The Hydrogen Heating Studies project in the Green Village at the TU Delft researches the safe application of hydrogen to heat buildings. This study aims to evaluate hydrogen sensor technologies for residential safety, including the determination of the sensor location inside a standard (Dutch) metering cabinet that achieves the fastest response to potentially dangerous leakages of hydrogen gas.
A range of commercially available sensor technologies was assessed to determine their suitability in residential applications. From this analysis on multiple criteria, the thermal conductivity sensors outperformed the other sensor technologies, albeit only by a small margin versus catalytic hydrogen sensors. Furthermore, an experimental study has been carried out by locating seven sensors at different locations inside the metering cabinet. The hydrogen concentrations have been measured in seven different conditions (case studies). It was found that sensors located at the top of the metering cabinet showed the highest concentrations, more specifically, the top-center.
The results of this research also confirmed that the condition of closed ventilation leads to a constant increase of hydrogen concentration in the metering cabinet. This has implications for managing the risks associated with high hydrogen concentration levels because of hydrogen leakage. Air ventilation inside the metering cabinet causes changes in the distribution mechanism, resulting in mixing and distribution of the hydrogen, reducing hydrogen concentrations. With open ventilation, the hydrogen concentration levels to trigger the alarm inside the metering cabinet should be lowered. Based on the results, it is advised to set the alarm to trigger when hydrogen concentration levels reach 5 %LEL. It was also found that, compared to methane, the release of hydrogen gas leads to a more buoyant gas mixture which mixes more easily with the air and rises three times quicker toward the ceiling. Finally, further research on worst-case scenarios is relevant to make specific recommendations for safe and economically feasible residential heating appliances.