## 4 Machine Learning with Big Data Analytics to Achieve Fuel Efficiency
### Data Acquisition  
#### 4.2.1 Telemetry  
Depending on the application of ML, various types of sensors must be installed on the ship to collect the necessary data. For ship energy efficiency, one of the most important data is the fuel consumption, which could be collected by the flowmeter. There are several flowmeters in the market such as the volumetric flowmeter that measures the volume of the fuel consumed and the more accurate Coriolis mass flowmeter that measures the mass of the fuel consumed. The installation of Coriolis mass flowmeter was made mandatory by the Singapore Maritime Port Authority (MPA) from 1 July 2019 [46] to increase fuel quality and reliability, and also to prepare the sector for the rise in distillate bunker fuel deliveries after the IMO implemented a 0.5 per cent worldwide Sulphur cap on 1 January 2020 [47]. A Coriolis meter is based on motion mechanics principles as shown in Figure 4. As fluids enter the device, a driving coil induces the tubes to vibrate in opposition at their natural resonant frequency thereby creating sine waves. The fluid induces Coriolis force which causes the flow tubes to twist. The density of the fluid (mass) is measured by analyzing the frequency of the sine waves and the readings are highly accurate with typical measurement errors of \(\pm\)0.2 per cent. Coriolis mass flowmeter is equipped with built-in sensors for temperature, pressure, and density measurements with a display system [48]; therefore, the results could be stored and transmitted readily. Moreover, the Coriolis mass flowmeter requires low maintenance as there are no moving parts. The volumetric flowmeter on the other hand has moving parts that can be degraded over time which will result in inaccurate readings. Additionally, volumetric type meters contain separate temperature and pressure gauges that might be readily tampered with or gauges that are inaccurate. Figure 3: Machine learning with BDA process flow. The ship energy efficiency depends on the ship resistance (Equation (4)) which in turn is affected by the environmental data such as wind, wave and current. Wind sensors, as shown in Figure 4, are used to collect data on the wind speed and direction the ship experienced. The mechanical wind sensor is shown in Figure 5a is also used to measure wind data; however, it operates with moving parts. The mechanical sensor operates by having a rotating cup and vane in measuring the wind speed and direction. The time it takes a mechanical sensor to physically start-up or record a change in wind direction causes observed variances in recorded wind speed [49]. For example, if a storm passes through a region and the wind abruptly changes direction, the sensor must slow down, stop, then resume to keep up with the shift. The inaccuracy in the mechanical wind sensor could be overcome by the ultrasonic wind sensor shown in Figure 5b. The Ultrasonic wind sensor [49], also known as a sonic anemometer, uses a microcontroller to measure the travelling time of the ultrasonic pulse in computing the wind speed and does not require any moving parts to operate, thus requires lesser maintenance and have a longer lifespan. Inertia does affect the ultrasonic sensor as it is capable of measuring changes of wind direction or high gust immediately and in real-time. Figure 4: Schematic of a Coriolis meter. Figure 5: Schematic diagram of wind sensor. (**a**) Ultrasonic wind sensor; (**b**) mechanical wind Sensor. Other sensors to be installed onboard the ship for better accuracy in the prediction of fuel consumption are such as the acoustic Doppler profiler (ADP) to measure the current flow as the resistance of the ship is significantly affected by the current flow. However, the installation of the ADP is expensive and requires modification of ship structural configuration to fit the ADP. Tidal tables are thus used for predicting the average current flow when the real-time current profile is not available. The driveshaft RPM sensor is also used to collect the rotational speed of the propeller shaft.