Project data

Summary of the project

The energy transition in Germany is leading to an increasing demand for electricity storage and balancing power plants due to the rising proportion of volatile feed-in. In Germany, the electrolytic production of hydrogen from water (power-to-gas) and subsequent reconversion into electricity is one of the most promising options for the long-term storage of electricity required in the medium term.

In principle, this reconversion of hydrogen can take place with fuel cells, gas turbines or combustion engines, whereby a current cost comparison shows that combustion engines in the medium power range currently represent a cost-effective and technologically established option for reconversion to electricity. As fuel cells for the reconversion of hydrogen into electrical energy still have development potential in terms of service life, costs and reliability, it makes sense to utilise the already advanced technology in the field of combustion engines for stationary applications in combined heat and power plants.

Until now, research and applications have mainly focussed on hydrogen combustion engines that run on ambient air. Since atmospheric air contains nitrogen, such engines emit toxic and environmentally harmful nitrogen oxides, especially at operating points that are favourable in terms of efficiency. A designed combined combustion and vapour process for a stationary internal combustion engine enables the reconversion of electricity without these nitrogen oxides, which are normally produced by hydrogen engines. The process is based on the combustion of hydrogen with pure oxygen, which is produced during electrolysis, and enables efficiencies and power densities above those of conventional hydrogen engines with direct injection. Stoichiometric combustion only produces water vapour, which can be used as an inert gas to control the combustion temperature and thus comply with the material limits and avoid knocking combustion. Thermodynamic modelling of the process as a comparative process provides a maximum effective efficiency of between 50 and 60 percent when wall heat and friction losses are taken into account semi-empirically, compared to a maximum of 45 percent in hydrogen engines.

In addition to thermodynamic models, numerical methods in the form of 3D CFD simulations are also used in the doctoral project to investigate and optimise the influences of geometry, timing, mixture formation strategy and ignition timing. The CFD calculations are intended to transfer the development from the concept phase to the design phase and prepare the construction of a prototype test bench by deriving design data and process parameters.