Estimation of Solar Radiation: A Case Study of Gansu Province, Northwest China

Since solar radiation observation stations in China are very few, it is necessary to use models to estimate total solar radiation for a small region because solar engineering is established in a specific location. The study selected Gansu province as a case study, in which 6 models were applied to calculate monthly total solar radiation with existing measured data. Through accuracy verification, the Angstrom–Prescot model is proved to be the suitable model for Gansu province. The annual and monthly average total solar radiation for 80 counties in Gansu during 1980–2020 were obtained. The study found that: (1) overall, the annual average total solar radiation showed a fluctuating and slightly downward trend, with a decline rate of 1.87MJ/(m² year) and values between 5102~5640 MJ/m²; (2) spatially, from west to east, the annual average total solar radiation shows a decreasing trend. The solar radiation in the west of Wuwei is the largest, reaching 6394 MJ/m², which is the “richest area” of solar radiation resources. The radiation in Longnan is the smallest with the value of 4259 MJ/m². The monthly average of the multi-year total solar radiation in 80 counties of Gansu province from 1981 to 2020 calculated by the A–P model provides a valuable data basis for solar energy utilization in Gansu province.