You can find a wide variety of hydrogen compressor and pump systems in use today. Kinds of compressors consist of diaphragm, reciprocating piston, and centrifugal. Pumping systems for hydrogen applications include various kinds of positive displacement techniques. Each diaphragm compressor and pump system functions utilizing various ways, and each is used for specific reasons and for particular marketplaces.

To introduce readers to this topic, we requested a number of hydrogen compressor and pump manufacturers to explain the techniques used in hydrogen programs today.

Basic principles

Hydrogen is the easiest and many plentiful element in the universe. (See CGI, Feb. 2008, p. 52.) It is an efficient, low-polluting, renewable energy. Growing hydrogen technologies require storage and the use of hydrogen at higher demands.

Compressors are used to boost the stress of gaseous hydrogen (H2). In general, however, liquids are certainly not considered compressible. Pumping systems consequently are used to increase the stress of liquid hydrogen (LH2) in the use point by offering a continuing flow. Limitations and last use back stress make the stress improve. LH2 at high-pressure will then be transformed into vapor because it passes via a vaporizer, and is also utilized or stored at the elevated stress. Gaseous compressors and fluid pumps are both utilized in hydrogen applications.

Even though the basic principles of compressing and pumping are common to the majority of fumes and liquids, you can find distinctive distinctions and specifications, including safety, while confronting hydrogen. One of the largest difficulties to using hyrogen is its secure containment, because of its reduced molecular mass.


The 3 fundamental varieties of compressors – diaphragm, reciprocating piston, and centrifugal (also called radial) – have different qualities which make them right for use in various settings.

Diaphragm Compressors

“Diaphragm compressors,” advises Osama Al-Qasem with Pdc Machines Inc., “are a good choice for compressing gases without having incurring toxic contamination from the process mass media or leakage of gas to background air.” H2 is remote from the mechanical areas of the compressor and through the atmosphere by a set of 3 metal diaphragms. These are generally clamped between two exactly contoured concave tooth decay in upper and lower plates. Three of the diaphragms are nested and act with each other as one. The top diaphragm is in contact with the H2 as well as the base is in touch with the hydraulic oil. A three-diaphragm set is used to make sure there is not any go across-contamination involving the hydraulic oil and also the H2 being compressed. The center diaphragm, used for leak detection, has outlines scribed on edges. When a leak grows within the top or lower diaphragm, or maybe the O-rings put on, the mass media will seep across the scribe lines into an accumulator. When an accumulator pressure gets to a set restrict, the oxygen compressor will automatically stop. “As static seals are employed,” advises Al-Qasem, “there is not any leakage of gases for the environment, and no reason to purge or vent the crankcase.”

A engine-driven crankshaft connected to a piston movements a column of hydraulic liquid up and down. Pressure occurs because the hydraulic fluid is pushed upwards to fill up the lower oil-plate cavity, exerting a uniform force against the bottom of the diaphragm set, deflecting it into the H2-filled gas-plate cavity above. The displacement from the diaphragm against the gas-plate cavity compresses the H2, driving it all out the discharge check valve. Since the piston, which movements the hydraulic fluid, cerebral vascular accidents downwards, the diaphragm is drawn back down into the lower cavity, the inlet check device opens up, as well as the top cavity fills up with H2. The period is repetitive.

The key benefit to diaphragm compressors will there be is not really the concern for leakage as with other compressors or pumping systems.

Stephen Saint. Martin of Gas And Air Techniques, Inc. reviews that “Diaphragm compressors are utilized to compress H2 in tube trans-satisfying and pipe trailers offloading procedures, and for gasoline recovery from the vapour space of cryogenic storage vessels. Due to the high pressure ability, and inherently oil-totally free pressure, the diaphragm compressor is also frequently used in vehicle hydrogen fueling stations, where pressures of ten thousand psi and above are presently used.”

The hydrogen energy cell requires ultra-purity H2 to function properly. “The diaphragm compressors,” according to Osama Al-Qasem, “are created to provide precisely this function. Numerous diaphragm compressors happen to be installed around the world as part of the renewable power system to find option resources for oil.” Al-Qasem claims that 85 to 90 percent of the market needing diaphragm compressors had been provided by Pdc.

Diaphragm compressors are ideal for high pressure applications. It is far from surprising that diaphragm compressors are perfect for hydrogen applications, particularly in the development from the emerging hydrogen economy. Osama Al-Qasem noted one distinctive and interesting emerging “double-green” technologies. Pdc has compressors being used together with wind turbines. The electric power from wind turbines can be employed to supply a water electrolyzer to electrochemically split water into its elements, hydrogen and o2. One feature that makes the relationship of those two systems this kind of fascinating match would be that the electrolyzer can run with adjustable power enter, as windmills transform at different rates of speed, in accordance with the wind. Hydrogen therefore produced is compressed and kept for later use, either inside a stationary energy cell to create electricity should there be no wind, or to supply a hydrogen car.

Hydrogen compressor programs are many. They consist of making use of solar technology to electrolyze water to produce H2, which, like the windmill application, is then compressed and stored for later on use, either within a stationary energy cell to produce electricity when there is no sunshine, or energy a hydrogen vehicle. Compressors are utilized at hydrogen energy cell stations, such as these for vehicles, buses, fork-lifts, scooters, and household re-fuelers for fuel cell (FC) cars; for filling and away-launching H2 from pipe trailers, gas cylinders, and storage space tanks; for your pressure of syngas from green resources; as well as for wind and solar technology. H2 compressors are employed in these disparate programs as gasoline mixing, trying to recycle, and mixing, metal handling, hydrogenation of edible oils, specialty gasoline purification, float glass creation, and power plant turbine cooling. Gases for semiconductor, electronics and fiber optics manufacturing need compressors. They are also used for feedstock for chemical substance, petrochemical and pharmaceutic industries, stress improving and storage space of fumes from on-site generation systems, and for energy back-up using hydrogen FC for telecom towers, as well as study and development.

Multiple-phase Reciprocating Piston Compressors

Multiple-phase reciprocating piston compressors are normally utilized for compression of H2 gas. Piston compressors work on the simple idea. Rick Turnquist, with RIX Industries instructs, “The piston inside a big cylinder forces a set level of gasoline in to a smaller cylinder, thereby creating a pressure improve. This is dependant on the ideal gasoline law, which in abbreviated form is: PV=nT (stress x volume = Moles of gas x heat). Thus as volume will go down, pressure goes up (note right after the last stage the stress improve is forced through the back stress in the user’s tank or piping).”

Turnquist continues to explain that “H2 compressors are like those employed to compress other gases; nevertheless you will find sometimes style differences because of the tiny molecular scale of the H2. These may be: a unique device design; special piston ring components; overlapping piston ring design to lower leakage; lower pressure ratios; or tube and head castings may must be impregnated to stop leaks due to throwing porosity. Additionally, the quality of metal used in the pressure end components may must be changed.”

Hydrogen, like all fumes, is heated by pressure. “Intercooling” from the gasoline is needed when you use multiple-stage high-pressure compressors.

The largest finish-users of multi-stage reciprocating screw air compressor are refineries and chemical plants. Clients include such businesses as Air Products, Praxair, and Chevron Study. These compressors can also be utilized lrnhbl some refueling programs, for syngas, pilot plants, and laboratory R&D.

Centrifugal Compressors

Centrifugal compressors are seldom employed for hydrogen applications because of the molecule’s low molecular weight. However, centrifugal compressors are used in cryogenic H2 applications where flow is fairly high and also the stress head preferred is fairly low. Barbers Nichols Inc. (BNI), developer and producer of specialized turbo-machinery, has created cryogenic H2 centrifugal compressors for just two programs. Both of these programs involve sub-chilling H2 by drawing down fluid boil-off gasoline stress listed below atmospheric. Jeff Shull, with Barber Nichols, clarifies that “this results in a much more packed liquid that can then be applied in a rocket better (occupies less space and reduces overall weight). BNI used 4 individual centrifugal phases (4 solitary phase machines each having a motor) to draw down the pressure to approximately 3 psia with an atmospheric stress outlet and flows to get a propellant densification check at NASA. BNI’s H2 cryogenic compressors use a engine and bearings working at space temperature with the overhung impeller on a hollow shaft to lower warmth enter for the liquid. No powerful closes are employed so designs are hermetic. BNI also has provided a number of H2 circulators in supercritical applications (supercritical H2 is more like a fluid when compared to a gas, however) for cryogenic cooling.”

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