Publications

Given that conversion efficiencies of incident solar radiation to liquid fuels e.g. H2 are of the order of a few percent or less as quantified by ‘solar to hydrogen’ (STH) economically inexpensive and operationally straightforward ways to boost photo-electrochemcial (PEC) H2 production from solar-driven water splitting are important. In this work externally-applied static electric fields have led to enhanced H2 production in an energy-efficient manner with up to ~30–40% increase in H2 (bearing in mind fieldinput energy) in a prototype open-type solar cell featuring rutile/titania and hematite/iron-oxide (Fe2O3) respectively in contact with an alkaline aqueous medium (corresponding to respective relative increases of STH by ~12 and 16%). We have also performed non-equilibrium ab-initio molecular dynamics in both static electric and electromagnetic (e/m) fields for water in contact with a hematite/iron-oxide (0 0 1) surface observing enhanced break-up of water molecules by up to ~70% in the linear-response régime. We discuss the microscopic origin of such enhanced water-splitting based on experimental and simulation-based insights. In particular we external-field direction at the hematite surfaces and scrutinise properties of the adsorbed water molecules and OH– and H3O+ species e.g. hydrogen bonds between water-protons and the hematite surfaces’ bridging oxygen atoms as well as interactions between oxygen atoms in adsorbed water molecules and underlying iron atoms.

The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC) in which with an optimal combination of hydrogen injection timing and controlled jet geometry the plume of the hydrogen jet is spark-ignited to accomplish combustion of a rich mixture. This combustion process markedly improves thermal efficiency by reducing cooling loss which is essential for increasing thermal efficiency in a hydrogen engine while maintaining high power. In order to improve thermal efficiency and reduce NOx formation further PCC was applied to a lean-burn regime to burn a leaner mixture globally. In this study the effect of supercharging which was applied to recover the reduced output power due to the leaner mixture on improving thermal efficiency was confirmed along with clarifying the cause.

The aim of this study is to assess numerically the influence of terrain landscape on the distribution of probable harmful consequences to personnel of hydrogen fueling station caused by an accidentally released and exploded hydrogen. In order to extract damaging factors of the hydrogen explosion wave (maximum overpressure and impulse of pressure phase) a three-dimensional mathematical model of gas mixture dynamics with chemical interaction is used. It allows controlling current pressure in every local point of actual space taking into account complex terrain. This information is used locally in every computational cell to evaluate the conditional probability of such consequences on human beings as ear-drum rupture and lethal ones on the basis of probit analysis. In order to use this technique automatically during the computational process the tabular dependence ""probit-functionimpact probability"" is replaced by a piecewise cubic spline. To evaluate the influence of the landscape profile on the non-stationary three-dimensional overpressure distribution above the earth surface near an epicenter of accidental hydrogen explosion a series of computational experiments with different variants of the terrain is carried out. Each variant differs in the level of mutual arrangement of the explosion epicenter and the places of possible location of personnel. Two control points with different distances from the explosion epicenter are considered. Diagrams of lethal and ear-drum rupture conditional probabilities are build to compare different variants of landscape profile. It is found that the increase or decrease in the level of the location of the control points relative to the level of the epicenter of the explosion significantly changes the scale of the consequences in the actual zone around the working places and should be taken into account by the risk managing experts at the stage of deciding on the level of safety at hydrogen fueling stations.

Decarbonization in several countries is now linked to the prospect of implementing a national hydrogen economy. In countries with extensive natural gas infrastructure hydrogen may provide a real opportunity to decarbonize space heating. While this approach may prove technically and economically feasible in the longterm it is unclear whether consumers will be willing to adopt hydrogen-fueled appliances for heating and cooking should techno-economic feasibility be achieved. In response this paper develops an analytical framework for examining hydrogen acceptance which links together socio-technical barriers and social acceptance factors. Applying this framework the study synthesizes the existing knowledge on public perceptions of hydrogen and identifies critical knowledge gaps which should be addressed to support domestic hydrogen acceptance. The paper demonstrates that a future research agenda should account for the interactions between acceptance factors at the attitudinal socio-political market community and behavioral level. The analysis concludes that hydrogen is yet to permeate the public consciousness due to a lack of knowledge and awareness owing to an absence of information dissemination. In response consumer engagement in energy markets and stronger public trust in key stakeholders will help support social acceptance as the hydrogen transition unfolds. Affordability may prove the most critical barrier to the large-scale adoption of hydrogen homes while the disruptive impacts of the switchover and distributional injustice represent key concerns. As a starting point the promise of economic environmental and community benefits must be communicated and fulfilled to endorse the value of hydrogen homes.

Supercritical water gasification is a promising technology for wet biomass utilization. In this paper Ni and other metal catalysts were synthesized by wet impregnation. The stability and catalytic activities of Ni catalysts were evaluated. Firstly catalytic activities of Ni Fe Cu catalysts supported on MgO were tested using wheat straw as raw material in a batch reactor at 723 K and water density of 0.07 cm³/g. Experimental results showed that the order of metal catalyst activity for hydrogen generation was Ni/MgO > Fe/MgO > Cu/MgO. Secondly the influence of different supports on Ni catalysts performance was investigated. The results showed that the order of the Ni catalysts’ activity with different supports was Ni/MgO > Ni/ZnO > Ni/Al2O3 > Ni/ZrO2. Finally the effects of Ni loading and the amount of Ni catalyst addition on hydrogen production and the stability of Ni/MgO catalyst were studied. It was found that serious deactivation of Ni catalyst in the process of supercritical water gasification took place. Even if carbon deposited on the catalyst surface was removed by high temperature calcination and the catalyst was reduced with hydrogen the activity of used catalyst was only partially restored.

This paper discusses the performance improvement of a green building by optimization procedures and the influences of load characteristics on optimization. The green building is equipped with a self-sustained hybrid power system consisting of solar cells wind turbines batteries proton exchange membrane fuel cell (PEMFC) electrolyzer and power electronic devices. We develop a simulation model using the Matlab/SimPowerSystemTM and tune the model parameters based on experimental responses so that we can predict and analyze system responses without conducting extensive experiments. Three performance indexes are then defined to optimize the design of the hybrid system for three typical load profiles: the household the laboratory and the office loads. The results indicate that the total system cost was reduced by 38.9% 40% and 28.6% for the household laboratory and office loads respectively while the system reliability was improved by 4.89% 24.42% and 5.08%. That is the component sizes and power management strategies could greatly improve system cost and reliability while the performance improvement can be greatly influenced by the characteristics of the load profiles. A safety index is applied to evaluate the sustainability of the hybrid power system under extreme weather conditions. We further discuss two methods for improving the system safety: the use of sub-optimal settings or the additional chemical hydride. Adding 20 kg of NaBH4 can provide 63 kWh and increase system safety by 3.33 2.10 and 2.90 days for the household laboratory and office loads respectively. In future the proposed method can be applied to explore the potential benefits when constructing customized hybrid power systems.

The extensive usage of fossil fuels has caused significant environmental pollution climate change and energy crises. The significant advantages of hydrogen such as cleanliness high efficiency and a wide range of sources make it quite promising. Hydrogen is prone to material damage which may lead to leakage. High-pressure leaking hydrogen is highly susceptible to spontaneous combustion due to its combustion characteristics which may cause jet fire or explosion accidents resulting in serious casualties and property damage. This paper presents a detailed review of the research progress on hydrogen leak diffusion characteristics leak spontaneous combustion mechanisms and material hydrogen damage mechanisms from the perspectives of theoretical analysis experiments and numerical simulations. This review points out that although a large number of research results have been obtained on the safety characteristics of hydrogen there are still some deficiencies and limitations. Further research topics are clarified such as further optimizing the kinetic mechanism of the high-pressure hydrogen leakage reaction and turbulence model exploring the expansion and dilution law of hydrogen clouds after liquid hydrogen flooding further studying the spontaneous combustion mechanism of leaked hydrogen and the interaction between mechanisms and investigating the synergistic damage effect of hydrogen and other components on materials. The leakage spontaneous combustion process in open space the development process of the bidirectional effect of hydrogen jet fuel and crack growth under the impact of high-pressure hydrogen jet fuel on the material may need to be explored next.

IGEM/SR/23 (“Venting of natural gas”) provides recommendations for the conceptual design operation and safety aspects of permanent temporary and emergency venting of natural gas. The document was originally developed many years ago and the current edition dates to 1995. The document is due to be reviewed and updated for application to natural gas but the aim of this study is not to review the applicability of the document for natural gas but to assess the possible impact of 100% hydrogen on specific aspects of the existing guidance.<br/>A key element of the guidance concerns the safe dispersion distances for natural gas as vents are intended to provide a means of safely dispersing gas in the atmosphere without ignition. Guidance on safe dispersion distances for venting are provided in Section 6.6 accompanied by graphs showing the relationship between the mass flow rate through the vent and the safe (horizontal) dispersion distance. Details of the model used to predict the dispersion distances are given in Appendix 1. However for dispersion the guidance in IGEM/SR/23 has been superseded by similar guidance on hazard distances for unignited releases in IGEM/SR/25 (“Hazardous area classification of natural gas installations”) [2]. A comprehensive review of the applicability of IGEM/SR/25 to hydrogen is already underway for the LTS Futures project and is not duplicated here.<br/>However IGEM/SR/23 contains guidance on other important aspects relevant to the safe design and operation of vents which are not addressed elsewhere in the IGEM suite of standards; in particular guidance on hazard ranges for thermal radiation (in the event of an unplanned ignition of the venting gas) and noise.<br/>The main aim of this report is to assess the potential impact of replacing natural gas with 100% hydrogen on the guidance in IGEM/SR/23 concerned with thermal hazards with a secondary objective of assessing the available information to comment on the possible influence of hydrogen on noise.

In this report a 5 kW PEFC system running on dry hydrogen with an appropriately sized Balance of Plant (BoP) was used to conduct experimental studies and analyses of gas supply subsystems. The improper rating and use of BoP components has been found to increase parasitic loads which consequently has a direct effect on the polymer electrolyte fuel cell (PEFC) system efficiency. Therefore the minimisation of parasitic loads while maintaining desired performance is crucial. Nevertheless little has been found in the literature regarding experimental work on large stacks and BoP with the majority of papers concentrating on modelling. A particular interest of our study was the anode side of the fuel cell. Additionally the rationale behind the use of hydrogen anode recirculation was scrutinised and a novel anode purging strategy was developed and implemented. Through experimental modelling the use of cathode air blower was minimised since it was found to be the biggest contributor to the parasitic loads.

There is a great deal of knowledge and experience on the safe handling of hydrogen and the safe operation and management of hydrogen systems in South Africa. This knowledge and experience mostly sits within large gas supply companies and other large producers and consumers of hydrogen. However there appears to be less experience leading to a level of discomfort within regulatory bodies such as provincial and municipal fire departments and the national standards association. This compounded by a national policy of disallowing gas cylinders indoors has resulted in delays and indeed stalling in the process of obtaining permission to operate laboratories such as those of the national hydrogen programme HySA. In an effort to break this impasse two workshops were organised by HySA. The first was held at the CSIR’s facilities in Pretoria in October 2016. The second was held at the campus of the University of the Western Cape in Cape Town in May 2018. Four international experts and local experts in hydrogen regulations codes standards and safety addressed the 50-strong South African audiences via 5-way videoconferencing. This proved to be a very powerful tool to educate the audience and in particular the Tshwane (Pretoria) and Western Cape Fire Departments on the real issues risks and safety of hydrogen. The paper describes the South African Hydrogen RCS landscape the organisation and running of the workshops and the outputs achieved.