The stack of solid oxide electrochemical cells (SOC) which has been under development at the Institute of Power Engineering stands as one of the key components of the value chain of hydrogen technologies. While contributing to the establishing of hydrogen economy in Poland, it serves in decarbonizing various sectors. Depending on the specific application and the requirements of the end user, SOC stack can be operated in a fuel cell mode (Solid Oxide Fuel Cell or SOFC) generating electricity and by-product heat or in electrolysis mode (Solid Oxide Electrolyzer or SOE) generating hydrogen and by-product oxygen. In addition, the possibility of switching between the SOFC and SOE modes or vice versa during the reversible operation (reversible Solid Oxide Cell or rSOC) it can be employed as a key component of an energy storage system. Because of the high temperature of operation in the range from 650 to 750 °C, SOC stacks offer exceptionally high efficiency and can utilize numerous fuels including methane and ammonia. This is one of additional advantages, that the can be thermally integrated with various industrial processes and facilities. That increases the overall performance of industrial processes and makes it possible to fully utilize the functionality of SOC.

One of the key features of the technology is its modular design. The stack is built by combining repeatable units which, when combined and multiplied, enable to reach higher power (in SOFC mode) or to produce more hydrogen (in SOE mode). The scalability of systems based on SOC stacks, adapting them to specific market demands and expected functionality is almost unlimited. In addition, it should be emphasized that SOC stacks developed at the Institute of Power Engineering are fabricated using innovative techniques which are zero-waste processes. The developed technology is therefore an attractive alternative when compared with foreign products with similar functionality which offer comparable operating parameters. Moreover, the structure is more compact hence the reduce dimensions lower the production cost. This reduction was possible thanks to highly automated production processes such as high pressure moulding of ceramic (injection of ceramics) and 3D printing which are not used elsewhere.

Advantages of the technology

The key advantage of the presented solution is the inherently high efficiency of the stack in both modes, namely, the fuel cell and the electrolysis mode. Additionally, the ability of the same device to operate in one of three modes (SOFC, SOE or rSOC) make it possible to tailor the design and functionality of systems based on SOC stack to the specific needs and requirement of a customer. In the case when the stack is fuelled by hydrogen steam is the only product of generation of electricity, therefore no pollutants, either in gaseous or solid form are introduced to the atmosphere. This makes the technology zero-emission.

It should be emphasized that the SOFC technology is characterized by high electrical efficiency in a typical range from 50 to 65% (system-level efficiency), and the total efficiency (combined generation of heat and power) exceeding 90%, which means higher energy efficiency of the system. In addition, unlike the low-temperature fuel cell technologies, it is possible to use various fuels, e.g. methane or ammonia, besides high-purity hydrogen.

When the SOC stack is used in electrolysis mode its consumption of electricity to produce 1 kg of hydrogen is lower by approx. 15-25% compared to low-temperature PEM and alkaline electrolysers. Replacing steam reforming of methane which is the well-established process for industrial-scale production of hydrogen results in the reduction of carbon footprint of H₂ production can be reduced from 8-12 CO₂/kg H₂ to 0 kg CO₂/kg H₂. Such a low value is achieved when the electricity which drives the SOC electrolysis comes from renewable energy sources such as wind or solar.

In addition, the manufacturing techniques used in the production of stack components, including 3D printing of seals and high-pressure injection of ceramics, not only reduce the cost of the technology but are zero-waste thanks to the possibility of utilizing the unused paste or injection mass.

Technology recipients

The SOC stack can be applied in various sectors. This is possible because the technology can be operated in alternative modes (SOFC, SOE and rSOC), is scalable enabling perfect match between the functionality and what customer expects. The primary fields of applications include, however are not limited to:

• chemical and petrochemical plants which include steam reformers of hydrocarbons which will have to be replaced by electrolysers,
• energy sectors based on gas turbines which are currently retrofitted and design to accommodate large amounts of hydrogen in the gas. Integration of electrolysis with gas turbines, and combined gas and steam cycles results in the reduction of carbon footprint of electricity,
• smart districts and hydrogen hubs which integrated multiple users seeking for near zero- and zero-emission energy sources which rely of renewable fuels such as hydrogen for production of electricity and heat,
• hydrogen mobility which expects zero-emission hydrogen for powering fleets,
• long-distance transportation including railway, truck, ships which require low-emission electrified propulsion systems. With its high efficiency and fuel flexibility, the SOC stack operated as a SOFC becomes an attractive prime mover in such applications,
• chemical and petrochemical plants and the heavy industry which has hard to abate CO₂ emissions. Hydrogen produced at high efficiency in SOE may become an efficient tool to decarbonize these sectors,
• energy storage systems which can convert excess renewable electricity into synthetic fuels such as hydrogen which limits the level of curtailment of renewables. Reversible SOC unit offer a great advantage as a solution of hourly or daily energy storage with the SOC operated interchangeably between the fuel cell and electricity modes,
• power systems which are excepted to go beyond state-of-the-art efficiency and/or emissions which can be achieved by implementation in power plants, e.g. in hybrid systems with a gas turbine or compensation of surplus/shortage of energy in the grid or connection with RES systems – energy storage (electricity converted into hydrogen and vice versa).

Information about implementations – examples

The technology of SOC stacks developed at the Institute of Power Engineering was implemented under the following commercial project:

– „Industrial research and R&D work on high-efficiency micro-cogeneration based on solid oxide fuel cells powered by hydrogen or a mixture of natural gas and hydrogen (mCHP-SOFC)”, Polskie Górnictwo Naftowe i Gazownictwo S.A., Orlen Group – construction of micro-cogeneration systems using SOC stacks. Two installations have been delivered under the contract so far.

– Under the contract of which the subject was „Modular system based on reversible solid oxide cells (rSOC) designed for integration with an industrial power plant in order to improve its flexibility, and increase utilization of renewable energy sources in power sector” – construction of a 10 kW class rSOC installation integrated with the biomass unit of the Heat and Power Plant in Elbląg (Energa, Orlen Group) based on SOC stacks developed in the Institute of Power Engineering. As part of the project, one installation was designed, built and delivered.

Instytut Energetyki – Instytut Badawczy
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01-330 Warszawa

Jakub Kupecki
+48 501 495 321
Marek Skrzypkiewicz
+48 797 905 395
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