Multi-step solar radiation prediction using transformer: A case study from solar radiation data in Tokyo

The widespread advancement of computer technology resulted in the increasing usage of deep learning models for predicting solar radiation. Numerous studies have been conducted to explore their research potential. Nevertheless, the application of deep learning models in optimizing building energy systems, particularly in a multi-step solar radiation prediction model for model predictive control (MPC), remains a challenging task. This is mainly due to the intricacy of the time series and the possibility of accumulating errors in multistep forecasts. In this study, we propose the development of a transformer-based attention model for predicting multi-step solar irradiation at least 24 h in advance. The model is trained and tested using measured solar irradiation data and temperature forecast data obtained from the Tokyo Meteorological Agency. The findings indicate that the transformer model has the capability to effectively mitigate the issue of error accumulation. Additionally, the generative model exhibits a significant improvement in accuracy, with a 62.35% increase when compared to the conventional regression LSTM model. Additionally, the transformer model has been shown to attain superior prediction stability, mitigate the effects of error accumulation in multi-step forecasting, and circumvent training challenges stemming from gradient propagation issues that can occur with recurrent neural networks.