Gas turbines in a low-carbon economy

alt à‚  Christer Bjàƒ¶rkqvist, Managing Director, European Turbine Network – ETN a.i.s.b.l

Gas turbines continue to become more environment friendly, with their high efficiency and very low emissions.

Modern combined-cycle plants have surpassed the ‘magic’ 60 per cent efficiency target, making gas turbines one of the most efficient available energy conversion technologies.

In Europe, we are facing new requirements and development challenges, which ask for high efficiency and low emissions even in load-following operation mode. The European electricity sector is undergoing a major transition to achieve an almost carbon-neutral electricity generation mix by 2050. With renewable energies drastically increasing their share in Europe’s power mix, dispatchable power plants have been forced to move from baseload to load-following operations, with vastly reduced operating hours and an increasing amount of starts and stops. To avoid a mismatch between demand and production, fast-reacting back-up is needed.

Gas turbines can ensure this flexibility in the electricity system, but today’s designs are not optimised for this, resulting in shorter maintenance intervals and higher cost per kWh produced. Thus, increased investments and R&D are required to improve part-load efficiency through better component performance and intelligent system integration, which will enhance the fuel efficiency and environmental performance of future power generation.

Aeroderivative open-cycle gas turbines are designed for frequent starts and stops and could therefore play an increasingly important role because of their lower capital investment costs, shorter construction/installation time and smaller footprint. However, even these machines require additional developments to ensure low nitrogen oxides (NOx) emissions, increased fuel flexibility and low maintenance costs.

Hybridisation of concentrated solar power with gas turbines is one new development route, promising superior efficiency and emission, and operating characteristics in line with the market requirements that warrants further investigation and demonstration.

Compressed air energy storage is another potential feature of future energy systems, which is based on gas turbine technology allowing for large-scale storage of surplus electricity with a subsequent quick release of power when needed.

Increased fuel flexibility, retaining reliability and low emissions are clearly ‘no regret’ developments for both combined-cycle and open-cycle gas turbines.

With the existing extensive experience of operating with a wide variety of gaseous fuels, including syngas, the transition towards a scenario more focused on hydrogen-rich fuels – even pure hydrogen – has an excellent basis from which to evolve. We must also find an urgent solution to enable gas turbines to cope with the rapidly varying natural gas quality in the gas grid caused by cross-border pipelines, liquefied natural gas supply and the introduction of fuels, such as shale gas.

Turning to carbon emissions, uncertainties in the European market, together with the extremely low-carbon price and the high cost of carbon capture and storage, has led to many demonstration initiatives being stalled. Large-scale deployment of this technology, including at gas-fired power plants, is only likely with new strong political commitments to intermediate and long-term emission reduction goals together with near-term incentives.

The future potential of the gas turbine looks very bright and its highly-flexible load response characteristics and fuel flexibility will be an asset of growing importance in future energy networks. However, increased co-operation between industry partners and the research community on the multitude of development opportunities for gas turbines lies at the heart of guaranteeing the continuation of this technology’s success story.

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