A new technique of estimating global solar radiation¹

Uma nova técnica para estimativa da radiação solar global

ABSTRACT

Global solar radiation (Qg) is of paramount importance for several functions, such as photosynthesis and other biological processes, technologies based on solar energy (production of electricity and hot water), estimation of evapotranspiration (irrigation management), and forecast of crops, among other activities, at zero cost. This study aimed to develop a new methodology to estimate the daily and monthly value of global solar radiation based on the power generated by a 10 W photovoltaic solar panel. The methodology performance was assessed by comparing the Qg values estimated by the new method and the Qg values observed in a weather station, and also calculated by the SunDATA software and observed in the NASA POWER system. High r, R², and Willmott coefficient values (close to 1), a low mean absolute error (MAE) of 0.202 kWh m⁻² per day, a low mean bias error (MBE) of −0.146 kWh m⁻² per day, a low mean percentage error (MPE) of 3.25%, and a low root mean square error (RMSE) of 0.292 kWh m⁻² per day were obtained, confirming the excellent accuracy and reliability of the proposed methodology to estimate Qg. The NASA POWER system and SunDATA software presented similar values for the entire study period compared to the observed data, but not as good as the proposed technique. Thus, the proposed methodology had high performance in estimating Qg.

Key words:
solar energy; IoT; photovoltaic solar panel

HIGHLIGHTS:

The data acquisition system monitors the daily variations of solar irradiance and, in real-time, integrated global solar radiation.

Estimated data for global solar radiation is similar to the obtained data.

The methodology can be reproduced worldwide.