Publications

Burning hydrogen emits thermal radiation in UV NIR and IR spectral range. Especially in the case of large cloud explosion the risk of heat radiation is commonly underestimated due to the non-visible flame of hydrogen-air combustion. In the case of a real explosion accident organic substances or inert dust might be entrained from outer sources to produce soot or heated solids to substantially increase the heat release by continuum radiation. To investigate the corresponding combustion phenomena different hydrogen-air mixtures were ignited in a closed vessel and the combustion was observed with fast scanning spectrometers using a sampling rate up to 1000 spectra/s. In some experiments to take into account the influence of organic co-combustion a spray of a liquid glycol-ester and milk powder was added to the mixture. The spectra evaluation uses the BAM code of ICT to model bands of reaction products and thus to get the temperatures. The code calculates NIR/IR-spectra (1 - 10 μm) of non-homogenous gas mixtures of H2O CO2 CO NO and HCl taking into consideration also emission of soot particles. It is based on a single line group model and makes also use of tabulated data of H2O and CO2 and a Least Squares Fit of calculated spectra to experimental ones enables the estimation of flame temperatures. During hydrogen combustion OH emits an intense spectrum at 306 nm. This intermediary radical allows monitoring the reaction progress. Intense water band systems between 1.2 and 3 μm emit remarkable amounts of heat radiation according to a measured flame temperature of 2000 K. At this temperature broad optically-thick water bands between 4.5 μm and 10 μm contribute only scarcely to the total heat output. In case of co-combustion of organic materials additional emission bands of CO and CO2 as well as a continuum radiation of soot and other particles occur and particularly increase the total thermal output drastically.

Thermally sprayed aluminium (TSA) coatings provide protection to offshore steel structures without the use of external cathodic protection (CP) systems. These coatings provide sacrificial protection in the same way as a galvanic anode and thus hydrogen embrittlement (HE) becomes a major concern with the use of high strength steels. The effect of TSA on the HE of steel seems to remain largely unknown. Further the location of hydrogen in TSA-coated steel has not been explored. To address the above knowledge gap API 5L X80 and AISI 4137 steel coupons with and without TSA were prepared and the amount of hydrogen present in these steels when cathodically polarised to −1.1 V (Ag/AgCl) for 30 days in synthetic seawater was determined. One set of TSA-coated specimens was left at open circuit potential (OCP). The study indicates that the amount of hydrogen present in TSA-coated steel is ~100 times more than the amount found in uncoated steel and that the hydrogen seems to be largely localised in the TSA layer.

The onset and further development of the hydrogen economy are known to be constrained by safety barriers as well as by the level of public acceptance of new applications. Educational and training programmes in hydrogen safety which are currently absent in Europe are considered to be a key instrument in lifting these limitations and to ensure the safe introduction of hydrogen as an energy carrier. Therefore the European Network of Excellence ‘Safety of Hydrogen as an Energy Carrier’ (NoE HySafe) embarked on the establishment of the e-Academy of Hydrogen Safety. This work is led by the University of Ulster and carried out in cooperation with international partners from five other universities (Universidad Politecnica de Madrid Spain; University of Pisa Italy; Warsaw University of Technology Poland; Instituto Superior Technico Portugal; University of Calgary Canada) two research institutions (Forschungszentrum Karlsruhe and Forschungszentrum Juelich Germany) and one enterprise (GexCon Norway). The development of an International Curriculum on Hydrogen Safety Engineering aided by world-class experts from within and outside NoE HySafe is of central importance to the establishment of the e-Academy of Hydrogen Safety. Despite its key role in identifying the knowledge framework of the subject matter and its role in aiding educators with the development of teaching programmes on hydrogen safety no such curriculum appears to have been developed previously. The current structure of the International Curriculum on Hydrogen Safety Engineering and the motivation behind it are described in this paper. Future steps in the development of a system of hydrogen safety education and training in Europe are briefly described.

Natural gas plays a central role in the UK energy system today but it is also a significant source of greenhouse gas (GHG) emissions. The UK committed in 2008 to reduce GHG emissions by at least 80% compared to 1990 levels by 2050. In June 2019 a more ambitious target was adopted into law and the UK became the first major economy to commit to “net-zero” emissions by 2050. In this context the Energy Networks Association (ENA) commissioned Navigant to explore the role that the gas sector can play in the decarbonisation of the Great Britain (GB) energy system. In this report we demonstrate that low carbon and renewable gases can make a fundamental contribution to the decarbonisation pathway between now and 2050.

Developing renewable energy-driven water splitting for sustainable hydrogen production plays a key role in achieving the carbon neutrality goal. Nevertheless the efficiency of traditional pure water electrolysis is severely hampered by the anodic oxygen evolution reaction (OER) due to its sluggish kinetics. In this context replacing OER with thermodynamically more favorable oxidation reactions to produce hydrogen via hybrid water electrolysis becomes an energy-saving hydrogen production scheme. Here the recent advances in hybrid water electrolysis are critically reviewed. First the fundamentals of electrochemical oxidation of typical organic molecules such as urea hydrazine and biomass are presented. Then the recent achievements in electrocatalysts for hybrid water electrolysis are introduced with an emphasis on outlining catalyst design strategies and the correlation between catalyst structure and performance. Finally future perspectives in this field for a sustainable hydrogen economy are proposed.

Ni-based catalysts are attractive alternatives to noble metal electrocatalysts for the hydrogen evolution reaction (HER). Herein we present a dispersion-corrected density functional theory (DFT-D3) insight into HER activity on the (111) (110) (001) and (100) surfaces of metallic nickel nitride (Ni₃N). A combination of water and hydrogen adsorption was used to model the electrode interactions within the water splitting cell. Surface energies were used to characterise the stabilities of the Ni3N surfaces along with adsorption energies to determine preferable sites for adsorbate interactions. The surface stability order was found to be (111) < (100) < (001) < (110) with calculated surface energies of 2.10 2.27 2.37 and 2.38 Jm⁻² respectively. Water adsorption was found to be exothermic at all surfaces and most favourable on the (111) surface with E_ads = −0.79 eV followed closely by the (100) (110) and (001) surfaces at −0.66 −0.65 and −0.56 eV respectively. The water splitting reaction was investigated at each surface to determine the rate determining Volmer step and the activation energies (Ea) for alkaline HER which has thus far not been studied in detail for Ni₃N. The E_a values for water splitting on the Ni₃N surfaces were predicted in the order (001) < (111) < (110) < (100) which were 0.17 0.73 1.11 and 1.60 eV respectively overall showing the (001) surface to be most active for the Volmer step of water dissociation. Active hydrogen adsorption sites are also presented for acidic HER evaluated through the ΔG_H descriptor. The (110) surface was shown to have an extremely active Ni–N bridging site with ΔG_H = −0.05 eV.

In this paper CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank to ambient through a Pressure Relieve Device (PRD) 6 mm (¼”) opening. The numerical simulations using the TOPAZ software developed by Sandia National Laboratory addressed the changes of pressure density and flow rate variations at the leak orifice during release while the PHOENICS software package predicted extents of various hydrogen concentration envelopes as well as the velocities of gas mixture for the dispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFD model implemented through the TOPAZ and PHOENICS software to accurately predict the real gas properties for hydrogen release and dispersion under high pressures. The numerical results were compared with those obtained from using the ideal gas law and it was found that the ideal gas law overestimates the hydrogen mass release rates by up to 35% during the first 25 seconds of release. Based on the findings the authors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRD releases.

Direct internal reforming enables optimal heat integration and reduced complexity in solid oxide fuel cell (SOFC) systems but thermal stresses induced by the increased temperature gradients may inflict damage to the stack. Therefore the development of adequate control strategies requires models that can accurately predict the temperature profiles in the stack. A 1D dynamic modelling platform is developed in this study and used to simulate SOFCs in both single cell and stack configurations. The single cell model is used to validate power law and Hougen-Watson reforming kinetics derived from experiments in previous work. The stack model based on the same type of cells accounts for heat transfer in the inactive area and to the environment and is validated with data reported by the manufacturer. The reforming kinetics are then implemented in the stack model to simulate operation with direct internal reforming. Although there are differences between the temperature profiles predicted by the two kinetic models both are more realistic than assuming chemical equilibrium. The results highlight the need to identify rate limiting steps for the reforming and hydrogen oxidation reactions on anodes of functional SOFC assemblies. The modelling approach can be used to study off-design conditions transient operation and system integration as well as to develop adequate energy management and control strategies.

The study is focused on the technology and manipulation of production strategies for the cultivation of biomass from four strains of microalgae. Species of microalgae studied are: Chlorella vulgaris Dunaliella Scenedesmus quadricauda and Synechococcus spp. The effects of the rate and amount of CO₂ removal from the atmosphere and sequestration with dissolved oxygen on lipid production from accumulated biomass were studied. Also the rate of sequestration of both total and dissolved carbon was  investigated. Daily measurements of total organic and inorganic carbon sequestrated optical densities proximate analysis and kinetic parameters of the growing and cultivated microalga were monitored and carried out during the two phases of cultivation: dark and light phases. The values of maximum rate of carbon (IV) oxide removed rmax varied from 11.73 mg L ^-1 min ^-1 to 18.84 mg L ^-1 min ^-1 from Chlorella vulgaris to Synechoccocus spp. Important parameters such as biomass productivity maximum pH values obtained at cultivation lipid content of the produced biomass and the hydraulic detection time for all four strains of microalgae were considered and presented in comparison and with their individual and collective effects. The ratios of the rate of CO₂ absorption constant and the constant for the CO₂ desorption rate (k1/k2) occurred highest in Dunaliella suggesting that with a high uptake of CO₂ the algal strain is more effective in CO₂ CO2 sequestration. The best biomass producer in this study was the C. vulgaris (Xmax = 5400 mg L^-1 and Px = 35.1 mg L h ^-1) where biomass productivity is Px and the maximum cellular concentration is Xmax. C. vulgaris has the highest lipids productivity of 27% while Synechoccocus has the least (11.72%). In general biomass productivity may be inversely related; this fact may be explained by greater metabolic involvement of lipid biosynthesis. This pioneer study may be advanced further to developing models for strategic manipulation and optimisation approach in micro algal biomass cultivation.

Anion exchange membrane (AEM) water electrolysis is considered a promising solution to future cost reduction of electrochemically produced hydrogen. We present an AEM water electrolyzer with CuCoOx as the anode catalyst and Aemion as membrane and electrode binder. Full cell experiments in pure water and 0.1 M KOH revealed that the optimum binder content depended on the type of electrolyte employed. Online dissolution measurements suggested that Aemion alone was not sufficient to establish an alkaline environment for thermodynamically stabilizing the synthesized CuCoOx in a neutral electrolyte feed. A feed of base is thus indispensable to ensure the thermodynamic stability of such non-noble catalyst materials. Particle loss and delamination of the catalyst layer during MEA operation could be reduced by employing a heat treatment step after electrode fabrication. This work summarizes possible degradation pathways for low-cost anodes in AEMWE and mitigation strategies for enhanced system durability and performance.