Heat recycling on board maritime platforms : A concept study on improved vessel sustainability

Sammanfattning

Most studies that tried to minimize carbon emissions from marine vessels have used the recycled waste heat generated from the propulsion engines to generate heating and minimize the electricity needed for the cooling systems. In this Master Thesis, a collaboration with Saab Kockums was conducted which had a goal to evaluate the possibilities to use waste heat from a cooling machine to create a more energy-efficient, sustainable and cost-efficient system for a surface vessel. The aim was to reduce carbon emissions and energy consumption without compromising the economic costs. But to also evaluate the advantages and disadvantages of using a cooling machine as a heating system for common areas and to examine the functionality and performance of such a system. This system would remove the current existing heating systems on a maritime platform and supplement the heating demand by recycling the waste heat from the cooling machines. The research questions posed were as follows: What structure would a system have that can integrate cooling and heating systems into a sustainable system? How can the functionality and performance of a cooling and heating system, designed with a focus on sustainability and economy, be evaluated both qualitatively and quantitatively? How will the functional flow of the concept operate under different operating conditions? What advantages and disadvantages will the concept have in different operating conditions? The research engineering methods applied in this thesis consists of interviews with system engineers, a design of a new heating battery, and a new concept generation. Furthermore, evaluation and systematic design drawing of the system’s connections to its subsystems and a functional flow diagram of the system are included. The result of this thesis shows that there is a possibility to use the water mixed with 20% glycol from the condenser side of a cooling machine with a temperature at 42℃ to provide heat to the platforms heating demands while maintaining its cooling functionality. The implementation would require some new pipelines and multiple valves between certain components so that the cooling machine would operate as a heat pump and/or as a cooling machine despite the weather conditions. Finally, a new heating battery would be needed and created. An operating year was determined to be 292 days and the system would switch between the two operating cases: summer- and winter-mode, in two geographical areas, the Mediterranean and the Baltic Sea. The new system compared to the current system of a Visby class corvette resulted in a reduction of carbon emissions up to 14%, 9% reduction in weight, and up to and 25% reduction in power usage. The fuel reduction cost is estimated up to 14%, for each operating year.