Optical transmittance and reflectance of a translucent plastic PTFE film have been measured over the solar wavelength range using different integrating spheres. The same sample has been measured with small and large spheres and the total solar transmittance has been obtained from both broad band measurements and from integration of spectral data. The fact that the sum of reflectance and transmittance often exceeds 100% shows that all types of spheres tend to overestimate the transmittance of this highly scattering sample. This error can be attributed to the sphere geometry in combination with the light scattering properties of the sample, and unless proper correction of recorded data is carried out the error may be as large as 5-10%. Some specific errors are presented and an approximate correction procedure is suggested. These results show that there is a need for a transmittance standard which can be used to calibrate integrating spheres. Such a standard with negligible thickness would be especially useful for measurements with large, broadband integrating spheres, but would also be helpful for the correct handling of data from small spectral instruments. © 1998 Elsevier Science B.V. All rights reserved.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
Chevalier, B., Hutchins, M. G., Maccari, A., Olive, F., Oversloot, H., Platzer, W., ... Yoshimura, K. (1998). Solar energy transmittance of translucent samples: A comparison between large and small integrating sphere measurements. Solar Energy Materials and Solar Cells, 54(1-4), 197 - 202. https://doi.org/10.1016/S0927-0248(98)00071-3