Subtopic Future power plants for fossil or mixed fuels

Small and medium-sized combustion plants

Energy conversion processes based on complex fuels, i.e. residues, biomass, low-quality fossil fuels, are no constituent of the energy system at present. New, unconventional power plant concepts are presently being discussed and developed in order to integrate complex fuels alone or in combination with other fuels, e.g. geothermal energy, into the energy system. The power plant concepts shall serve as a basis of viable small and medium-sized cogeneration power plants (20–50 MW).

The scope of complex fuels available is characterised by various suitabilities of the fuels for input in conversion technologies and by a regionally limited and seasonally varying availability. These aspects have to be taken into account by the new concepts.

Research focuses on the systems analysis of potentials of novel concepts for small and medium-sized power plants for complex fuels (fossil, renewable resources, secondary resources). Parallel to the technical development work under the REUN programme, material and energy balances, life cycle assessment and cost analysis of plants and components will be developed. On this basis, integration of the power plants based on the concepts developed in regional energy systems shall be modelled and analysed.

Highly efficient fossil power plants  

Increase in efficiency of conventional (large) power plants will contribute considerably to ensuring a reliable and sustainable energy supply. An important method to increase the efficiency is to increase the steam parameters of the power plant boilers, which will require the use of novel materials. Novel materials, for example nickel-based alloys or austenitic steels, will allow for steam parameters in excess of 700°C and 350 bar in the power plant boiler and for efficiencies of more than 50%. Use of these novel materials will not only be limited to conventional power plants, but combined with the separation of CO₂ from the flue gas by IGCC and oxyfuel processes.

Future decisions in the design of power plants will require methods to analyse energy efficiency and the impacts of these novel materials on the environment and costs. For this purpose, the exergo-environmental analysis can be used. This method consists of an exergy analysis to identify thermodynamic inefficiencies of power plant processes as well as a life cycle assessment (LCA). The most efficient solution from the exergy point of view does not automatically represent the environmentally most benign solution. By coupling both analyses in an integrated approach, the ecological optimum can be determined taking into account the modifications made in the material production process chains.

Research is aimed at generating an exergetic model of a power plant boiler based on the novel materials and performing optimisation calculations using exergo-environmental analyses, supplemented by a cost analysis. The use of the novel materials is associated with higher costs. The results determined will be incorporated in an analysis of national carbon flows using the CarboMoG carbon carrier model.

Carbon capture and storage (CCS)

Capture and storage of carbon dioxide in case of large point-type sources, such as electricity production, is a measure to reach the ambitious reduction targets. A very promising technology for the long-term, large-scale implementation of CO₂ capture are membrane-based methods, so-called “second generation” methods. To reach technical maturity, adequate membrane materials, an optimum process design and a sufficient service life of the membranes will be required. All these aspects have not yet been studied sufficiently, research and development activities have just started (HGF-Allianz „MEM-BRAIN“).

These research activities shall be accompanied by systems analyses. The topic  focuses on an ecological assessment of membrane separation by a screening LCA. In this case, membrane technologies are compared with conventional CCS technologies. Other important aspects, such as CCS economy or framework conditions of CCS as a component of avoidance strategies, are parts of the topic "Transformation of Energy Systems".