The producers

Electrolysis systems produce the hydrogen, Jülich researchers improve them.

The windmills are turning fast. Production of green electricity is running at full speed. Electricity, not needed by the computers in offices, households and industry at the given moment, can be used to split water in electrolysis systems. In this way, hydrogen is produced and the electrical energy is converted into chemical energy. This allows excess electricity to be stored.

“We are working on the optimisation of three different electrolysis processes,” says Dr. Martin Müller, process engineering specialist at the Institute of Energy and Climate Research (IEK-14). “Each process has its strengths and weaknesses. It is still open which one will win the race, and it also depends on whether the electrolysis system is installed directly at a wind farm, a home solar power system or in a chemical network, for example.”

Electrolysis system

The producers

Where Jülich researchers improve the cell

1. PEM systems require expensive and rare noble metals such as platinum and iridium. Yet, Jülich researchers have recently developed an anode (positive pole) which needs no more than a touch of iridium oxide to achieve excellent results. With such electrodes, PEM systems could be realised that only require about 10 per cent of the iridium quantity used so far.

2. Jülicher scientists have produced the unit, which consists of a coated membrane and electrodes, using a process that is suitable for mass production and yet flexible: the substances for the individual layers are each finely distributed in liquids and the resulting dispersions are applied step by step with a slotted nozzle.

3. A new design of PEM electrolysis systems with very thin membranes makes it possible to supply the water in a different way than conventionally. According to calculations, this results in a 15 per cent reduction in investment costs.

Types of electrolysis plants

The classical one
The promising one
The hot one

Plants where the central component, the electrolyte, is an alkaline liquid can be bought off the shelf, so to speak. Alkaline electrolysis plants make do with inexpensive materials. A major disadvantage is their low power density: they produce comparatively little hydrogen per square centimetre of surface area. Large space requirement and high material consumption are the result. “Alkaline electroly­sers are generally considered to be technically mature, but we are pursuing new approaches to increase their power density,” says Müller. One of these approaches is based on new partitions which are installed in the liquid electrolyte to electrically isolate the negative pole (cathode) and the positive pole (anode) from each other.

Higher power densities than alkaline electrolysers are achieved in systems in which the electrolyte does not consist of a liquid but of an extremely thin layer, a so-called polymer electrolyte membrane (PEM). However, the high costs of PEM plants stand in the way of wider dissemination. “Jülich researchers have their sights set on various parts of the facility to change this,” says Dr. Marcelo Carmo, electrochemist at IEK-14.

While alkaline and PEM electrolysis systems are usually operated at around 80 °C, the third electrolysis process requires more than 650 °C. In these so-called SOE systems (Solid Oxide Electrolysis), the high operating temperature must be maintained even when no current is available. This is because starting and stopping the system would cost even more energy – and this would also tire out the material more quickly. The technology is economically interesting nevertheless: “The SOE systems are very well suited to use the heat generated by many industrial processes. Then, they convert the electricity very efficiently into the chemical energy of hydrogen,” explains Prof. Ludger Blum of IEK-14. In recent years, Jülich researchers have made SOE electrolysers more reliable and durable through various improvements.

Last Modified: 08.08.2022