Analysis of Waste Heat to Power Technologies in a Maritime Engine System

Abstract

In EU, maritime transport sector contributed to emit 124 million tonnes of CO2 in 2021 (or equal to around 3-4% of EU total CO2 emissions). This could grow even higher in the future since maritime transport is considered the most energy efficient modes of distribution. Hence, Europe commission (EC) deliver “Fit for 55” and “FuelEU maritime” that limits the emission in maritime sector. In order to cope with the challenge, engine efficiency is crucial factor to consider. One solution to improve the efficiency is to recover the amount of wasted heat from a ship engine to electrical power, or usually called waste heat-to-power (WHP). This thesis evaluates 10 WHP technologies that might be implemented into two ship engines, i.e., Wärtsilä W8L46DF and W6L46TS-DF. Both of these engines have considerable amount source of waste heat at exhaust gas line at outlet turbocharger (EG) and cooling water line at charge air outlet (CW). The evaluation started by shortlisting WHP technology based on its compatibility within the waste heat source, technology maturity level, and its potential performance. This results in 3 technologies, i.e., steam Rankine cycle (SRC), basic organic Rankine cycle (B-ORC), recuperated organic Rankine cycle (R-ORC), and thermoelectric generator (TEG). Each of these 3 technology integrations were then modelled using Aspen HYSYS v12.1 in order to estimate their capability to recover heat, unit dimension, economic viability, and GHG reduction potential. Based on the evaluations, for both 1-stage engine and 2-stage engine, R-ORC has the highest %energy recovery and GHG emission reduction, achieving up to 5.6% fuel reduction and 29.2 tons of CO2 per year reduction. However, from economic perspective, the R-ORC has extensive pay- back period, requiring between 30 - 86 years of operations. On the other hand, the B-ORC offers significantly lower payback period between 18 – 44 years, while still gives huge impact, i.e., fuel reduction up to 5.1% and emission reduction up to 26.6 tCO2 yearly. Therefore, the feasible and most suitable WHP technology to be imple- mented in both 1-stage engine and 2-stage engine is the basic ORC system at ex- haust gas line outlet of turbocharger and cooling water line of charge air cooler.