Performance analysis of ship air condition systems in terms of variable environment conditions

Kyoto Protocol forces the states to decrease carbon emissions due to the combustion of hydrocarbon content fuels in the energy plants. When current technologies have been investigated, it seems that there is no method that directly decreases carbon emissions from internal combustion engines, boilers etc. Nowadays, the most effective way for decreasing carbon emissions is to develop methods that increase the energy efficiency of systems. In the last few years, carbon emissions that originate from ships have been aimed to be decreased as it is observed in the applications of energy consumers such as land facilities and transportation vehicles. After 1 January 2013, according to IMO (International Maritime Organization) MARPOL Annex VI MEPC-63 regulation, preparing SEEMP (Ship Energy Efficiency Management Plan) has become mandatory in all ships that is 400 gross ton and above for the purpose of controlling carbon emissions. In addition, according to MARPOL Annex VI MEPC.1/Circ.684 regulation evaluation of monitoring parameters named as EEOI (Energy Efficiency Operation Index) has been come into force. One of the components that consume energy in ships is HVAC (Heating, Ventilating and Air Conditioning) System. In existing ships, refrigeration systems are designed to operate under extreme conditions and compressors work at constant speed. In these systems, sea water is used as a coolant in condenser. When sea water temperature increases, the compressor outlet pressure must be kept higher in order to ensure condensation in condenser outlet. This situation causes increase in power demand of compressors which result in decrease of COP. On the other hand, when the sea water temperature decreases, the power demand of compressor decreases. In that case, it can not be benefited from energy saving potential of refrigeration system occurred in lower sea water temperature conditions. In this thesis, refrigeration cycle analysis at constant cooling capacity is performed with 5 different refrigerants by utilizing data from a real ship HVAC system at different evaporation and condensation temperatures. In this context, in case of using variable speed compressor, cost equivalent of energy saving potential, obtained cost savings equivalent for variable fuel prices, payback period of variable speed compressor's investment cost and reduction in pollutant emissions releasing to atmosphere by fuel saving, has been calculated. Also, exergy destruction of refrigeration system has been calculated in case of variable environment conditions and factors that cause exergy destruction have been analysed.