Introduction
Solid Oxide Electrolysis Cell (SOEC) technology is emerging as one of the most promising pathways to produce “green hydrogen” with high electrical-to-hydrogen efficiency. This article provides an overview of the SOEC principle, details DENSO’s progress in its development, advantages, challenges, and recent field applications.
1) Principle of SOEC
SOEC operates at high temperatures (typically 600–800°C or above) and electrolyzes steam to generate hydrogen. Operating at elevated temperatures allows part of the energy input to come from heat rather than electricity, which improves efficiency compared with low-temperature electrolysis technologies (PEM, alkaline).
-
At the cathode: steam is reduced to hydrogen and oxide ions (O²⁻).
-
The oxide ions migrate through a ceramic electrolyte to the anode, where oxygen is released.
2) DENSO’s Development Roadmap
-
In-house pilot testing (2023): DENSO began trial operation of SOEC at its Hirose Plant in Kariya, using hydrogen produced onsite to test industrial applications.
-
Licensing & technology partnership (2024): In August 2024, DENSO signed a licensing agreement with UK-based Ceres Power to manufacture SOEC stacks, accelerating commercialization by leveraging proven stack designs.
-
Field trials with JERA (2024–2025): DENSO partnered with JERA to integrate SOEC into thermal power plants by utilizing waste heat and steam. In September 2025, the two companies launched Japan’s first demonstration of SOEC-based hydrogen production at JERA’s Shin-Nagoya Thermal Power Plant. The 200 kW system aims to achieve world-class electrolysis efficiency by capturing waste heat.
3) Strengths of SOEC (and DENSO’s approach)
-
High efficiency: SOEC can reach electricity-to-hydrogen efficiencies of 70–80% (LHV basis) under optimal conditions, significantly higher than PEM or alkaline electrolysis. Waste heat integration further boosts overall performance.
-
Industrial integration: Ideal for locations with abundant steam or high-temperature waste heat (e.g., thermal power plants, steel plants).
-
Reversibility: Solid oxide cells can operate in both directions — as fuel cells (SOFC) generating electricity from H₂, or as SOEC producing H₂ from steam. This flexibility enables energy storage and grid balancing applications.
4) Challenges to Overcome
-
Durability: High operating temperatures accelerate degradation mechanisms (material phase changes, microstructural evolution, thermal stress), leading to reduced lifetime.
-
Materials & stack fabrication: Matching thermal expansion, corrosion resistance, and manufacturing scalability remain technical barriers.
-
Thermal management: Safe and stable operation requires careful control of temperature gradients and steam flow, especially when powered by fluctuating renewable energy.
-
Cost: Current SOEC systems are more capital-intensive than PEM/alkaline, and scaling supply chains is necessary for cost reduction.
5) DENSO’s Strategy to Address Challenges
-
Partnerships & licensing: Collaborating with Ceres Power for mature stack technology shortens the timeline to large-scale commercialization.
-
Real-world testing: From in-house trials to demonstration at JERA’s power plant, DENSO is validating SOEC under industrial conditions.
-
Thermal management expertise: Leveraging DENSO’s strengths in heat management, the system design focuses on maximizing efficiency by recovering and reusing plant waste heat.
6) Applications & Market Potential
-
Industrial hydrogen supply: Onsite hydrogen generation at thermal power or industrial plants can be more cost-effective with SOEC due to integrated heat recovery.
-
Energy storage: SOEC allows surplus renewable electricity to be stored as hydrogen for long-term use in power generation, mobility, or chemical feedstock.
7) Conclusion
DENSO’s SOEC program has advanced from internal pilot testing (2023), through technology licensing (2024), to real-world demonstration with JERA (2025). By combining proven stack technology with its own integration and heat management expertise, DENSO is positioning SOEC as a high-efficiency solution for green hydrogen production in industrial environments. If durability and cost challenges are addressed through ongoing trials, SOEC could become a competitive cornerstone technology in the global hydrogen economy.
Main references: DENSO press releases (2023–2025), JERA announcements (2024–2025), technical reviews on SOEC durability and efficiency (RSC, Chemical Reviews, CATF).
