Proceedings in the Development of PCM Modules for Seasonal Heat Storage

Abstract

ABSTRACT This thesis deals with thermal energy storage (TES) by the aid of supercooled phase change materials (PCM) based on sodium acetate trihydrate, and addressing certain issues encountered in on-going research, while elucidating the importance TES with PCM might hold in a future energy system. This technology seeks to counter the consequences of the fluctuating supply of renewable energy sources of energy and provide seasonally independent heat at a high security of supply, whilst aiding the introduction of higher shares of renewable power into the energy system. Thermal energy storage have been researched and utilized for well over a century, while the supercooling property of several heat storage materials have been largely overlooked. Using this property actively, significant amounts of energy can be stored latently for extended periods of time - without any losses related to the length of storage. When combined with solar heating, this proves an interesting opportunity for dwellings to be self-sufficient with heat for all building technical services, like heating and hot water, etc. Simulations conducted by Schultz & Furbo (2007) demonstrates that a reasonably small amount of collector surface and storage volume respectively proves sufficient to supply a Danish household, without any auxiliary heating, if constructed in accordance with Energistyrelsens Bygningsklasse 2020-directive. Issues surfacing during the attempts do develop successful prototypes of such PCM-modules are being addressed during the course of this project, and among them follows: − Small-scale experiments on the PCM composition (ratio of water to sodium acetate) for improved stability during supercooling, and; − Determine latent heat of fusion for compositions exceeding 42 % water. − Strength analysis to determine and improve problem areas in preceeding, deformed and failed module prototypes, incapable of cooping with high pressure. − Socioeconomic perspectives on potential impacts on the existing energy system. − Private economic analysis, simulating performance on the tested compositions and degree of solar fraction. Recognizing the world as an entity with a finite amount of resources, mankind is quickly running out of our primary carriers of energy as fossil fuels are being depleted at an everincreasing rate. While renewable sources of energy are being implemented worldwide as a response to the fossil depletion, one common denominator identifies and problematize them: With the exception of hydropower, they are all highly fluctuating and rather unpredictable - very much in contrast to mankind’s demand for power and heat, thus emphasizing the importance thermal energy storage might hold in a future energy system. REFERENCES Schultz, J. M. & Furbo, S. (2007) Solar Heating Systems With Heat of Fusion Storage With 100 % Solar Fraction for Solar Low Energy Buildings, ISES Solar World 2007 Congress Proceedings, Beijing, China.