GE’s next generation CCGT plants: operational flexibility is the key

08 July 2011

GE’s new FlexEfficiency combined cycle technology aims to couple unprecedented operational flexibility with extremely high efficiency.


When they first appeared on the electric power generation scene more than three decades ago, large-scale gas turbine combined cycle power plants were intended as baseload units to replace ageing coal-fired units. With the introduction of F-class gas turbines, their thermal efficiency percentage rapidly reached the high 50s and pushed towards the 60% level via ever-increasing firing temperatures. This, coupled with relatively low natural gas prices and the favourable emission characteristics relative to other fossil fuels, largely ensured that, at least until recently, they maintained their baseload role.

Today, however, large fluctuations in natural gas prices, liberalisation of the electricity markets and increasing adoption of renewables (wind and solar in particular) – with their intermittency and unpredictability – have significantly changed the operating duties required of combined cycle power plants. In particular, modern day combined cycle power plants are primarily operated cyclically, at varying load factors with fairly large numbers of shutdowns and start-ups.

Therefore, in addition to having a respectable baseload performance rating, the following operability features are imperative for a competitive combined cycle offering:

  • Fast start after overnight and/or weekend shut-downs with high starting reliability and good equipment life, with low start-up emissions.
  • Ability to run at lowloadswithin applicable emissions regulations.
  •  Fast load ramping (or start from standstill) upon demand and at short notice, exploiting unforeseen market opportunities (such as loss of load caused by renewable units going unexpectedly off-line).

A combined cycle power plant that offers all of these features provides the owner/operator with the flexibility to make money under a wide range of scenarios while minimising risk and life cycle costs

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Modern Power Systems
July 2011


S. Can Gülen
CharlesM. Jones, General Electric, USA