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Hydrogen in Power Generation – A Safety Perspective

A major step in decarbonising the power industry is the use of hydrogen—or hydrogen/natural gas blends—in gas turbines to generate electricity. While replacing natural gas with hydrogen significantly reduces the plant’s carbon footprint, it’s not without substantial design and safety challenges. 

I'll leave the functional and operational hurdles to the design engineers and focus on the safety challenges—the domain of the safety engineer. 

Hydrogen Isn’t Just Another Fuel 

As covered in previous posts, hydrogen behaves very differently from methane or natural gas. Key differences include: 

  • Much lower density 

  • Faster flame speeds (3 m/s H₂ vs. 0.3 m/s CH₄) 

  • Higher flame temperatures 

  • Wider flammability range 

  • Higher thermal expansion 

  • Larger fuel volumes required for equivalent energy output 

Each of these factors presents safety challenges that must be understood and addressed—especially when dealing with high H₂/NG blends, which can introduce hybrid risk behaviours. 

Key Safety Challenges 

1. Flammable Cloud Formation in Run-Up Piping 

One of the most critical risks is the formation of a flammable gas cloud within the run-up piping. This can ignite through: 

  • Static discharge (in pure H₂ scenarios) 

  • Adiabatic compression during valve operations 

  • External ignition sources, like hot surfaces 

Due to hydrogen’s wide flammability range and high flame speed, ignition could lead to a deflagration-to-detonation transition (DDT) event—an extremely violent explosion. For low H₂ blends, a deflagration is more likely, but still hazardous. 

2. Flame-Out and Cloud Formation in the Combustion Chamber 

Because more hydrogen is needed compared to NG for the same output, the volume of combustible mixture within the ignition chamber can be significantly larger. In the event of a flame-out, this presents a serious risk of uncontrolled ignition or explosion. 

3. Turbine Enclosure Ventilation and Pressure Peaking Phenomenon (PPP) 

Perhaps the most complex and underappreciated issue is overpressure in the turbine enclosure. This isn’t necessarily due to ignition—hydrogen’s very low molecular weight allows it to: 

  • Displace heavier air, increasing the number of gas moles in the enclosure 

  • Lead to Pressure Peaking Phenomenon (PPP)—a rise in internal pressure without ignition 

This pressure increase can easily exceed the typical 10 kPa structural resistance of a standard enclosure. In jetfire scenarios, overpressures can reach 22x higher than an unignited release. 

The mitigation? A well-designed ventilation system, specifically tailored to hydrogen’s behaviour. Unlike conventional NG systems, PPP must be evaluated and factored into the design. 

More Than Just Modelling 

This is not an exhaustive list of the hazards a safety engineer must address. From the moment hydrogen is introduced to the system until it becomes H₂O and NOx, every stage of the process must be understood and assessed. 

Modelling tools are essential—but for hydrogen applications, they can’t provide all the answers. Sound engineering judgement and deep knowledge of hydrogen behaviour are just as critical. 

Hydrogen, New EnergyAndrew CareyHydrogen