Extensive material tests were carried out in preparation for the test and during the test phase. In total, the team injected several thousand standard cubic meters of gaseous hydrogen from sustainable, "green" production into the well.

At over two months, the test period was significantly longer than is the case with comparable tightness tests under nitrogen. “We wanted to make sure that the result was reproducible and to continue to gain experience in dealing with hydrogen as a medium,” says project manager Carsten Reekers, explaining the long period.

Among other things, the test – which the mining authority LBEG approved – provided insights into how current measurement results under hydrogen can be compared with standardized procedures under nitrogen as the test medium.

“Hydrogen was introduced into a cavern for the first time at the Etzel site. The results of the test run were consistently positive – the processes were controlled at all times and proceeded as planned. However, we still have major tasks and questions to deal with within the framework of the H2CAST project, but we see ourselves on a very positive path,” says Reekers.

The next step will be to complete the planning for the further expansion of the hydrogen caverns. Before the end of this year, two cavern boreholes are to be equipped so that the storage of larger quantities of hydrogen can begin as part of the H2CAST demonstration project. Detailed tests will be carried out again later using the maximum permissible rock mechanical pressure of the caverns. After that, the filling with hydrogen can begin.