Energy, exergy and exergoenvironmental analyses on gas-diesel fuel marine engine used for trigeneration system

Abstract

This study has addressed a trigeneration system driven by dual fuel marine engine. The marine engine manufacturers have developed the dual fuel (DF) version to improve the combustion and reduce the pollutant gaseous emissions. The aim was evaluated the performances of gas diesel fuel and full diesel based on exergy and exergoenvironmental analyses. The energy, exergy and exergoenvironmental balances were conducted considering the effect of pollutant emissions. The specific exergy cost (SPECO) approach was applied, which use the fuel and product definition. The diesel marine engine original produced 6.90 MW of electrical power, 28.16 kW of cooling water and 278.2 and 588 kW of heating. The findings revealed that the effect of gas diesel fuel has reduced the energy and exergy efficiencies by 87% in relation to full diesel mode. The diesel engine has the highest exergy destruction with 3051 kW. The NO emission has a portion of 92% of environmental impact rate associated to pollutant formation. The lowest energy and exergetic efficiencies and the highest environmental impact rates of components were investigated. The environmental impact rate per exergy unit of electricity power, cooling water of absorption chiller and heating water were presented. The reduction of environmental impact rate of pollutant formation is the main responsible for the better environmental performance of gas diesel fuel marine engine. Despite the reduction in energy and exergy efficiencies, the dual fuel (DF) technology was able to controlling pollutant emissions and improved the exergoenvironmental performance without great modification into engine. Further recommendations were proposed.