Abstract
Background
Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations.
Methods
The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because of the highly diffusive behaviour of the PCM layer when in the solid state of aggregation.
Results
The paper provides a data set of luminous and solar properties of glazing units with PCMs in gaps; the data set uses results from an advanced optical facility that overcomes the intrinsic limitations of commercial spectrophotometers in measuring the optical properties of the advanced transparent materials. In detail, transmittance, reflectance and absorptance spectra of double glazing units characterised by different PCM layer thicknesses in the gap, measured at different incident beam angles, are reported. Integrated values calculated according to relevant international standards are thus provided. Optical features of PCM glazing systems are also highlighted and issues related to the integration of these systems in buildings are discussed.
Abstract:
Background
Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations.
Methods
The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because of the highly diffusive behaviour of the PCM layer when in the solid state of aggregation.
Results
The paper provides a data set of luminous and solar properties of glazing units with PCMs in gaps; the data set uses results from an advanced optical facility that overcomes the intrinsic limitations of commercial spectrophotometers in measuring the optical properties of the advanced transparent materials. In detail, transmittance, reflectance and absorptance spectra of double glazing units characterised by different PCM layer thicknesses in the gap, measured at different incident beam angles, are reported. Integrated values calculated according to relevant international standards are thus provided. Optical features of PCM glazing systems are also highlighted and issues related to the integration of these systems in buildings are discussed.
The optical characteristics of an advanced glazing system are presented in this paper. The investigated glazing system is based on the incorporation of a paraffin-based Phase Change Material (PCM) into a transparent component, made of two extra-clear glass panes and a cavity where the PCM layer is placed. Due to the highly scattering property of the system (when the PCM is in solid state), the use of a large integrating sphere equipment (75 cm diameter) is necessary to obtain reliable results. The spectral transmission, reflection and absorption coefficients of the PCM glazing system are measured between 400 and 2000 nanometers, and the integrated values are calculated according to the relevant standards. The optical properties are determined with a maximum relative error of 4% (on the sum of the transmission, reflection and absorption coefficients), when the PCM layer is either in complete solid state or liquid state. The average error for all the optical properties is 2%. Different thicknesses of the PCM layer are used in order to assess the dependency of the optical properties on the PCM layer thickness. The angular dependency is also investigated for beam angle up to 45 deg