Hydrogen – a versatile energy carrier

Hydrogen is a versatile element that can form compounds with a wide range of other elements. For example, hydrogen combines with oxygen to make water and with nitrogen to produce ammonia. Hydrogen is therefore used in the chemical industry to produce nitrogen fertiliser and in petroleum refineries to refine mineral oil. New processes for the production of green hydrogen, i.e. completely CO2-free hydrogen, open up new possibilities for the use of hydrogen in various sectors of the energy industry as climate-friendly and innovative alternatives, and to advance the energy revolution.

Green hydrogen is produced through electrolysis, a process whereby water is split into its constituent elements of oxygen and hydrogen using electricity from renewable energies. As hydrogen is an efficient energy carrier, electrolysis can also be used for the indirect storage of electricity and its subsequent reconversion. Renewable energy sources are particularly subject to seasonal fluctuations, in that sometimes more electricity is generated than can be used, and at other times too little electricity is available. Surplus electricity can be converted into hydrogen using electrolysis and stored in storage caverns. When more electricity is then needed, the stored hydrogen can be combined with oxygen in a fuel cell as part of a reverse electrolysis process, which generates a great deal of energy. This energy can then be fed back into the electricity network. So hydrogen offers a solution to the long-term storage of electricity generated from renewable energies. Alternatively, the stored hydrogen can also be converted into methane and water by adding CO2 and fed into the natural gas infrastructure instead of extracted natural gas.

The shift away from fossil fuels, for example in the form of petrol and diesel, is becoming increasingly important in the mobility sector. Battery-powered electric vehicles are already a major presence on our roads. However, vehicles that carry heavy loads, such as lorries and transport trucks, consume an enormous amount of energy on long hauls. A hydrogen-powered fuel cell with a long range can serve as an alternative to the battery in these cases. Oxygen and hydrogen combine in the fuel cell to produce energy and water. Fuel-cell vehicles can be refuelled with hydrogen at special fuelling stations. Their particularly fast refuelling time is another advantage over electric batteries. However, the installation of a comprehensive network of hydrogen fuelling stations is still in the early stages of development.

Hydrogen-powered vehicles are equally suitable for local passenger transport and urban traffic as they are for transport fleets. Buses and waste collection trucks, for example, haul a large load and cover a predictable distance every day. This means that they can be conveniently refuelled with hydrogen in the vehicle fleet at the end of the day. There are also already pilot projects testing the use of hydrogen trains on certain routes. The use of fuel cells and hydrogen is a viable alternative, especially on routes where overhead power lines have not yet been installed or where the construction of such lines is complicated.

Large segments of industry continue to use fossil fuels and emit a large amount of CO2. Factories for the production of steel, glass and ammonia, for example, are powered by coal or natural gas and their conversion to electric-powered processes is not always possible. Green hydrogen, by contrast, can replace natural gas and deliver enormous savings in emissions. Because of its high heat capacity, hydrogen can also be used as a coolant in power plants, for instance.

The storage of hydrogen and its reconversion using reverse electrolysis also offers potential for the heat and heating sector. The conversion of hydrogen into energy produces both water and a considerable amount of heat, which could also be used to heat buildings in the future. Older buildings not yet converted to electric heating offer the ideal situation for heating with hydrogen using existing gas pipes. Heat generation plants in district and local heating networks could also be operated on a climate-neutral basis with green hydrogen, but they would have to be retrofitted to do so.

Hydrogen is also used to produce synthetic fuels, such as e-fuels, for internal combustion engines. With more development, these e-fuels could help to reduce emissions in long-distance and shipping traffic.

The use of hydrogen offers significant potential for climate protection and the implementation of the energy revolution. Surplus electricity from renewable energy sources can be stored as chemical energy in the form of hydrogen and made available for long periods of time. In the mobility sector, vehicles powered by hydrogen and fuel cells are a practical complement to electric vehicles, and hydrogen can also work as a substitute for natural gas in industry to reduce emissions. In the long term, the best option for protecting the climate is a complete switch from blue hydrogen, the production of which generates CO2 and which is stored underground, to green hydrogen. Power-to-gas processes can use hydrogen to convert electricity into natural gas in a climate-friendly way. In addition, new and more efficient heating options are emerging and hydrogen-based e-fuels open up climate-friendly perspectives for long-distance and shipping transport. The entire energy industry can benefit from hydrogen energy supply systems, making hydrogen a central piece of the puzzle towards realising the energy revolution.

Hydrogen can be used in a variety of ways to achieve many of the objectives of the energy industry. Although hydrogen applications have great potential for energy supply systems, they also face challenges.

The overarching objective of almost all hydrogen applications is the climate neutrality of all energy supply systems. Green hydrogen is completely free of emissions and can be used without reservations. As a substitute for natural gas, hydrogen helps protect the climate while also offering an alternative to the expensive and contentious extraction of natural gas. The use of hydrogen is also expanding options in the mobility sector and aims to make zero-emission driving possible for heavy goods vehicles as well. Another major goal of hydrogen applications is sector coupling. Hydrogen interlinks the three sectors of the energy industry (electricity, mobility and heat supply) and offers comprehensive solutions across all sectors.

Hydrogen’s great potential for climate protection is also bound up with challenges. First, the hydrogen used in various applications must be guaranteed to be green, i.e. produced only using renewable energies. Moreover, many of the hydrogen applications in the different sectors are still in their infancy. If the use of hydrogen-powered vehicles is to be feasible, a nationwide network of hydrogen fuelling stations would have to be put in place. In many places, the technical infrastructure required for heat and heating still needs to be created, or existing systems converted. Storage caverns required for reconversion will also have to be built on a large scale. The large number of hydrogen applications in different locations also makes transporting it a challenge.

Nevertheless, most of these challenges are due to the comparatively recent development and popularity of hydrogen applications. In 2020, the German government’s National Hydrogen Strategy advocated the promotion of the hydrogen economy to overcome many challenges in the future. EWE considers hydrogen to be one of the key elements for sustainable, successful climate protection.