A hydrogen-powered train.Credit: Coradia
Hydrogen is the ultimate clean fuel. When it burns in air it creates just water vapor (along with trace amounts of nitrogen oxides). It is widely used in industry, particularly refineries and chemical plants so there is plenty of experience to do with its handling and transportation.
There are virtually no natural sources of hydrogen. One reason for this is that the gas has a very low density (it is the first element in the periodic table). Consequently any hydrogen that is in the atmosphere will escape into space. Hydrogen is, however, abundant in many chemical compounds and fossil fuels. It can also be obtained by electrolyzing water using non-carbon based energy sources such as solar or nuclear power.
Difficulties to do with the handling of hydrogen have limited its use as an energy source. However, there is increased interest in its use in fuel cells, particularly as a source of clean energy for vehicles.
The status of hydrogen as a fuel, as distinct from an industrial chemical, is shown in the above Phase-Gate sketch. It is placed in Phase II (see Project Status for the background to this sketch). There are a few limited commercial applications such as the Toyota Mirai automobile, but there is very little infrastructure.
Production and Use of Hydrogen
The sketch provides an overview of how hydrogen is manufactured and used. The boxes on the left shows different types of hydrogen production. The boxes on the right show how the hydrogen is used.
We start with the ‘Black/Gray/Brown’ section. This is how almost all hydrogen is produced now. A fossil fuel — often methane — and steam are reacted to form hydrogen and carbon dioxide (CO2). The CO2 is discharged to the atmosphere where it increases the concentration of greenhouse gases.
Next comes the ‘Blue’ section. Hydrogen is manufactured from methane and steam, but the CO2 is sent to a Carbon Capture and Sequestration facility. There are no significant additions of CO2 to the atmosphere.
The third production box shows ‘Green’ production of hydrogen. Water is electrolyzed to create hydrogen and oxygen. The oxygen can be sold commercially.
On the right side of the sketch are four types of user.
The first user is ‘Ammonia’. Although hydrogen has a high energy content, it is difficult to handle. One option is to convert it to ammonia, which can then be used as a fuel.
Next come the industrial users. They purchase the hydrogen for use in a wide range of facilities, including oil refineries.
Next are fuel cells. The hydrogen is converted to electricity.
Finally, there is combustion. The hydrogen is burned directly. Its exhaust is water vapor, which is benign.
The following articles, blogs and videos provide more information on the topics discussed in this chapter.