Waste heat recovery from marine engines using absorption chillers for comfort application: a case study based on Hamilton and Saryu ship classes

Abstract

With the growing environmental concerns and the emission regulations already in place, as well as upcoming regulations in the future, there is a need to reduce emissions from marine vessels. The maritime industry is essential to the massive global movement of people and goods. Nonetheless, it is acknowledged that the maritime industry is responsible for 3% of the world's greenhouse gas (GHGs) emissions. The engine efficiencies of the modern marine ships are in the range of 30- 45%, highlighting that 70-55% of the fuel energy is discharged as waste heat to the surrounding atmosphere by the engine cooling system and the exhaust system. Energy efficiency measures and stringent emission regulations have not been implemented in marine vessels and transport sector yet considering the cruise's reliability and safety due to the operating environment. However, the scope and the use of maritime transportation sector is expanding rapidly around the clock due to economic consideration and globalization. As mentioned above, approximately 2/3rd of the energy produced in the marine engines is wasted via the exhaust and the cooling system without being recovered. During the literature review, it was observed that theses mobile power plants used in maritime industry have not adopted waste heat recovery techniques adequately as much as the road transportation sector due to several reasons such that lack of attention to enhance the power train efficiency due to the lack of emission standards. Turbocharging, turbo-compounding, bottoming cycles (ORCs) and thermoelectric generation have been identified as the most promising and established energy recovery techniques that can be adopted to recover the waste heat and convert it to power in the marine vessels. However, no studies have been conducted to investigate waste heat recovery from marine engines using absorption chillers for air conditioning and passenger comfort in marine applications so far. Therefore, this study will investigate the applicability and possibility of exhaust energy recovery from absorption chillers to provide and handle the on-board cooling demand for thermal comfort applications. The study was conducted using the real engine data obtained from two classes of marine vessels (Hamilton class and Saryu class) use in Sri Lanka Navy. Results of the numerical analysis show that the heat which can be recovered from the main exhaust system of both classes of ships, is able to cater for the cooling load of the respective ship class. The analysis was performed based on LiBraq absorption refrigeration, which will ensure the selected air conditioning system does not exhaust GHGs during the operation.