## 2 Materials and Methods
### Measuring and Analysis Methodology  
The PEMS and fuel flowmeter were installed as shown in Figure 1 to measure CO\({}_{2}\) concentrations in exhaust gases and determine real-time fuel consumption. IMO NOx TECHNICAL CODE 2008 recommends that exhaust gas measurement equipment be installed at least 0.5 m from the end of the exhaust pipe or three times the pipe diameter (3D) [17]. The PEMS connection was manufactured in the form of a tailpipe and installed on the straight part of the exhaust pipe to minimize the effects of turbulence. Figure 2 shows a schematic of the PEMS and fuel flowmeter installed on the experimental ship. Most of the ship's environment is inadequate and there is insufficient space to install each piece of equipment. Therefore, sufficient consideration is required for the installation of measuring equipment and each accessory, and it is essential to determine in advance whether or not the power supply of the ship can be used. In the case of fishing boats, it was impossible to supply power on its own, and power was supplied using a portable generator. A PEMS is a device capable of measuring the CO\({}_{2}\) concentration (%) in exhaust gas using an NDIR method, and exhaust flow rate data are essential to convert the concentration (%) into gram (g) units. In general, since the engines installed on ships are larger than those in road mobile sources, it is impossible to use an exhaust flowmeter due to the high exhaust flow rate. Therefore, the U.S. Environmental Protection Agency (EPA) developed a carbon balance method to calculate the exhaust flow rate using the concentration of CO\({}_{2}\), carbon monoxide (CO), and total hydrocarbon (THC) in exhaust gas \begin{table}
\begin{tabular}{c c c} \hline \hline
**Model** & **SEMTECH DS+** & **HORIBA OBS-ONE (HDV)** \\ \hline Measurement range & 0–18\% vol & 0–20\% vol \\ Measurement principle & NDIR & Heat NDIR \\  & \(<\pm\)0.1\% vol & \(<\pm\)0.5\% vol \\ Zero drift & (over 4 h) & (over 4 h) \\ Span drift & \(\leq\)2\% of span value or \(\leq\pm\)0.1\% vol & \(\leq\)1\% of span value or \(\leq\pm\)0.1\% vol \\ Accuracy & \(<\pm\)2\% of reading or \(\leq\pm\)0.3\% of full scale & - \\  & \(|\)Xminx(a1–1) + a0\(|\leq\) 0.5\% of span & Intercept: \(|\)Xmin(a1–1) + a0\(|\,\pm\) 0.5\% of full scale \\ Linearity & Standard Error of estimates \(\leq\) 1\% of span & Slope: 0.99 \(\leq\) a1 \(\leq\) 1.01 \\ Repeatability & \(\leq\pm\)2\% of point or \(\leq\pm\)1\% of span & \(\leq\pm\)1\% of full scale \\ Sample flow rate & 3 LPM & 2.5 LPM \\ Data rate & 1–5 Hz & 1–10 Hz \\ Vessel installed & SSD 1, SSD 2 & HSD 1, HSD 2. HSD 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental CO\({}_{2}\) emission measurement system specifications. \begin{table}
\begin{tabular}{c c} \hline \hline
**Model** & **RHM 03L** \\ \hline Accuracy & 0.10\% \\ Repeatability & 0.05\% \\ Responsibility & 30 s \\ Pressure rating & Up to 1379 bar/20,000 psi \\ (dependent upon material) & \(-\)196–350 \({}^{\circ}\)C \\ Operating temperature & \(-\)196–350 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental fuel flowmeter specifications. and fuel consumption [18; 19]. In this study, that method was used to calculate the exhaust gas flow rate. \[q_{exh}=\frac{F\times f_{fuel}}{f_{CO_{2}}\times u_{CO_{2}}\times c_{CO_{2}}+f_{ CO}\times u_{CO}\times c_{CO}+f_{THC}\times u_{THC}\times c_{THC}} \tag{1}\]  
where \(q_{exh}\) = exhaust flow rate(kg/s); \(F\) = fuel consumption (kg/h); \(f_{fuel}\) = carbon percentage in the fuel (mc/mfuel); \(f_{gas}\) = carbon percentage of the pollutant according to the fuel (mc/mgas); \(u_{gas}\) = pollutant density ratio to the total exhaust gas density; and \(c_{gas}\) = measured pollutant concentration (ppm). The experimental design for data analysis of this paper is shown in Figure 3. The fuel consumption (kg/s) was measured with a Coriolis-type fuel flowmeter and the exhaust gas flow was calculated using the carbon balance method based on fuel consumption and fuel properties.