4.3.2. Analysis of Fuel Consumption and CO2 Emissions Reduction in Hybrid Power Source

The test bed used in this study consisted of a hybrid power source with a combined capacity of 180 kW (100 kW fuel cell, 30 kW battery, and 50 kW diesel generator). The power generation in the hybrid power source was designed such that the fuel cell was set for base-load operation and the battery and diesel generator operated in sequence. At 100 kW in Figure 7, there is a 1% difference in the fuel consumption of the commercial diesel generator and the fuel cell. At 130 kW, the difference in fuel consumption with the diesel generator increases because the fuel cell and the battery, which does not need fuel supply, are operating. At 180 kW, the fuel cell, battery, and diesel generator were operating, and it can be seen that there was a reduction in the fuel consumption and CO2 emissions of the hybrid power source compared to the commercial diesel generator. At 100 kW in Figure 8, the CO2 emissions of the fuel cell are 9% of those of the commercial diesel engine. At 130 kW, at which the fuel cell and battery were operating, the difference in CO2 emissions compared with the diesel generator increases. At 180 kW, at which the fuel cell, battery, and diesel generator were operating, the CO2 emissions of the hybrid power source were reduced by 39% compared to that of the commercial diesel generator. Table 13 shows the CO2 emission reduction rates.

**Figure 7.** Comparison of fuel consumption of the commercial diesel generator and the hybrid power source.

**Figure 8.** Comparison of CO2 emissions of the commercial diesel generator and the hybrid power source.


**Table 13.** CO2 emission reduction rates in the commercial diesel generator vs. the hybrid power source.

#### **5. Analysis of Fuel Consumption and CO2 Emission Reduction in a Fuel-Cell-Based Hybrid Power Source Using Simulations of Operating Profiles by Type of Ship**

The actual electric load analysis values that were used in this study were taken from the operating profiles of ships, including a 5500 TEU Reefer Container, a 13000 TEU Container, a 40 k DWT Bulk Carrier, 130 k DWT LNG Carrier, and 300 k DWT very large crude oil carrier (VLCC). These values were scaled down for each operation mode and suitable load scenarios for each ship type were used. To utilize scale-down methodology, the linear interpolation method is applied [48]. For example, if the original 5500 TEU Reefer Container's rated power is 4154 kW, the rated power of the test bed is 180 kW, when applying the scale down method. At part load, 1424 kW will be converted to 61 kW. All following test bed operating loads were calculated in this way. For the load scenarios in Table 14, according to the ship type operating scenarios, the following power sources were applied.


**Table 14.** Load scenario according to the ship type.

#### *5.1. 5500 TEU Reefer Container*

The 5500 TEU reefer container uses the following operating modes during operations: Normal seagoing (without reefer), normal seagoing (with reefer), port in/out (without thruster), port in/out (with thruster), and load/unload. To perform the test bed experiments, the scale of the values obtained as a result of the electric load analysis were adjusted to reflect the output of each operating mode of an actual ship. As shown in Figure 9, the hybrid power source was used in the load scenarios of this ship. Normal seagoing (without reefer) was a fuel cell operation interval. Normal seagoing (with reefer) was a fuel cell + battery + diesel generator operation interval. Port in/out (without thruster) was a fuel cell operation interval. Port in/out (with thruster) and load/unload were fuel cell + battery + diesel generator operation intervals. The scale-adjusted electric load analysis was applied to the test bed, and the output tests were carried out.

**Figure 9.** Power consumption of 5500 TEU reefer container during different operation modes.

Figure 10 compares the fuel consumption during each operating mode of this ship. The fuel consumption reached a maximum during the normal seagoing (with reefer) mode and a minimum during the normal seagoing (without reefer) mode. As the load increased, the fuel consumption increased; similarly, as the load decreased, the fuel consumption decreased. However, when observing the CO2 emission reduction rates shown in Figure 11, it can be seen that the CO2 emission reduction rate was the highest in the port in/out (without thruster) mode, during which the second least amount of fuel was consumed.

**Figure 10.** Fuel consumption in each operating mode of the 5500 TEU reefer container.

**Figure 11.** Comparison of CO2 emissions and CO2 emission reduction rate in each operating mode of the 5500 TEU reefer container.
