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All-sky imager-based solar power forecasting system for smart-grid operation














Solar Platform








The main objective of this project consists of an improvement in PV power forecasts quality, on the road to a smart-grid management. This is planned to be achieved by developing an innovative forecasting instrument ASIFOR based on tracking the state-of-the-sky using all-sky imager data.


ASIFOR includes three interconnected components:

(1) Radiometric station (RS). RS consists of minimum two pyranometers one for measuring global solar irradiance (GHI) and the other for measuring diffuse solar irradiance (DHI). GHI is straightforwardly exploited for estimating the solar resource, while post-processed data series of GHI and DHI are used for inferring various parameters, the topmost being sunshine number (SSN), a binary indicator stating whether the Sun is shining or not.

(2) Sky monitoring system (SMS). SMS includes an all-sky imager which will provide a streaming of sky images. Essentially, all-sky imager defines a device equipped with 180-degree wide angle lens or mirror optical system able to acquire time series of hemispherical images of the sky vault. Post-processing of the sky images streaming is expected to contribute at increasing the accuracy in forecasting the relative position of the Sun and clouds.

(3) Computational system (CS). CS plays multiple roles: real-time control of the forecasting process, database management, post-processing data, communication with RS and SMS, providing forecasts to the grid operator via internet. The forecasting applications developed within this project will be implemented and run by CS. Sky image processing will be performed also by CS.


The main objective will be reached through the following actions:


(1) Development of new procedures for image processing aiming to accurate forecasting of the relative position of the Sun and clouds. The outcome of this specific objective is the operational SMS module of the forecasting instrument.

(2) Development of new procedures or enhancement of existing procedures for accurate solar PV power forecasts. The outcome of this specific objective is the operational RS module of the forecasting instrument.

(3) Establishing a forecasting mechanism for solar electricity production by joining the SMS and RS information. The outcome of this specific objective is the operational CS module of the forecasting instrument.


ASIFOR itself is the main outcome of the project. It hve to fulfill three essential characteristics:

(1) The forecasts of PV power are generated at different horizons of time within one hour;

(2) The forecasts are of high-quality (the mean absolut percentage error MAPE is less than 20% for all the forecasts generated in a month);

(3) the forecasting instrument is effectively structured in order to address the needs of grid operators.