How to store hydrogen?

2005/09/01 Kortabitarte Egiguren, Irati - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Teknologia
• Energia berriztagarriak

Many car companies have developed cars with hydrogen fuel cells, but we still don't see them on the street.

A team of researchers from the Public University of Navarra is designing and developing adsorbent materials for hydrogen storage. This team of researchers is led by Antonio Gil and Sophia Korili.

In fact, hydrogen storage is a fundamental key in cars that use this element as fuel. In fact, in addition to being flammable, hydrogen is a very light gas and a very small amount occupies a huge volume. Therefore, it is very difficult to find a way to take the cars in a hydrogen car enough to move.

In addition, hydrogen is a clean fuel, since when burned, only water is produced. Being so small its mass, it can provide more energy than any other element, in addition to clean energy. And it can replace fossil fuel derivatives such as gasoline or diesel. However, in nature it is scarce in freedom and there is no choice but to produce by transversal channels. In general, fossil fuels and water are the usual starting points.

Hydrogen as fuel

Currently the production of hydrogen is quite expensive, but technically it is not a problem. Until now, hydrogen has been obtained both by catalytic reformation and by the electrolysis of water.

The problem is that they are generated in large quantities and are stored and transported without danger.

Under normal conditions, hydrogen is in a gaseous state, so to store a lot of gas in a small volume it is necessary to increase the pressure. If you want to keep under pressure, the storage temperature should be drastically reduced. Both situations generate technological and security problems, among others.

Physical adsorption

Hydrogen storage can be carried out pressurized, liquefied, stored as a metal hydride and physically adsorbed in suitable materials.

This is the table for photos that are aligned to the right

And what is adsorption? On the surface of a solid, the molecules of a gas or liquid are trapped without chemical reactions. It is used to separate substances (both gases and liquids) from a mixture or dissolution. This is the method that is being developed at the Public University of Navarra. Specifically, they use nanoporous pore materials between 0 and 10 and 6 meters.

The research team works with three materials: activated carbon, zeolites and clay. All these materials meet four requirements: they have mechanical strength, are safe and are light and economical.

Storage based on physical adsorption provides greater energy efficiency than the rest of methods. There is no chemical reaction and 100% of the adsorbed hydrogen is recovered.

The hydrogen passes from the gaseous state to the liquid state at -253º C. Logically, in liquid state hydrogen is more manageable, but this low temperature is not reached in any way. Therefore, another option is to work with liquid nitrogen. Nitrogen is liquid at -196 °C and it is currently economically viable to reach this temperature.

In these conditions and with the help of a microporous material the physical adsorption is facilitated and the hydrogen is stored as if it were almost in liquid state. The process of releasing physically adsorbed hydrogen is fast, as it is small variations in pressure and/or temperature.

Will hydrogen be the fuel of the future? Due to its abundance and lightness, it can be adequate, but for this it is necessary to find an adequate and economic route for its production and conservation.

Possible impact of hydrogen

Hydrogen can be substituted from current energy sources, according to experts. The use of this gas as fuel, that is, the oxidation of hydrogen, has a great hope for the generation of water in this process. This means that no hazardous waste is generated, so it is a clean fuel for the environment. But now there are scientists who have doubts about this idea.

What if hydrogen was our main source of energy? In this case, a lot of hydrogen should be burned, for which the infrastructures should be fully adapted. It is not the same to do small-scale tests, for example in a laboratory, that produce hydrogen in large quantities. Industrial production, in short, is not at all efficient and hydrogen emissions into the atmosphere would be high. The determination of the consequences that this would entail is not a simple task, since the influence of hydrogen is very influenced by many factors. However, experts consider that one way or another could cause damage to the environment (atmosphere, ozone layer, etc. ).