Hydrogen-fueled gas turbines represent a promising pathway for decarbonizing power generation, particularly in applications requiring high efficiency and operational flexibility. Unlike natural gas turbines, hydrogen combustion produces no carbon dioxide emissions, but it does generate nitrogen oxides (NOx) due to high flame temperatures. The emission performance of these turbines depends on combustion technology, with dry-low-NOx (DLN) systems and conventional designs offering distinct trade-offs. Material challenges also arise from hydrogen’s combustion characteristics, necessitating advanced engineering solutions such as steam injection.

Combustion of hydrogen in gas turbines primarily emits water vapor and NOx, the latter formed when nitrogen and oxygen in the air react at elevated temperatures. Hydrogen’s adiabatic flame temperature is approximately 2,200°C, significantly higher than natural gas, which peaks around 1,950°C. This increase exacerbates thermal NOx formation, a concern for compliance with stringent environmental regulations. Conventional combustion systems, which rely on diffusion flames, struggle to mitigate NOx emissions when using hydrogen due to localized hot spots. In contrast, DLN systems premix fuel and air to create a lean, uniform mixture that burns at lower temperatures, reducing NOx formation.

DLN combustors achieve NOx emissions below 15 ppm for natural gas, but their performance with hydrogen is more complex. Hydrogen’s high reactivity and wide flammability range can lead to flashback or auto-ignition in premixed systems, posing safety risks. To address this, modified DLN designs incorporate advanced mixing strategies and flame stabilization techniques. For example, some systems use micromixers to create numerous small flamelets, distributing heat more evenly and keeping temperatures below the NOx threshold. Experimental results indicate that such systems can achieve NOx levels under 25 ppm with hydrogen blends up to 100%, though operational limits vary by turbine size and design.

Conventional diffusion flame combustors, while more tolerant of hydrogen’s properties, produce higher NOx emissions—often exceeding 100 ppm at full load. These systems are simpler and more robust but require post-combustion treatments like selective catalytic reduction (SCR) to meet emission standards. SCR systems inject ammonia to convert NOx into nitrogen and water, adding complexity and cost. The trade-off between DLN and conventional systems thus hinges on the balance between upfront engineering challenges and long-term emission control costs.

Material limitations further complicate hydrogen turbine deployment. The high flame temperatures accelerate component degradation, particularly in combustor liners, nozzles, and turbine blades. Nickel-based superalloys, commonly used in gas turbines, face reduced lifespan under hydrogen combustion due to thermal fatigue and oxidation. Coatings like thermal barrier coatings (TBCs) help mitigate these effects, but their longevity requires validation under sustained hydrogen operation. Another approach involves using ceramics or ceramic matrix composites (CMCs), which withstand higher temperatures but present manufacturing and integration challenges.

Steam injection is a proven method to lower flame temperatures and curb NOx emissions without major hardware modifications. By diluting the combustion mixture, steam reduces peak temperatures and thermal NOx formation. Field data from natural gas turbines show that steam injection can cut NOx emissions by up to 50%, and similar benefits are expected with hydrogen. However, steam injection carries trade-offs, including reduced cycle efficiency due to the energy required for steam generation and increased water consumption. In regions with water scarcity, this may limit feasibility.

Hydrogen’s potential in gas turbines also depends on fuel purity. Impurities like methane or nitrogen can alter combustion dynamics and emission profiles. For instance, hydrogen derived from steam methane reforming may contain residual carbon monoxide, which affects flame stability and emissions. Electrolytic hydrogen, while cleaner, demands rigorous quality control to ensure consistent turbine performance.

The scalability of hydrogen gas turbines faces infrastructure hurdles. Existing natural gas pipelines require upgrades to transport hydrogen safely, and storage solutions must address hydrogen’s low energy density per unit volume. Despite these challenges, several demonstration projects have validated hydrogen turbine operation. For example, Mitsubishi Power’s Takasago Hydrogen Park achieved successful test runs of a 30% hydrogen blend in a large-scale turbine, with plans to transition to 100% hydrogen.

Regulatory frameworks will play a critical role in adoption. Emission standards for hydrogen turbines are still evolving, with some jurisdictions applying the same NOx limits as natural gas turbines. Others are developing separate guidelines to account for hydrogen’s unique properties. Clarity in regulations will incentivize investment and guide technology development.

In summary, hydrogen-fueled gas turbines offer a viable route to zero-carbon power generation, but their emission performance depends on combustion technology and operational strategies. DLN systems provide lower NOx emissions but require careful design to handle hydrogen’s reactivity, while conventional combustors rely on post-treatment. Material challenges necessitate advanced alloys or alternative materials, and steam injection presents a short-term solution for emission control. As the hydrogen economy matures, continued innovation and supportive policies will be essential to unlock the full potential of this technology.