# Analysis of Hybrid Ship Machinery System with Proton Exchange Membrane Fuel Cells and Battery Pack
## 1 Introduction  
Most countries in the world encourage reductions in harmful emissions [1], which as a consequence causes the price increase of fossil fuels to drive the decrease of greenhouse gas emissions [2], which is an unpopular measure, as fossil fuels are the driving force of marine traffic. From 2008 to 2018, emissions of CO\({}_{2}\) increased by 90%, and predictions are that they will further increase. With IMO regulations for NO\({}_{x}\), CO\({}_{2}\), SO\({}_{x}\), and other emissions becoming more stringent, stakeholders across the board recognize the need for the maritime sector to reduce emissions and decarbonize in order to sustain itself as a business in the future. When a hydrogen fuel cell system is used, the emissions of NO\({}_{x}\), sulfur oxides (SO\({}_{x}\)), or PM can be fully eliminated since the fuel cells have no incomplete combustion products, and no pilot fuel is needed [3]. The main measures to reduce consumption and consequently pollution in the shipbuilding industry are to optimize ship engines, propellers, and the hull, which are limiting factors, as the efficiency of each part can only go so far to reach limits of maximal efficiency. To overcome that, anew approach is necessary. The power system generates all power and pollution, and one promising solution is to replace it with a proton exchange membrane fuel cell (PEMFC) in combination with a battery pack. PEMCs differentiate from internal combustion engines, as they are electrochemical devices for conversion of fuels with hydrogen as an energy carrier to electricity with high efficiency [4]. Other benefits include their generation of completely emission-free energy, their ease of implementation on existing systems that use electricity, and their electrochemical reaction byproduct generation of only pure water and heat. With that said, the PEMFC system is good for long-distance voyages with a constant load and for vessels that travel at relatively short distances with power demand variations, as shown in this paper. Hybrid systems are advantageous in applications where the load is constantly changed, such as the maneuvering of vessels in ports and short distance travel with variable power demand. When a constant load is applied, the PEMFC stack system can be incorporated without the requirement for a high-power battery system; in usage, it can be compared to a diesel system with power demand up to 300 kW. At the moment, diesels outperforms all other systems in towing capability and long-distance range for systems with high output power. A hybrid system that uses a combination of the PEMFC stack and a battery package is very effective and has good dynamic load characteristics, which makes it compatible for replacing the classic marine power systems, like diesel. To analyze and incorporate such a system into vessels for our case, a numerical model was developed. Additionally, this numerical model can be used to simulate different configurations of a hybrid or PEMFC stack system incorporated with other systems that use diesel-electric power (trains or vessels) or any other system that use electricity offshore, off grid, or connected to the grid; it can be scaled, and additional sources of electricity production can be added to give this numerical model offering an even bigger paltete of implementation. Corvus Energy developed sustainable marine hydrogen fuel cell systems, which represents a clean and safe alternative power for ships [5]. [PERSON] et al. focused in their study [6] on PEM fuel cells as an energy supply for ships. Their experimental results confirmed that PEM fuel cells are an emission-free solution for electricity generation in ships. The PEM fuel cell was found to be a promising option for marine applications. The main obstacles are the power capacity, cost, and lifetime of the fuel cell assembly [7]. CO\({}_{2}\) emissions are up to 8% lower in the solid oxide fuel cell hybrid system in comparison to a diesel-powered ship during a typical passenger ship voyage [8]. [PERSON]. [PERSON] et al.