# Developments in Electric and Green Marine Ships
## 3 Technologies that Did or Will Shape the Future of Naval Travel and Trade
### Importance and Development of Battery Storage Systems  
It should be clear by now that whether the conversation is on integrated systems that exploit wind or solar energy, and whether these technologies are currently on trial stage or already commercially operating, the computer system that manages all the data plays a vital role. Digitalization has given birth to numerous new capabilities, but at the same time, the reliability of the computer system has become of great importance [56; 57; 58]. Furthermore, digital equipment requires electric power from a reliable on-board source. These facts could possibly give further motivation for electric propulsion in the naval sector. For example, a modern vessel with many installed sensors and an integrated system of operational optimization would require a battery storage system. Such a system is also mandatory if a vessel has photovoltaics installed or an electric propulsion system, as it will require power that could, among other ways, be provided from batteries. Additionally, as mentioned above in Section 3.4, there are companies and projects that consider electric propulsion. In these vessels, the battery storage system is of paramount importance, as it works as the main source of power for all the electrical and electronic systems. Even as the main power source for propulsion, in the case of electric propulsion vessels, the battery system also generates propulsion power. Therefore, a more detailed presentation of the different types of batteries is being included in the present paper, as shown in Figure 6. Starting by the battery types that are already used in the maritime industry according to [59; 60; 61; 62; 63; 64; 65], a draft of the different marine battery types is presented. From Table 1, it becomes clear that for a battery system based on batteries that are already used in the maritime industry, in order to provide 10 MWh under the most ideal circumstances, the weight will theoretically surpass 100 tons. This hypothesis will play a significant role in the present paper, specifically in the calculations in Section 4, where the appropriate battery storage system, in order to meet the biggest possible percentage of the vessel's energy needs, is chosen. Although battery storage in the naval sector is very promising, there are discussions concerning the environmental impact of large-scale batteries entering the energy storage sector. According to [66], the environmental impacts of large-scale battery use remain a major challenge that requires further study. In this paper, batteries from various aspects including design features, advantages, disadvantages, and environmental impacts were assessed. This review reaffirms that batteries are efficient, convenient, reliable, and easy-to-use energy storage systems (ESSs). However, it also confirms that battery shelf life and use life are limited. This fact translates to a large amount and wide range of raw materials, including metals, non-metals, and rare earth elements, which will be used to produce batteries. This results in the generation of considerable amounts of environmental pollutants (e.g., hazardous waste,  
Figure 6: Marine batteries comparison. greenhouse gas emissions, and toxic gases). These pollutants will be generated throughout the entire life cycle of the batteries, during different processes such as mining, manufacturing, use, transportation, collection, storage, treatment, and disposal [67]. Apart from the environmental impact, large-scale batteries are forecasted to create significant social impacts. This negative impact of large-scale battery usage and development could significantly alter their implementation in the naval sector. Thus, a draft presentation of a possible partial solution in the present paper is justified. One of the six different battery types already used in marine and offshore operations has the advantage of being recyclable. More specifically, these hybrid batteries are safe, reliable, easy to install, and have comparable performance to lithium-ion batteries.