Forecasting Solar Energy Using a Single Image

TL;DR

This paper introduces a novel method that uses a single urban image to forecast solar panel irradiance, improving accuracy over traditional models and enabling better assessment of solar energy potential.

Contribution

The authors develop a single-image based approach to predict solar irradiance and panel orientation, capturing effects of nearby structures and reflections more accurately than existing methods.

Findings

Single-image approach often outperforms conventional irradiance-based methods.

The method accurately forecasts temporal variations in irradiance due to reflections.

A device called Solaris captures images for practical urban solar assessment.

Abstract

Solar panels are increasingly deployed in cities on rooftops, walls, and urban infrastructure. Although the panel costs have fallen in recent years, the soft costs of installing them have not. These soft costs include assessing the illumination (irradiance) of a panel, which is typically performed using a 3D model that fails to capture small nearby structures that impact the irradiance. Our approach uses a single image taken at the panel's location to forecast its irradiance at any time in the future. We use visual cues in the image to find the camera's orientation and the portion of the sky visible to the panel in order to forecast the irradiance due to the sun and the sky. In addition, we show that the irradiance due to reflections from nearby buildings varies smoothly over time and can be forecasted from the image. This approach enables assessing the solar energy potential of any surface and forecasting the temporal variation of a panel's irradiance. We validate our approach using real irradiance measurements in urban canyons. We show that our approach often yields more accurate irradiance forecasts compared to conventional irradiance-based transposition methods and 3D model-based simulations. We also show that a single spherical image can be used to find the best fixed orientation of a panel. Finally, we present Solaris, a device to capture the image seen by a panel in a variety of urban settings.