Assessment of the potential of using phase change materials for latent heat thermal storage

Abstract

This work was part of the European Union’s Horizon 2020 Making-City program aiming to increase information regarding the positive energy districts. In this study as part of the project, possible use of phase change materials (PCM) in thermal storage was studied to increase its capacity by adding encapsulated materials to the conventional hot water tank. Although the use of PCMs has been studied previously, there still is a need for more practical research regarding the increase of energy content and its discharge properties. Therefore, we studied the theory of PCMs, commercial availability, theoretical viability, and practical viability of PCMs to set up practical test equipment to monitor temperature changes and to measure their efficiency in increasing the energy content.

Four different PCM materials from multiple commercial PCM producers were tested in comparable tests with temperature measured in the function of time. Encapsulated PCMs were selected as they have been suggested to be the best option to nullify the negative properties according to previous studies. Increased energy gained by using the PCM was calculated for thermal storage based on previous studies and using commercial materials technical specifications. Finally, practical testing equipment was made to test PCMs and compare the results with theoretical calculations. All selected materials were tested in four different temperatures 70, 67.5, 65, and 62.5 °C with three cycles for each temperature. All experiments had consistent PCM/water volume relation (1/3) with additional control tests containing just water. After the automated test cycles were finished, temperature data with 30 seconds intervals were collected. Although, the mean temperature showed that all PCMs increased the overall energy content of the storage, the amount of latent energy stored differed as well as thermal conduction rates. The results revealed that compared to the control test with water, the highest calculated energy increase was in the range of 28 to 37 % depending on test temperature, which was lower in comparison to the expected theoretical energy increase.