Scientific research has just focused on systems that use direct methods of hydrogen production without CO2 emissions, where certainly the greatest role-plays splitting of water that is present in sufficient quantity.
Between all techniques of water splitting the most known is water electrolysis as the only commercial technique, then thermochemical water dissociation, and water biophytolysis. Among other techniques, there are mechanical – catalytic water dissociation, water plasmolysis, magnetolysis and radiolysis, and photoelectrolysis.
Hydrogen storage is divided into mass (stationary) and mobile (for vehicles). Effective hydrogen storage is the key to wider acceptance of hydrogen technologies in general.
The first category is atomic hydrogen storage where the material requires the redistribution of the hydrogen molecule in the hydrogen atoms and the binding of the same atoms with the storage mesh of the medium;
The second category is the molecular hydrogen storage into the surface of a material with a microporosity feature. Hydrogen molecular storage is achieved via surface forces. Such materials include nanotubes and nano grid structures that can have different dimensions, shapes, and surface modifications.
Except by pressure, releasing hydrogen from the storage medium is also achieved by increasing the temperature of the metal hydride.
Hydrogen transportation and distribution
Hydrogen can be transported through pipelines already existing in hundreds of miles across Europe and the United States (US). Furthermore, it can be compressed into the above-ground and underground pressurized storage tanks.
It can also be liquefied and stored in cryogenic storage tanks. In practice, there is present hydrogen storage on a large scale near the facility for its production, as well as hydrogen storage on a small scale on special vehicles for hydrogen distribution in compressed and liquid form. Fuel cells electric vehicles (FCEV) have smaller tanks, which is a particular area of interest due to their large share in global energy consumption for the transport sector.
Hydrogen can be used as a fuel in internal combustion engines and gas turbines or can be mixed with natural gas and burn on steam generator burners. But the most attractive technique is hydrogen usage in fuel cells.
The main product of the process in the fuel cell is electric energy with heat and water as by-products (water can be further used for electrolysis process in the electrolyzer stack – the closed process of hydrogen circulation in nature).
Hence, the intermediate step with conversion to mechanical energy is avoided. The potential for the use of hydrogen fuel cells is presented in all areas where there is a need for energy (industry, households, transport, ICT, etc.).
The theoretical efficiency of hydrogen fuel cell goes over 83%. A major challenge in fuel cell applications is to maintain their efficiency over the set number of operating hours. However, development research has a steady upward trend, so significant improvements can be expected in the short-term period.
Teorijska učinkovitost vodikovih gorivnih članaka
State of the Art and Perspectives
Considering the awareness of global warming and the importance of environmental protection, today’s market trends are such that hydrogen is a constituent part of all energy strategies and directives. Scientific researches on hydrogen fuel cells in conjunction with renewable energy sources (RES), demonstration projects, and their application are present in all EU framework programs as one of the seven key technologies of the 21st century.
In the developed world technology is developing exponentially and it is in political focus because it is a condition of survival and retention of the existing global positions of the state economy.
Thus, the EU has issued a directive to ensure the flow of hydrogen vehicles in a way that hydrogen refuelling stations need to be installed every 300 km by 2025.
Large oil companies and the automotive industry are backing up this kind of development because it is already quite clear about the end of the oil era (not so much because of the lack of reserves as it is because of harmful effects on the environment).
Billions of dollars have already been spent on research and development of hydrogen fuel cells that have been funded by EU, US, Canada, and Japan governments, including the private sector as well. It is very important that these new age technologies be accepted and incorporated into the energy strategy of the Republic of Croatia on time.
If we consider the millions of motorized tourists who will come to us increasingly by using electric vehicles, it is quite clear that it is necessary to speed up the installation of refuelling stations both for hydrogen fuel cells powered electric vehicles and battery-powered electric vehicles.