Improving solar energy estimates for tilted planes in the Arctic using a multi-pyranometer array

Solar energy use in the Arctic requires exploiting the optimal low sun elevation and utilizing snow reflection. For this, a reliable assessment of solar irradiance on inclined planes is crucial. However, traditional transposition models often fail to accurately estimate tilted irradiance from global horizontal irradiance at high latitudes, and methods to improve such estimations have received little attention. This study proposes using a 25-pyranometer array to estimate global tilted irradiance on any plane by estimating the beam and diffuse components first, using a least-squares approach, and then recombining them. Combinations with different number of pyranometers revealed that the more pyranometers the lower the estimations errors for tilted irradiance. However, a 5-pyranometer array achieved errors that were relatively close to the best configuration. The greatest errors occurred for ground-facing orientations due to albedo measurement uncertainties. Excluding the albedo input improved results and reduced the required pyranometers by one. An error-minimization method described the set of three pyranometers that could best estimate the beam, diffuse, and tilted irradiance components. The tilted irradiance potential for Longyearbyen is depicted at a 5° tilt angle resolution. While the optimal three-pyranometer setup introduced more uncertainty than using five or more, it still outperformed traditional decomposition and transposition models. As the first Arctic-focused study on tilted irradiance estimation, this work lays a foundation for the assessment of solar energy on tilted collectors, enabling better planning.