First estimation of high-resolution solar photovoltaic resource maps over China with Fengyun-4A satellite and machine learning

Fengyun-4A (FY-4A), which is the latest-generation Chinese geostationary meteorological satellite, measures solar reflection and thermal emission with high temporal, spatial, and spectral resolutions. It is expected to be highly beneficial for solar resource assessment and forecasting in China. This study is the first to estimate, using FY-4A and a random forest model, the global horizontal irradiance (GHI) at a 4-km-15-min spatio-temporal resolution over China, as a means to arrive at a solar photovoltaic (PV) resource map. In terms of GHI esti-mates, the root mean square error and mean bias error between hourly measured and retrieved values are 147.02 (35.2%),-5.64 W/m2 (-1.4%), respectively, whereas the values of daily estimates are 29.20 (18.0%),-2.97 W/ m2 (-1.3%). The retrieval accuracy is found much better for instances with solar zenith angles smaller than 60 degrees. Relatively larger errors are found at locations in the Sichuan Basin and northeastern China, which can be attributed to bright surfaces and/or strong cloud transients. With the retrieved irradiance, PV resource is derived through a physical model chain. The annual mean PV resource map suggests that, over most of the west areas, the annual mean effective irradiance exceeds 1700 kWh/m2, with the highest value found in Tibet (around 2000 kWh/m2 per annum). Eastern China has an annual effective irradiance of only 1300-1500 kWh/m2. The region with poorest solar resource is the Sichuan Basin (less than 1100 kWh/m2 per annum).

Automated summary

The latest Chinese geostationary meteorological satellite, FY-4A, provides precise measurements of solar reflection and thermal emission. This study utilizes FY-4A and a random forest model to estimate the global horizontal irradiance (GHI) over China, resulting in a solar photovoltaic (PV) resource map with high accuracy. The GHI retrieval shows better accuracy for lower solar zenith angles and larger errors in areas with bright surfaces and/or strong cloud transients. The annual mean PV resource map indicates significant regional variations, with the highest irradiance in Tibet and the poorest resource in the Sichuan Basin.