Multi-Objective Thermo-Economic Optimization of a Combined Organic Rankine Cycle (ORC) System Based on Waste Heat of Dual Fuel Marine Engine and LNG Cold Energy Recovery

Abstract

In this paper, a combined organic Rankine cycle (ORC) system that can effectively utilize the cold energy of Liquefied Nature Gas (LNG) and the waste heat of dual fuel (DF) marine engine was proposed. Particularly, the engine exhaust gas and the jacket cooling water of the DF marine engine were used as heat sources. Firstly, a thorough assessment of thermo-economic performance was conducted for the combined ORC system using 11 environmentally friendly working fluids (WFs). Afterwards, the effects of evaporation and condensation pressures on the net output work, energy efficiency, exergy efficiency, total investment cost and payback period were examined. Furthermore, the thermo-economic performances of the ORC system were optimized via multi-objective optimization with a genetic algorithm. Finally, exergy destructions and investment costs of each component under the optimal operating conditions were analyzed to make suggestions for further improvement. The results show that R1150-R1234yf-R600a and R170-R1270-R152a are the two most promising WF combinations. The exergy destruction of the combined ORC system mainly exists in heat exchangers. Through WF optimization, the exergy destruction in the intermediate heat exchanger was reduced by 18.99%. The proportion of expanders investment cost could be greater than 50% and the payback period of the combined ORC system varies in the range of 7.68–9.43 years. This study demonstrated that the selection of WF and the optimization of operating conditions had important potential to improve thermo-economic performances of ORC systems.

Thermo‐economic analysis and optimization of a combined Organic Rankine Cycle ( ORC ) system with LNG cold energy and waste heat recovery of dual‐fuel marine engine

“…To guarantee operation stability, EG is preferred as the heat source for the ORC2 while JCW as the heat source for the ORC3. The results of EG as the heat source for the ORC3 could refer to the authors' work 28 …”

“…The system calculation procedure is shown in Figure 4. The detailed solving process and model validation could refer to Reference 28. The average relative errors of W net and η ex are 10.8% and 10.3% with JCW, while the average relative errors of W net and η ex are 22% and 27.3% with EG.…”

“…The results of EG as the heat source for the ORC3 could refer to the authors' work. 28 The LNG is firstly pressurized by the pump (P0) and then sent to the condensers in the ORC1 (CON1) and ORC2 (CON2). After that, LNG enters the DF engine and becomes the EG.…”

Potential of liquefied natural gas cold energy recovery on board ships

“…The most recent developments in the field aimed at integrating the use of multiple heat sources (exhaust gases and jacket water) and LNG cold energy recovery by means of multiple ORC units (Han et al, 2019), comparing the potential of different ORC architectures as a function of the installed LNG supply system (Koo et al, 2019), and evaluating the thermo-economic feasibility of installing such systems (Tian et al, 2020). Lastly, with respect to the range of possible applications, (Liu and Wu, 2020) most recently proposed the use of LNG cold energy recovery for seawater desalination.…”

Suitability of the Reforming-Controlled Compression Ignition Concept for UAV Applications

“…Mapping the exergy destruction causes allows redesign of the tested system to minimize exergy destruction [20] and consequently to improve system efficiency [21]. This approach is very common in many different engineering areas [22] such as gas turbines [23,24], power plants with CO 2 capture [25], and organic Rankine cycle-based waste energy recovery [26]. The second-law analysis concept is also extensively applied in the ICE field.…”