Due to the serious concern regarding energy globally, the ocean, which obtains infinity clean energies, has been come into the spotlight and many researches converting these energies into the electricity have been being conducting around the world. The grid-off(stand-alone) system using the battery is particularly essential for ocean facilities, such as lighthouses, buoys, etc. However, it is difficult to operate it compared to do it on land because of many constrains such as long distances, severe weather conditions, etc. As a result, the self-charging/discharging battery system using a PV generator has recently been studied, particularly to apply it to the marine signal light on a buoy. However, according to characteristics of the PV generator, the generated electric power is not steady, for example it usually over-generates the electricity in the sunny day but it hardly generates the electricity in a rainy and heavy cloudy day. Therefore using the PV alone is difficult to supply the steady electric power to a buoy, as a result, it cannot guaranty of the safety for a ship's voyage. In order to overcome this main drawback of the PV system, researchers have recently been studied to hybrid between the PV generator and the wind generator or the PV generator and the wave power generator. Although the wind power generator and the wave power generator intermittently generate the electric power, they are able to generate at night. As a result, they can compensate the main drawback of the PV system.
The aim of this study is to supply the steady power to ocean traffic facilities using the hybrid system and in order to achieve this aim, the hybrid system consisted of the PV generator and the wave power generator is proposed in this work. However, each system interferes each other in the hybrid system and the high frequency of charging/discharging makes the battery's lifetime shorter. Therefore in order to improve the efficiency of the system and also increase the lifetime of the battery, the battery must be charged/discharged by the controller which is able to maximize the efficiency of the system respectively. Addition to this, it needs to monitor the condition of the system in real time. Therefore the systematic monitoring system in this study is consisted to optimally operate the system to supply the steady power to the marine signal light on the buoy, and addition to this the wireless communication system is constructed to monitor the system in real time.
Furthermore it is tested on the sea and data from the PV system and the wave power generator is collected to analyze its output characteristics. In addition to this, data regarding load conditions is also collected and analyzed. Through the analyzed results, it proves it's feasibility of the proposed hybrid power generation system and the proposed monitoring system which is increased the efficiency of the system. Therefore, not only the proposed system in this work improves the efficiency, but also it brings the system's reliability and safety due to being controlled by generation characteristics and monitored the battery's condition.
As a result, it will take a big role to prevent marine accident on the sea. Furthermore it can reduce the frequency of visit on site because the steady power is supplied by the stand-alone power system and using clean energies will achieve great financial savings and also reduce the emission of greenhouse gases into the atmosphere. For future works, it requires to study more about control techniques of various power generation systems using renewable energies and their monitoring systems fitted with ocean facilities as well.