Fengyun-4 Geostationary Satellite-Based Solar Energy Nowcasting System and Its Application in North China

Abstract

Surface solar irradiance (SSI) nowcasting (0–3 h) is an effective way to overcome the intermittency of solar energy and to ensure the safe operation of grid-connected solar power plants. In this study, an SSI estimate and nowcasting system was established using the near-infrared channel of Fengyun-4A (FY-4A) geostationary satellite. The system is composed of two key components: The first is a hybrid SSI estimation method combining a physical clear-sky model and an empirical cloudy-sky model. The second component is the SSI nowcasting model, the core of which is the derivation of the cloud motion vector (CMV) using the block-matching method. The goal of simultaneous estimation and nowcasting of global horizontal irradiance (GHI) and direct normal irradiance (DNI) is fulfilled. The system was evaluated under different sky conditions using SSI measurements at Xianghe, a radiation station in the North China Plain. The results show that the accuracy of GHI estimation is higher than that of DNI estimation, with a normalized root-mean-square error (nRMSE) of 22.4% relative to 45.4%. The nRMSE of forecasting GHI and DNI at 30–180 min ahead varied within 25.1%–30.8% and 48.1%–53.4%, respectively. The discrepancy of SSI estimation depends on cloud occurrence frequency and shows a seasonal pattern, being lower in spring—summer and higher in autumn—winter. The FY-4A has great potential in supporting SSI nowcasting, which promotes the development of photovoltaic energy and the reduction of carbon emissions in China. The system can be improved further if calibration of the empirical method is improved.

摘要

碳中和目标背景下,中国未来将显著增加光伏等新能源在能源结构中的占比。光伏太阳能的间接性和不稳定性是太阳能并网利用中的重大挑战之一。除了发展新能源储能等技术之外,发展太阳能短临预报技术是提高太阳能利用率的经济有效途径。我国新一代静止气象卫星风云四号(FY-4A)的发射给太阳能短临预报(<3小时)提供了新的观测手段。本文利用FY-4A多通道反射率数据建立了地表太阳辐照度估算和短临预报系统。该系统由两个关键部分组成,第一部分为基于物理晴天模型和经验云天模型构建的地表太阳辐照度混合估算方法,第二部分为地表太阳辐照度短临预报模型,其核心是通过块状匹配法推导出云运动矢量,进而预报未来3小时内地表太阳辐照度场。该系统目前能够同时实现水平面总辐射和法向直接辐射的估算和短临预报。验证结果表明:水平面总辐射估算值的准确性高于法向直接辐射,二者归一化均方根误差分别为22.4%和45.4%。30-180分钟预测范围内水平面总辐射和法向直接辐射预测值的归一化均方根误差分别在25.1%-30.8%和48.1%-53.4%之间。地表太阳辐照度估算结果的准确性取决于云的出现频率,即春夏较低,秋冬较高。本研究工作表明新一代静止气象卫星在地表太阳辐射短时临近预报中的广阔应用前景,将显著促进我国光伏太阳能能源发展和利用。该系统在华北地区具备良好的性能,未来进一步改进将侧重于对地表太阳辐照度估算模型的校准并推广其在整个中国地区的适用性。