A promising path for long-term energy storage is the production of e-fuels via Power-to-X processes (PtX). “Green” hydrogen is generated via water electrolysis and serves as a basic feedstock for the synthesis of chemicals and fuels such as methane, ammonia, methanol and other synthetic hydrocarbons. These fuels offer the advantage of an existing storage infrastructure and furthermore allow for the coupling of all energy sectors, e.g. transportation, industry, heating etc., to wind and solar power.

Within the German flagship project H2Mare the consortium PtX-Wind is developing experimental, research and production offshore & off-grid PtX platforms that are directly coupled to wind power. In case of wind calm, storm, maintenance and system failures, a CO2-free, electrochemical storage unit should provide enough energy for stand-by & emergency operation of electrolysis & PtX plants as well as for vital platform instruments. Furthermore, the battery should, if economically viable, support the PtX-plant operation due to wind power variability.

Together with industrial & academic partners the main task at the DFI focuses on dimensioning a battery storage system for a research PtX platform, comprising a 5 MW electrolysis unit & a 1.7 MW PtX-platform. Therefore, suitable battery technologies such as PbAc, PbGel, LFP, NMC and supercapacitors are being tested to verify battery properties provided by the manufacturer. The performance of some pre-selected candidates at module level (0.5 kWh, PbAc, PbGel, LFP) will be presented. Combined with a year-round wind farm power profile, the battery properties were implemented into the software “System Advisor Model (SAM)”1 and a minimal battery size (0.52 MWh) for the stand-by/emergency operation (0.47 MW) was determined, based on the 1C rate capability of state-of-the-art LFP batteries. Economic considerations on stand-by battery size will be presented, as well as a battery size for the improvement of PtX-plant productivity.
Literature: [1] Open source software website: https://sam.nrel.gov/download.html;