Possibilities for characterization of a PCM window system using large scale measurements
Journal article, Peer reviewed
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OriginalversjonInternational Journal of Sustainable Built Environment. 2013, (2), 56-64. 10.1016/j.ijsbe.2013.09.003
The introduction of dynamic envelope components and systems can have a significant reduction effect on heating and cooling demands. In addition, it can contribute to reduce the energy demand for artificial lighting by better utilization of daylight. One of these promising technologies is Phase Change Materials (PCM). Here, the latent heat storage potential of the transition between solid and liquid state of a material is exploited to increase the thermal mass of the component. A PCM layer incorporated in a transparent component can increase the possibilities to harvest energy from solar radiation by reducing the heating/cooling demand and still allowing the utilization of daylight. Measurements have been performed on a state-of-the-art, commercially available window that integrates PCM using a large scale climate simulator. The glazing unit consists of a four-pane glazing with an integrated layer that dynamically controls the solar transmittance (prismatic glass) in the outer glazing cavity. The innermost cavity is filled with a PCM, contained in transparent plastic containers. When dynamic components are incorporated in the building envelope, it makes the characterization of static performance (e.g. the thermal transmittance, U-value; the solar heat gain coefficient) insufficient in giving the full picture regarding the performance of the component in question. This article presents a series of preliminary measurements, and the related methodologies, carried out on a window with incorporated PCM. The tests have been carried out using several test cycles comprised of temperature and solar radiation cycling, where the aim has been to delve deeper into the possibilities for the characterization of dynamic building envelope components by full scale testing in a climate simulator, showing potentials and limitations of this approach and measurement facility. It was found that even for temperatures similar to a warm day in Nordic climate, the potential latent heat storage capacity of the PCM was fully activated. Long periods of sun combined with high exterior temperatures are needed.