Stationary Hydrogen Engines: Industrial Applications and International Experience
Presentation of Clark Energy
I am Dalia Si Ahmed, in charge of hydrogen applications at Clark Energy. Before joining the company, I was project manager for fuel cells at Alstom Hydrogène, with an academic background in energy, process engineering and cogeneration.
Clark Energy is an international EPC group — Engineering, Procurement and Construction — offering turnkey energy and gas solutions, present in 27 countries, headquartered in Liverpool, with over 1,400 employees, more than half of whom are technicians specializing in commissioning and maintenance.
In terms of engine installations, Clark Energy represents over 9 GW worldwide, including 1.6 GW of biogas-powered engines.
Markets covered include: gas cogeneration, hydrogen production by electrolysis, biogas upgrading to biomethane and CO₂, industrial pumping and battery energy storage.
Operating Principle: The Four-Stroke Cycle
The internal combustion engine operates on the Beau de Rochas cycle (or Otto cycle) in four strokes:
— Intake: the intake valve opens, air and hydrogen enter, the piston moves down
— Compression: the piston moves up, increasing the pressure of the gas mixture
— Combustion-expansion: a spark plug ignites the mixture, pressure and temperature rise, generating mechanical motion
— Exhaust: the exhaust valve opens, burnt gases are expelled
This mechanical motion is converted into electricity and heat — the principle of cogeneration. A variant, trigeneration, uses the heat in an absorption cycle to also produce cooling.
Applications and Compatible Hydrogen Types
Stationary engines serve industry, residential and commercial sectors to produce heat and electricity.
Compatible low-carbon hydrogen types:
— Green hydrogen: electrolysis using renewable energy
— Pink hydrogen: electrolysis using nuclear power
— Blue hydrogen: fossil-based production with CO₂ capture
— White hydrogen: native or geological, currently under exploration
— Residual hydrogen: from industrial processes, usually flared or under-utilized
Advantages Over Fuel Cells
The internal combustion engine offers several distinctive advantages:
— Insensitive to hydrogen purity — no membranes sensitive to contaminants
— Compatible with varied gas mixtures: natural gas + hydrogen, CO + hydrogen
— Capex approximately half that of a PEM fuel cell
— Mature, proven technology with decades of operational history
— Well-established multi-year maintenance contracts
Electrical efficiency: 40 to 42%, versus approximately 50% for a fuel cell. In cogeneration mode, overall efficiency reaches 90%.
Key consideration: combustion produces NOx (from nitrogen in the air), filtered at the catalytic converter outlet to meet regulatory standards. This differs from fuel cells, which produce zero emissions.
Jenbacher Product Range (Authorized Distributor)
Clark Energy is an authorized distributor of Jenbacher (Austria), a reference manufacturer of gas engines from 0.5 kW to several MW.
— Up to 5% H₂: no modifications required
— Up to 20% H₂: minor hardware and software modifications
— Up to 60% H₂: more significant mechanical modifications
— 100% H₂: Type 4 — 1 MW electric + ~1 MW thermal
Operating pressure: 8 to 10 bar, similar to a fuel cell.
Capex for 100% H₂ engine: ~€1,600/kW. Maintenance Opex: ~2.5% of Capex/year, i.e. €150,000 to €200,000 depending on service level.
Case Studies and Field Experience
Heramet Project — Norway (metallurgy)
Context: valorization of a residual gas composed of 60% CO, nitrogen and 7% H₂, previously flared.
Solution: H₂-CO blend engine installed in two phases.
— Phase 1 (2021): single-engine demonstrator
— Phase 2 (end 2024): addition of six units
Output: 12 MW electric + 11 MW thermal at ~100°C.
Feedback: operation very similar to a natural gas engine. Key point: constant monitoring of gas quality required — an H₂ content above 7% raises the catalytic converter temperature beyond 600°C, requiring load reduction or engine shutdown.
Petrochemical Project — South Korea (100% H₂)
Context: polypropylene production process generating hydrogen-rich gas, treated to reach 100% H₂.
Solution: Type 4 demonstrator — 1 MW electric + ~2 MW thermal, operational since 2023.
Key figure: the engine consumes 83 kg of H₂/hour to produce 1 MW of electricity. For reference, a 2 to 2.5 MW electrolyzer produces approximately 50 kg/hour — highlighting the importance of buffer storage.
RAG Project — Austria (seasonal storage)
Context: storage of photovoltaic and wind surplus as hydrogen, as an alternative to batteries.
Solution: electrolysis during periods of overproduction → storage in saline cavities converted from natural gas → restitution via H₂ engine during periods of demand.
Output: electricity and heat with an overall cogeneration efficiency of 90%. Operational project, serving as a demonstrator for underground hydrogen storage.
Data Center Project — Netherlands (H₂ backup)
Context: decarbonization of backup power systems for a data center.
Solution: six Type 4 engines (6 MW electric total) replacing diesel generators. Primary operation on H₂, with automatic switchover to natural gas in case of supply interruption, without loss of electrical output.
H₂ Engine vs PEM Fuel Cell Comparison
CriterionH₂ EnginePEM Fuel CellElectrical efficiency40–42%~50%Capex~€1,600/kW~€3,500/kWH₂ purity requiredLowHighNOx emissionsYes (filtered)NoneMaturityVery highHigh
Conclusion
Hydrogen internal combustion engines are mature, proven technologies offering a wide range of applications: industrial cogeneration, seasonal storage, and backup power for data centers. Their main competitive advantage over fuel cells is their tolerance for impure gas mixtures and their lower Capex.
The main constraint remains the availability of low-carbon hydrogen in sufficient volumes. As electrolysis production scales up and white hydrogen exploitation progresses, these engines represent an immediately operational valorization solution.
