In accordance with the European Environment Agency and the International Energy Agency, shipping operations generate about 34% of the total nitrogen oxide emissions and 11% of the total carbon dioxide emissions produced by the transportation industry. The capacity of fuel cells to reduce harmful emissions makes them a very attractive and environmentally friendly energy conversion system. This work studies the application of a fuel cell–based auxiliary power plant fed with hydrogen on-board an existing oceanographic vessel. The objective is to eliminate emissions at port and to reduce pollution near inhabited areas. In addition, the power plant was sized to propel the ship at low speed reducing the noise emitted to the water during research tasks that require a low noise level. The type of fuel cell chosen is proton-exchange membrane fuel cell and the hydrogen that feeds it is stored in compressed form at 70 MPa reaching a total storage amount of 771 kg. The results show that a solution, as the one proposed in this study, is conceptually feasible. The amount of emissions avoided totals 7.95 t of carbon dioxide and more than 121 kg of nitrogen oxides per mission. Furthermore, the noise levels in the engine room are reduced under 90 dBA allowing a silent navigation mode as well as a noiseless ship at port.
Green hydrogen plays a key role in
decarbonizing the economy. However,
the best conditions for producing it are often far from consumption
places. This work compares three alternatives for large-scale green
hydrogen distribution based on the levelized cost of hydrogen (LCOH):
the use of green ammonia as a hydrogen carrier, the use of liquid
hydrogen, and on-site production. All of the alternatives include
production, packing, transport, and unpacking of hydrogen. Results
show that liquid hydrogen outperforms the other alternatives in most
cases. Only if the renewable electricity price in the destination
site and hydrogen demand are low enough does on-site production become
attractive. A demand of 1 MtH2
/y leads to a
LCOH equal to 5.14 USD/kgH2
when imported by
ship as liquid hydrogen from 7,200 km away and considering electricity
prices of 40 USD/MWh in the production site and 100 USD/MWh in the
destination. Analogously, LCOH is 9.01 USD/kgH2
when produced in situ and 10.25 USD/kgH2
using
ammonia as a hydrogen carrier. The ammonia alternative is attractive
if ammonia is the desired good at the destination, or when it does
not matter to import any of both fuels from the levelized cost of
energy viewpoint. Blue hydrogen LCOH is estimated to be 65% cheaper
than green hydrogen under similar scenarios.
Investigation, conservation, and exploitation of seas require platforms capable of accomplishing a wide variety of missions in harsh environments with restricted human intervention for long periods of time. Autonomous Underwater Vehicles (AUVs) are excellent tools for carrying out these missions due to their versatility and ability to access remote sites. However, despite the improvement of their capabilities, their development is not devoid of challenges. Endurance, among others, such as underwater communications or autonomy, is still a pending subject. Current battery-based solutions do not offer sufficient endurance and innovative power plants with higher energy content are needed. This work studies the advantages, in terms of endurance, of using a power plant based on Direct Methanol Fuel Cells (DMFCs) to power AUVs. In order to accomplish this, a multi-objective optimization tool that makes use of a genetic algorithm was developed. This tool allows quick preliminary design of AUVs with a DMFC-based power plant, complying with a user-defined payload, operation profile, and restrictions. Six designs based on a real AUV model were studied, and endurance values up to 2 times longer than the corresponding reference AUV were obtained. These results support the benefits of using DMFCs to power AUVs to increase their endurance.
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