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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - ODes aCCES (Optimal design and control of cruise ship energy systems)

Teaser

Summary

International shipping is one of the major contributors to different categories of pollution, including greenhouse gas emissions. In these regards, international shipping is estimated to contribute today to approximately 2% of global CO2 emissions. The International Maritime Organization officially released in 2018 its goals for the reduction of CO2 emissions from shipping: 50% by 2050, and full decarbonisation by 2100.

In this context, cruise ships make up a special category, for different reasons:
â€¢ The cruise shipping sector is growing much faster than the rest of the shipping industry. The number of passenger has grown from 18 million in 2009 to 28 million in 2018.
â€¢ Cruise ships are very large energy consumers.
â€¢ Cruise ships have also a very complex power plant, as a result of the different needs arising from different final uses
â€¢ Cruise ships are particularly relevant for the shipbuilding industry in Europe: most other ship types are for the largest part built in China, Korea and Japan, while cruise ships are still today almost entirely built in Europe.
â€¢ Cruise ships have a very direct connection with the end-users, making them a particularly favorable subject for green marketing.

For these reasons, the work of this project focused on the optimization of design and control of cruise ship energy systems. The objective of this project was to take state-of-the-art methodologies from other sectors, such as the automotive or the process industry, and adapt them to the specific demands of ship systems and to apply them to cruise ships, in order to propose holistic solutions for the minimization of the greenhouse gas emissions from these ships.

Work performed

\"The work in this project developed in three, main phases.

In the first phase, a set of tools and methods called \"\"process integration\"\" was applied to the design of a cruise ship. Process integration techniques are based on an holistic approach to process design and optimization, which exploits the interactions between different units in order to employ resources effectively and minimize costs.

In the first part of the project, these methods were applied to a reference cruise ship powered by Diesel engines. Despite the existing means for waste heat recovery on board, there are large amounts of heat at low temperature that could be better used, mainly for the purpose of \"\"freeing\"\" waste heat at high temperature for being used in a more efficient way. The combined use of Rankine cycles, that can be used for converting high-temperature waste heat to electricity, and of heat pumps, that can be used to \"\"upgrade\"\" low-temperature heat to become usable for heat demand on board, was estimated to have the potential to contribute to up to 4-7% fuel savings. While these are promising results, they are not high enough to bring emissions from cruise ships down to a sustainable level. This led to the investigation of more radical changes of the ship\'s energy system.

Fuel cells are considered as a very promising technology for ship propulsion: they can reach high efficiency and o not have emissions of pollutants such as nitrogen oxides and particulate matter. At the current state, solid-oxide fuel cells (SOFC) are considered to be the most promising for application to shipping because can relatively easily run on a number of conventional fuels.

The second part of this study focused on the evaluation of the potential of using SOFCs on cruise ships, and on how to optimally design a system based on this technology. This part of the study led to the conclusion that there is a very significant potential for the use of fuel cells in ships. Firstly, their higher efficiency in converting fuel to electricity makes them better from the perspective of reducing fuel consumption; this was estimated to provide up to approximately 15% savings when compared to a system based on Diesel engines. In addition, SOFCs allow for the use of different fuels: the use of natural gas can lead to reducing emissions by an additional 15%. In addition, SOFCs are suitable to running on other fuels, such as hydrogen or ammonia, that have potentially no direct emissions of CO2. Hence, the conclusion of this phase of the project was that SOFCs have an important potential for use on ships, and that the development and spread of this technology should be pushed if sustainable shipping operations are expected.

Finally, a third part of the study focused on optimal control. Because of their poor dynamics, SOFCs require the installation of storage technologies. More generally, the use of energy storage is gaining ground in the shipping sector, and the appropriate management of the energy flows in systems equipped with energy storage devices is not trivial. The scope of this part of the project was to test whether the assumption of optimal control is valid when applied to ships. The question that was addressed was: can the system be controlled to be as efficient as we could operate it if we knew the future? The results were very promising, and allowed to validate the approach employed in the other phases of the project. A relatively simple control algorithm was proposed, where predictions about future operations are based on what was learned from the previous ones, recorded over time. The results showed that by doing this the system can be operated very close to optimal efficiency (approximately 90-95% of the maximum) even when the operations of the real voyage are remarkably different from the ones that the system had encountered before.
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Final results

The work and results of this project contributed to an advance in the state of the art within the field of maritime engineering. This was achieved firstly through the application of process integration to ship energy systems: these methods allow a thorough, system-wise analysis and optimization of ship energy systems, and had never been applied before to ships. By showing the potential of these methods and how their application can help improving ship energy systems, this is considered a step forward in the state of the art, as it is expected that an increasing number of professionals, both in the industry and in academia, will follow up on this way.

Secondly, the work in this project represented a clear contribution to the state of the art for the application of fuel cells to ships. As fuel cells are considered a very promising technology as prime mover for ship energy systems, the analysis and optimization that were performed in this project brought fuel cells one step closer to implementation.

The results above are expected to have an impact in the development of ship energy systems towards more energy efficient and less polluting systems. The results are also expected to contribute towards the use of more advanced energy optimization techniques in the design of (cruise) ship energy systems, and towards a more widespread and faster adoption of fuel cells (particularly SOFCs) in shipping. The final impact of these developments will be a decrease in pollution and CO2 emissions from shipping, with positive impacts on the environment and on human health. In addition, as the European shipbuilding industry is today fighting for maintaining its position in a global, competitive market, the advancements here proposed in the field will, hopefully, contribute to maintaining the European industry competitiveness, and its technological advantage, with the consequent positive effects on the European job market.