Towards Non-Mechanical Hybrid Hydrogen Compression for Decentralized Hydrogen Facilities

Abstract

The cost of the hydrogen value chain needs to be reduced to allow the widespread development of hydrogen applications. Mechanical compressors, widely used for compressing hydrogen to date, account for more than 50% of the CAPEX (capital expenditure) in a hydrogen refueling station. Moreover, mechanical compressors have several disadvantages, such as the presence of many moving parts, hydrogen embrittlement, and high consumption of energy. Non-mechanical hydrogen compressors have proven to be a valid alternative to mechanical compressors. Among these, electrochemical compressors allow isothermal, and therefore highly efficient, compression of hydrogen. On the other hand, adsorption-desorption compressors allow hydrogen to be compressed through cooling/heating cycles using highly microporous materials as hydrogen adsorbents. A non-mechanical hybrid hydrogen compressor, consisting of a first electrochemical stage followed by a second stage driven by adsorption-desorption of hydrogen on activated carbons, allows hydrogen to be produced at 70 MPa, a value currently required for the development of hydrogen automotive applications. This system has several advantages over mechanical compressors, such as the absence of moving parts and high compactness. Its use in decentralized hydrogen facilities, such as hydrogen refueling stations, can be considered.

The Key Techno-Economic and Manufacturing Drivers for Reducing the Cost of Power-to-Gas and a Hydrogen-Enabled Energy System

“…The ×10 scale-up in installed capacity case assumes that the BOP costs can be improved by 60 $/kW; Symbiosis and heat recovery: Additionally, as low-grade heat is the principle waste product, opportunities for heat recovery and utilisation can also be exploited [39]. Hydrogen compression via sorption technology also represents an opportunity for direct recovery and utilisation of heat from the PEM system [40]. The ×100 scale-up in installed capacity case assumes that the installation of symbiotic technology costs can be improved by 20 $/kW.…”

A Step Forward in Understanding the Hydrogen Adsorption and Compression on Activated Carbons

“…Type IV tanks, which are made of carbon fibers and a polymer inner lining, are most commonly used for storing hydrogen at high pressures. 16 The cost of a Type IV tank has been estimated at approximately $ 633 kg -1 . 6 Nevertheless, high-pressure systems require safety measures that may alarm public opinion.…”

“…High-pressure hydrogen storage requires heavy and bulky tanks. Type IV tanks, which are made of carbon fibers and a polymer inner lining, are most commonly used for storing hydrogen at high pressures . The cost of a Type IV tank has been estimated at approximately $ 633 kg ‑1 .…”

Characterization of Carbon Materials for Hydrogen Storage and Compression

“…An emerging technology for hydrogen compression is based on thermally driven, cyclic, adsorption-desorption on porous materials [140]. In addition to carbon materials [141], thoroughly reviewed in the present paper, other candidates for this purpose are: (i) MOFs, with their exceptional A BET sometimes higher than 6000 m 2 g −1 , thereby allowing excess uptakes of around 10 wt.% at 77 K and 6 MPa [142] (however, the main drawback of MOF for a wide application is their high price and the degradation of their properties with ageing [143]); (ii) organic polymers, which ensure hydrogen uptakes of about 4 wt.% at 77 K and approximately 1 MPa [144,145]; and (iii) silicas, aluminas, and zeolites, but giving amounts of adsorbed hydrogen lower than carbons of similar A BET [146].…”