Spectral directional emissivity measurements of benchmark materials for passive radiative cooling (PaRaMetriC, 21GRD03)

PaRaMetriC Dataset Overview This dataset contains experimental measurement data used in the publication: Adibekyan, A., Schumacher, J., Pattelli, L., Manara, J., et al.Emissivity and Reflectivity Measurements for Passive Radiative Cooling Technologies,International Journal of Thermophysics, 2025.DOI: 10.1007/s10765-025-03532-6 The dataset supports the reproducibility of the published results and enables reuse of high-quality spectral emissivity data for modeling, comparison, and design of passive radiative cooling materials. Description of the Dataset The dataset includes spectral directional emissivity measurements of benchmark materials developed and investigated within the PaRaMetriC project (21GRD03). Measurements were performed using the Emissivity Measurements in Air Facility (EMAF) at the Physikalisch-Technische Bundesanstalt (PTB), covering the following conditions: • Wavelength range: 5 µm to 50 µm• Angular range: 10° to 70° with respect to the surface normal• Temperature conditions: 60 °C or 100 °C, depending on the material Measurement uncertainty is reported as expanded measurement uncertainty (coverage factor k = 2).Detailed descriptions of the measurement principles, experimental configurations, calibration procedures, and data analysis methods are provided in the associated publication. Materials Investigated SPACECOOL A self-adhesive multilayer silver–polymer optical film with specular reflection and surface-roughness-induced light scattering, provided by SPACECOOL INC., was applied to a copper substrate with a diameter of 50 mm and a thickness of 5 mm.The substrate includes a 2 mm diameter hole to accommodate a platinum resistance thermometer (PRT) for monitoring the substrate temperature. V98RF (Cooling Photonics S.L. / Almeco Group) A selective emitting polymer coating (“RF”) developed by Cooling Photonics S.L. was applied to a silver-based mirror labeled Vega 98® (V98), provided by Almeco Group and cut to a size of 40 mm × 40 mm. Vega 98® consists of a high-purity aluminum substrate enhanced by a specific PVD multilayer coating system based on silver. It is manufactured using a continuous coil vacuum coating process, making it a fully scalable product.The RF coating preserves the high reflectivity of the V98 substrate while providing high emissivity in the infrared atmospheric window, resulting in a high-performance selective emitter (V98RF). 3M R&D PRCF A self-adhesive, metal-free, white-diffuse R&D developmental Passive Radiative Cooling Foil (PRCF) provided by 3M was adhered to an aluminum substrate with a diameter of 90 mm using Apiezon thermal paste.A 2 mm diameter hole was included in the substrate for placement of a platinum resistance thermometer (PRT). Data Format and Structure All data files are provided in CSV (comma-separated values) format. • Wavelength: micrometers (µm)• Angle: degrees (°) with respect to the surface normal• Emissivity: dimensionless Each CSV file contains a header row describing the columns.Expanded measurement uncertainty (k = 2) applies to the emissivity values and is discussed in detail in the associated publication. Uncertainty values are not provided as separate columns in the CSV files. Files Included • Fig6_directional_emissivity_material_SPACECOOL.csvSpectral directional emissivity measured at angles from 10° to 70° at 60 °C. • Fig6_directional_emissivity_material_3M_R&D_PRCF.csvSpectral directional emissivity measured at angles from 10° to 70° at 60 °C. • Fig6_directional_emissivity_material_V98RF.csvSpectral directional emissivity measured at angles from 10° to 70° at 100 °C. • Fig5_directional_total_hemispherical_material_SPACECOOL.csvDirectional total and hemispherical emissivity at 60 °C. • Fig5_directional_total_hemispherical_material_3M_R&D_PRCF.csvDirectional total and hemispherical emissivity at 60 °C. • Fig5_directional_total_hemispherical_material_V98RF.csvDirectional total and hemispherical emissivity at 100 °C. • README.mdDescription of the dataset, measurement context, and file structure. Contact Name: Albert AdibekyanAffiliation: Physikalisch-Technische Bundesanstalt (PTB)Email: [e-mail] Funding The project 21GRD03 PaRaMetriC received funding from the European Partnership on Metrology, co-financed by the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.