Zero Pollution: design of a river tourist pontoon with electric propulsion based on hydrogen fuel cell

del Bureau Veritas, y todas aquellas normativas nacionales e internacionales que sean de aplicación. Debido a la problemática que genera el uso cotidiano de los diferentes medios de transporte fl uvial, que sin lugar a dudas, podría generar una afectación irreversible al medio ambiente y una pérdida considerable de biodiversidad en los ecosistemas acuáticos, que se agrava con el paso del tiempo, este prototipo de diseño podría ser presentado a la construcción naval nacional, como una posibilidad de diseño de embarcaciones turísticas ecológicas para las zonas fl uviales del país, como ejemplo para futuras construcciones que se esperan con el auge del turismo en el país

In 2019, the tourism sector was the second largest generator of foreign exchange in the country, and the national government began to invest several e orts in it, to arouse the interest of businessmen and investors from all over the world, expecting a special boom in tourists in regions with river areas in the country, with high environmental interest (Santoro, 2019). Considering that situation, it is important to invest in research and development of products that enhance tourism in the country, while adequately protecting the environment. e main function of the tourist pontoon to be designed is the performance of tourism functions in the rivers located in regions with high ecological value, that are protected from contamination. For example, one of the rivers where the project can be implemented is the Bita river, which is protected in Colombia. Here, the State and other social actors must take measures before the water resources su er irreversible damages, including the loss of species that bene t from that speci c environment, such as jaguars, dolphins, giant otters, turtles and "arawanas" (Colprensa, 2015).
is is one of the fundamental missions for both the Colombian National Navy and the di erent tourism companies, that seek compliance with standards that protect these pollution-free areas.
Hydrogen abounds on Earth and could be produced in quantities that satisfy demands of all means of transportation. If it is produced through renewable energies, it could be the fuel of the coming decades. Fuel cells are directly associated with hydrogen, and propulsion systems based on them appear to be the most immediate clean solution to fuel alternatives. is project seeks to implement an electric propulsion solution based on a hydrogen fuel cell, which is also able to operate in rivers located in protected areas of the country. For this development, the physical and chemical properties of hydrogen, its production, storage systems, the operating principle of fuel cells (Balbona, 2014) and all relevant studies for the design of the vessel must be covered, such as, hydrostatic curves, structural calculations and ship weight, design of electrical generation and distribution, and the design of propulsion and auxiliary systems. ese bases must be clearly re ected due to the importance of hydrogen technologies (Valdés et al, 2018), being essential in the future of electricity production to solve the problem of greenhouse gas emissions, and particularly CO , which causes huge environmental damages.
According to the National Center for Experimentation of Hydrogen Technologies and Fuel Cells of Spain (CNH2), a fuel cell (FC) is an electrochemical device that transforms chemical energy directly into electricity. It starts with a fuel, usually hydrogen, and an oxidant, in many cases oxygen, to produce water, electricity in a continuous electric current and heat. In those fuel cells that consume hydrogen (H ) or which contain a proton exchange membrane or Proton Exchange Membrane Fuel Cell (PEMFC), the current is generated from the reaction shown in the following equation (1) (Leo, 2008). e fuel is H and the O would be supplied by the air. It should be clear that it is not an H combustion reaction, but rather, an electrochemical process consisting of oxidation-reduction reactions, in which the energy released by the spontaneous reaction is converted into electricity and electrical energy and can be used to make a non-spontaneous reaction occur; requiring electrochemical techniques and microbial fuel cells (Peña, et.al., 2020). FCs are not heat engines; therefore, their operation is not limited by the Carnot yield. Equation (2) shows how hydrogen decomposes at the anodes according to the oxidation reaction and equation (3) shows the reduction at the cathode.

Fuel Cell
Ship Science & Technology -Vol. 17 (3) ese equations depend on the type of applications for fuel cells.
at is, variables such as chemical reactions, the type of catalysts required for the reaction to take place, the range of operating temperatures of the cell and the fuel required, have a direct impact on their applications. (CNH2, 2020). ese fuel cells present great results such as high e ciency, long-term stability, fuel exibility, low emissions, and relatively low cost. Fig. 2 shows an example of a fuel cell diagram, and Fig. 3 (see page 12) shows that the e ciency of the cell is little dependent on the size of the system, which allows, in addition to its use in di erent energy ranges, the design of modular fuel cell systems. Furthermore, they can operate at half load while maintaining optimal fuel usage. e design process of the vessel was carried out with the support of the concept of the design spiral ( Fig. 4), as a guide to achieve a single result.
is is the development of the vessel through an optimal and e ective process, following an established order which must be respected. us, the design tool ensures the adequate proportion and balance of the project. Its viability, approximate budget, fundamental speci cations such as its useful life, speed, passenger and crew capacity, vessel limits and type of propulsion were determined. Legal and safety regulations were also identi ed and applied during the planning of the project. e aim is for the boat elaboration to be accepted by the nation o cial entities. Finally, the intention is to present a product ready for construction, with plans that comply with all the legal safe-conducts to allow the project to be executed without any impediment, as shown in Fig. 5.   Fig. 8. e selection of the fuel cell type was made searching in the supplier market and a PEM type fuel cell was selected, which has a power range of 0 to 250 KW and which is mainly used to feed transportation systems. vessel, Fuel Cell supported by Toyota Motor Corporation, (Yanmar Holdings, 2021). Data of the operation of the hydrogen fuel cell system and the control of the electric power train during real tests at sea and river areas were collected, evidencing an energy management system that coordinates and controls the operation of the fuel cells, lithium ion batteries and motors (Guerrero, 2022). Fig. 7 shows it in detail.  where η is the yield and S the cell area.

Propulsion System and Power Management
Amount of hydrogen in kilos required for the PEMtype fuel cell in stack. e following equation (6) is applied in which the following variables must be known:  this case, 700 bar is referenced as the maximum pressure that each type IV commercial cylinder can withstand and thus, the mass of each cylinder. So, for the storage of compressed hydrogen, in a bottle along the length, the conditions were established at 700 bars and 15°C. Fig. 9 is an example of this.
• e hydrogen society is knocking at the door (Fig. 11), Colombia must promote R&D e costs of the exposed project are re ected in the following table (2): programs to integrate hydrogen logistics within its technologies as soon as possible. shouldn't exceed the 5 or 6 knots, speed wich is enough for a leisure or turistic boat.

Conclusions
• e design of this prototype of a ship with alternative fuel sources, is attractive do to the high interest within the ship market for ships displacing less than 100 tons, primarily like touristic riverine vessels, barges and river boats working in rivers, for whom hydrogen o eers enourmous environmental bene ts.

References
• is work focused on demonstrating that in tourism logistics, it is possible to design boats to enjoy the rivers richness in the regions of the country without producing pollution. For instance, the Bita River, which is a tributary of the Orinoco River, and is in Puerto Carreño with an extension of 500 kilometers and considered one of the healthiest rivers in the country, (Colprensa, 2015).
• In accordance with the above, and as an example of the importance of this research, in 2022, the Colombian Ministry of Commerce, Industry and Tourism registered 15,871,329 domestic passenger arrivals, 3,303,582 international arrivals, 1,615,355 non-resident foreign visitors, 80,565 active tourism service providers in RNT (national register of tourism) and 58,896 cruise ship passengers, demonstrating that one of the main attractions is the biodiversity and fauna of Colombia, which generates a great business opportunity for the pontoon proposed in this article, (Díaz, 2023).
• Currently, the hydrogen economy is not mature enough to compete with fossil fuels. But it is a solution that prevents the accumulation of CO2 in the atmosphere and contributes to reduce climate change on the planet. e use of hydrogen as an energy source provides a reduction in emissions, polluting substances and the greenhouse e ect.
• From the research development, it can be stated that hydrogen could be a perfect alternative fuel for this type of tourist vessel. And the fact that its use as an energy vector reduces the emissions of polluting substances and its silent operation, presents an optimum solution for propulsion in areas of enormous environmental value, such as the regions located in river areas in the country.
• e main obstacle with the use of hydrogen in ship's, is that because of its low density, it occupies a signi cant amount of volume. Hence, for a single hydrogen pipe to be used per operation day, the speed of the boat