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Solid Oxide Electrolysis

Solid Oxide Electrolysis (SOEC): Next generation green hydrogen production

Even as targets are set and pledges made, humanity’s greatest industrial undertaking – the  energy transition – continues to represent an enormous logistic and economic challenge. At TOPSOE™, we know that challenges of this magnitude can only be addressed through a diverse ecosystem of solutions — applying different technologies and strategies so each industry has a unique and effective pathway to decarbonization. For the hard-to-electrify industries, Power-to-X is one of these key solutions. 

PtX offerings

The core of TOPSOE™’s PtX offering is our proprietary solid-oxide electrolysis cell (SOEC) technology that leverages high-temperature electrolysis to enable the industrial scale production of green hydrogen. High-temperature electrolysis, empowers companies in the hard-to-electrify sectors to generate ultra-low carbon hydrogen or carbon monoxide using renewable electricity. The unmatched efficiency and industrial scalability of SOEC technology position it as an ideal means to an ideal end: producing more hydrogen per total power input and maximizing your investment in renewable energy.

Benefits of TOPSOE™ SOEC? 

Our SOEC technology is designed to integrate seamlessly with downstream processes, so green hydrogen can be processed into green ammonia, for use in chemical applications or energy storage; eMethanol, for use in chemical or transportation-fuel production; or one of many other green chemicals and fuels.

With decades of experience as a world-leading solution provider for all of these applications, TOPSOE™ is one of the few companies capable of providing the insights and technology needed to facilitate the production and large-scale availability of next-generation fuels and chemicals. We are already engaged in several projects aimed at proving the viability of SOEC, including our work with First Ammonia, a pioneering integrated green ammonia producer developing modular, commercial scale plants using TOPSOE™’s electrolysis technology.

TOPSOE™’s SOEC technology is a modular design that leverages high-temperature electrolysis — a tested and proven process that enables industrial-scale production of green hydrogen using renewable electricity. Due to the nature of the intrinsic fast-reaction kinetics and optimized conductivity found in high-temperature electrolysis, TOPSOE™’s SOEC technology produces more hydrogen per total power input when compared to the alternatives of alkaline and PEM electrolysis. 

Additionally, when coupled with waste heat-producing technologies (such as those used in ammonia production, methanol production or steel production), SOEC allows for the lowest levelized hydrogen cost with the highest level of energy efficiency per megawatt or gigawatt volume, no matter the industry.

Illustrating the energy flows

With TOPSOE™’s SOEC, the value of a renewable electricity investment is utilized optimally to produce green hydrogen. This results in ultra-low carbon, highly efficient processes for Power-to-X solutions.

How does SOEC work? 

Demineralized water is evaporated, and then heated to the required temperature range from 675ºC to 825ºC at the entrance of the SOEC section; low-value steam can be imported to aid in the evaporation process. In the SOEC section, further heating takes place along with the reaction itself. SOEC has a wide operating range, which allows for mitigation against degradation of the stacks. 

The SOEC cells are compact structures built primarily from abundant, low-cost ceramic materials. The steam flows in metal structures and is evenly distributed through microchannels into the cells. Within these cells, the electrolysis reaction splits the steam into hydrogen and oxygen, after which the latter leaves the electrolyzer while the hydrogen is cooled; excess water is then recycled via a separation process. The saturated, green hydrogen can then be compressed or purified to meet the clients’ 

Green hydrogen production process-1

The TOPSOE™ SOEC electrolyzer is a compact stack built primarily from abundant, low-cost ceramic materials enclosed within a metal housing. To produce hydrogen, it utilizes electricity to split water molecules (H2O) into hydrogen (H2) and oxygen (O2). This is accomplished by three components: an anode, a cathode, and an electrolyte. The cathode splits water molecules, via reduction, into hydrogen and oxide ions, after which the oxide ions are transported through the electrolyte to the anode and oxidized into oxygen.

How does SOEC compare with PEM & Alkaline?

The higher efficiency of TOPSOE™'s SOEC technology over 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 solution runs at a lower voltage, which translates into a lower power consumption per unit of hydrogen produced. 

Energy Demand for Water Electrolysis

1. SOEC electrolysis benefits from operation at a lower voltage

SOEC is more efficient than both alkaline and PEM technologies since it operates at a lower voltage. SOEC operates at a voltage covering exactly the sum of the electricity and heat demand, while alkaline and PEM processes both operate above the sum of these two. The reason for this is that SOEC operates at the thermo-neutral voltage, which is the point at which the heat demand is balanced out by the Joule Heat. Joule Heat is produced from resistance that occurs when an electric current is applied to the electrolysis cells. This, in turn, means that temperature gradients do not occur within the SOEC, as the temperature of the steam supplied is equivalent to the temperature of the resulting green hydrogen product.

 2. SOEC electrolysis benefits from optimal design and plant integration

When compared to alkaline and PEM alternatives, the SOEC electrolysis process requires less power overall. Additionally, with the integration of a steam feed, the SOEC process becomes even more efficient. Since the hydrogen product is in a gaseous state, extra energy is required to evaporate any water needed for alkaline or PEM processes. In the case 
of SOEC, steam is utilized, resulting in further reduction of the total energy demand.

3. SOEC electrolysis produces more hydrogen per unit of power consumed

More hydrogen is produced, per total power input, by SOEC technology compared to alkaline and PEM, making SOEC a more efficient solution. This efficiency is further improved when steam is imported, whereby SOEC’s hydrogen-production capacity per total power input increases compared with that of alkaline or PEM. By comparing the three technologies’ energy flows, it is evident, that SOEC is significantly more efficient. The advantage of operating a SOEC comes from its highly optimized design, which 
produces more green hydrogen while exhibiting only minor low-grade heat losses from the total heat input.


At TOPSOE™ we follow the solution all the way from production to end customer, ensuring a safe start-up and fully optimized, scalable plant performance that we guarantee from initial electricity intake to the final product molecule. We consider it our responsibility to alleviate as much customer risk as possible. We do this through long-term production, optimization and maintenance, and by providing comprehensive optimization across the entire plant, facilitated by decades of troubleshooting experience within the petrochemical and refinery sectors. By managing the development of the full SOEC electrolyzer system, we give our customers the certainty they need to manage their energy consumption and production costs.

Download our Bridging the Gap whitepaper to learn more about the benefits of TOPSOE™ SOEC electrolysis.

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Sundus Cordelia Ramli
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