Hydrogen in paste, coating or underground?

Researchers from the German Fraunhofer Institute have developed a method of storing hydrogen energy in the form of magnesium hydrate, which has the form of ... paste. However, producing Powerpaste, as the substance is called, is expensive because it requires high pressure and temperature.

For the time being, the most common way of storing hydrogen is by compressing it and storing it in pressure tanks. The higher the pressure, and the lower the mass, the greater the 'capacity' of the tank. Therefore, a technological arms race is underway worldwide to develop safe, cheap and durable tanks. A black horse in this competition may be a method created by researchers from the Wrocław University of Technology, who have developed a coating that improves the tightness of composite hydrogen tanks.

– We can already boast of some results in reducing the permeability of this gas - says Engineer. Justyna Krzak D.Sc. from the Sol-gel Materials Research Group in the Department of Mechanics, Materials Science and Biomedical Engineering. The oxide coatings developed in Wrocław improve the barrier properties of HDPE polyethylene by 36 percent. - This is a great potential, which arouses considerable interest among foreign companies manufacturing the so-called liners for high pressure tanks, i.e. the part directly responsible for stopping the gas inside - adds Dr Krzak.

Scientists from Wrocław continue research on polymer sealing, studying details of the blocking mechanism, interactions between gas molecules and the coating material, as well as the influence of the mechanical field on these interactions. There is also a need to develop a method for manufacturing containers.

– In the case of small surfaces, the immersion technique is used to apply the coating, explains Dr Krzak. - Here, however, we are dealing with large samples, and actually tanks. Therefore, we need to develop a method to be applied on an industrial scale. To this end, we will build a head for depositing the layer, its stabilisation and detection of possible discontinuities in the coating.

In addition to compressed gas, hydrogen is also stored in cryogenic liquid form. Hybrid methods are also used - hydrogen in semi-liquid form (slush) or cooled and compressed (30 MPa, -235° C). Hydrogen can also be combined with organic carriers and ammonia or mixed with natural gas.

As with natural gas, the cost of building and maintaining aboveground tanks is high. Therefore, underground tanks are used for gas storage, which save space and also provide additional insulation and no exposure to weather conditions. Hydrogen can be stored in depleted natural gas and oil deposits, in deep aquifers and in salt caverns, which have been used in the United Kingdom and the United States for several decades.

Polish fuel companies are also working on hydrogen storage. The Hestor project implemented by the Lotos Group confirmed the possibility of storing energy from RES in the form of hydrogen in salt caverns and using it in refinery processes and to power fuel cells. Investments in underground gas storage tanks are also carried out by PGNiG, which in October launched Cluster B in the Kosakowo cavernous underground gas storage facility. Thanks to five new storage chambers, the total capacity of KPMG Kosakowo has increased to 300 million m3 of natural gas. Will it also be possible to store hydrogen in the caverns? This is according to the announcement of the operator, who in Odolanów is testing the installation in terms of mixing and transporting hydrogen with natural gas. We will still have to wait for underground storage of hydrogen in Poland.

Is hydrogen storage safe?

In terms of safety, hydrogen is comparable to other gases we use every day - propane, butane, natural gas or petrol vapour. The difference lies largely in the fact that the equipment used to store and transport it must be very tight, as the hydrogen molecules are very small. However, hydrogen has an auto-ignition temperature of 585 °C and disperses several times faster than other fuels, so the potential danger is lower than with petrol vapour, for example. Of course, as with other flammable gases, safety is essential. Above all, avoid contact with fire sources and, if hydrogen is used in rooms or confined spaces, use special detectors.

Regardless of which method of hydrogen storage - in vapour, gel or underground - is used, open communication about hydrogen technologies is needed. Australian researchers have proposed using existing experience in communicating energy projects, including underground carbon dioxide storage. As with any new technology, the use of hydrogen may raise public concerns, and therefore, according to the researchers, there is a need to prepare open communication as well as to involve social partners in the communication. The researchers point out that possible hydrogen leaks are relatively easy to monitor, which may facilitate public readiness to adopt hydrogen technologies.