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Abstract
Typically, shipboard gas turbine exhibits higher exhaust temperatures (ranging from about 4500C at around 25% load, up to around 5750C at the rated load) as compared to their diesel engine equivalent, which implies that a higher amount of useful thermal energy vents out through its exhaust. The thermal exergy contained in a typical LM2500 exhaust can be tapped to generate additional power by thermodynamically inter-connecting a supercritical CO2based bottoming power cycle. This research article therefore presents investigations of Energy-Exergy-Economic & Environment (4E) performance analyses of supercritical carbon dioxide regenerative waste heat recovery (bottoming cycle) power cycle thermodynamically coupled with LM2500 gas turbines (topping cycle) onboard a typical frigate class platform to improve overall plant efficiency and produce additional power. A range of 100% to 10% load has been considered since onboard naval ships, gas turbines scarcely operate at 100% power (only around 1-2% of the entire life) while because of the parabolic nature of the propeller (load) curve, fleet speeds between 12 to 16 knots are achieved with GTs running around 40 % (8.8 MW) or lower of their rated power (22 MW). With the proposed integration, significant improvement (~ 11%) in both energy and exergy efficiency of the shipboard GT is accruable, besides an additional power increment of around 4.8 MW (~ 22% of the GT rated power) without any extra fuel and carbon emissions. With the novel energy recovery system, ship can achieve additional range (26490 nm) and additional endurance (almost 69 days-at-sea) per year. In addition, the fleets can save significant carbon emissions of 4100 (ton-[CO2]/yr/ship) at 60% relative GT load, besides earning carbon-credits worth about USD 61501 at 60% relative GT load per ship annually.