# Developments, Trends, and Challenges in Optimization of Ship Energy Systems
## Appendix A Main Characteristics of Journal Articles on Optimization of Ship Energy Systems
The speed of the ship and, consequently, the propulsion power, is under optimization. Electric and thermal loads are calculated as functions of the brake power of the main engines during the travel, while they are considered constant and known in port. Additionally, the weather conditions along the route are taken into consideration. A mixed integer-nonlinear programming problem is formulated. Initially continuous and then discretized load profile. Objective: minimize PWC. Solution method: direct sequential. Algorithm: CVP-SS software: gPROMS. * [80] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]. _Journal of Cleaner Production_**2019. ** System: superconfiguration including diesel engine with exhaust gas after treatment facilities, gas turbine, dual-fuel engine, EGBs, wind turbines and PV panels with battery, and compression chiller in cruise ship. SDO optimization. Objectives: (i) minimize total annual cost and (ii) minimize size (space occupied and weight). They are considered in separate or together (multiobjective optimization). Operation profile: operation state is divided into three types: (i) navigation, (ii) port stay and sea stay, and (iii) maneuvering, which accounts for 59%, 33%, and 8% of the operation period, respectively. Three typical days to represent winter, summer, and mid-season with a duration of 182, 62, and 121 days, respectively. Hourly profile of each load in each typical day. Algorithms: GUROBI 8.1.0 for the single-objective problem and augmented \(\epsilon\)-constraint method for the biobjective problem. * [81][PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] _Energy_**2020**. System: alternative systems with diesel or dual fuel engines and various fuels in cruise ship. Each combination is optimized in separate. Design optimization: the operating profile in the form of frequency of occurrence of loads is considered. Objectives: (i) life cycle cost and (ii) lifetime CO\({}_{2}\) emissions. Independent variables for each alternative configuration: number of DG sets and nominal power output of each set. The blackout frequency and the unavailability of a generator (safety metrics) are estimated for the optimal plant. Algorithm: Nonsorting Genetic Algorithm II (NSGA-II). * [82][PERSON]; [PERSON]; [PERSON]; [PERSON] _Energy_**2020**. System: hydrogen fuel cell stack with battery and supercapacitors for electric energy storage (HESS: hybrid energy storage system) in passenger boat. Design and operation optimization: sizing of the system and power allocation (power flow between the fuel cell and the storage system). Objective function: weighted summation of the battery degradation, power quality as expressed by voltage fluctuation, useful energy losses (in place of energy efficiency), and device cost. Algorithm: While Optimization Algorithm. * [83][PERSON]; [PERSON]; [PERSON]; [PERSON] _Thermal Science and Engineering Progress_**2020**. System: absorption power cycle (APC), i.e., Kalina cycle, and a humidification- dehumidification desalination (HDH) unit. APC uses heat from the cooling water and HDH heat from exhaust gases of the main engine. Multiobjective design optimization. Objectives: maximize energy efficiency, maximize energy efficiency, maximize energy efficiency, and minimize unit cost of fresh water. Finally, one objective function is formulated as a properly weighted summation of the individual objectives. Algorithm: GA.
* [84][PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] _Energy Conversion and Management_**2020**. System: supercritical CO\({}_{2}\) Brayton cycle (SCBC) combined with Kalina cycle (KC) with heat from the exhaust gas of MAN 8890 ME-C10.2 low-speed two-stroke diesel engine. At load of the diesel engine lower than 85%, only the KC recovers energy from the exhaust gas. Design optimization at nominal point of the engine. Single objective: maximize net power output of each cycle in separate.