An overview of hydrogen as a vehicle fuel

As hydrogen fuel cell vehicles move from manifestation to commercialization, the users expect safe, convenient and customer-friendly fuelling. Hydrogen quality affects fuel cell stack performance and lifetime, as well as other factors such as valve operation. In this paper, previous researcher's development on hydrogen as a possible major fuel of the future has been studied thoroughly. Hydrogen is one of the energy carriers which can replace fossil fuel and can be used as fuel in an internal combustion engines and as a fuel cell in vehicles. To use hydrogen as a fuel of internal combustion engine, engine design should be considered for avoiding abnormal combustion. As a result it can improve engine efficiency, power output and reduce NO_x emissions. The emission of fuel cell is low as compared to conventional vehicles but as penalty, fuel cell vehicles need additional space and weight to install the battery and storage tank, thus increases it production cost. The production of hydrogen can be ‘carbon-free’ only if it is generated by employing genuinely carbon-free renewable energy sources. The acceptability of hydrogen technology depends on the knowledge and awareness of the hydrogen benefits towards environment and human life. Recent study shows that people still do not have the sufficient information of hydrogen.     

The potential role of hydrogen as a sustainable transportation fuel to combat global warming

Hydrogen is recognized as a key source of the sustainable energy solutions. The transportation sector is known as one of the largest fuel consumers of the global energy market. Hydrogen can become a promising fuel for sustainable transportation by providing clean, reliable, safe, convenient, customer friendly, and affordable energy. In this study, the possibility of hydrogen as the major fuel for transportation systems is investigated comprehensively based on the recent data published in the literature. Due to its several characteristic advantages, such as energy density, abundance, ease of transportation, a wide variety of production methods from clean and renewable fuels with zero or minimal emissions; hydrogen appears to be a great chemical fuel which can potentially replace fossil fuel use in internal combustion engines. In order to take advantage of hydrogen as an internal combustion engine fuel, existing engines should be redesigned to avoid abnormal combustion. Hydrogen use in internal combustion engines could enhance system efficiencies, offer higher power outputs per vehicle, and emit lower amounts of greenhouse gases. Even though hydrogen-powered fuel cells have lower emissions than internal combustion engines, they require additional space and weight and they are generally more expensive. Therefore, the scope of this study is hydrogen-fueled internal combustion engines. It is also highlighted that in order to become a truly sustainable and clean fuel, hydrogen should be produced from renewable energy and material resources with zero or minimal emissions at high efficiencies. In addition, in this study, conventional, hybrid, electric, biofuel, fuel cell, and hydrogen fueled ICE vehicles are comparatively assessed based on their CO₂ and SO₂ emissions, social cost of carbon, energy and exergy efficiencies, fuel consumption, fuel price, and driving range. The results show that when all of these criteria are taken into account, fuel cell vehicles have the highest average performance ranking (4.97/10), followed by hydrogen fueled ICEs (4.81/10) and biofuel vehicles (4.71/10). On the other hand, conventional vehicles have the lowest average performance ranking (1.21/10), followed by electric vehicles (4.24/10) and hybrid vehicles (4.53/10).     

Liquid hydrogen as a vehicular fuel—a challenge for cryogenic engineering

Present and developing technologies of liquid hydrogen onboard storage and handling are reviewed. Substantial improvement in operating hydrogen fueled internal combustion engines can be made by intense use of the cold hydrogen gas available from the LH₂-fuel tank. Because of the large heat sink capability of liquid hydrogen the volumetric heating value of the cylinder charge can be increased considerably even for external mixture formation. Further success in hydrogen engine development will depend mainly upon the development of suitable internal fuel mixing techniques based on cryogenic liquid fuel injection pumps.     

An onboard hydrogen generator for hydrogen enhanced combustion with internal combustion engine

Hydrogen enhanced combustion (HEC) for internal combustion engine is known to be a simple mean for improving engine efficiency in fuel saving and cleaner exhaust. An onboard compact and high efficient methanol steam reformer is made and installed in the tailpipe of a vehicle to produce hydrogen continuously onboard by using the waste heat of the engine for heating up the reformer; this provides a practical device for the HEC to become a reality. This use of waste heat from engine enables an extremely high process efficiency of 113% to convert methanol (8.68 MJ) for 1.0 NM of hydrogen (9.83 MJ) and low cost of using hydrogen as an enhancer or as a fuel itself. The test results of HEC from the onboard hydrogen production are presented with 2 gasoline engine vehicles and 2 diesel engines; the results indicate a hike of engine efficiency in 15–25% fuel saving and a 40–50% pollutants reduction including 70% reduction of exhaust smoke. The use of hydrogen as an enhancer brings about 2–3 fold of net reductions in energy, carbon dioxide emission and fuel cost expense over the input of methanol feed for hydrogen production.     

Ethanol–electric propulsion as a sustainable technological alternative for urban buses in Brazil

The option of fitting electric motors to vehicles that are more efficient and quieter than internal combustion engines has been hampered considerably, looking only at the use of conventional batteries supplying electricity. This is basically due to low gravimetric and volumetric energy densities of these devices that result in shorter autonomy, in addition to more weight and less usable space in the vehicle. An alternative that could make electric motors more attractive for vehicular applications by replacing batteries as the main electricity source is the fuel cell. Hydrogen is the main fuel used in these cells, but the hydrogen storage systems developed so far are heavier and bulkier than their equivalent for conventional liquid fuels such as diesel, gasoline and alcohol, despite heavier energy densities compared to batteries.This paper reviews technological aspects of fuel cells, the main storage systems for hydrogen and other energy sources, data on fuel use and the types of vehicles most commonly used in the Brazilian road transportation sector, followed by an overview of the insertion of hybrid ethanol–electric buses in Brazil.     

Use of hydrogen in dual-fuel diesel engines

Hydrogen is a promising future energy carrier due to its potential for production from renewable resources. It can be used in existing compression ignition diesel engines in a dual-fuel mode with little modification. Hydrogen's unique physiochemical properties, such as higher calorific value, flame speed, and diffusivity in air, can effectively improve the performance and combustion characteristics of diesel engines. As a carbon-free fuel, hydrogen can also mitigate harmful emissions from diesel engines, including carbon monoxide, unburned hydrocarbons, particulate matter, soot, and smoke. However, hydrogen-fueled diesel engines suffer from knocking combustion and higher nitrogen oxide emissions. This paper comprehensively reviews the effects of hydrogen or hydrogen-containing gaseous fuels (i.e., syngas and hydroxy gas) on the behavior of dual-fuel diesel engines. The opportunities and limitations of using hydrogen in diesel engines are discussed thoroughly. It is not possible for hydrogen to improve all the performance indicators and exhaust emissions of diesel engines simultaneously. However, reformulating pilot fuel by additives, blending hydrogen with other gaseous fuels, adjusting engine parameters, optimizing operating conditions, modifying engine structure, using hydroxy gas, and employing exhaust gas catalysts could pave the way for realizing safe, efficient, and economical hydrogen-fueled diesel engines. Future work should focus on preventing knocking combustion and nitrogen oxide emissions in hydrogen-fueled diesel engines by adjusting the hydrogen inclusion rate in real time.     

A comprehensive review on synthesis,chemical kinetics,and practical application of ammonia as future fuel for combustion

Recently, ammonia has been explored as a potential fuel for internal combustion engines, gas turbines and other industrial purposes. Ammonia consists of 17.6% by weight of hydrogen and is thus considered a carbon-free emission fuel. The synthesis of ammonia for bulk production takes place using the Haber-Bosch process. The production, storage and transportation of ammonia is relatively safe. This paper reports various aspects of ammonia as an alternative fuel for combustors. Several studies reporting the laminar burning velocity of ammonia and its blends are discussed. Recent advances in the development of chemical kinetics for ammonia combustion are presented. The paper explores all experimental and numerical works on ammonia as a fuel for I C engines, gas turbines and other combustion systems.This review further suggests ways to overcome the disadvantages associated with ammonia combustion, such as lower burning velocities and high NOx emissions.     

On-board fuel processor modelling for hydrogen-enriched gasoline fuelled engine

Hydrogen as a fuel for automotive engines is generally coupled with advanced conversion systems (fuel cells) but, due to energy crises and environmental pollution, hydrogen fuelling of internal combustion engines is of great interest as well.In the near-term, the use of hydrogen as gasoline additional fuel in ICE is a very interesting and accredited approach. However the employment of hydrogen introduces problems in the fuel distribution and storage systems. These drawbacks could be overcome by using on-board hydrogen production systems.In this paper, a numerical model of a simple reforming system, based on a partial oxidation process, has been developed. The model has been tested using the experimental data of a plasma-assisted reformer. The conversions of methane, propane, heptane, toluene and gasoline to hydrogen have been investigated and a thermodynamic analysis of the reforming system has been conducted by means of the AspenPlus software. The efficiency of the reformer/engine system has been also evaluated.     

A review of hydrogen utilization in power generation and transportation sectors: Achievements and future challenges

Decarbonizing the power generation and transportation sectors, responsible for ∼65% of Green House Gas (GHG) emissions globally, constitutes a crucial step to addressing climate change. Accordingly, the energy paradigm is shifting towards carbon-free and low-emission alternative fuels. Even though the current decarbonization using hydrogen is not large since 96% of global hydrogen production is relying on conventional fossil fuels that produce GHGs in the process, hydrogen fuel has been considered a promising fuel for fuel cell and combustion engines. Various renewable approaches utilizing biomass and water have been investigated to produce green hydrogen. With this, recent developments showed viability to achieve deep decarbonization in the power generation and transportation sectors. Hydrogen-powered vehicles are commercially available in many countries, and over 300,000 fuel cell appliances were sold to produce hot water and electricity. This review aims to provide an overview of the potential role of hydrogen in power generation and transportation systems, recent achievements in research development, and technical challenges to successfully applying hydrogen as a primary fuel. Especially this review will focus on the hydrogen application in power generation and transportation sectors using fuel cells, gas turbines, and internal combustion engines (ICEs).     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Examining the trends of technological development in hydrogen energy using patent co-word map analysis

Hydrogen fuel is a zero CO₂ emission fuel which uses in electrochemical cells, or internal combustion engines, to power vehicles and electric devices. It is also can potentially be mass-produced for various applications and be used in propulsion of spacecraft with safely high pressure storage. Therefore, it is an interesting subject to identify the technological trends of hydrogen energy. This study suggests a patent co-word map analysis (PCMA) to examine the trends of technological development in the area of hydrogen energy. The PCMA provides a systematic procedure to demonstrate the overall relationship among patents and produces the important technological insights regarding hydrogen energy. The results of analysis firstly indicate that the technological trends of worldwide hydrogen energy focus on the converting and application of hydrogen. Furthermore, critical technologies obtained from three patent sub-maps can be identified as the production, storage and conversion for hydrogen energy. Finally, hydrogen application is taken for the key factor in sustainable energy research works to improve the use for hydrogen.     

Hydrogen engine-specific properties

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as an energy carrier, provides the potential for a sustainable development particularly in the transportation sector. A hydrogen fueled engine has the potential for substantially cleaner emissions than other internal combustion engines. Other benefits arise from the wide flammability limits and the high flame propagation speed, both allowing better efficiency. The Laboratory of Transporttechnology (University of Ghent) converted a GM/Crusader V8 SI engine for hydrogen use, to be built in a city bus. A sequential timed multipoint injection system was implemented. Attention is directed towards special characteristics related to the use of hydrogen as a fuel in IC engines: ignition properties (smaller spark plug gap), injection pressure (dependent on the means of storage: compressed gas or liquid), quality of the lubricating oil (due to higher blow-by volumes, a substantial amount of hydrogen is present in the crankcase), oxygen sensors (very lean operating conditions). The advantages and disadvantages of a power regulation by changing the air to fuel ratio (as for diesel engines), as compared to throttle regulation (SI engines) are judged.     

State of the art of multi-fuel reformers for fuel cell vehicles: problem identification and research needs

This review is focused on discussions about multi-fuel reformer technology for fuel cell vehicles where techniques for onboard hydrogen generation and gas clean-up processes, as well as fuel considerations and emissions are included. Our conclusion is that the potential for developing a highly efficient, durable and reliable reformer system for automotive applications is considerably higher if dedicated fuel reformers are used instead of applications where all types of fuels ranging from natural gas to heavy diesel fuels can be used. The authors propose that petroleum-derived fuels should be designed for potential use in mobile fuel cell applications. The present literature review together with site visit discussions has led to the conclusion that there are relatively low emissions from fuel cell engines compared to internal combustion engines. However, the major research work on reformers/fuel cells have been performed during steady-state operation. Emissions during start-up, shutdown and transient operation are basically unknown and must be investigated in more detail.     

Hydrogen energy pilot introduction – Technology competition

Hydrogen energy technologies are considered as the cutting-edge clean energy technologies all over the world. Novel concept of hydrogen energy development in Russia, proposed by Government has hydrogen technologies equipment development, production and introduction into domestic market as one of the tasks. Foreign experience shows that governmental support is very important for successful branch development. Waste hydrogen from chlorine industry utilization can be energy-efficient and attractive niche for fuel cells and hydrogen-fuelled heat engines application. Lifetime and capital costs are important parameters for technology choice decision. Energy cost and hydrogen consumption comparison were carried out for gas microturbines (MGT), fuel cells (FC) and internal combustion engines (ICE) in this paper. Analysis showed polymer electrolyte membrane fuel cells and gas microturbines to be the most promising technology in this niche while for internal combustion engines lifetime is an issue. Solid oxide fuel cells need significant capital costs decrease for successful market introduction. Solid oxide fuel cells, MGT and ICE have also additional advantage for Russian conditions due to high-potential heat production possibility.     

Effect of natural gas enrichment with hydrogen on combustion characteristics of a dual fuel diesel engine

Environmental benefits are one of the main motivations encouraging the use of natural gas as fuel for internal combustion engines. In addition to the better impact on pollution, natural gas is available in many areas. In this context, the present work investigates the effect of hydrogen addition to natural gas in dual fuel mode, on combustion characteristics improvement, in relation with engine performance. Various hydrogen fractions (10, 20 and 30 by v%) are examined. Results showed that natural gas enrichment with hydrogen leads in general to an improved gaseous fuel combustion, which corresponds to an enhanced heat release rate during gaseous fuel premixed phase, resulting in an increase in the in-cylinder peak pressure, especially at high engine load (4.1 bar at 70% load). The highest cumulative and rate of heat release correspond to 10% Hydrogen addition. The combustion duration of gaseous fuel combustion phase is reduced for all hydrogen blends. Moreover, this technique resulted in better combustion stability. For all hydrogen test blends, COV_IMEP does not exceed 10%. However, no major effect on combustion noise was noticed and the ignition delay was not affected significantly. Regarding performance, an important improvement in energy conversion was obtained with almost all hydrogen blends as a result of improved gaseous fuel combustion. A maximum thermal efficiency of 32.5%, almost similar to the one under diesel operation, and a minimum fuel consumption of 236 g/kWh, are achieved with 10% hydrogen enrichment at 70% engine load.     

Progress on the studies about NOx emission in PFI-H2ICE

Owing to its brilliant combustion performance and cleanest combustion products, hydrogen has been widely considered as one best alternative fuel for internal combustion engines. However, in the cylinder of hydrogen internal combustion engines, high combustion temperature and oxygen enrichment make NOx is still one but the only combustion pollutant. Therefore, it is particularly important to control NOx emission for hydrogen fuelled engines. Since PFI-H₂ICE (port-fuel-injection hydrogen internal combustion engine) is the normal type of hydrogen fuelled engines, the present article will focus on the studies about NOx emission in PFI-H₂ICE researches. First, the present article reviews the mechanism of NOx generation in PFI-H₂ICE; upon chemical kinetics, the generation of NOx will be summarized and discussed into three major paths which including thermal NO path, NNH–NO path and N₂O–NO path. Then, the researches on the control methods of NOx for PFI-H₂ICE in recent years will be systematically reviewed, the influencing factors to reduce NOx emission will be summarized in some aspects which including combustion component control strategy, injection control strategy, ignition control strategy and engine compression ratio control strategy. To the PFI-H₂ICE operated at lean fuel conditions (like equivalence ratio is less than 0.5) or rich fuel conditions (like equivalence ratio is higher than 1), the technologies and the strategies of EGR (exhaust gas re-circulation) will be reviewed and discussed. It is hoped this literature review would enable researchers to systematically understand the progress of NOx emissions research in PFI-H₂ICE and explore further research directions.     

Effect of induction on exhaust gas recirculation and hydrogen gas in compression ignition engine with simarouba oil in dual fuel mode

Biofuels extracted from non-edible oil is sustainable and can be used as an alternative fuel for internal combustion engines. This study presents the performance, emission and combustion characteristic analysis by using simarouba oil (obtained from Simarouba seed) as an alternative fuel along with hydrogen and exhaust gas recirculation (EGR) in a compression ignition (CI) engine operating on dual fuel mode. Simarouba biofuel blend (B20) was prepared on volumetric basis by mixing simarouba oil and diesel in the proportion of 20% and 80% (v/v), respectively. Hydrogen gas was introduced at the flow rate of 2.67 kg/min, and EGR concentration was maintained at 30% of total air introduction. Performance, combustion and emission characteristics analysis were examined with biodiesel (B20), biodiesel with hydrogen substitution and biodiesel, hydrogen with EGR and were compared with neat diesel operation. Results indicate that BTE of the engine operating with biodiesel B20 was decreased when compared to neat diesel operation. However, introducing hydrogen along with B20 blend into the combustion chamber shows a slight increase in the BTE by 1%. NO_x emission was increased to 18.13% with the introduction of hydrogen than that of base fuel (diesel) operation. With the introduction of EGR, there is a significant reduction in NO_x emission due to decrease in in-cylinder temperature by 19.07%. A significant reduction in CO, CO_2, and smoke emissions were also noted with the introduction of both hydrogen and EGR. The ignition delay and combustion duration were increased with the introduction of hydrogen, EGR with biodiesel than neat diesel operation. Hence, the proposed biodiesel B20 with H₂ and EGR combination can be applied as an alternative fuel in CI engines.     

Controlled autoignition of hydrogen in a direct-injection optical engine

Research into novel internal combustion engines requires consideration of the diversity in future fuels in an attempt to reduce drastically CO₂ emissions from vehicles and promote energy sustainability. Hydrogen has been proposed as a possible fuel for future internal combustion engines and can be produced from renewable sources. Hydrogen’s wide flammability range allows higher engine efficiency than conventional fuels with both reduced toxic emissions and no CO₂ gases. Most previous work on hydrogen engines has focused on spark-ignition operation. The current paper presents results from an optical study of controlled autoignition (or homogeneous charge compression ignition) of hydrogen in an engine of latest spark-ignition pentroof combustion chamber geometry with direct injection of hydrogen (100 bar). This was achieved by a combination of inlet air preheating in the range 200–400 °C and residual gas recirculated internally by negative valve overlap. Hydrogen fuelling was set to various values of equivalence ratio, typically in the range ? = 0.40–0.63. Crank-angle resolved flame chemiluminescence images were acquired for a series of consecutive cycles at 1000 RPM in order to calculate in-cylinder rates of flame expansion and motion. Planar Laser Induced Fluorescence (LIF) of OH was also applied to record more detailed features of the autoignition pattern. Single and double (i.e. ‘split’ per cycle) hydrogen injection strategies were employed in order to identify the effect of mixture preparation on autoignition’s timing and spatial development. An attempt was also made to review relevant in-cylinder phenomena from the limited literature on hydrogen-fuelled spark-ignition optical engines and make comparisons were appropriate.     

Technico-economic study of distributing hydrogen for automotive vehicles

The objective of this study is to estimate the technical and economic feasibilities of hydrogen applied to automotive traction. The problems of mass storage and transportation of hydrogen, capillary distribution, storage aboard vehicles and those concerning hydrogen thermal engines and hydrogen fuel cells are investigated. The different ways of using hydrogen, either compressed or liquefied or combined in hydrides, are taken into account.Energy and economic balance sheets lead to the conclusion that hydrogen internal combustion engines cannot compete with gasoline engines with regard to primary energy consumption and fuel cost. To the contrary, a hydrogen fuel cell, thanks to its high efficiency, provides for appreciable energy saving and leads to a fuel expense of the same order of magnitude as premium gasoline in an urban vehicle.     

Optimal power allocation for a FCHV based on linear programming and PID controller

Hybrid electric vehicles positively influence the transportation industry with regards to reducing the use of fossil fuels and minimizing polluting emissions. A class of such vehicles incorporates fuel cells and energy storage systems as alternatives to internal combustion engines. This paper develops a dynamically efficient energy management system for fuel cell hybrid vehicles for the purpose of achieving an optimal power allocation between the energy sources while adhering to component requirements and maintaining the essential operational performance. The paper addresses a two stage control methodologies, pre-driving optimization using linear programming algorithms and on-line optimization using PID controllers and component mechanisms. The performance criteria are based on the overall operational cost as well as the hydrogen consumption per trip. Comparison against a state control algorithm shows improvements in hydrogen consumption.