion under the guidance of Prof. Bernd Ponick. The research focuses on the following topics:
- Oscillation transfer by electrical machines between thermal-mechanical energy converters and the power grid
- Power electronics, drive control, and battery storage for a mechanical-to-electrical stabilisation
IV. Dynamic coupling of the energy conversion process
The flexibilisation and diversification of the energy conversion by coupling large and small, central and decentral energy facilities and power plants is an interdisciplinary task. A comprehensive modelling of the power grid, including volatile energy-supply, -storage and -consumers, is ultimately meant to lead to an intelligent control and system stabilisation.
Under Prof. Roland Scharf’s guidance, the research area Dynamic coupling of the energy conversion process aims to develop cross-system models to efficiently combine existing and to be developed technologies. The considerations divide in:
- Flexibilisation of the thermal power plant processes
- System stability of the electrical power grid
- Convergence of gas and electricity networks
- Economic efficiency analysis of energy conversion and storage options
- Identification and definition of interfaces
V. Energy Markets
Under the direction of Prof. Michael H. Breitner the economical coupling from power stations to the energy market is developed in the research field “Energy markets”. This includes the location- and time-dependent pricing for the purchase and the selling of electricity and heat over spot- and derivative markets at the stock market and in other auctions. The volatility of electricity and heat prices has a considerable influence on the operational planning of power plants and storage facilities and their economic efficiency. This means modern energy markets lead to an economic-electrical-mechanical coupling. Business models for power plants are specifically questioned and newly developed, and their effects on the technical requirements for power plants are derived.