Optimization of a CO2-based shipboard waste heat recovery system

Under the resolution adopted at the 62nd Marine Environment Protection Committee (MEPC), carbon emission restrictions have been implemented for large ships since 2013. In order to comply with this, a number of efforts are being made to reduce fuel consumption in ships. In this study, in order to utilize engine exhaust waste heat, a carbon dioxide power cycle, which utilizes a carbon dioxide as a working fluid in contrast to conventional steam power cycle, was investigated. The power cycle was modeled and simulated to investigate its characteristics and performances under the shipboard waste heat recovery condition. The cycle power was maximized by using multivariate optimization method at various cycle minimum temperature conditions. Simulation results show that when the cycle's lowest temperature varied in the range of 16–40 degC, the waste heat recovery system increases power by 7.1–3.5%.