What is electrolysis?

How is green hydrogen obtained? What is electrolysis? Learn what this process consists of and its benefits here.

The most efficient process of hydrogen manufacturing from electrical energy is through electrolysis. This process involves the separation of water into its elements, hydrogen and oxygen, when an external electric current (electricity from renewable sources) is applied. In this way, renewable electricity will be stored in the form of hydrogen.

Benefits and disadvantages of electrolysis

The benefits of this process is that it produces no waste and is completely renewable.

One of the major disadvantages is the price of the hydrogen produced. The current price of green hydrogen production from a renewable energy source is around 5-8 €/kg, but this cost (OPEX) depends mainly on the price of renewable energies, therefore it is estimated that this price will be reduced in the coming years as the cost of the renewable energies decreases, making it competitive with hydrogen from fossil fuels.

Cost of manufacturing

In the last decade, electrolytic technology for green hydrogen production has been greatly improved and has reached commercial development, but improvements are still needed to enable its expansion.

These technologies still need to be improved in order to increase their efficiency and reduce their CAPEX cost. This cost includes the cost of the electrolyser, but also the cost of the plant (current converters, water accumulators, pressurisers, auxiliary systems).

This price depends largely on the increased manufacturing of electrolysers and an increase in their capacity.

For example, the price of an electrolyser + Plant Balance of a 200 kW proton-conducting polymeric membrane electrolysis (PEM) system producing 10 units is approximately € 1100 / kW.

However, the price of an electrolyser + Balance of Plant of a 1 MW PEM system producing 1000 units is reduced to approximately 237 €/kW.

[Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, NREL, 2019]

Types of electrolysers:

There are several electrolytic technologies and all of them have in common the presence of two electrodes where hydrogen (reduction, cathode) and oxygen (oxidation, anode) are produced:

We will address them in detail in our next post, click if you want to know all the types of electrolysers.

By María Retuerto, researcher at CSIC and Hydrogen expert.
Collaborator at IDEA.