TEG-ORC combined cycle performance for cascade recovery of various types of waste heat from vessels

High energy consumption and low energy efficiency are problems that have plagued vessels in operation for many years. Traditional technologies such as thermoelectric generator (TEG) and organic Rankine cycle (ORC) are difficult to take into account the different characteristics to various waste heat of vessels. Simultaneously, the utilization rate of vessel waste heat is relatively low. To achieve the purpose of various types of waste heat from vessels, this study presents a vessel waste heat cascade utilization device system, which is based on the TEG-ORC combined cycle. The effects of the ORC evaporation pressure on the performance of the system were analyzed, which includes the combined cycle system output power, system thermal efficiency, multi-stage waste heat utilization and power generation cost of the system. The results show that the TEG-ORC combined cycle system improves the waste heat utilization performance and the combined cycle enables the optimization of power generation cost and system thermal efficiency. Based on the condition that the TEG-ORC basic cycle ratio of 0.615, the utilization rate of flue gas waste heat generated by the main engine, fluctuates in a small interval with the increase of ORC evaporation pressure. The waste heat utilization power of each unit, output power and thermal efficiency of the system enhance with the increase in the ORC evaporation pressure. At the same time, the unit power generation cost of the system decreases with the increase in the ORC evaporation pressure. When the ORC evaporation pressure reaches 0.9 MPa, the waste heat utilization rate of the flue gas generated by the main engine is 62.15%, the waste heat utilization power of the system is 1919.68 W, the output power of the system is 139.22 W, the thermal efficiency of the system is 7.25%, and the cost of system unit power generation is 3.09 ¥·(kW·h)^–1.