Hydrogen refueling stations (HRS) supply pressurised hydrogen for fuel cell electric vehicles at 350 and 700 bar. They operate similar to gas pumps for conventional vehicles in terms of consumer retail sales (accept credit cards and adhere to state standards for measurement and fuel quality).
What compressors are used in hydrogen service?
HRS require a large capacity compressor to increase the pressure of the stored hydrogen compressors for hydrogen refueling stations to enable sufficient flow rates at dispensing points. This is typically achieved using a metal hydride compressor which uses a combination of metallic hydrides to form and release hydrogen in a highly exothermic process. The high compression ratio enables a low gas flow to be generated at the compressor inlet and a very fast response at the dispenser inlet.
A large volume of the compressed hydrogen is then stored in an external storage tank at the station, where it is cooled to sub-zero temperatures. A heat exchanger is also provided to remove the excess heat. Throughout the system, specially designed hydrogen compliant valves and fittings are used to control the highly pressurised gas, ensuring that it is safely handled at all times.
The HRS buffer is designed to hold a mass of hydrogen, mpeak, equal to 27.5% of its average daily dispensed quantity. As a result, the compressor can run 12 h/day with this value and be capable of addressing a 3 h peak demand at 8% of its average. This is a key consideration when designing an HRS.