Combined cycle gas turbine power plants

CCGT: improving the environmental performance of fossil-fired power plants

With their flexible operation and reduced environmental impact, combined cycle gas turbine power plants (CCGT) improve energy efficiency and reduce atmospheric emissions. EDF is helping to further develop the state-of-the-art technology, notably with the new-generation Bouchain CCGT power plant built in partnership with General Electric, which will be a world first when brought into operation in the summer of 2016.

Reducing atmospheric emissions while enhancing electricity system reliability

A combined cycle gas turbine is composed of a combustion turbine (CT) and a steam turbine (ST). To start with, natural gas drives the CT. Then the hot off-gases from the CT are used to produce steam, which is channelled to a second turbine, the ST. The CT and ST drive one or two alternators. The same quantity of fuel therefore generates electricity twice: once in the CT and once in the ST, thus improving the power plant’s efficiency.
In addition to reducing the amount of fuel required, CCGT power plants emit only half the amount of carbon dioxide (CO₂) and one-third the amount of nitrogen oxides (NO_x), and virtually eliminate emissions of sulphur dioxide (SO₂) compared with conventional fossil-fired generation resources, coal-fired plants in particular.
At a time when the use of intermittent renewable energy is increasing, EDF uses CCGT power plants to improve the flexibility needed for electricity system reliability. In France, EDF commissioned a 430 MW combined cycle gas turbine power plant at Blénod-Lès-Pont-à-Mousson in 2011 and converted the Martigues oil-fired power plant into two combined cycle gas turbine units with a combined capacity of 930 MW, which have been operating since 2011 and 2012. These new facilities, in addition to ensuring long-term operation of the sites, help to improve the overall environmental performance of EDF’s fossil-fired fleet. EDF operates about 20 CCGT power plants around the world.

The Bouchain combined cycle gas turbine power plant, a world first

At the Bouchain site in northern France, EDF is working with turbine manufacturer General Electric (GE) to build a new-generation CCGT. Located at the site of a coal-fired plant that was shut down in 2015, the project represents a total investment of €400 million.
The CCGT power plant, equipped with state-of-the-art General Electric technology, will achieve record efficiency and thereby further reduce atmospheric emissions:

• 62% efficiency compared with 58% for a conventional CCGT and 37% for a conventional coal-fired power plant
• CO₂  emissions 10% lower than those of a conventional CCGT and 55% lower than those of a conventional coal-fired power plant, and reduced atmospheric emissions of other gases (nitrogen oxide: 50 mg/Nm³)

It will also offer greater flexibility:

• Maximum power reached in less than 30 minutes, with a ramp rate of more than 50 MW per minute, nearly double the current rate
• Load reduction of up to 40% while complying with emission guarantees