Estimating Solar Irradiance Using Sky Imagers
This work addresses localized solar energy forecasting by providing a more accurate method for estimating solar irradiance using sky imagers, which is incremental as it builds on existing ground-based observation techniques.
The paper tackles the problem of estimating solar irradiance from ground-based sky images, achieving better performance in estimating irradiance and its short-term variations compared to other methods using ground-based observations.
Ground-based whole sky cameras are extensively used for localized monitoring of clouds nowadays. They capture hemispherical images of the sky at regular intervals using a fisheye lens. In this paper, we propose a framework for estimating solar irradiance from pictures taken by those imagers. Unlike pyranometers, such sky images contain information about cloud coverage and can be used to derive cloud movement. An accurate estimation of solar irradiance using solely those images is thus a first step towards short-term forecasting of solar energy generation based on cloud movement. We derive and validate our model using pyranometers co-located with our whole sky imagers. We achieve a better performance in estimating solar irradiance and in particular its short-term variations as compared to other related methods using ground-based observations.