The new development at Marchwood will be an 842MW natural gas combined cycle gas turbine (CCGT) power plant. Modern facilities of this kind represent advanced generating technology as they offer high operating efficiencies and low emissions. Marchwood Power will operate at circa 58% fuel efficiency, compared to circa 30%-35% efficiencies in the case of the former power station.

The diagram above shows the combined cycle process. In Marchwood, two gas turbines and associated electric generators with heat recovery steam generators and one steam turbine will operate in combined cycle.

Natural gas is burnt in the combustion chamber of the gas turbines from where hot combustion gases expand through the gas turbine, which in turn drive generators to produce electricity. The hot exhaust gases contain recoverable energy and are, therefore, used in waste heat recovery boilers to generate steam. The high-pressure steam produced is used to drive the steam turbine to generate additional electricity.

The spent steam leaving the turbines is condensed and the resultant “condensate” returned to the waste heat recovery boilers for reuse. In the case of Marchwood, cooling water will be taken from the river Test via the intake structure remaining from the former power station. The water is returned to the River Test at a quality level and temperature limit that meet environmental legislation requirements.




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