Pure hydrogen

Specifically designed gas turbines can run on pure hydrogen or a hydrogen-rich syngas/natural gas mixtures. These gas turbines using hydrogen-rich mixtures have accumulated millions of hours of operation at large scale, whereas in the case of using pure hydrogen, they have reached a few thousands of operating hours at precommercial scale.
There are technical challenges associated with the high combustion temperature of hydrogen (NOx emissions, reliability/flame instabilities/flashback). For these reasons, the combustor of the gas turbine needs to be modified for gases with high hydrogen contents.
Burning (undiluted) fuel gas mixtures with hydrogen concentrations of 5-60% is possible in certain gas turbines, depending on the degree to which they have been modified.
Burning (diluted) fuel gas mixtures containing hydrogen up to concentrations of 100% is possible in certain gas turbines with the addition of significant amounts of diluents such as N2/steam to the fuel gas.
Commercial operation of F-class gas turbines with mixtures of up to 20% of hydrogen in natural gas mixture without hardware modifications is expected by 2025. In the case of H-class gas turbines, commercial operation with mixtures containing over 50% of hydrogen is expected in new combined cycle by 2027. But many open questions and challenges remain, such as efficiency gains, NOx (reduced, for example, by steam injection, which can lead to reduced system performance) and response to variability in fuel flow composition. In many cases, the H2 mixing ratio will fluctuate, and the extent to which the combustion process can respond to large variations in %H2 requires further R&D.