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Vessel operators operating in the maritime industry are under increasing pressure to improve the efficiency. CO₂ emissions have about 3% of global emissions from Shipping, and the IMO wants to reduce them drastically by around 2050 on an aim of zero emissions. As pioneers in the industry with more than 20 years of experience and over 500 projects each year servicing more than 1,000 ships, we know that one of the best ways to decarbonize is through optimization of the vessels' onboard heat exchange systems. Led by more than 100 electrical and mechanical technicians, the team is regularly involved in waste heat recovery solutions ranging from shell and tube and plate heat exchangers to S-CO₂ power cycle hybrid units, with the aim of helping to save fuel. We describe four key ways that a good heat exchange directly reduces CO₂ emissions below.
Waste Heat Recovery: Turning Losses into Power
Modern marine diesel engines are able to get thermal efficiency of about 50%, the remaining energy of fuel is lost to heat, mostly via exhaust gases (usually more than 250 °C) and as jacket cooling water . This lost thermal energy is extracted by the efficient heat exchangers to be used in the form of useful power or on-board heat. In marine applications, the waste heat recovery (WHR) systems like Joule cycle are able to enhance the overall engine power output by 2%-12%. This is a direct result of reduced fuel burn per nautical mile and as such reduced CO₂ emissions per voyage. The energy to be recovered in the exhaust gas varies according to the engine load and heat capacity ratio, depending on the amount of exhaust gas to be recovered and working fluid. This is optimised within a heat recovery loop, designed by SME's engineering team, which may be operated with different exhaust gas and working fluid heat capacities.
Supporting Onboard Carbon Capture Systems
An efficient exchange of heat is very important for some systems within the OCCS project intended to be placed on a vessel. For example, CO₂ is captured as part of a capture system and the captured CO₂ needs to be separated from the captured solvent by applying a sufficient amount of thermal energy, in case the capture system uses monoethanolamine (MEA) as the captured solvent. The heat exchangers powered by SME allow engine exhaust sensible heat to be used as the main energy source for this energy regeneration process, which thereby is given up or cut down the need for extra fuel fired auxiliary heating. When optimised, CO₂ reduction rates for heat recovery systems coupled with capture systems can be in excess of 70%. For ships being deployed in cold climates, the additional benefit of advanced/exotic heat exchangers is also recovering the heat for the ship's accommodation and fuel preheating, thereby reducing the auxiliary boiler requirement, another substantial source of additional emissions.
Supercritical CO₂ Power Cycles for Compact Efficiency
Due to limited space on board, high density and miniaturization of power generation devices are required. SME also contributes to the deployment of supercritical CO₂ Brayton cycles that transfer the waste heat from the exhaust to CO₂ in the supercritical state through heat exchangers. Compared to traditional Rankine cycles the S-CO₂ cycle has smaller footprint and high energy conversion efficiency. Heat exchanger designs, which include the effect of inlet temperature, mass and inlet pressure of the exhaust have a critical role on the performance of these systems. These variables are included in the technical specifications of SME so the hybrid heat exchangers, which combine etched plates and fins, provide the best possible thermal results while minimizing penalties for pressure drop.
Cold Recovery from LNG Vaporisation
A special opportunity exists for LNG vessels being fueled with LNG, in recovering cold energy from LNG vaporisation. The ability of LNG to take up such a large amount of thermal energy as it warms up to gas allows for use of this "cold" resource in heat exchangers for condensing captured CO₂ for liquefied storage, or the efficiency of the vessel's air conditioning and refrigeration systems. SME's heat exchanger solutions combine cold recovery systems (CRS) that can help to lower the electrical load on compressors, decreasing power onboard and associated fuel consumption. Our SMEs offer the same level of efficiency on existing ships, with our ISO-certified processes and 5000 m² Nantong workshop. We can apply the same techniques to existing vessels, especially those with a favourable vessel size vs LNG fuel consumption ratio.
Conclusion: SME’s Commitment to Decarbonisation
Effective heat exchange: a vital area where action today can deliver significant leverage on emissions reductions in the total worldwide Fleet. SME Group provides engineered heat transfer solutions to reduce fuel use and environmental footprint including waste heat recovery, carbon capture support, S-CO₂ cycles and LNG cold recovery. Accredited by ANAB, IAF, UKAS, ISO 9001 and 14001 certified, with more than 100 specialists at our disposal, year round services are offered at all worldwide shipyards, particularly mainland China. We offer a 12-month warranty along with a legacy of "Beyond Concern" to ensure all projects play their part in a greener and more sustainable maritime future. Talk to the experts at SME today to see how energy efficient heat exchange can help you decrease your ship's carbon footprint and cut operational expenses.