Hydrogen compressors are closely related to hydrogen pumps and gas compressors: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of hydrogen gas, whereas the main result of a pump raising the pressure of a liquid is to allow the liquid hydrogen to be transported elsewhere.
A proven method to compress hydrogen is to apply reciprocating piston compressors. Widely used in refineries, they are the backbone of refining crude oil. Reciprocating piston compressors are commonly available as either oil-lubricated or non-lubricated; for high pressure, non-lubricated compressors are preferred to avoid oil contamination of the hydrogen. Expert know-how on piston sealing and packing rings can ensure that reciprocating compressors outperform the competing technologies in terms of MTBO.
A multi-stage electrochemical hydrogen compressor incorporates a series of membrane-electrode-assemblies, similar to those used in proton exchange membranefuel cells; this type of compressor has no moving parts and is compact. The electrochemical compressor works similar to a fuel cell, a voltage is applied to the membrane and the resulting electric current pulls hydrogen through the membrane. With electrochemical compression of hydrogen, a pressure of 14500 psi is achieved. A patent is pending claiming an exergy efficiency of 70 to 80% for pressures up to 10,000 psi or 700 bars. A single stage electrochemical compression to 800 bar was reported in 2011. DOE has supported developments related to developing low cost electrochemical hydrogen compressors for heat pumps with Xergy Inc.
Hydride compressor
In a hydride compressor, thermal and pressure properties of a hydride are used to absorb low-pressure hydrogen gas at ambient temperatures and then release high-pressure hydrogen gas at higher temperatures; the bed of hydride is heated with hot water or an electric coil.
Piston-metal diaphragm compressor
-metal diaphragm compressors are stationary high-pressure compressors, four-staged water-cooled, 11–15 kW, 30–50 Nm3/h 40 MPa for dispensation of hydrogen. Since compression generates heat, the compressed gas is to be cooled between stages making the compression less adiabatic and more isothermal. The default assumption on diaphragm hydrogen compressors is an adiabatic efficiency of 70%. Used in hydrogen stations.
Guided rotor compressor
The guided rotor compressor is a positive-displacement rotary compressor based upon an envoluted trochoid geometry which utilizes a parallel trochoid curve to define its basic compression volume. It has a typical 80 to 85% adiabatic efficiency.
Linear compressor
The single-piston linear compressor uses dynamic counterbalancing, where an auxiliary movable mass is flexibly attached to a movable piston assembly and to the stationary compressor casing using auxiliary mechanical springs with zero vibration export at minimum electrical power and current consumed by the motor. It is used in cryogenics
