In 2018, hydrogen production stood at around 115 Mt, 97% of which is obtained through the chemical process of reforming light hydrocarbons (mainly methane) or from the cracking of heavier hydrocarbons (oil) and coal gasification. Only 1% is produced by electrolysis and the remaining 2% by other technologies. Hydrogen can be used to produce other compounds or as a fuel to produce energy. In particular, the hydrogen produced is used in the chemical industry, to produce ammonia, methyl alcohol (methanol), agricultural fertilisers and petroleum products, and in the metallurgical industry for metal processing.
Hydrogen is also an excellent fuel. It can be used to produce energy in two ways. The first method is by burning hydrogen alone or added to other fuels. The second method is based on a chemical reaction between hydrogen and oxygen (without burning it), obtaining electric energy directly through a device called fuel cell.
Directly as a fuel.
The combustion of hydrogen does not provoke particular problems and produces emissions that are much less polluting than other fuels. Combustion in the air produces water, un-burnt hydrogen and traces of ammonia. Thus, using this gas to supply a household boiler or a car engine, energy would be produced avoiding the emission of toxic substances. For a few years now, hydrogen vehicles have been circulating experimentally. Moreover, any other fuel mixed with hydrogen improves its combustion and efficiency. Therefore, in the United States the use of methane to which hydrogen is added in the tune of 15% of the weight – commercially known as Hythane – is being assessed.
Hydrogen can be used to supply cars operated with fuels cells. Liquid hydrogen is also used as a fuel for the cells that supply electricity to activate the equipment on board of space ships. The water obtained as a by-product from fuel cells can be drunk by the crew. As well as in transports, fuel cells could be usefully applied in buildings. Finally, hydrogen could soon supply many popular electronic devices, such as mobile phones, laptop computers, toys, that today require heavy and expensive batteries. A miniature fuel cell is light, cheap and lasts longer than an ordinary battery. Mobile phones, for example, could work constantly for months, and it would be sufficient to periodically buy a small tube of fuel rich in hydrogen (such as methane or methanol) to be inserted into the device, in order to supply the small fuel cell.
The devices that use hydrogen to directly produce electric energy are called “fuels cells”. Hydrogen fuel cells are electrochemical generators where electric energy is produced from threaction between a fuel (hydrogen) and a gaseous oxidizing compound (oxygen and air). Together with electricity, heat and water are produced.
In this sector both internal combustion engines and fuel cell engines are being developed. The latter are essentially important in order to obtain a transport system with a minimum environmental impact.
In the first case, the engine has cylinders and pistons, it burns hydrogen instead of petrol or gas oil and does not force to review the internal combustion engine technology. In the second case, fuel cells produce power and supply electric engines.
In particular hydrogen can offer a solution to the problem of emissions (including greenhouse gas emissions) generated from the transport sector. Hybrid vehicles with internal combustion engine working with fossil fuels or fuel cells, could reduce CO2 emissions by approximately 25% as compared to the most advanced internal combustion engines.
Hydrogen is a gas that burns in the air according to a simple reaction: hydrogen plus oxygen equal water and heat, resulting in the production of pure water. It can be produced from fossil sources, renewable sources and nuclear sources; it can be distributed into the network quite easily according to its end use and the development of transport and storage technologies; it can be used for different applications (centralized or distributed electric energy production, heat generation, engine propulsion) with no or extremely reduced environmental impact.
Therefore we can say that hydrogen is the ideal component of a future sustainable energy system. It gives an incentive to the widespread use of renewable sources, but already in the short-medium term it will make fossil fuels compatible with environmental needs.
Its characteristics make hydrogen complementary to electricity (which is another energy carrier), although the former can be accumulated and transported. Hydrogen, then, can pave the way to renewable energy sources distributed all around the world, by providing Third World countries with the chance to export energy and be more independent from fossil fuel exporting countries.
There are still many doubts about the safety of this energy carrier, mainly because it is still scarcely known. Anyhow, a more careful analysis reduces the concept of hydrogen dangerousness. This gas is less inflammable than petrol (it has a higher self-ignition temperature). Hydrogen is the lightest element and therefore can be rapidly diluted and dispersed into the open space.
Hydrogen is an extremely environmentally friendly fuel. Its combustion produces water and small quantities of nitrogen oxides. Moreover, hydrogen can be extracted from a range of compounds, and this is one of the aspects that make it considered as the fuel of the future. In order to produce hydrogen, it is necessary to consume energy, and this operation has certain costs.