Increasing energy efficiency in dishwashers by using thermal energy storage in phase change materials

Increasing energy efficiency of domestic appliances will help decrease energy consumption in residential sector. In dishwashers, waste heat from the discharge water of first washing cycle can be stored as latent heat in an appropriate Phase Change Material (PCM). The stored heat can later be recovered to preheat the second washing cycle water. In this study, design, development, testing and building the prototype of a suitable Thermal Energy Storage (TES) system to store waste heat with the purpose of more efficient energy utilization in dishwashers were carried out.Thermophysical properties and thermal stabilities of paraffin based PCMs and their paraffin binary mixtures with different compositions were determined and storage and recovery experiments were carried out. In experiments with waste heat recovery at 52 oC highest temperature increase was obtained for PCM-A as 14.3 oC and a corresponding increase in energy efficiency as 24.1 %.The experimental results were tested in the prototype that was built by Arçelik Company in Çayırova Plant. The prototype with PCM-A prepared by Çukurova University to store waste heat at 52ºC did not give the expected increase in energy efficiency. As an alternative solution, prototype tests were repeated for PCM-B with lower melting temperature and energy efficiency was increased by 3.6 %. This increase is yet not enough for large scale economical production of the prototype and further R&D activities are needed.Key Words: Energy Efficiency, Dishwasher, Waste Heat, Phase Change Material (PCM), Thermal Energy Storage (TES)