A
system and method for increasing the specific output of a
combined cycle power
plant and providing flexibility in the power
plant rating, both without a commensurate increase in the
plant heat rate, is disclosed. The present invention demonstrates that the process of upgrading thermal efficiencies of combined cycles can often be accomplished through the strategic use of additional fuel and / or heat input. In particular,
gas turbines that exhaust into HRSGs, can be supplemental fired to obtain much higher
steam turbine outputs and greater overall plant ratings, but without a penalty on efficiency. This
system and method by in large defines a high efficiency
combined cycle power plant that is predominantly a Rankine (bottoming) cycle. Exemplary embodiments of the present invention include a load driven by a
topping cycle engine (TCE), powered by a
topping cycle fluid (TCF) which exhausts into a heat
recovery device (HRD). The HRD is fired with a supplementary fuel or provided an additional heat source to produce more energetic and / or a larger quantity of the bottoming cycle fluid (BCF) which is used to power a bottoming cycle engine, (BCE) which drives a load (potentially the same load as the
topping cycle engine). Energy contained in either the TCF or BCF is used to power the TCE and BCE respectively, but these fluids, and / or their respective engine exhausts, may also be used to support a wide variety of
cogeneration applications.