The effect of environmental conditions on the operation of a hydrogen refuelling station

In this study, the effect of environmental conditions on plant operation was investigated for hydrogen refuelling stations with an external storage facility. Hydrogen storage pressure with respect to tank surface temperatures have been measured and used to create empirical equations for each tank showing the effect of surface temperature on the tank pressure. A physical model of the hydrogen storage tanks has been created in DesignBuilder (EnergyPlus) to simulate the surface temperature of tanks throughout the course of a year with respect to location, site orientation, tank size and surface colour, shading and operating pressure. Finally, the effect that environmental conditions may have on a plant operation is assessed through the prediction of pressure dependent events, namely the frequency of alarms and pressure relief occurrences and hours of plant downtime over the course of a year. The modelling results indicate that location, tank size, surface colour and sunshade can have substantial impacts on the plant operation, whereas the influence of site orientation is less significant. Frequency of pressure dependant events increase as the tank size decreases due to more significant heat gain observed with higher surface-to-volume ratios. Simulation results also prove that the provision of a sunshade or white paint colour could avoid/minimise the interference of ambient conditions in plant operation in cold and mild climates. However, they are not sufficient enough to mitigate against solar gain effect in warmer climates. Although reducing the maximum operating pressure would also help reduce the number of solar gain pressure events, it would also result in increased cushion level and hence reduced plant performance. The optimum design and operating strategy should be chosen for each individual station considering the daily and annual temperature profiles of the location.