Green hydrogen is produced from renewable electricity and water by electrolysis. Water (H2O) consists of hydrogen (H2) and oxygen (O2). Electric current can be used to break down the water into its components H2 and O2. The hydrogen produced in gaseous form can then be processed further depending on the application.
Hydrogen can be stored as a gas over long periods of time. To reduce the necessary storage volume, hydrogen is often compressed to 200 bar. If necessary, the hydrogen can be converted back to electricity and water vapour together with oxygen. This can be done in a fuel cell or in a combustion engine. In this way, hydrogen serves as an energy storage medium for renewable electricity. For example, electricity can be harvested in summer and stored for winter. Hydrogen is therefore well suited as a seasonal storage medium.
Research is currently being carried out into alternative storage possibilities for storage under pressure.
Hydrogen is the basis for the production of so-called synthetic fuels. Together with carbon dioxide (CO2) or carbon monoxide (CO), a number of chemical substances can be produced which serve as fuel.
The simplest chemical substance that can be produced from hydrogen and carbon dioxide is methane. In a first step, hydrogen is produced by electrolysis and in a second step, called methanisation, methane is produced from H2 and CO2. The term “power-to-gas” is often used to describe the production of methane. Other possible synthetic fuels are methanol, DME, or even synthetic petroleum.
Many applications in the chemical industry require hydrogen. This hydrogen is still produced from fossil raw materials such as natural gas. Gradually, attempts are being made to replace hydrogen with green hydrogen. Examples of applications in industry include:
- Starting material for the production of ammonia, hydrochloric acid, methanol, aniline and many other substances
- Use as welding gas (for autogenous welding)
- As reducing agent for the extraction of metals
- As inert gas in steel processing and steel production for direct reduction
- In the laboratory
Hydrogen can be used as a fuel for vehicles. To do so, the gaseous hydrogen is carried in a pressurised tank at a pressure of 700 bar for passenger cars and 350 bar for commercial vehicles. On board of the vehicle, the hydrogen is converted into electricity in a fuel cell with high efficiency. The oxygen required for this comes from the ambient air. Only water vapour is produced as the end product. The resulting electricity is used to drive one or more electric motors in the vehicle. The vehicle has no further emissions.