Publications

There are new safety challenges with an increased use of hydrogen e.g. that people may not see dangerous jet flames in case of an incident. Compared to conventional fuels hydrogen has very different characteristics and physical properties and is stored at very high pressure or at very low temperatures. Thus the nature of hazard scenarios will be very different. Consequence modelling of ventilation releases explosions and fires can be used to predict and thus understand hazards. In order to describe the detailed development of a hazard scenario and evaluate ways of mitigation 3D Computational Fluid Dynamics (CFD) models will be required. Even with accurate modelling the communication of risk can be challenging. For this visualization in virtual reality (VR) may be of good help in which the CFD model predictions are presented in a realistic 3D environment with the possibility to include sounds like noise from a high pressure release explosion or fire. In cooperation with Statoil Christian Michelsen Research (CMR) and GexCon have developed the VRSafety application. VRSafety can visualize simulation results from FLACS (and another CFD-tool KFX) in an immersive VR-lab or on a PC. VRSafety can further be used to interactively control and start new CFD-simulations during the sessions. The combination of accurate CFD-modelling visualization and interactive use through VRSafety represents a powerful toolbox for safety training and risk communication to first-responders employees media and other stakeholders. It can also be used for lessons learned sessions studying incidents and accidents and to demonstrate what went wrong and how mitigation could have prevented accidents from happening. This paper will describe possibilities with VRSafety and give examples of use.

Hydrogen (H2 ) can be a promising energy carrier for decarbonizing the economy and especially the transport sector which is considered as one of the sectors with high carbon emissions due to the extensive use of fossil fuels. H2 is a nontoxic energy carrier that could replace fossil fuels. Fuel Cell Electric Vehicles (FCEVs) can decrease air pollution and reduce greenhouse gases when H2 is produced from Renewable Energy Sources (RES) and at the same time being accessible through a widespread network of Hydrogen Refueling Stations (HRSs). In this study both the sizing of the equipment and financial analysis were performed for an HRS supplied with H2 from the excess electrical energy of a 10 MW wind park. The aim was to determine the optimum configuration of an HRS under the investigation of six different scenarios with various numbers of FCEVs and monthly demands as well as ascertaining the economic viability of each examined scenario. The effect of the number of vehicles that the installation can refuel to balance the initial cost of the investment and the fuel cost in remote regions was investigated. The results showed that a wind-powered HRS could be a viable solution when sized appropriately and H2 can be used as a storage mean for the rejected wind energy. It was concluded that scenarios with low FCEVs penetration have low economic performance since the payback period presented significantly high values.

"Because of the contrasting chemical kinetics of methane and hydrogen combustion the development of blending laws for laminar burning velocity ul and Markstein length for constituent mixtures of CH₄/air and H₂/air presents a formidable challenge. Guidance is sought through a study of analytical expressions for laminar burning velocity. For the prediction of burning velocities of blends six blending laws were scrutinised. The predictions were compared with the measured burning velocities made by Hu et al. under atmospheric conditions. These covered equivalence ratios ranging from 0.6 to 1.3 and the full fuel range for H₂ addition to CH₄. This enabled assessments to be made of the predictive accuracy of the six laws. The most successful law is one developed in the course of the present study involving the mass fraction weighting of the product of ul density heat of reaction and specific heat divided by the thermal conductivity of the mixture. There was less success from attempts to obtain a comparably successful blending law for the flame speed Markstein length Lb despite scrutiny of several possibilities. Details are given of two possible approaches one based on the fractional mole concentration of the deficient reactant. A satisfactory empirical law employs mass fraction weighting of the product ulLb.

This study is driven by the need to understand requirements to safe blow-down of hydrogen onboard storage tanks through a pressure relief device (PRD) inside a garage-like enclosure with low natural ventilation. Current composite tanks for high pressure hydrogen storage have been shown to rupture in 3.5–6.5 min in fire conditions. As a result a large PRD venting area is currently used to release hydrogen from the tank before its catastrophic failure. However even if unignited the release of hydrogen from such PRDs has been shown in our previous studies to result in unacceptable overpressures within the garage capable of causing major damage and possible collapse of the structure. Thus to prevent collapse of the garage in the case of a malfunction of the PRD and an unignited hydrogen release there is a clear need to increase blow-down time by reducing PRD venting area. Calculations of PRD diameter to safely blow-down storage tanks with inventories of 1 5 and 13 kg hydrogen are considered here for a range of garage volumes and natural ventilation expressed in air changes per hour (ACH). The phenomenological model is used to examine the pressure dynamics within a garage with low natural ventilation down to the known minimum of 0.03 ACH. Thus with moderate hydrogen flow rate from the PRD and small vents providing ventilation of the enclosure there will be only outflow from the garage without any air intake from outside. The PRD diameter which ensures that the pressure in the garage does not exceed a value of 20 kPa (accepted in this study as a safe overpressure for civil structures) was calculated for varying garage volumes and natural ventilation (ACH). The results are presented in the form of simple to use engineering nomograms. The conclusion is drawn that PRDs currently available for hydrogen-powered vehicles should be redesigned along with either a change of requirements for the fire resistance rating or innovative design of the onboard storage system as hydrogen-powered vehicles are intended for garage parking. Further research is needed to develop safety strategies and engineering solutions to tackle the problem of fire resistance of onboard storage tanks and requirements to PRD performance. Regulation codes and standards in the field should address this issue.

The scenario of detonative ignition in shocked mixture is significant because it is a contributor to deflagration to detonation transition for example following shock reflections. However even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into a combustible mixture is difficult because of the singular nature of the initial conditions. Initially as the shock starts moving into reactive mixture the region filled with reactive mixture has zero thickness. On a fixed grid the number of grid points between the shock and the contact surface increases as the shock moves away from the latter. Due to initial lack of resolution in the region of interest staircasing may occur whereby the resulting plots consist of jumps between few values a few grid points and these numerical artifacts are amplified by the chemistry which is very sensitive to temperature leading to unreliable results. The formulation is transformed replacing time and space by time and space over time as the independent variables. This frame of reference corresponds to the self-similar formulation in which the non-reactive problem remains stationary and the initial conditions are well-resolved. Additionally a solution obtained from short time perturbation is used as initial condition at a time still short enough for the perturbation to be very accurate but long enough so that there is sufficient resolution. The numerical solution to the transformed problem is obtained using an essentially non-oscillatory algorithm which is adequate not only for the early part of the process but also for the latter part when chemistry leads to appearance of a shock and eventually a detonation wave is formed. A validation study was performed and the results were compared with the literature for single step Arrhenius chemistry. The method and its implementation were found to be effective. Results are presented for values of activation energy ranging from mild to stiff.

As a developing country the Philippines must balance its rapid industrialization efforts with the realities and consequences of climate change on the country. A feasible option to achieve this is increasing the share of renewables in power generation coupled with energy storage technology. This paper examines the present situation and opportunities for development of hydrogen and fuel cell technology in the Philippines as promising alternatives with proven applications in niche energy demand sectors aside from renewables integration. Although the Philippines is considered a latecomer there is significant renewable resource potential available local experts and trained talents and enabling legislations in the country that provide opportunities in harnessing fuel cell technologies for the transition to energy self-sufficient and low-carbon society. Current advancement of the technology in the country is limited to an initial 5-year roadmap focused on component development from cheap and local materials. Provisions for large-scale hydrogen infrastructure have not yet been realized which is comparable to the early stages of development in other countries that are also pursuing fuel cell technology. Strong industry-academe partnerships should be pursued through a specific legislated agency to ensure future development of this technology for the country’s benefit. Lastly applications in distributed power generation poised to be a lucrative direction as demonstration and validation with other potential uses such as transportation remains a challenge.

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates electrical power energy efficiency Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance and this results in lower ohmic and activation resistances.

Experience makes a superior teacher. Sharing the details surrounding safety events is one of the best ways to help prevent their recurrence elsewhere. This approach requires an open non-punitive environment to achieve broad benefits. The Hydrogen Incident Reporting Tool (www.h2incidents.org) is intended to facilitate the sharing of lessons learned and other relevant information gained from actual experiences using and working with hydrogen and hydrogen systems. Its intended audience includes those involved in virtually any aspect of hydrogen technology systems and use with an emphasis towards energy and transportation applications. The database contains records of safety events both publicly available and/or voluntarily submitted. Typical records contain a general description of the occurrence contributing factors equipment involved and some detailing of consequences and changes that have been subsequently implemented to prevent recurrence of similar events in the future. The voluntary and confidential nature and other characteristics surrounding the database mean that any analysis of apparent trends in its contents cannot be considered statistically valid for a universal population. A large portion of reported incidents have occurred in a laboratory setting due to the typical background of the reporting projects for example. Yet some interesting trends are becoming apparent even at this early stage of the database’s existence and general lessons can already be taken away from these experiences. This paper discusses the database and a few trends that have already become apparent for the reported incidents. Anticipated future uses of this information are also described. This paper is intended to encourage wider participation and usage of the incidents reporting database and to promote the safety benefits offered by its contents.

Numerical simulations have been carried out for spontaneous ignition of pressurized hydrogen release directly into air. Results showed a possible mechanism for spontaneous ignition due to molecular diffusion. To accurately calculate the molecular transport of species momentum and energy in a multi-component gaseous mixture a mixture-averaged multi-component approach was employed in which thermal diffusion is accounted for. To reduce false numerical diffusion extremely fine meshes were used along with the ALE (Arbitrary Lagrangian-Eulerian) method. The ALE method was employed to track the moving contact surface with moving clustered grids. A detailed kinetic scheme with 21 elementary steps and 8 reactive chemical species was implemented for combustion chemistry. The scheme gives due consideration to third body reactions and reaction-rate pressure-dependant “fall-off” behavior. The autoignition of pressurized hydrogen release was previously observed in laboratory tests [2-3] and suspected as possible cause of some accidents. The present numerical study successfully captured this scenario. Autoignition was predicted to first take place at the tip region of the hydrogen-air contact surface due to mass and energy exchange between low temperature hydrogen and shock-heated air at the contact surface through molecular diffusion. The initial flame thickness is extremely thin due to the limiting molecular diffusion. The combustion region extends downward along the contact surface as it moves downstream. As the hydrogen jet developed downstream the front contact surface tends to be distorted by the developed flow of the air. Turbulence plays an important role in mixing at the region of the distorted contact surface. This is thought to be a major factor for the initial laminar flame to turn into a final stable turbulent flame.

Hydrogen production through methanol reforming processes has been stimulated over the years due to increasing interest in fuel cell technology and clean energy production. Among different types of methanol reforming the steam reforming of methanol has attracted great interest as reformate gas stream where high concentration of hydrogen is produced with a negligible amount of carbon monoxide. In this review recent progress of the main reforming processes of methanol towards hydrogen production is summarized. Different catalytic systems are reviewed for the steam reforming of methanol: mainly copper- and group 8–10-based catalysts highlighting the catalytic key properties while the promoting effect of the latter group in copper activity and selectivity is also discussed. The effect of different preparation methods different promoters/stabilizers and the formation mechanism is analyzed. Moreover the integration of methanol steam reforming process and the high temperature–polymer electrolyte membrane fuel cells (HT-PEMFCs) for the development of clean energy production is discussed.