Hydrogen: Lighter than air

How it works

Hydrogen (H) is the most abundant element in the universe. It is an component of water (H2O) and nearly all organic compounds.

Furthermore, it is the chemical element with the lowest atomic mass. Atomic hydrogen (H) does not occur in our daily lives, but molecular hydrogen does: H2, an invisi-ble, colourless, odourless gas (more about the chemical element in Wikipedia). It is 14 times lighter than air and has a very low volumetric energy density (energy per m3). Pro unit of mass, hydrogen holds a great deal of energy (calorific value), for example 3 times more than petrol and 7 times more than wood pellets. 

Hydrogen can be recovered in two ways. Today’s most common method is by means of steam reformation from natural gas. The natural gas is split and reacts with the ambient air; so-called grey hydrogen occurs and CO2 is emitted into the atmosphere. When the produced CO2 is captured and stored, the hydrogen is designated as blue, and, accordingly, has a very low CO2 intensity. Today this rarely takes place.

Green hydrogen: CO2-free and climat neutral

The second method requires water in place of natural gas as the source material. The water is split into water and air by means of electrolysis. If the power used in the process is renewable, this hydrogen is designated as green. The following film explains how green hydrogen is produced, what it means and how Axpo is involved in this area.

Since the transport and storage of hydrogen is complicated, it makes sense to process it into more easily manageable products. One option is to extract nitrogen from the ambient air and use it to convert the hydrogen into ammonia. Another method is to extract CO2 from the atmosphere and convert the hydrogen into methane or methanol. These derivatives can be used as energy sources or as chemical source materials. 

Hydrogen can also be converted back into electricity. How this is done is explained in the next paragraph. However, it must be noted that every conversion step leads to efficiency losses.

Conversion into electricity

Converting hydrogen back into electricity can take place by means of a thermochemical process or a fuel cell. This fuel cell is an electro-chemical device used to directly convert the fuel cell's chemical energy into electricity.

Similar to batteries, fuel cells produce direct current at low voltages. A battery uses a chemical substance that is contained in the cell unit. In contrast, in fuel cells the fuel is continuously supplied to the cell unit, similar to gasoline or diesel fuel in a combustion engine.

Our hydrogen

Green hydrogen, which is produced with power from renewable energy sources, is considered a pillar for the energy transition, in Switzerland as well as abroad. Axpo has decided to engage in this activity and is developing the following projects:

Reichenau hydropower plant (2,5 MW)

Following the building permit procedure, Axpo and Rhiienergie began construction work on the 2.5 MW hydrogen production plant at the Reichenau hydropower plant on 23rd January 2023. The plant will be connected directly to the Reichenau hydropower plant, in which Axpo holds a majority stake. It will produce up to 350 tonnes of green hydrogen per year using Swiss hydropower. This corresponds to around 1.5 million litres of diesel fuel, which can be saved in the canton of Graubünden and the neighbouring Rhine Valley in future. The green hydrogen produced in Domat/Ems makes a decisive contribution to decarbonisation and can be supplied to both industrial customers and filling stations. Commissioning is planned for the beginning of 2024. Axpo and Rhiienergie are jointly investing an amount in the high single-digit million range in the plant in the canton of Grison.

Axpo and SGV plan hydrogen passenger vessel on Lake Lucerne

Axpo is participating in the H2Uri company, which is building a hydrogen production plant in Bürglen, central Switzerland. The regionally produced hydrogen will be used to power a passenger vessel on nearby Lake Lucerne, operated by the Lake Lucerne Navigation Company SGV AG. In addition to Axpo and SGV, EWA-energieUri and AVIA Schätzle are also involved in the project. The hydrogen plant is to follow at Bürglen in the Swiss canton of Uri, with hydrogen production expected to commence in 2025. Among other benefits, the plant’s production will be used to power the first hydrogen passenger vessel on Lake Lucerne. The conversion of the SGV-Vessel "MS Saphir" to a hydrogen fuel cell system will be completed by autumn 2025.

Wildegg-Brugg hydropower plant (up to 15 MW)

Another climate-friendly hydrogen production facility will be built on the Wildischachen industrial location in Brugg (AG), and will be Switzerland's largest hydrogen plant. Axpo, Voegtlin-Meyer, IBB Energie AG (IBB) and the city of Brugg have signed a memorandum of understanding to this end. Axpo plans to deliver clean hydrogen from domestic hydropower directly to the nearby Voegtlin-Meyer filling stations via a pipeline. From there, the green hydrogen will be made available to private users and for the buses operated on behalf of PostAuto AG. The produced volume can be used to drive about 300 trucks, post or other buses for one year. 

43-percent share in Swiss Green Gas International 

Axpo holds a 43% interest in Swiss Green Gas International, in short SGGI. The joint venture company founded in 2020 plans and realises power-to-X facilities in Northern Europe (more on power-to-X on Wikipedia). The plants produce hydrogen and synthetic methane (green gas) from renewable electricity. This will promote the urgent, rapid exit from fossil energy sources. Other SGGI shareholders are Holdigaz SA, which primarily supplies the Cantons of Vaud, Valais and Freiburg with gas, and Nordur Group GmbH, a development and investment company.   

The solutions offered that Axpo offers to businesses can be found on the business page

White paper: Role and potential of hydrogen in Switzerland

In the white paper, Axpo shows the economic viability and possible uses of the energy source with concrete figures. The document also addresses the central challenges of the hydrogen economy in Switzerland.

Hydrogen from A to Z

Like electricity, hydrogen is not necessarily green. Depending on the production method, hydrogen is labelled differently. Below you find the most important answers about the different colors of hydrogen.

The most important answers about hydrogen

Green hydrogen is produced through the electrolysis of water. Electricity generated from renewable energy sources like hydropower, wind and solar energy is used. As a result, green hydrogen is CO2-free and of great importance because it is climate neutral and contributes to decarbonization. 

Grey hydrogen is produced by means of steam reformation, usually from natural gas. Some 10 tonnes of CO2 per tonne of hydrogen are produced. The unused CO2 is released into the atmosphere. Steam reformation is the most widely used process in Europe. 

Blue hydrogen is grey hydrogen, which captures CO2 during the production process and then stores it in the ground (carbon capture and storage CCS). 

Turquoise hydrogen is hydrogen that is produced through the thermal decomposition of methane (methane pyrolysis). Solid carbon is produced instead of CO2. The methane pyrolysis process is still in the development stage.

Yellow hydrogen is hydrogen that is generated from the power mix in the existing grid. In Switzerland, this is mainly electricity from hydro and nuclear power.

Pink hydrogen is produced with electricity from nuclear power. Nuclear power is nearly CO2 free in operation, but its energy source is not renewable.


Hydrogen is an important pillar of the energy transition. First, it allows areas such as transportation (e.g. freight transport and air traffic), certain industries (e.g. steel and fertilizer production) and heat production to be decarbonized. Second, as an energy carrier, it can be used to store and transport renewable electricity over long distances in the form of derivatives. This allows renewable energy to be produced in the most favourable locations and decoupled from consumption. Hydrogen is therefore central to the strategies of many countries and the EU.

Not feasible everywhere

Hydrogen must be used in areas where electrification is not efficient or possible as a substitute for fossil energy sources from a process-technical perspective. 

This graphic simplifies matters. How "feasible" an application is often depends on local conditions.

A few examples

The production of ammonia from hydrogen is energetically useful. The bonding of water and nitrogen is primarily used as fertiliser, but also in the chemical industry, for example in plastic production.

Hydrogen is also suitable for the generation of industrial heat, for example, for machine operation or chemical processes that require high heat. According to the Inter-national Energy Agency IEA, this heat generation makes up two thirds of industrial energy consumption and currently comes almost solely from fossil fuels.

Another example is steel production where large CO2 volumes occur: To extract steel from ore, hydrogen could be used instead of coking coal. 

Hydrogen is also an options in areas where long distances have to be covered. For example, Airbus is planning to produce a hydrogen aircraft in series as of 2035. Hydrogen can also replace heavy fuel in ships or diesel in trucks. For passenger cars the use of hydrogen is not really feasible.  

And: Hydrogen and its storage capability in the form of its derivatives can balance out electricity supply and demand, which must be more closely monitored with the expan-sion of renewable energies – a contribution to security of supply with electricity.

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