United States

Liquid hydrogen (LH2) storage is viewed as a viable approach to assure sufficient hydrogen capacity at commercial fuelling stations. Presently LH2 is produced at remote facilities and then transported to the end-use site by road vehicles (i.e. LH2 tanker trucks). Venting of hydrogen to depressurize the transport storage tank is a routine part of the LH2 delivery and site transfer process. The behaviour of cold hydrogen plumes has not been well characterized because of the sparsity of empirical field data which can lead to overly conservative safety requirements. Committee members of the National Fire Protection Association (NFPA) Standard 2 [1] formed the Hydrogen Storage Safety Task Group which consists of hydrogen producers safety experts and computational fluid dynamics modellers has identified the lack of understanding of hydrogen dispersion during LH2 venting of storage vessels as a critical gap for establishing safety distances at LH2 facilities especially commercial hydrogen fuelling stations. To address this need the National Renewable Energy Laboratory Sensor Laboratory in collaboration with the NFPA Hydrogen Storage Task Group developed a prototype Cold Hydrogen Plume Analyzer to empirically characterize the hydrogen plume formed during LH2 storage tank venting. The prototype analyzer was field deployed during an actual LH2 venting process. Critical findings included

• Hydrogen above the lower flammable limit (LFL) was detected as much as 2 m lower than the release point which is not predicted by existing models.
• Personal monitors detected hydrogen at ground level although at levels below the LFL.
• A small but inconsistent correlation was found between oxygen depletion and the hydrogen concentration.
• A negligible to non-existent correlation was found between in-situ temperature measurements and the hydrogen concentration.

The prototype analyzer is being upgraded for enhanced metrological capabilities including improved real-time spatial and temporal profiling of hydrogen plumes and tracking of prevailing weather conditions. Additional deployments are planned to monitor plume behaviour under different wind humidity and temperature conditions. The data will be shared with the Hydrogen Storage Task Group and ultimately will be used support theoretical models and code requirements prescribed in NFPA 2.

Polymers for O-rings valve seats gaskets and other sealing applications in the hydrogen infrastructure face extreme conditions of high-pressure H2 (0.1 to 100 MPa) during normal operation. To fill current knowledge gaps and to establish standard test methods for polymers in H2 environments these materials can be tested in laboratory scale H2 manifolds mimicking end use pressure and temperature conditions. Beyond the influence of high pressure H2 the selection of gases used for leak detection in the H2 test manifold their pressures and times of exposure gas types relative diffusion and permeation rates are all important influences on the polymers being tested. These effects can be studied ex-situ with post-exposure characterization. In a previous study four polymers (Viton A Buna N High Density Polyethylene (HDPE) and Polytetrafluoroethylene (PTFE)) commonly used in the H2 infrastructure were exposed to high-pressure H2 (100 MPa). The observed effects of H2 were consistent with typical polymer property-structure relationships; in particular H2 affected elastomers more than thermoplastics. However since high pressure He was used for purging and leak detection prior to filling with H2 a study of the influence of the purge gas on these polymers was considered necessary to isolate the effects of H2 from those of the purge gas. Therefore in this study Viton A Buna N and PTFE were exposed to the He purge procedure without the subsequent H2 exposure. Additionally six polymers Viton A Buna N PTFE Polyoxymethylene (POM) Polyamide 11 (Nylon) and Ethylenepropylenediene monomer rubber (EPDM) were subjected to high pressure Ar (100 MPa) followed by high pressure H2 (100 MPa) under the same static isothermal conditions to identify the effect of a purge gas with a significantly larger molecular size than He. Viton A and Buna N elastomers are more prone to irreversible changes as a result of H2 exposure from both Ar and He leak tests as indicated by influences on storage modulus extent of swelling and increased compression set. EPDM even though it is an elastomer is not as prone to high-pressure gas influences. The thermoplastics are generally less influenced by high pressure regardless of the gas type. Conclusions from these experiments will provide insight into the influence of purging processes and purge gases on the subsequent testing in high pressure gaseous H2. Control for the influence of purging on testing results is essential for the development of robust test methods for evaluating the effects of H2 and other high-pressure gases on the properties of polymers.

Recent interest in biomass-based fuel blendstocks and chemical compounds has stimulated research efforts on conversion and upgrading pathways which are considered as critical commercialization drivers. Existing pre-/post-conversion pathways are energy intense (e.g. pyrolysis and hydrogenation) and economically unsustainable thus more efficient process solutions can result in supporting the renewable fuels and green chemicals industry. This study proposes a process including biomass conversion and bio-oil upgrading using mixed fast and slow pyrolysis conversion pathway as well as sono-catalytic transfer hydrogenation (SCTH) treatment process. The proposed SCTH treatment employs ammonium formate as a hydrogen transfer additive and palladium supported on carbon as the catalyst. Utilizing SCTH bio-oil molecular bonds were broken and restructured via the phenomena of cavitation rarefaction and hydrogenation with the resulting product composition investigated using ultimate analysis and spectroscopy. Additionally an in-line characterization approach is proposed using near-infrared spectroscopy calibrated by multivariate analysis and modelling. The results indicate the potentiality of ultrasonic cavitation catalytic transfer hydrogenation and SCTH for incorporating hydrogen into the organic phase of bio-oil. It is concluded that the integration of pyrolysis with SCTH can improve bio-oil for enabling the production of fuel blendstocks and chemical compounds from lignocellulosic biomass.

Sustainable energy conversion requires zero emissions of greenhouse gases and criteria pollutants using primary energy sources that the earth naturally replenishes quickly like renewable resources. Solar and wind power conversion technologies have become cost effective recently but challenges remain to manage electrical grid dynamics and to meet end-use requirements for energy dense fuels and chemicals. Renewable hydrogen provides the best opportunity for a zero emissions fuel and is the best feedstock for production of zero emission liquid fuels and some chemical and heat end-uses. Renewable hydrogen can be made at very high efficiency using electrolysis systems that are dynamically operated to complement renewable wind and solar power dynamics. Hydrogen can be stored within the existing natural gas system to provide low cost massive storage capacity that (1) could be sufficient to enable a 100% zero emissions grid; (2) has sufficient energy density for end-uses including heavy duty transport; (3) is a building block for zero emissions fertilizer and chemicals; and (4) enables sustainable primary energy in all sectors of the economy.

This paper investigates the optimal planning of microgrids including the hydrogen energy system through mixed-integer linear programming model. A real case study is analyzed by extending the only microgrid lab facility in Austria. The case study considers the hydrogen production via electrolysis seasonal storage and fuelling station for meeting the hydrogen fuel demand of fuel cell vehicles busses and trucks. The optimization is performed relative to two different reference cases which satisfy the mobility demand by diesel fuel and utility electricity based hydrogen fuel production respectively. The key results indicate that the low emission hydrogen mobility framework is achieved by high share of renewable energy sources and seasonal hydrogen storage in the microgrid. The investment optimization scenarios provide at least 66% and at most 99% carbon emission savings at increased costs of 30% and 100% respectively relative to the costs of the diesel reference case (current situation)

Hydrogen (H₂) shows great promise as zero-carbon emission fuel but there are several challenges to overcome in regards to storage and transportation to make it a more universal energy solution. Gaseous hydrogen requires high pressures and large volume tanks while storage of liquid hydrogen requires cryogenic temperatures; neither option is ideal due to cost and the hazards involved. Storage in the solid state presents an attractive alternative and can meet the U.S. Department of Energy (DOE) constraints to find materials containing > 7 % H₂ (gravimetric weight) with a maximum H₂ release under 125 °C.

While there are many candidate hydrogen storage materials the vast majority are metal hydrides. Of the hydrides this review focuses solely on sodium borohydride (NaBH4) which is often not covered in other hydride reviews. However as it contains 10.6% (by weight) H₂ that can release at 133 ± 3 JK−1mol⁻¹ this inexpensive material has received renewed attention. NaBH4 should decompose to H₂g) Na(s) and B(s) and could be recycled into its original form. Unfortunately metal to ligand charge transfer in NaBH4 induces high thermodynamic stability creating a high decomposition temperature of 530 °C. In an effort make H₂ more accessible at lower temperatures researchers have incorporated additives to destabilize the structure.

This review highlights metal additives that have successfully reduced the decomposition temperature of NaBH₄ with temperatures ranging from 522 °C (titanium (IV) fluoride) to 379 °C (niobium (V) fluoride). We describe synthetic methods employed chemical pathways taken and the challenges of boron derivative formation on H₂ cycling. Though no trends can be found across all additives it is our hope that compiling the data here will enable researchers to gain a better understanding of the additives’ influence and to determine how a new system might be designed to make NaBH4 a more viable H2 fuel source.

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work two-dimensional simulations with detailed chemistry are used to study the reaction pathways of the transient flow and ignition of a stoichiometric hydrogen-air mixture by moving hot spheres. For temperatures above the ignition threshold ignition takes place after a short time between the front stagnation point and separation location depending upon the sphere's surface temperature. Closer to the threshold the volume of gas adjacent to the separation region ignites homogeneously after a longer time. These results demonstrate the importance of boundary layer development and flow separation in the ignition process.

Biomass derived porous nanostructured nitrogen doped carbon (PNC) has been extensively investigated as the electrode material for electrochemical catalytic reactions and rechargeable batteries. Biomass with and without containing nitrogen could be designed and optimized to prepare PNC via hydrothermal carbonization pyrolysis and other methods. The presence of nitrogen in carbon can provide more active sites for ion absorption improve the electronic conductivity increase the bonding between carbon and sulfur and enhance the electrochemical catalytic reaction. The synthetic methods of natural biomass derived PNC heteroatomic co- or tri-doping into biomass derived carbon and the application of biomass derived PNC in rechargeable Li/Na batteries high energy density Li–S batteries supercapacitors metal-air batteries and electrochemical catalytic reaction (oxygen reduction and evolution reactions hydrogen evolution reaction) are summarized and discussed in this review. Biomass derived PNCs deliver high performance electrochemical storage properties for rechargeable batteries/supercapacitors and superior electrochemical catalytic performance toward hydrogen evolution oxygen reduction and evolution as promising electrodes for electrochemical devices including battery technologies fuel cell and electrolyzer.

A viable hydrogen economy has thus far been hampered by the lack of an inexpensive and convenient hydrogen storage solution meeting all requirements especially in the areas of long hauls and delivery infrastructure. Current approaches require high pressure and/or complex heat management systems to achieve acceptable storage densities. Herein we present a manganese hydride molecular sieve that can be readily synthesized from inexpensive precursors and demonstrates a reversible excess adsorption performance of 10.5 wt% and 197 kgH₂ m^-3 at 120 bar at ambient temperature with no loss of activity after 54 cycles. Inelastic neutron scattering and computational studies confirm Kubas binding as the principal mechanism. The thermodynamically neutral adsorption process allows for a simple system without the need for heat management using moderate pressure as a toggle. A storage material with these properties will allow the DOE system targets for storage and delivery to be achieved providing a practical alternative to incumbents such as 700 bar systems which generally provide volumetric storage values of 40 kgH₂ m^-3 or less while retaining advantages over batteries such as fill time and energy density. Reasonable estimates for production costs and loss of performance due to system implementation project total energy storage costs roughly 5 times cheaper than those for 700 bar tanks potentially opening doors for increased adoption of hydrogen as an energy vector.

This manuscript presents the results of a multi-lateral international activity intended to understand how to execute a cycle stress test as specified in a chosen standard (GTR SAE ISO EIHP …). The purpose of this work was to establish a harmonized test method protocol to ensure that the same results would be achieved regardless of the testing facility. It was found that accurate temperature measurement of the working fluid is necessary to ensure the test conditions remain within the tolerances specified. Continuous operation is possible with adequate cooling of the working fluid but this becomes more demanding if the cycle frequency increases. Recommendations for future test system design and operation are presented.