To meet climate targets the share of renewable energy needs to be increased. Changing weather conditions lead to fluctuating power outputs and thus to increasing demand in energy storage solutions. Transformation to hydrogen via electrolysis is an option, but due to the absence of a sufficient hydrogen storing and transportation infrastructure, production of renewable natural gas seems to be the best solution so far. Within the project “Underground Sun Conversion” those issues are addressed by using a unique microbiological methanation process and utilizing existing infrastructure for storage plus transportation of the obtained natural gas. A sustainable carbon cycle is established.
The technical suitability of the steel grades L80, P110, 42CrMo4, L360NB and P235 for the application in an underground gas production facility is investigated. Therefore, the materials are tested with respect to their susceptibility to embrittlement by hydrogen gas, up to a maximum H2-partial pressure of 20 bar, by means of constant load tests (CLTs) and immersion tests. Tests are done under realistic field conditions and hence samples are periodically wetted by the aqueous part of the test medium, which contains chloride in a concentration of 15 000 mg/l. The gaseous part of the medium consists of H2 and CO2.
Tests are performed with or without a corrosion inhibitor and last 720 hours. Tensile specimens that do not fail during CLTs are subjected to a tensile test afterwards and mechanical properties are compared to those of the non-immersed ones. In general, the examined steel grades show a good resistance to hydrogen embrittlement.