Hydrogen Energy Compressor Magnet

Hydrogen Energy Compressor Magnet

Hydrogen is one of the most promising eco-friendly energies of the future. As the universe’s most abundant element, it provides a never-ending source of clean energy that can be converted to electricity by fuel cells with no toxic waste or greenhouse gas emissions. However, the key to hydrogen’s widespread use lies in efficient strategies for storage and delivery, especially when used for stationary and automotive applications.

Hydrogen can be stored in liquid or gaseous form, either for long-term storage in natural geological formations (such as salt caverns, lined hard rock caverns and depleted oil and gas fields) or short-term as a compressed hydrogen gas for transportation and on-board applications in fuel cell electric vehicles. Liquid storage is preferred because it requires less space for a given level of energy density.

In order to achieve sufficient energy densities for practical use, hydrogen needs to be compressed to high pressure levels. This can be achieved using conventional mechanical compression technologies such as reciprocating, diaphragm and linear compressors or innovative non-mechanical technologies specifically conceived for hydrogen, such as cryogenic, metal hydride and electrochemical compressors.

In the case of gaseous storage, it is likely that hydrogen will be mixed with natural gas for transport in existing pipeline infrastructure. The energy density of this solution is limited by the capacity of the pipeline and its material integrity, as well as the capabilities of end-users to handle large volumes of hydrogen. Several research efforts are underway to determine the performance of this type of system (see Kurz et al., 2020a and b).

For liquid storage, the best option currently available is to store hydrogen as an alkali metal boride, such as nickel borohydride (NbH), which can sustain operation to 1,000 °C with a Carnot efficiency loss of only 40%. Nevertheless, this type of material is vulnerable to poisoning by the traces of oxygen and water found in ambient air at such high temperatures. Furthermore, it is expensive and time-consuming to produce NbH.

A faster and more cost-effective approach is to compress hydrogen using centrifugal pumps, a technique that is already widely used in industrial applications. However, the operating conditions of such pumps are highly demanding and can lead to a high degree of wear on the pump components. This is particularly true in the case of the rotors, which are subject to large rotational accelerations and vibrations. The resulting damage to the rotor blades and seals increases maintenance and repair costs, and can compromise the efficiency of the pump and, consequently, the overall reliability of the system.

To address this issue, Southwest Research Institute (SwRI) has developed a linear motor-driven reciprocating compressor, called the LMRC, that is specifically designed to compress hydrogen for fuel cell electric vehicles (FCEVs). This airtight, hermetically sealed machine uses a combination of SwRI-developed solutions to protect against embrittlement and decrepitation, including coatings, valve designs and hermetic pistons. It also features a linear motor design that reduces power consumption and the number of moving parts, thus increasing efficiency, reliability and product lifecycle.


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