Developing a Novel Approach for Estimating Daily Global Solar Radiation in China: Reference Station and Empirical Models

Abstract

Solar radiation is an indispensable variable in developing building thermal and solar energy applications. Under the trend of carbon peak and neutral, it is extremely urgent to provide wide spatial coverage and high accuracy of global solar radiation data. Zone model is a commonly used method to obtain solar radiation data in regions with only meteorological measurements. However, the method including dividing zones and empirical models is rough and cannot reflect local climate differences. The approach which solar climate characteristics are similar and the models are consistent is proposed in present study. Finding the most similarity solar radiation stations and developing models fitting climates are two key issues. Latitude, altitude, H and S measurements obtained from 1042 (112 with H measurements) stations across China are collected and analyzed to recognize similarity stations through Euclidean distance. The minimum Euclidean distance of latitude, altitude and monthly average S/S0 and the consistent change trend of monthly average S/S0 is proposed as selection criterion of reference station. The reference station of 832 meteorological stations has been identified. Three H models are established and evaluated by using statistical error indicators (MABE and RMSE%). In regions with annual average S/S0 higher than 0.55, the linear model based on S/S0 is best optimal. The model cubic polynomial of S/S0 and combing with S/S0 and T are more suitable to regions with annual average S/S0 varying from 0.48 to 0.55 and lower than 0.48. The reference station models obtain good accuracy with RMSE% reduced by 4% compared to zone models. The selection criterion of reference station and H model can be reliable and generalized to other regions with available meteorological measurements.

Keywords: Clearness index, Daily global solar radiation, Euclidean distance, Sunshine duration