| Turbine technology developments


Decarbonisation pathways for gas turbines


Meeting the growing demand for energy while paving the way for a climate-friendly future using sustainable, reliable, and affordable technology is one of our most urgent challenges. Siemens Energy is actively engaged in this endeavour, having already achieved major successes in firing sustainable fuels in gas turbines, such as hydrogen, hydrogen derivatives, and biofuels. A new white paper emphasises the company’s commitment to decarbonising energy systems – including gas turbines – as a key objective. Some of the key findings are presented here. The complete white paper can be found on the Modern Power Systems website


Erik Zindel, Alastair Clegg, et al.


Global warming is a pressing challenge, with GHG emissions having raised global temperatures by 1.1° Celsius since the pre-industrial era. If unchecked, temperatures could rise by 2.9° Celsius by century’s end, causing severe climate impacts and economic burdens. CO2


emissions,


largely from combustion of fossil fuels, constitute 67% of GHG emissions, with the power sector and heating responsible for significant portions. Fossil fuelled power plants currently cover the residual load (ie, the load not met by renewables), but with more renewables in the grid, the residual load will fluctuate daily and seasonally even more. There will also be “dark doldrum” events lasting weeks, as seen in Germany in January of 2017, and climate change may extend these events. Importing electricity can help, but similar weather conditions will affect neighbouring regions simultaneously, and long-distance HVDC connections – even in ideal conditions – won’t fully address the issue.


Demand-side management (DSM) can reduce the load gap, but it’s limited by its scale and duration and the need for the right conditions and pricing to be in place to determine consumer behaviour. Energy storage technologies such as batteries and pumped hydro can cover a range of timescales, but are not feasible for long periods or even seasonal storage of energy. Therefore, efficient, decarbonised, and flexible gas turbines are an essential prerequisite for the future energy system. Due to their fuel flexibility, gas turbines are pivotal in the transition because they’re capable of using biogenic, synthetic, and carbon-free fuels or fossil fuels with CC(U)S. Siemens Energy is actively developing technologies for decarbonisation across various fronts. In an energy system with a large share of intermittent renewables, power shortfalls for heat pumps and electric furnaces may occur, especially during winter in high-latitude regions. Gas turbines and CHP plants can bridge these gaps by utilising hot-water heat storage to decouple power and heat production. By following the electricity market and supplying heat, CHP plants offer high energy utilisation rates, up to 90%, making them efficient for both residual load and heat demand coverage. To achieve either full gas turbine


decarbonisation or carbon neutrality, two main transformation routes appear to be feasible:


Hydrogen


Green hydrogen using renewable energy, pink hydrogen using nuclear energy, white hydrogen formed by natural processes, blue hydrogen derived from natural gas via steam–methane reforming, or turquoise hydrogen via methane pyrolysis.


Synthetic fuels


Derived from sustainable hydrogen, eg, e-methanol and e-ammonia. Of these, hydrocarbon-based e-fuels such as methanol must use CO2


carbon source.


Fuels from a biogenic source


Such as biodiesels like HVO and FAME, bio-methanol, or bio-ethanol. A growing supply base for sustainable aviation fuel from biogenic sources may also present opportunities for land-based gas turbine applications.


from a sustainable


Alternative fuels for gas turbines (source Siemens Energy)


operating gas turbines on decarbonised or carbon- neutral fuels; or continuing to operate them on fossil fuel, such as natural gas, with CC(U)S.


Sustainable gaseous and liquid fuels for gas turbines


Hydrogen


Hydrogen is gaining traction for power sector decarbonisation, with all manufacturers aiming for 100% H2


-capable frames earlier. Technical challenges include hydrogen’s combustion properties, notably lower ignition energy and higher flame speed. Sustainable hydrogen production methods range from renewables and nuclear energy powered electrolysis (green and pink H2 (blue H2


) or pyrolysis (turquoise H2


) to natural gas with CCS ).


The EU-Horizon-2020-supported HYFLEXPOWER project demonstrated renewable-power-to-H2


-to-power at a


cogeneration plant in France employing an SGT-400 gas turbine equipped with dry low emissions (DLE) combustion technology. Successful operation was demonstrated at 100% H2


– a world first for an industrial gas


turbine of this size (>10 MW). Biogas


Biogas produced from organic matter decomposition typically contains 40 to 75% methane along with CO2


and other minor Renewable natural gas


gas turbine capability by 2030, and some OEMs, such as Siemens Energy, releasing selected H2


Renewable natural gas (RNG), or bio-methane, is pipeline-quality gas compatible with gas turbines. It’s made by purifying biogas or gasifying dry biomass such as wood waste and then methanating the resulting H2


and CO.


RNG’s use is cost-driven, with incentives like tax breaks and renewable certificates for its distribution and use.


Synthetic methane


Synthetic methane, also known as e-methane, is created by methanating H2


and CO2 . It can


derived from direct air capture, and it can even enable carbon-negative operations with CCS. E-methane is anticipated to be used primarily in chemical processing, while gas turbines are likely to opt for green H2


be utilised in gas turbines without modifying them. It has the lowest carbon footprint when produced from green H2 or CO2


and biogenic CO2


contaminants. It has a relatively low heating value, making it suitable for small to medium gas turbines. Incentives for using biogas to fuel gas turbines include reducing CO2


and CH4


emissions from natural decay, although gas pre- processing and biomass transportation lead to additional costs.


or easier-


to-handle hydrogen derivatives like e-methanol. Sustainable liquid fuels


Sustainable liquid fuels are also an alternative for gas turbine operation. These include


www.modernpowersystems.com | September 2024 | 17


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