- Home
- A-Z Publications
- Publications
Publications
Everything About Hydrogen Podcast: So, What's the Big Deal with Hydrogen?
Aug 2019
Publication
This episode is a whistle-stop tour of the hydrogen world. The team explore why hydrogen is making a resurgence as an energy carrier how decarbonising the existing hydrogen market is a huge opportunity and how fuel cells fit into the story.
The podcast can be found on their website
The podcast can be found on their website
Hybrid Hydrogen PEM Fuel Cell and Batteries Without DC–DC Converter
Sep 2013
Publication
Concerns about greenhouse gases as well as the price and security of oil supply have acted as a spur to sustainable automobile development. The hydrogen fuel cells electric vehicle (HFCEV) is generally recognised by leading automobile manufacturers and scientists as one of the optimum technologies for long-term future low carbon vehicle. In a typical HFCEV power train a DC–DC converter is required to balance the voltage difference between the fuel cells (FCs) stack and batteries. However research shows that a considerable amount of energy generated by the hydrogen FCs stack is deplete during this conversion process as heat. This experiment aims to improve the power train efficiency by eliminating the DC–DC converter by finding the best combination of FC stack and batteries matching the size and capacity of the electrical components.
Autonomous Hydrogen Production for Proton Exchange Membrane Fuel Cells PEMFC
Apr 2020
Publication
This paper focuses on hydrogen production for green mobility applications (other applications are currently under investigation). Firstly a brief state of the art of hydrogen generation by hydrolysis with magnesium is shown. The hydrolysis performance of Magnesium powder ball–milled along with different additives (graphite and transition metals TM = Ni Fe and Al) is taken for comparison. The best performance was observed with Mg–10 wt.% g mixtures (95% of theoretical hydrogen generation yield in about 3 min). An efficient solution to control this hydrolysis reaction is proposed to produce hydrogen on demand and to feed a PEM fuel cell. Tests on a bench fitted with a 100 W Proton Exchange Membrane (PEM) fuel cell have demonstrated the technological potential of this solution for electric assistance applications in the field of light mobility.
Characterization of the Hazards from Jet Releases of Hydrogen
Sep 2005
Publication
Hydrogen is a convenient energy storage medium; it can be produced from fossil fuels and biomass via chemical conversion processes or from intermittent renewable sources like wind and solar via electrolysis. It is the fuel of choice for the clean fuel-cell vehicles of the future. If the general public are to use hydrogen as a vehicle fuel customers must be able to handle hydrogen with the same degree of confidence and with comparable risk as conventional liquid and gaseous fuels. For the safe design of retail facilities through the development of appropriate codes and standards it is essential to understand all the hazards that could arise following an accidental release of hydrogen. If it is to be stored and used as a high-pressure gas the hazards associated with jet releases from accidental leaks must be considered. This paper describes work by Shell and the Health and Safety Laboratory to characterise the hazards from jet releases of hydrogen. Jet release experiments have been carried out using small leaks (circular holes ranging from 1 mm to 12 mm diameter) at system pressures up to 150 barg. Concentration measurements were made in the unignited free jets to determine the extent of the flammable cloud generated. Ignited jets were observed both in the visible and infrared to determine the flame size and shape. The experimental results for the extent of the flammable cloud and jet flame length were found to be in good agreement with model predictions.
Narratives for Natural Gas in a Decarbonising European Energy Market
Feb 2019
Publication
The advocacy narrative of the European Union gas community which focused on coal to gas switching and backing up renewables has failed to convince governments NGOs and media commentators that it can achieve post-2030 decarbonisation targets. The gas community therefore needs to develop decarbonisation narratives showing how it will develop commercial scale projects for biogas biomethane and hydrogen from power to gas (electrolysis) and reformed methane. COP21 carbon targets require an accelerating decline in EU methane demand starting around 2030. In 2050 the maximum projected availability of renewable gas is equivalent to 25 per cent of current EU gas demand. Maintaining current demand levels will therefore require very substantial volumes of hydrogen from reformed methane with carbon capture and storage (CCS). Pipeline gas and LNG suppliers will need to progressively decarbonise their product if it is to remain saleable in Europe. However networks face an existential threat unless they can maintain existing throughput while simultaneously adapting to a decarbonised product. Significant threats and challenges to these narratives include: short term geopolitical concerns stemming from dependence on Russian gas ‘hydrocarbon rejectionism’ and an inability of companies to invest for a post-2030 decarbonised future. Governments will need to shift current policy and regulatory frameworks from competition to decarbonisation which will require a ‘regulatory revolution’. In addition to government funding and regulatory support there will need to be very substantial corporate investment in projects for which there is currently no business case. Failure of the gas community to create and deliver credible decarbonisation narratives is likely to result in the adoption of electrification rather than gas decarbonisation options.
Hydrogen Double Compression-expansion Engine (H2DCEE): A Sustainable Internal Combustion Engine with 60%+ Brake Thermal Efficiency Potential at 45 Bar BMEP
May 2022
Publication
Hydrogen (H2) internal combustion engines may represent cost-effective and quick solution to the issue of the road transport decarbonization. A major factor limiting their competitiveness relative to fuel cells (FC) is the lower efficiency. The present work aims to demonstrate the feasibility of a H2 engine with FC-like 60%+ brake thermal efficiency (BTE) levels using a double compression-expansion engine (DCEE) concept combined with a high pressure direct injection (HPDI) nonpremixed H2 combustion. Experimentally validated 3D CFD simulations are combined with 1D GT-Power simulations to make the predictions. Several modifications to the system design and operating conditions are systematically implemented and their effects are investigated. Addition of a catalytic burner in the combustor exhaust insulation of the expander dehumidification of the EGR and removal of the intercooling yielded 1.5 1.3 0.8 and 0.5%-point BTE improvements respectively. Raising the peak pressure to 300 bar via a larger compressor further improved the BTE by 1.8%-points but should be accompanied with a higher injector-cylinder differential pressure. The λ of ~1.4 gave the optimum tradeoff between the mechanical and combustion efficiencies. A peak BTE of 60.3% is reported with H2DCEE which is ~5%-points higher than the best diesel-fueled DCEE alternative.
The Benefit of Collaboration in the North European Electricity System Transition—System and Sector Perspectives
Dec 2019
Publication
This work investigates the connection between electrification of the industry transport and heat sector and the integration of wind and solar power in the electricity system. The impact of combining electrification of the steel industry passenger vehicles and residential heat supply with flexibility provision is evaluated from a systems and sector perspective. Deploying a parallel computing approach to the capacity expansion problem the impact of flexibility provision throughout the north European electricity system transition is investigated. It is found that a strategic collaboration between the electricity system an electrified steel industry an electrified transport sector in the form of passenger electric vehicles (EVs) and residential heat supply can reduce total system cost by 8% in the north European electricity system compared to if no collaboration is achieved. The flexibility provision by new electricity consumers enables a faster transition from fossil fuels in the European electricity system and reduces thermal generation. From a sector perspective strategic consumption of electricity for hydrogen production and EV charging and discharging to the grid reduces the number of hours with very high electricity prices resulting in a reduction in annual electricity prices by up to 20%.
Consumer Attitudes to Fuel Cell Vehicles Post Trial in the United Kingdom
Mar 2016
Publication
Fuel cell vehicles (FCVs) have clear societal and environmental benefits and can help mitigate the issues of climate change urban air pollution and oil dependence. In order for FCVs to have the biggest impact on these issues they need to be employed in large numbers. First though they need to be adopted by consumers. Their acceptance depends on positive consumer attitudes towards the vehicles. Currently there is a limited understanding within the literature on how consumers perceive FCVs and what the likelihood of adoption by consumers would be despite significant governmental and organisational investments into the technology. Therefore this study assesses consumer attitudes towards FCVs in the United Kingdom. 81 persons drove a Hyundai FCV at the Low Carbon Vehicle Event in September 2015 of which 30 took part in this study. The results show that at present FCVs are perceived mostly as being similar to incumbent internal combustion engine vehicles. This is an admirable technical achievement however in order for consumers to adopt FCVs they will need to be perceived as having distinctive benefits. Two significant barriers to the adoption of FCVs are observed in this sample: high costs and lack of refuelling infrastructure. This paper goes on to make suggestions on how and which beneficial attributes of the vehicles can be promoted to consumers and also makes suggestions on how the barriers can be overcame so that FCVs will be adopted by consumers.
Strategies for the Sampling of Hydrogen at Refuelling Stations for Purity Assessment
Aug 2021
Publication
Hydrogen delivered at hydrogen refuelling station must be compliant with requirements stated in different standards which require specialized sampling device and personnel to operate it. Currently different strategies are implemented in different parts of the world and these strategies have already been used to perform 100s of hydrogen fuel sampling in USA EU and Japan. However these strategies have never been compared on a large systematic study. The purpose of this paper is to describe and compare the different strategies for sampling hydrogen at the nozzle and summarize the key aspects of all the existing hydrogen fuel sampling including discussion on material compatibility with the impurities that must be assessed. This review highlights the fact it is currently difficult to evaluate the impact or the difference these strategies would have on the hydrogen fuel quality assessment. Therefore comparative sampling studies are required to evaluate the equivalence between the different sampling strategies. This is the first step to support the standardization of hydrogen fuel sampling and to identify future research and development area for hydrogen fuel sampling.
Particle Size and Crystal Phase Effects in Fischer-Tropsch Catalysts
Aug 2017
Publication
Fischer-Tropsch synthesis (FTS) is an increasingly important approach for producing liquid fuels and chemicals via syngas—that is synthesis gas a mixture of carbon monoxide and hydrogen—generated from coal natural gas or biomass. In FTS dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles which depend on the particle size morphology and crystallographic phase of the nanoparticles. In this article we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active selective and stable FTS catalysts.
The Sector Coupling Concept: A Critical Review
Jun 2020
Publication
Pursued climate goals require reduced greenhouse gas emissions by substituting fossil fuels with energy from renewable sources in all energy-consuming processes. On a large-scale this can mainly be achieved through electricity from wind and sun which are subject to intermittency. To efficiently integrate this variable energy a coupling of the power sector to the residential transport industry and commercial/trade sector is often promoted called sector coupling (SC). Nevertheless our literature review indicates that SC is frequently misinterpreted and its scope varies among available research from exclusively considering the use of excess renewable electricity to a rather holistic view of integrated energy systems including excess heat or even biomass sources. The core objective of this article is to provide a thorough understanding of the SC concept through an analysis of its origin and its main purpose as described in the current literature. We provide a structured categorization of SC derived from our findings and critically discuss its remaining challenges as well as its value for renewable energy systems. We find that SC is rooted in the increasing use of variable renewable energy sources and its main assets are the flexibility it provides for renewable energy systems decarbonization potential for fossil-fuel-based end-consumption sectors and consequently reduced dependency on oil and gas extracting countries. However the enabling technologies face great challenges in their economic feasibility because of the uncertain future development of competing solutions.
Refuelling Infrastructure Requirements for Renewable Hydrogen Road Fuel through the Energy Transition
Nov 2022
Publication
Current commercially available options for decarbonisation of road transport are battery electric vehicles or hydrogen fuel cell electric vehicles. BEVs are increasingly deployed while hydrogen is in its infancy. We examine the infrastructure necessary to support hydrogen fuelling to various degrees of market penetration. Scotland makes a good exemplar of transport transition with a world leading Net-Zero ambition and proven pathways for generating ample renewable energy. We identified essential elements of the new transport systems and the associated capital expenditure. We developed nine scenarios based on the pace of change and the ultimate market share of hydrogen and constructed a model to analyse their infrastructure requirements. This is a multi-period model incorporating Monte Carlo and Markov Chain elements. A “no-regrets” initial action is rapid deployment of enough hydrogen infrastructure to facilitate the early years of a scenario where diesel fuel becomes replaced with hydrogen. Even in a lower demand scenario of only large and heavy goods vehicles using hydrogen the same infrastructure would be required within a further two years. Subsequent investment in infrastructure could be considered in the light of this initial development.
Numerical Characterization of Under-expanded Cryogenic Hydrogen Gas Jets
Sep 2022
Publication
High-resolution direct numerical simulations are conducted for under-expanded cryogenic hydrogen gas jets to characterize the nearfield flow physics. The basic flow features and jet dynamics are analyzed in detail revealing the existence of four stages during early jet development namely (a) initial penetration (b) establishment of near-nozzle expansion (c) formation of downstream compression and (d) wave propagation. Complex acoustic waves are formed around the under-expanded jets. The jet expansion can also lead to conditions for local liquefaction from the pressurized cryogenic hydrogen gas release. A series of simulations are conducted with systematically varied nozzle pressure ratios and systematically changed exit diameters. The acoustic waves around the jets are found to waken with the decrease in the nozzle pressure ratio. The increase in the nozzle pressure ratio is found to accelerate hydrogen dispersion and widen the regions with hydrogen liquefaction potential. The increase in the nozzle exit diameter also widens the region with hydrogen liquefaction potential but slows down the evolution of the flow structures.
Recent Development of Biomass Gasification for H2 Rich Gas Production
Mar 2022
Publication
Biomass gasification for hydrogen (H2) production provides outstanding advantages in terms of renewable energy resources carbon neutral high efficiency and environmental benefits. However the factors influencing H2 production from biomass gasification are complex which makes determining the optimal operating conditions challenging. Biomass gasification also poses challenges owing to the high associated tar content and low gas yield which need to be overcome. This review summarizes the influence of the gasification parameters on H2 production. Catalytic gasification technology and some of the latest catalysts such as composites and special structure catalysts are also summarized herein based on the requirements of high-purity H2 production. Moreover novel technologies such as staged gasification chemical looping gasification and adsorption-enhanced reforming for producing H2 rich gas are introduced. Finally the challenges and prospects associated with biomass gasification for H2 production are presented.
Exploring the Complexity of Hydrogen Perception and Acceptance Among Key Stakeholders in Norway
Nov 2022
Publication
This article explores the complexity of factors or mechanisms that can influence hydrogen stakeholder perception and acceptance in Norway. We systematically analyze 16 semi-structured in-depth interviews with industry stakeholders at local municipal regional and national levels of interest and authority in Norway. Four empirical dimensions are identified that highlight the need for whole system approaches in hydrogen technology research: (1) several challenges incentives and synergy effects influence the hydrogen transition; (2) transport preferences are influenced by combined needs and limitations; (3) levels of knowledge and societal trust determinant to perceptions of risk and acceptance; and (4) national and international hydrogen stakeholders are crucial to building incentives and securing commitment among key actors. Our findings imply that project management planners engineers and policymakers need to apply a whole system perspective and work across local regional and national levels before proceeding with large-scale development and implementation of the hydrogen supply chain.
Operation of a Circular Economy, Energy, Environmental System at a Wastewater Treatment Plant
Oct 2022
Publication
Decarbonising economies and improving environment can be enhanced through circular economy energy and environmental systems integrating electricity water and gas utilities. Hydrogen production can facilitate intermittent renewable electricity through reduced curtailment of electricity in periods of over production. Positioning an electrolyser at a wastewater treatment plant with existing sludge digesters offers significant advantages over stand-alone facilities. This paper proposes co-locating electrolysis and biological methanation technologies at a wastewater treatment plant. Electrolysis can produce oxygen for use in pure or enhanced oxygen aeration offering a 40% reduction in emissions and power demand at the treatment facility. The hydrogen may be used in a novel biological methanation system upgrading carbon dioxide (CO2)in biogas from sludge digestion yielding a 54% increase in biomethane production. A 10MW electrolyser operating at 80% capacity would be capable of supplying the oxygen demand for a 426400 population equivalent wastewater treatment plant producing 8500 tDS/a of sludge. Digesting the sludge could generate 1409000 m 3 CH4/a and 776000 m 3 CO2/a. Upgrading the CO2 to methane would consume 22.2% of the electrolyser generated hydrogen and capture 1.534 ktCO2e/a. Hydrogen and methane are viable advanced transport fuels that can be utilised in decarbonising heavy transport. In the proposed circular economy energy and environment system sufficient fuel would be generated annually for 94 compressed biomethane gas (CBG) heavy goods vehicles (HGV) and 296 compressed hydrogen gas fuel cell (CHG) HGVs. Replacement of the equivalent number of diesel HGVs would offset approximately 16.1 ktCO2e/a.
Comparative Study of Spark-Ignited and Pre-Chamber Hydrogen-Fueled Engine: A Computational Approach
Nov 2022
Publication
Hydrogen is a promising future fuel to enable the transition of transportation sector toward carbon neutrality. The direct utilization of H2 in internal combustion engines (ICEs) faces three major challenges: high NOx emissions severe pressure rise rates and pre-ignition at mid to high loads. In this study the potential of H2 combustion in a truck-size engine operated in spark ignition (SI) and pre-chamber (PC) mode was investigated. To mitigate the high pressure rise rate with the SI configuration the effects of three primary parameters on the engine combustion performance and NOx emissions were evaluated including the compression ratio (CR) the air–fuel ratio and the spark timing. In the simulations the severity of the pressure rise was evaluated based on the maximum pressure rise rate (MPRR). Lower compression ratios were assessed as a means to mitigate the auto-ignition while enabling a wider range of engine operation. The study showed that by lowering CR from 16.5:1 to 12.5:1 an indicated thermal efficiency of 47.5% can be achieved at 9.4 bar indicated mean effective pressure (IMEP) conditions. Aiming to restrain the auto-ignition while maintaining good efficiency growth in λ was examined under different CRs. The simulated data suggested that higher CRs require a higher λ and due to practical limitations of the boosting system λ at 4.0 was set as the limit. At a fixed spark timing using a CR of 13.5 combined with λ at 3.33 resulted in an indicated thermal efficiency of 48.6%. It was found that under such lean conditions the exhaust losses were high. Thus advancing the spark time was assessed as a possible solution. The results demonstrated the advantages of advancing the spark time where an indicated thermal efficiency exceeding 50% was achieved while maintaining a very low NOx level. Finally the optimized case in the SI mode was used to investigate the effect of using the PC. For the current design of the PC the results indicated that even though the mixture is lean the flame speed of H2 is sufficiently high to burn the lean charge without using a PC. In addition the PC design used in the current work induced a high MPRR inside the PC and MC leading to an increased tendency to engine knock. The operation with PC also increased the heat transfer losses in the MC leading to lower thermal efficiency compared to the SI mode. Consequently the PC combustion mode needs further optimizations to be employed in hydrogen engine applications.
Low Temperature Autoignition of Diesel Fuel Under Dual Operation with Hydrogen and Hydrogen-carriers
Mar 2022
Publication
While electrification of light duty vehicles is becoming a real solution to abate local pollutant as well as greenhouse gases emission heavy duty applications (such as long distance freight and maritime transport) will keep requiring fuel-based propulsion systems. In these sectors dominated by compression ignition engines research on alternative biofuels and new combustion modes is still highly necessary. Dual-fuel combustion appears as a very promising concept to replace conventional diesel fuel by sustainable ones. Among the latter hydrogen-derived fuels (the so-called electrofuels or e-fuels) are maybe the most interesting. This work addresses the effect of partial substitution of diesel fuel by hydrogen and hydrogen-carriers (ammonia and methane) on the autoignition process under low temperature conditions. Tests were carried out in a constant volume combustion chamber at different temperatures (535 600 and 650 ◦C) and pressures (11 16 and 21 bar). While the cool flames timing and intensity was only slightly affected by the low reactivity fuel energy content the main ignition was delayed this effect being much more noticeable for ammonia followed by hydrogen and finally methane. Kinetic simulations showed a clear competition for active radicals between both fuels (diesel and low reactivity fuel). The combustion duration also increased with the hydrogen or hydrogen-carrier content which greatly points to the need of modifications in the injection strategy of compression ignition engines operating under dual mode. A correlation was proposed for estimating the autoignition delay time for dual-fuel lean combustion at low temperature.
Development of Dispensing Hardware for Safe Fueling of Heavy Duty Vehicles
Sep 2021
Publication
The development of safe dispensing equipment for the fueling of heavy duty (HD) vehicles is critical to the expansion of this newly and quickly expanding market. This paper discusses the development of a HD dispenser and nozzles assembly (nozzle hose breakaway) for these new larger vehicles where flow rates are more than double compared to light duty (LD) vehicles. This equipment must operate at nominal pressures of 700 bar -40o C gas temperature and average flow rate of 5-10 kg/min at a high throughput commercial hydrogen fueling station without leaking hydrogen. The project surveyed HD vehicle manufacturers station developers and component suppliers to determine the basic specifications of the dispensing equipment and nozzle assembly. The team also examined existing codes and standards to determine necessary changes to accommodate HD components. From this information the team developed a set of specifications which will be used to design the dispensing equipment. In order to meet these goals the team performed computational fluid dynamic pressure modelling and temperature analysis in order to determine the necessary parameters to meet existing safety standards modified for HD fueling. The team also considered user operational and maintenance requirements such as freeze lock which has been an issue which prevents the removal of the nozzle from LD vehicles. The team also performed a failure mode and effects analysis (FMEA) to identify the possible failures in the design. The dispenser and nozzle assembly will be tested separately and then installed on an innovative HD fueling station which will use a HD vehicle simulator to test the entire system.
Numerical Study of the Effects of Tunnel Inclination and Ventilation on the Dispersion of Hydrogen Released from a Car
Sep 2021
Publication
Hydrogen cars are expected to play an important role in a decarbonised clean-transport future. Safety issues arise though in tunnels due to the possibility of accidental release and accumulation of hydrogen. This Computational Fluid Dynamics (CFD) study focuses on the effect of tunnel inclination and ventilation on hydrogen dispersion. A horseshoe shaped tunnel of 200 m length is considered in all seventeen cases examined. In most cases hydrogen is released from the bottom of a car placed at the center of the tunnel. Various inclinations in-tunnel wind speeds and fuel tank Pressure Relief Device (PRD) diameters were considered in order to assess their influence on safety. It was found that even if the long-term influence of the inclination is positive there is no systematic effect at initial stages nor at the most dangerous ‘nearly-stoichiometric’ cloud volumes (25% - 35% v/v). Adverse effects may also exist like the occasionally higher flammable cloud (4% - 75% v/v). Regarding ventilation it was found that even low wind speeds (e.g. 1 m/s) can reduce the flammable cloud by several times. However no significant effect on the total nearly-stoichiometric volumes was found for most of the cases examined. Ventilation can also cause adverse effects as for example at mid-term of the release duration in some cases. Concerning the PRD diameter a reduction from 4 mm to 2 mm resulted in about five times smaller maximum of the nearly-stoichiometric cloud volume. In addition the effect of release orientation on hydrogen cloud was examined and it was found that the downwards direction presents drawbacks compared to the backwards and upwards release directions.
No more items...