4.2.5. Intelligent Energy Management System (IEMS)

The intelligent energy management system (IEMS) is a control system which monitors the voltage, current, and output of each device and the system state in real time and enables the system to be operated reliably. It adjusts the load of the load bank according to the load pattern in real time and allows the different devices to be synchronized [42–46].

The test bed was organized such that the IEMS and power sources (MCFC, diesel generator system (DGS), and ESS) could send and receive device statuses and operation commands through an interface, as shown in Figure 6. Communications were based on an RS-285 and Ethernet to take into account noise and effects of external factors, such as surrounding devices. In addition, an external connection to the internet was used to allow the operating test bed system to be monitored from locations with internet connectivity.

**Figure 6.** Diagram of interface design.

As shown in the Table 10 below, the control logic was configured to control the complex power system according to the SOC of the ESS according to the load.


**Table 10.** Configuration of control logic for power system.

*4.3. Comparison of Fuel Consumption and CO2 Emission Reduction Rates of the Conventional Commercial Diesel Engine vs. the Hybrid Power Source*

4.3.1. Conventional Commercial Diesel Power Source vs. the Fuel-Cell-Based Hybrid Power Source (FCHPS)

The conventional commercial diesel power source was selected from the Doosan Infracore's P126-TI model with a capacity of 241 kW, which was optimized for an average load of 80%. This generator's specific rated power was 80% load of 241 kW, 192.8 kW and selected as the standard model of the diesel generator of the test bed. The diesel generator for fuel cell-based hybrid power source was selected as a DB-58 model with a capacity of 70 kW among the diesel engines of the Doosan Infracore's generator. The generator was also optimized for an average load of 80%, 56 kW was selected as the diesel generator reference model for the combined power source of the test bed.

In order to analyze the CO2 emissions reduction of the combined power source, the fuel consumption and the carbon dioxide emissions of the commercial diesel generator optimized for the same power as the hybrid power source were applied to the baseload. To compare the fuel consumption of the MCFC and the diesel generator of the combined power source, each fuel consumption amount was converted into the petroleum conversion factor (1 Tonnage of oil equivalent [TOE] = 1000 kgoe). As shown in the Tables 11 and 12, the fuel consumption factor of the diesel generator and the MCFC were matched by applying the energy calorific value conversion factor to each fuel consumption amount for application of the petroleum conversion factor.




Estimation of greenhouse gas emissions was based on the methodology presented in the IPCC Guidelines. In international organizations and countries, emission factors are calculated and used according to the IPCC Guidelines. IMO has also developed a method for estimating carbon dioxide emissions for ships based on the IPCC Guidelines. However, the IPCC Guidelines provide a methodology for estimating emission factors, but IMO suggests a calculation method using conversion factors [47]. Tables 11 and 12 show a calculation formula and conversion standard.
