The German energy economy is being changed from a currently fossil and nuclear basis towards renewable energy spurces ('Energiewende'). Since biomass and hydro do not have sufficient potential in Germany, it is necessary to use wind and solar energy for power supply as well. However these provide their energy independent of demand and therefore require both long time and large scale storage. A favourable energy carrier for this is hydrogen created through electrolysis.
In this work an exergy analysis of a hydrogen based electricity storage system is carried out. The scenario consists of a central proton exchange membrane type electrolyser fed by excess solar and wind power. Following to the production it is considered to store the hydrogen gas in high pressure tanks or in caverns. The following distribution can be performed by a hydrogen grid consisting either of pipelines or trailers. The energetic reconversion of hydrogen to electricity is then conducted in households using proton exchange membrane type fuel cells with integrated calorific value boilers. Due to the intermittent nature of wind and solar energy as well as fluctuating demand of heat and power it is essential to consider part-load operation of the systems components. For this, load profiles for solar and wind power supply as well as for electricity and heat demand were deduced. By combining these, synthetic load profiles for both electrolyser and fuel cell operation could be established. Thus the complete process chain exergy efficiency of the considered system over one year of operation is simulated and exergy losses are identified. In a next step these losses can then be reduced and the overall efficiency can be increased.