Power to liquid and power to gas: An option for the German Energiewende

The large-scale deployment of renewable energy sources (RES) is an important aspect of decarbonising the energy supply, and represents a key part of the German Energiewende. However, significantly increasing the share of renewable power in the energy mix implies coping with the natural intermittency of RES like wind and solar. RES development also does not directly address non-electric energy needs such as fuels for transportation and industry feedstock, which are presently relying on fossil fuels. Therefore, the conversion of surplus renewable electricity (RES-E) into the more convenient form of a liquid or gas (power-to-liquid and power-to-gas) could help offset RES intermittency while providing a diverse mix of energy carriers. If recycled CO2 is used in the fuel synthesis process, overall emissions can be greatly reduced. This paper aims to sketch the possible contribution of RES-E combined with power-to-gas (PtG) and power-to-liquid (PtL) schemes in the 2050 German energy system, by modelling an increase in installed renewable power. Different scenarios are laid out and compared, and the results are utilised in a basic economic assessment of the fuel production cost for an hypothetical power-to-liquid plant.