Energy Efficiency and Exhaust Management for Military Vessels: ORC-TEG and Infrared Signature Control

Abstract

The infrared (IR) signature is a critical factor for operational secrecy in military vessels. Conventional IR reduction methods typically rely on cooling exhaust gases with seawater or air; however, these systems require additional energy and components, creating challenges in terms of energy efficiency and fuel security. Therefore, more efficient solutions are needed to both reduce IR signature and decrease energy dependency. Considering that nearly 30% of fuel energy is lost through exhaust, waste heat recovery offers significant potential. This study proposes a system for naval vessels that simultaneously enables waste heat recovery and IR signature reduction. Conventional-powered aircraft carriers were used as case studies, and exhaust heat was estimated using empirical methods. The proposed system operates in a cascade configuration: high-temperature heat is first converted into electricity using thermoelectric generators (TEG), while the remaining medium-grade heat is recovered through an Organic Rankine Cycle (ORC). The results show that the combined ORC-TEG system can generate approximately 1.86 MW of electrical power per gas turbine, achieving a heat-based efficiency of about 6%. This corresponds to an avoided fuel consumption of around 324 kg/h per gas turbine, offering substantial savings for long-range operations. In addition, the system significantly reduces the IR signature of the exhaust. The integration of ORC and TEG maximizes heat recovery while lowering detectability. Although TEG systems currently involve high capital costs, these are expected to decrease with ongoing technological advancements and wider adoption.