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A case study of rapid variation (ramp event) of photovoltaic (PV) power generation on 18 April 2016 for the Tokyo Electric Power Company (called “TEPCO”) power area is considered in this study. PV system installation in the TEPCO area has been increasing (approximately 10 GW PV system capacity). Quasi real-time monitoring of PV power generation by using satellite-estimated solar radiation is performed. Under assumptions of future PV system installation scenarios (from 21.78 GW to 85.76 GW in the TEPCO area), temporal and spatial variations of PV power generation are estimated.

The impact of aerosols on the forecast accuracy of solar irradiance calculated by a fine-scale, one day-ahead, and operational numerical weather prediction model (NWP) is investigated in this study. In order to investigate the impact of aerosols only, the clear sky period is chosen, which is defined as when there are no clouds in the observation data and in the forecast data at the same time. The evaluation of the forecast accuracy of the solar irradiance is done at a single observation point that is sometimes affected by aerosol events. The analysis period is one year from April 2010 to March 2011. During the clear sky period, the root mean square errors (RMSE) of the global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI) are 40.0 W m−2, 84.0 Wm−2, and 47.9 W m−2, respectively. During one extreme event, the RMSEs of the GHI, DNI, and DHI are 70.1 W m−2, 211.6 W m−2, and 141.7 W m−2, respectively. It is revealed that the extreme events were caused by aerosols such as dust or haze. In order to investigate the impact of the aerosols, the sensitivity experiments of the aerosol optical depth (AOD) for the extreme events are executed. The best result is obtained by changing the AOD to 2.5 times the original AOD. This changed AOD is consistent with the satellite observation. Thus, it is our conclusion that an accurate aerosol forecast is important for the forecast accuracy of the solar irradiance.

The impact of aerosols on the forecast accuracy of solar irradiance calculated by a fine-scale, one day-ahead, and operational numerical weather prediction model (NWP) is investigated in this study. In order to investigate the impact of aerosols only, the clear sky period is chosen, which is defined as when there are no clouds in the observation data and in the forecast data at the same time. The evaluation of the forecast accuracy of the solar irradiance is done at a single observation point that is sometimes affected by aerosol events. The analysis period is one year from April 2010 to March 2011. During the clear sky period, the root mean square errors (RMSE) of the global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI) are 40.0 W m−2, 84.0 Wm−2, and 47.9 W m−2, respectively. During one extreme event, the RMSEs of the GHI, DNI, and DHI are 70.1 W m−2, 211.6 W m−2, and 141.7 W m−2, respectively. It is revealed that the extreme events were caused by aerosols such as dust or haze. In order to investigate the impact of the aerosols, the sensitivity experiments of the aerosol optical depth (AOD) for the extreme events are executed. The best result is obtained by changing the AOD to 2.5 times the original AOD. This changed AOD is consistent with the satellite observation. Thus, it is our conclusion that an accurate aerosol forecast is important for the forecast accuracy of the solar irradiance.