Large scale leakage of liquid hydrogen (LH2) – tests related to bunkering and maritime use of liquid hydrogen

Hydrogen is a promising energy carrier, which itself does not contribute to greenhouse gas emissions. Liquid hydrogen (LH2) is an efficient solution for transportation and storage of hydrogen. Especially for large vessels, liquid hydrogen is more practical than compressed hydrogen due to more efficient storage, bunkering, and handling of the fuel. However, to introduce LH2 as a maritime fuel, more knowledge regarding the behavior of LH2 is needed. For this purpose, a number of large-scale leakage tests of LH2 were performed. To simulate spill from a bunkering operation, LH2 was released in an outdoor test facility. The objectives of the tests were to provide information about:  formation of a liquid pool caused by leakage of LH2, and/or condensations and freezing of components in air on the ground  hydrogen concentration within the gas cloud originating from the leakage  consequences of ignition of the gas cloud. To simulate leakage of LH2 in the technical room connected to the LH2 tank (Tank Connection Space, TCS), LH2 was released into a closed room connected to a ventilation mast. The objectives of the closed room and ventilation mast tests were to provide information about:  concentration of H2 in TCS due to leakage of LH2  flow rate of H2 out of, and spread of H2 downwards, from the ventilation mast  clogging of ventilation mast due to condensation and freezing of components in air  consequences of explosion in TCS. Releases of LH2 resulted in formation of a liquid pool on the ground. The radius of the liquid pool was limited to 0.5 to 1.0 m from the release point. The pool disappeared when the release stopped. The plume of H2 with flammable concentrations spread along the ground with neutral buoyancy, in a narrow passage from the release point. In the tests with horizontal release orientation, flammable concentrations of H2 were detected 50 m, but not 100 m, from the release point. No flammable concentrations of H2 were detected outside a 45° angle, relative to the wind direction. Frozen components from air was observed on the ground around the release point in the tests with a vertically downwards release orientation, but not from the cloud in general. Ignition of the gas cloud caused a combustion blast. No fast deflagration or detonation occurred anywhere or at any time during the tests. Release of LH2 into the closed room caused build-up of near 100%vol H2 in the room within 30 seconds. Hydrogen spread from the ventilation mast with a neutral buoyancy. No significant levels of H2 were measured at ground level. No clogging of the ventilation mast due to condensation and freezing of components in air was observed. The tests where H2 was ignited at top of the ventilation mast showed that oxygen flowing back through the ventilation mast could cause a low severity explosion in the TCS.