Hydrogen-Capable Gas Turbines: What Buyers Should Ask

Hydrogen behaves differently from natural gas

Hydrogen burns faster and hotter than natural gas and has a much lower energy content per unit volume. That affects combustion stability, flame temperature, emissions and the volume of fuel the system must deliver. It also makes hydrogen more prone to leaking and to causing certain metals to become brittle.

For these reasons, adding hydrogen is not simply a matter of changing the fuel contract. The combustor, fuel system, controls and safety systems may all be affected.

Blend percentage: by volume or by energy

Hydrogen capability is usually stated as a percentage blend. Check whether the figure is by volume or by energy. Because hydrogen has low energy per volume, a blend that sounds high by volume delivers a much smaller share of the energy.

Ask what blend the turbine can burn as supplied, what blend requires modifications, and whether the higher figure has been demonstrated on that model or is a development target.

Combustor technology

Low-emission combustors designed for natural gas can tolerate a certain hydrogen share before flame stability and flashback become concerns. Higher shares may need a different combustor design. Our page on gas turbine combustion explains the basics.

Ask whether a combustor change would be needed for higher blends, how long it would take and whether the turbine’s other parts are already suitable.

Emissions and NOx

Hotter hydrogen flames tend to raise nitrogen oxide formation. Combustors and emissions controls must be designed to keep within permit limits at the blends intended. Emissions may also need to be measured and reported differently when hydrogen is in the fuel.

Confirm with each bidder the emissions guarantees at each blend level. The NOx control guide covers the control options.

Fuel system and materials

Hydrogen requires attention to piping materials, seals, valves and instruments. Metering and fuel control must handle varying blend ratios. Where hydrogen is blended on site, a mixing skid and gas analysis are needed.

Check whether the turbine package’s fuel system is rated for hydrogen at the stated blend, and what parts would need replacing for higher blends.

Safety

Hydrogen leaks are hard to see and ignite easily. Enclosure ventilation, gas detection, fire detection and hazardous area classification must reflect hydrogen. These requirements can affect the turbine enclosure and the surrounding plant layout.

Plan for this at the design stage. Retrofitting hazardous area equipment later is more disruptive than allowing for it from the start.

Controls and operation

Turbine controls must manage fuel changes, blend ratios and the transition between fuels. Ask whether the controls can handle varying hydrogen content in real time and whether the turbine can switch back to natural gas automatically if hydrogen supply is interrupted.

Operators need training on the new hazards and procedures. Include this in the plan for any hydrogen operation.

Supply reality

A hydrogen-capable turbine is only useful if hydrogen is available at the site in sufficient quantity, purity and pressure. For most sites today, supply is uncertain and the turbine will run on natural gas for years. That is not a reason to ignore capability, but it is a reason to weigh its value realistically.

Consider capability as an option for the future. The value lies in avoiding a costly redesign if hydrogen becomes available, not in immediate use.

Hydrogen and the rest of the plant

Hydrogen capability is not only about the turbine. Fuel supply pipework, metering stations, compressors, gas detection, ventilation and hazardous area classification across the plant may all need to change for higher blends. A turbine rated for a high blend in a plant whose fuel system and safety design are not suitable cannot use that capability.

Ask the EPC contractor to show how the plant layout, materials and safety systems would change at each blend level, and which changes can be built in at little extra cost during initial construction.

Emissions permits may also need revision. Some permits are written around natural gas, and burning a hydrogen blend could require new monitoring or a permit variation.

Questions for every bidder

Ask: what blend by volume and by energy is possible as supplied; what has been demonstrated on this model; what modifications are needed for higher blends; what emissions are guaranteed at each blend; which fuel system parts are rated for hydrogen; what safety changes are required; and what the upgrade path costs in time and scope.

Write the answers into the technical specification. Our page on turbine purchase specifications explains how to structure the request so answers can be compared.