Green Hydrogen

GREEN HYDROGEN

Lynchpin of the energy transition

Green hydrogen is widely regarded as a key enabler of the global energy transition, as it provides an essential pathway for the rapid decarbonization of industries that cannot be directly electrified. These carbon intensive industries include aviation, shipping, steel, cement, fertilizer, chemical production and many more - which together, account for approximately 30% of global CO₂ emissions. Whilst hydrogen has been used for over a century, its means of production must make way for newer and more sustainable methods.

About hydrogen?
Hydrogen is one of the most abundant elements on earth, and already plays a crucial role in today's energy landscape. According to the International Energy Agency (IEA), hydrogen's use tripled from 1975 to 2018. Whilst hydrogen is a dense and flexible energy carrier, when produced using fossil fuels, it emits a significant volume of CO2 emissions.

What is green hydrogen and how is it produced?
Green hydrogen is the product of electrolysis, a process that separates water into its two elemental components: hydrogen and oxygen. Electrolysis requires electrical current, which is supplied by renewable energy sources such as wind, solar, hydroelectric or nuclear power. This production method ensures that the hydrogen is generated with the lowest possible CO₂ emissions.

Green hydrogen's role in the energy transition?
Green hydrogen will transform the energy landscape by providing a sustainable and scalable solution to meet both current and future energy needs. From its use as direct replacement for the fossil fuels currently powering heavy transport and industrial processes, green hydrogen can be easily synthesized into a range of eFuel derivatives. From eMethanol and green ammonia, to its role in the production of electrified Sustainable Aviation Fuel (eSAF) - green hydrogen is a true lynchpin of the energy transition.

Green
Hydrogen
Production

PtX process

Understanding the electrolysis process

Green hydrogen is produced via electrolysis, which is commonly accomplished by using three different industrial technologies: high-temperature Solid-Oxide Electrolysis Cell (SOEC); low-temperature alkaline electrolysis; and low-temperature polymer electrolyte membrane (PEM) electrolysis. For alkaline and PEM electrolysis, water is supplied in a liquid state, whereas SOEC leverages steam.

The operation of the three technologies also differs. For SOEC, the breakdown of the steam takes place within the SOEC cell, with the steam being supplied at the cathode, where it is split via reduction into a green hydrogen molecule and oxide ions (O2-). The oxide ions are then transported through the electrolyte to the anode and oxidized into oxygen molecules.

During alkaline electrolysis, liquid is supplied at the cathode, where hydrogen production occurs. Hydroxide ions (OH-) are then transported over the electrolyte to produce oxygen molecules and water at the anode.

During PEM electrolysis, liquid water is supplied at the anode, where oxygen production occurs. Protons (H+) are then transported over the electrolyte to produce hydrogen at the cathode.

Three routes to H2

Conceptual New

Whilst there are three main routes to ulta-low carbon hydrogen, SOEC is the clear leader.

The higher efficiency of Topsoe's SOEC technology compared with alkaline and PEM is driven by the fact that SOEC operates at a higher temperature, benefitting from faster kinetics and higher conductivity. As a result, Topsoe's SOEC electrolyzer runs at a lower voltage, which translates into a lower power consumption per unit of hydrogen produced.

Illustrating the energy flows