Germany must become climate neutral in 2045
For a successful energy transition, we need clean energy sources. Electricity from renewable energies is already making an important contribution to the energy transition, butsignificantly more energy is needed to generate heat for buildings or in industry - and this isstill primarily generated with fossil fuels. A far-reaching transformation process needs to get underway here- and hydrogen as aCO2-free alternative plays a crucial role in this. The state of Lower Saxony is particularly committed to "green" hydrogen and has already launched a number of initiatives and events as well as funding programs at an early stage. As the No. 1 energy state, Lower Saxony is to become a central location for the German hydrogen economy.
What is hydrogen?
Hydrogen is the most common chemical element in the universean energy carrier that can be used in many ways: Either by combustion as a heat source and further processed as biofuel (e-fuels), methanol or ammoniaor directly as fuel for vehicles with a fuel cell.
At the same time, hydrogen can be stored very well and can be used to generate electricity again, thus ensuring security of supply.
Hydrogen - best green
Hydrogen is the most common chemical element in the universe. For industrial use, however, it must be produced by adding energy. Usually with the help of the electrolysis process, in which water is split into oxygen and hydrogen by means of electricity. Depending on where the electricity for this splitting comes from, hydrogen is sorted by colour, although hydrogen itself is always colourless.
Only green hydrogen helps us with the energy transition, as the electricity used comes from renewable energies such as wind power and is thereforeCO2-free. That is why Lower Saxony is concentrating on green hydrogen in its production.
Grey hydrogen is usually produced by reforming natural gas. The production of one tonne of H2 emits around ten tonnes ofCO2 into the atmosphere.
Blue hydrogen is produced in the same way as grey hydrogen - in the end, a large part of theCO2 is captured and stored underground (carbon capture and storage, CCS). CCS is controversial in Germany due to unclear geological risks and the limited storage possibilities. In addition, leakages can have a negative impact on the CO2 balance.
In the production of turquoise hydrogen, noCO2 is released in the production process because the carbon is bound and stored in solid form. However, energy must be used for the production process, which leads toCO2 emissions if fossil fuels are used. This process is still under development and is being researched mainly in Norway and the Netherlands.
There are other colours that have not yet become established on the market, such as red hydrogen from nuclear power.
Hydrogen can be produced in several ways. The most common is electrolysis. Here, a redox reaction is induced in an electrolyzer by electric current and hydrogen (H2) is produced by splitting water into its components. There are several processes for this.
Alkali Electrolysis (AEL)
Alkaline electrolysis is the oldest and most common electrolysis process. It works with cheaply available materials. A potassium hydroxide solution (KOH) is used as the electrolyte and nickel-based electrodes, for example, as the electrodes. A disadvantage is the low efficiency of approx. 68% and the lack of ability to react to fluctuating energy supply (dynamics).
PEM electrolysis (PMEL)
In PEM electrolysis, a solid polymer electrolyte is used as a solid membrane(proton exchange membrane) instead of a liquid electrolyte. This allows the current density to be increased and the dynamics (responsiveness of the electrolyzer to fluctuating power generation) to be enhanced. In addition, the efficiency of PEM electrolysis is slightly higher than that of the AEL process, reaching up to 71%.
High temperature electrolysis (HTE)
High-temperature electrolysis operates at temperatures of 100-900°C. As a result, efficiencies of up to 90% can be achieved. This is achieved by the fact that part of the required reaction energy is introduced thermally in the form of steam. Therefore, HTE is suitable where corresponding waste heat from production processes can be used (e.g. steel production).
High-temperature electrolysis is still in the development phase.
Pyrolysis and plasmalysis
Methane pyrolysis and plasmalysis are newly considered processes for the environmentally friendly production of hydrogen. In these processes, the energy required to split the methane into its components H2 and C is introduced in thermal form. The thermal energy must come from renewable sources.
Methane pyrolysis (or methane cracking) is an endothermic reaction in which methane (CH4) is decomposed into its components C and 2 H2 by the input of thermal energy.
There are different processes for methane pyrolysis. One way to decarbonize the methane is to pass it through an electrically melted tin bath, where the hydrogen escapes upward and the carbon is deposited as slag on the tin.
A special form of methane pyrolysis is plasma analysis, e.g. the Kvaerner process. Here, methane is broken down into its components in an electrically generated high-frequency plasma. The released hydrogen molecules are captured, and the carbon also accumulates in solid form. Compared with electrolysis, the electricity requirement is said to be up to 75% lower.
Plasma analysis can also be used to break down dirty water into its components, thereby purifying the water and recovering hydrogen at the same time.
Possible uses of hydrogen
Hydrogen is very convertible as an energy carrier and can therefore be used in many ways. As a result, it offers decarbonisation potential for many areas of application. However, since clean hydrogen is currently scarce and precious, politicians, business and science are currently discussing where it can be used most sensibly. In principle, it can be used in many branches of industry, such as steel production, the basic materials and chemical industries, as well as in the transport sector, in rail and air traffic.
Ultimately, its use is most needed where the greatest emissions reduction can be achieved and where there is no alternative to decarbonising our economy. Therefore, green hydrogen should be used to decarbonise the basic materials and chemical industries, as well as in hydrogen power plants. For the building sector and individual mobility, on the other hand, hydrogen should play a subordinate role, since significantly more energy-efficient technologies are already available through the use of heat pumps and battery-electric cars, which enable faster and more cost-effective greenhouse gas emission reductions.
Here you can find forward-looking projects for the production of hydrogen, storage, transport and applications in industry and mobility.