Hydrogen refuelling stations based on water electrolysers (WE-HRS) are under development as modular containerised units for distribution nationally, in order to provide a hydrogen infrastructure for refuelling fuel cell vehicles (FCEV). WE-HRS are being designed in a range of sizes from 100 to 1000 kgH2/day with integral compression and high pressure storage for dispensing hydrogen at 99.97% minimum hydrogen purity (maximum -27C dew point).
Hydrogen produced by a solid polymer electrolyser contains no significant impurities other
than water and oxygen, which affords the opportunity to condition the gas by refrigeration and so avoid the limitations of existing purification methods waste gas (regenerative desiccant dryers) or waste energy due to their high temperature operation (Palladium filters).
Once purified, the hydrogen is stored and then during dispensing it needs to be chilled to as low as -40C to ensure the vehicle’s tank will not overheat. A cost-effective energy-efficient integrated refrigeration system (IRS) is proposed to provide both the gas conditioning and the thermal management of the electrolysis and compression processes. The IRS will be developed to address five key aspects of the WE-HRS: (i) drying the hydrogen production stream to the required purity before storage by freeze drying the gas to the required dew point,
(ii) chilling the pure hydrogen as it is dispensed to the vehicle to ensure a rapid charge to 700 bar can be achieved, (iii) extracting waste heat efficiently from the electrolysis stacks to ensure optimal running temperatures are maintained irrespective of electrolyser load level or ambient temperature, (iv) extracting waste heat from the gas compressor, and (v) maintaining acceptable indoor temperatures inside the container during warm weather conditions. Consideration will also be given to using the recovered waste heat for frost protection of the WE-HRS and for space heating the forecourt shop and nearby buildings.