Decarbonisation and carbon intensity reductions for aeroderivative gas turbines

Carbon-neutral and zero-carbon fuels represent the final step for gas turbine operators who have completed hardware efficiency updates, optimized their operating profiles, and see economic advantages in moving beyond carbon capture.

Ammonia

Ammonia may offer a path to carbon-free operation for sites with ready access to the fuel and to liquid fuel storage. Ammonia has roughly half the energy density, as well as higher NO_x emissions, than diesel but storage and emissions treatment strategies exist in the market today.

Methanol

Methanol offers a 10% reduction in CO₂ and a 70% reduction in NO_x emissions versus diesel. Both “gray” carbon-emitting and “green” carbon-neutral variants are produced today, with “gray” methanol widely traded throughout the world. Operators converting to methanol operation can switch from the carbon-emitting “gray” variant to the carbon-neutral “green” variant simply by changing their fuel vendor.

Hydrogen

Hydrogen offers both zero-carbon and low-NO_x operation. When blended with methane, high concentrations of hydrogen are required to achieve significant reductions in emissions. For example, to reduce a natural gas-burning site’s CO₂ footprint by 10% would require a hydrogen concentration of 25% by volume. Access to hydrogen can come from some combination of onsite generation of green hydrogen, splitting ammonia, or receipt of a hydrogen blend into the existing gas transmission lines.

Each operator should consider their specific site’s operating requirements and layout in assessing alternative fuel solutions. Methanol conversions from diesel should generally be economically feasible for backup power stations today while gas transmission lines and peak power plants may consider carbon capture technologies as a stopgap solution until hydrogen economies of scale are reached later this decade.

Siemens Energy AGT offers a variety of solutions and site studies to guide customers on their net-zero journeys.

Turbomachinery upgrades

The overall thermal efficiency that can be achieved from a gas turbine package (and therefore also the heat rate and CO₂ emissions properties) is affected by both the efficiency characteristic of each of the individual components, and the conditions at which they are operating. Consequently, the thermal efficiency of an existing package could be optimised by carefully understanding the current hardware configuration and how it is operating, and assessing various upgrade options to identify improvement opportunities.

Power turbines: Power turbines operate within a speed window that is influenced by the driven equipment, and this speed window is typically sufficiently narrow that the power turbine characteristics do not change significantly. Therefore the greatest opportunity for power turbines upgrades to improve emissions and heat rate properties of the package is an improvement in the baseline efficiency of the power turbine. Within the AGT product line, upgraded blades, vanes and tip seals are available for some power turbine variants which give up to 3% increase in PT efficiency, fuel flow and CO₂ emissions. The upgrades also increase temperature, power and life capability which can provide more flexibility in the operation, potentially opening up other options for decarbonisation potential.

Gas generators: The efficiency of gas generators is influenced both by the turbomachinery itself and how it is operated. Within the AGT fleet there is a wide variation in the gas turbine operating conditions. Upgrade options for both compressors and turbines are available for a variety of AGT products that can either improve the efficiency at the current operating conditions or can change the power capacity of the engine(s) in such a way that they can be operated in a condition which is closer to the optimum. In some cases the reduction in fuel consumption and CO₂ emissions can be significant. There are numerous hardware configuration options that could be considered, and individual performance assessments can be conducted by Siemens Energy to identify potential benefits and which hardware configurations may be considered.