Hydrogen internal combustion engine vehicle

Francois Isaac de Rivaz designed in 1806 the De Rivaz engine, the first internal combustion engine, which ran on a hydrogen/oxygen mixture.[4] Étienne Lenoir produced the Hippomobile in 1863. Paul Dieges patented in 1970 a modification to internal combustion engines which allowed a gasoline-powered engine to run on hydrogen.[5]

Tokyo City University have been developing hydrogen internal combustion engines from 1970.[6] They recently developed a hydrogen fueled Bus[7] and Truck.

Mazda has developed Wankel engines that burn hydrogen. The advantage of using ICE (internal combustion engine) such as Wankel and piston engines is that the cost of retooling for production is much lower. Existing-technology ICE can still be used to solve those problems where fuel cells are not a viable solution as yet, for example in cold-weather applications.

Between 2005 - 2007, BMW tested a luxury car named the BMW Hydrogen 7, powered by a hydrogen ICE, which achieved 301 km/h (187 mph) in tests. At least two of these concepts have been manufactured.

HICE forklift trucks have been demonstrated [8] based on converted diesel internal combustion engines with direct injection.[9]

In the year 2000, a Shelby Cobra was converted to run on hydrogen in a project led by James W. Heffel (principal engineer at the time for the University of California, Riverside CE-CERT). The hydrogen conversion was done with the aim of making a vehicle capable of beating the current land speed record for hydrogen powered vehicles.[10][11][12] It achieved a respectable 108.16 mph, missing the world record for hydrogen powered vehicles by 0.1 mph.[13]

Alset GmbH developed a hybrid hydrogen systems that allows vehicle to use petrol and hydrogen fuels individually or at the same time with an internal combustion engine. This technology was used with Aston Martin Rapide S during the 24 Hours Nürburgring race. The Rapide S was the first vehicle to finish the race with hydrogen technology.[14]

Hydrogen internal combustion engine development has been receiving more interest recently, particularly for heavy duty commercial vehicles. Part of the motivation for this is as a bridging technology to meet future climate CO2 emission goals, and as technology more compatible with existing automotive knowledge and manufacturing.

Since hydrogen internal combustion engines are heat engines, their maximum efficiency is limited by the Carnot efficiency. In comparison, the efficiency of a fuel cell is limited by the Gibbs free energy, which is typically higher than that of Carnot.

Hydrogen combustion engines are particularly sensitive to transients in load, in terms of efficiency, and therefore more suited to constant load operations.

The combustion of hydrogen with oxygen produces water vapor as its only product:

2H₂ + O₂ → 2H₂O

However, within air hydrogen combustion can produce oxides of nitrogen, known as NO_x. In this way, the combustion process is much like other high temperature combustion fuels, such as kerosene, gasoline, diesel or natural gas. As such hydrogen combustion engines are not considered zero emission.

Hydrogen has a wide flammability range in comparison with other fuels. As a result, it can be combusted in an internal combustion engine over a wide range of fuel-air mixtures. An advantage here is it can thus be on a lean fuel-air mixture. Such a mixture is one in which the amount of fuel is less than the theoretical, stoichiometric or chemically ideal amount needed for combustion with a given amount of air. Fuel economy is then greater and the combustion reaction is more complete. Also, the combustion temperature is usually lower, which reduces the amount of pollutants (nitrogen oxides, ...) emitted through the exhaust.[15]

The European emission standards measure emissions of carbon monoxide, hydrocarbon, non-methane hydrocarbons, nitrogen oxides (NOx), atmospheric particulate matter, and particle numbers.

Although NOx is produced, hydrogen internal combustion generates little or no CO, CO2, SO2, HC or PM emissions.[16][17]

Tuning a hydrogen engine in 1976 to produce the greatest amount of emissions possible resulted in emissions comparable with consumer operated gasoline engines from that period. [18] More modern engines however often come equipped with exhaust gas recirculation. Equation when ignoring EGR:

H₂ + O₂ + N₂ → H₂O + NO_x [19]

This technology potentially benefits hydrogen combustion also in terms of NOx emissions.[20]

Since hydrogen combustion is not zero emission but has zero CO2 emissions, it is attractive to consider hydrogen internal combustion engines as part of a hybrid powertrain. In this configuration, the vehicle is able to offer short term zero emission capabilities such as operating in city zero emission zones.

The differences between a hydrogen ICE and a traditional gasoline engine include hardened valves and valve seats, stronger connecting rods, non-platinum tipped spark plugs, a higher voltage ignition coil, fuel injectors designed for a gas instead of a liquid, larger crankshaft damper, stronger head gasket material, modified (for supercharger) intake manifold, positive pressure supercharger, and a high temperature engine oil. All modifications would amount to about one point five times (1.5) the current cost of a gasoline engine.[21] These hydrogen engines burn fuel in the same manner that gasoline engines do.

The theoretical maximum power output from a hydrogen engine depends on the air/fuel ratio and fuel injection method used. The stoichiometric air/fuel ratio for hydrogen is 34:1. At this air/fuel ratio, hydrogen will displace 29% of the combustion chamber leaving only 71% for the air. As a result, the energy content of this mixture will be less than it would be if the fuel were gasoline. Since both the carbureted and port injection methods mix the fuel and air prior to it entering the combustion chamber, these systems limit the maximum theoretical power obtainable to approximately 85% of that of gasoline engines. For direct injection systems, which mix the fuel with the air after the intake valve has closed (and thus the combustion chamber has 100% air), the maximum output of the engine can be approximately 15% higher than that for gasoline engines.

Therefore, depending on how the fuel is metered, the maximum output for a hydrogen engine can be either 15% higher or 15% less than that of gasoline if a stoichiometric air/fuel ratio is used. However, at a stoichiometric air/fuel ratio, the combustion temperature is very high and as a result it will form a large amount of nitrogen oxides (NOx), which is a criteria pollutant. Since one of the reasons for using hydrogen is low exhaust emissions, hydrogen engines are not normally designed to run at a stoichiometric air/fuel ratio.

Typically hydrogen engines are designed to use about twice as much air as theoretically required for complete combustion. At this air/fuel ratio, the formation of NOx is reduced to near zero. Unfortunately, this also reduces the power output to about half that of a similarly sized gasoline engine. To make up for the power loss, hydrogen engines are usually larger than gasoline engines, and/or are equipped with turbochargers or superchargers.[22]

In the Netherlands, research organisation TNO has been working with industrial partners for the development of hydrogen internal combustion engines.[23]

• Bi-fuel vehicle: a possible solution to overcome the lack of H2 stations[24]
• Classic car fuel conversions
• Fuel gas-powered scooter
• Hydrogen fuel enhancement
• Home hydrogen fueling station
• Liquid nitrogen vehicle
• List of hydrogen internal combustion engine vehicles
• Phase-out of fossil fuel vehicles
• Timeline of hydrogen technologies

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