The reactions are as follows.
This remains the cheapest way to produce hydrogen on a commercial scale. The gas is heated to high temperatures up to C with steam and a Nickel catalyst.
This results in the methane molecules breaking into Carbon Monoxide and Hydrogen. What type of a reaction takes place i in the first case, and ii in the second case. In the first case, the two elements, hydrogen, and oxygen combine to form a single compound hence it is a combination reaction. In the second case, a decomposition reaction takes place as a single compound, i. This decomposition reaction takes place by the action of electricity.
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Suggested Videos. Introduction to Hydrogen. Preparation of Hydrogen. Water and Its Structure. Share with friends. The application options for hydrogen as a fuel for mobility can be differentiated firstly by the chemical form or bonding of hydrogen and secondly by the energy converter by means of which the energy stored in the hydrogen is made available. Read more about Power-to-X.
In civil aviation, hydrogen-powered fuel cells are regarded as potential energy providers for aircraft as they have been in space travel for some time now. Thus, fuel cell modules can supply electricity to the aircraft electrical system as emergency generator sets or as an auxiliary power unit. More advanced concepts include starting of the main engine and the nose wheel drive for airfield movements by commercial aircraft. As in aviation, fuel cells are currently being tested as energy providers for the on-board power supply. The use of hydrogen-powered fuel cells for ship propulsion, by contrast, is still at an early design or trial phase — with applications in smaller passenger ships, ferries or recreational craft.
As yet, however, no fuel cells have been scaled for and used on large merchant vessels. In electric locomotives, motive power is supplied via stationary current conductors overhead lines, conductor rails and current collectors on the vehicles. However, for technical, economic or other reasons, not every railway line can be electrified.
Especially on lines with a low transport volume, the high up-front investment that is needed for electrification of the lines cannot always be justified.
Moreover, overhead lines cannot be used for shunting if cranes are also in use for moving transport goods. In subsurface mining, by contrast, traction vehicles have to operate without air pollutants. Rail vehicles that use hydrogen as an energy store and energy source can offer an additional alternative. Fuel cell-powered rail vehicles combine the advantage of pollutant-free operation with the advantage of low infrastructure costs, comparable with those for diesel operation.
Fuel cell industrial trucks, like forklifts or towing trucks airports are especially suitable for indoor operation, because they produce no local pollutant emissions and only low noise emissions. Fuel cell vehicles have advantages over battery-operated industrial trucks in terms of refueling. Instead of having to replace the battery, the trucks can be refueled within two to three minutes. They take up less space and are cheaper to maintain and repair.
Fuel cell industrial trucks allow for uninterrupted use and are therefore particularly suitable for multi-shift fleet operation in material handling FCTO b. In the case of larger industrial truck fleets in multi-shift operation, moderate cost reductions can be achieved in comparison to battery technology, and productivity in material handling can also be increased. In terms of road transport, buses in the public transport network are the most thoroughly tested area of application for hydrogen and fuel cells. Since the early s, several hundred buses have been and are being operated with hydrogen worldwide — predominantly in North America, Europe and increasingly also in Asia.
Although hydrogen was initially still used in buses with internal combustion engines, bus developers are now concentrating almost entirely on fuel cell electric buses FCEB. The use of small FCEB fleets is being promoted in urban areas as a way of contributing to technological development and to clean air policy. Fuel cell buses have now reached a high level of technical maturity, although they are not yet in series production. Owing to the small numbers, until now they have still been much more expensive, at around 1 million EUR, than standard diesel buses, which cost in the region of , EUR.
The maintenance costs have also been significantly reduced and the reliable operating times increased Hua et al. Depending on annual production numbers, production costs for FCEBs should continue to fall, however, in future projects. The production costs for metre buses are projected to fall to around , purchase of buses EUR by and to approx.
Modern fuel cell buses draw their energy from two fuel cell stacks, each with an output of approx. They also have a relatively small traction battery and are able to recover brake energy. In addition, they carry approximately 30 to 50 kg of compressed hydrogen on board, stored in pressure tanks at bar. On the other hand, some battery electric bus models have large traction batteries and only small fuel cell stacks, which are used as range extenders. Fuel cell buses now have a range of to km and so offer almost the same flexibility as diesel buses in day-to-day operation.
In order to develop the market, demonstration projects with large fleets in long-term use are planned. Along with battery electric vehicles, hydrogen-powered fuel cell passenger cars are the only zero-emission alternative drive option for motorized private transport. The first fuel cell passenger cars were tested back in the s as demonstration projects. A new boost to fuel cell development came in the s.
In most cases the fuel cell test vehicles were converted cars that had originally been fitted with an internal combustion engine. At the time, however, the early test models were still not competitive, either technically or economically. In addition, up until about 10 years ago petrol engine prototypes were still being tested with hydrogen as an alternative energy and low-emission fuel.
These were vehicles with modified bivalent engines, which could run on both petrol and hydrogen. Owing to the fuel, hydrogen-powered internal combustion engines not only achieve somewhat higher efficiencies than in petrol operation, they also emit much lower levels of pollutants. Although hydrogen is a clean fuel with excellent physicochemical properties, it has been unable to gain acceptance as a fuel for motorized road transport.
For passenger cars the focus is now almost entirely on hydrogen-powered fuel cells as a source of drive energy. There is now a wealth of practical experience available with fuel cell prototype passenger cars.
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A number of major car manufacturers are starting to offer early series-production vehicles which are now just as good as conventional internal combustion engine cars in terms of functionality. The number of fuel cell cars manufactured over the coming years is projected to range from several hundred up to thousands of units.
To fulfill such requirements there are main problems for hydrogen storage such as:. For all approaches of hydrogen storage, vessel containment that is resistant to hydrogen permeation and corrosion is required. Research into new materials of construction such as metal ceramic composites, improved resins, and engineered fibbers is needed to meet cost targets without compromising performance. Materials to meet performance and cost requirements for hydrogen delivery and off-board storage are also needed [ 10 ]. Heavy hydrogen molecules green balls adsorbed in MOF pack into the tubes more densely than they would in solid form .
Moreover, for all methods of hydrogen storage thermal management is a key issue. In general, the main technical challenge is heat removal upon re-filling of hydrogen for compressed gas and onboard reversible materials within fuelling time requirements.
Onboard reversible materials typically require heat to release hydrogen. Heat must be provided to the storage media at reasonable temperatures to meet the flow rates needed by the vehicle power plant, preferably using the waste heat of the power plant. Depending upon the chemistry, chemical hydrogen approaches often are exothermic upon release of hydrogen to the power plant, or optimally thermal neutral. By virtue of the chemistry used, chemical hydrogen approaches require significant energy to regenerate the spent material and by-products prior to re-use; this is done off the vehicle.
At the moment, several kinds of technologies of hydrogen storage are available.
Some of them will be briefly described here. The simplest is compressed H 2 gas. It is possible at ambient temperature, and in- and out-flow are simple. However, the density of storage is low compared to other methods. In metal hydride storage the powdered metals absorb hydrogen under high pressures. During this process heat is produced upon insertion and with pressure release and applied heat, the process is reversed. More popular at this time is carbon absorption: the newest field of hydrogen storage.
At applied pressure, hydrogen will bond with porous carbon materials such as nanotubes. So, it can be summarized that even mobile hydrogen storage is currently not competitive with hydrocarbon fuels; it must become so in order for this potential environmentally life-saving technology to be realized on a great scale. Compressed hydrogen in hydrogen tanks at bar 5, psi and bar 10, psi is used in hydrogen vehicles. There are two approaches to increase the gravimetric and volumetric storage capacities of compressed gas tanks. The first approach involves cryo-compressed tanks as shown in Figure 2 [ 12 ].
This is based on the fact that, at fixed pressure and volume, gas tank volumetric capacity increases as the tank temperature decreases. Thus, by cooling a tank from room temperature to liquid nitrogen temperature 77K , its volumetric capacity increases. However, total system volumetric capacity is less than one because of the increased volume required for the cooling system. The limitation of this system is the energy needed to compression of the gas. The energy lost for hydrogen storage can be reduced by the development of new class of lightweight composite cylinders.
The energy density of hydrogen can be improved by storing hydrogen in a liquid state. This technology developed during the early space age, as liquid hydrogen was brought along on the space vessels but nowadays it is used on the on-board fuel cells. It is also possible to combine liquid hydrogen with a metal hydride, like Fe-Ti, and this way minimize hydrogen losses due to boil-off.