| Summary: | The increase in the oil price, the forecasts of the climate change and the stricter emission standards for vessels have made the shipping companies pay more attention to the energy consumption of vessels. Traditionally, the energy consumption has been tried to be reduced by decreasing the ship resistance and improving the efficiency of engines. The energy consumption of the vessels' internal systems has not received so much attention. The HVAC systems and structural solutions of the vessel can be used for finding new opportunities for decreasing the total energy consumption of the vessel. The purpose of this Master's thesis is to introduce a recommendation for improving the energy efficiency of the superstructure of an icebreaker. The thesis introduces the most cost effective solutions for insulation thicknesses, types of windows, wall panels and the ventilation heat recovery maximizing the thermal comfort. The analysis compares the envelope structures of an icebreaker planned for cold circumstances with a reference solution representing the traditional design practice. The design concept developed provides superstructure recommendations and guidelines for energy effective ship-building in cold circumstances. The energy consumption and thermal comfort of the design concept are calculated with a dynamic IDA-ICE simulation program. The life cycle costs are determined by calculating the investment costs for the selected components and the 20 year operating costs based on the energy consumption. The selected decision variables form altogether 23328 design concepts, among which the recommendations are found with multi-objective optimization. The optimization is made with the GenOpt optimization program using a genetic algorithm (GA), the target functions being the heating energy, minimizing the investment and life cycle costs and maximizing the thermal comfort. The thesis introduces a design concept according to the optimization results where annual savings of 38 % in the heating energy consumption of the ...
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