The paper presents the results of a theoretical investigation of use of phase change materials (PCM’s) with active use of super cooling as a measure for obtaining partly heat loss free seasonal storages for solar combi-systems with 100% coverage of the energy demand of both space heating and domestic hot water. The work is part of the IEA Solar Heating & Cooling Programme Task 32 “Advanced Storage Concepts for Solar Buildings”. The investigations are based on a newly developed TRNSYS type for simulation of a PCM-storage with controlled super-cooling. The super-cooling makes it possible to let storage parts already melted to cool down to surrounding temperature without solidification in which state that part of the storage will be heat loss free but still will hold the latent heat in form of the heat of fusion. At the time of energy demand the solidification of the super-cooled storage part is activated and the temperature rises to the melting point. In order to maximise the thermal performance of the storage it can be subdivided into several subsections individually controllable. A mixture of sodium acetate and xanthane rubber has been chosen for the PCM-storage. Sodium acetate has a melting point of 58°C and a heat of fusion capacity of 265 kJ/kg. The added xanthane rubber (approx. 2 weight-%) makes the sodium acetate super-cool in a stable way. The starting point for the investigations is an ideal heat storage with perfect heat transfer between charge/discharge fluid and PCM as well as a perfect control system resulting in the best possible energy utilisation. Solidification of the super cooled PCM can be activated on demand. The results of the ideal situation will form the background for further work towards a physical system. The paper will present the PCM-storage model as well as the theoretical results obtained for a solar combi system with the PCM-storage installed in a low energy house in a Danish climate. Parametric studies of collector area, storage volume and solar fraction for the PCM-system will be presented as well as an outline for a system with 100% coverage of the space heating and domestic hot water demand.
|Published - 2005
|EuroSun 2006 - Glasgow, United Kingdom
Duration: 27 Jun 2006 → 30 Jun 2006
Conference number: 6
|27/06/2006 → 30/06/2006
|Part of International Renewable Energy Conference and Trade Exhibition