Search

The concern with renewable energy has been growing. Large-scale installation of photovoltaic (PV) generation and electricity storage is expected to be installed into the power system in Japan. In this situation, we need to keep supply-demand balance by systematically using not only traditional power generation systems but also the PV generation and storage equipment. Towards this balancing, a number of prediction methods for PV generation and demand have been developed in literature. However, prediction-based balancing is not necessarily easy. This is because the prediction of PV generation and the demand forecasting inevitably includes some uncertainty. Against this background, we formulate a problem to plan battery charge pattern while minimizing the fuel cost of generators with explicit consideration of prediction uncertainty. In this problem, given as interval quadratic programming, the prediction uncertainty is described as a parameter in constraint condition. Furthermore, we propose a method to find a solution to this problem from the viewpoint of monotonicity analysis. Finally, by numerical analysis based on this problem and its solution method, we discuss the relation between the minimal regulating capacity and the required battery charge/discharge pattern to tolerate a given amount of prediction uncertainty.

Recently, building-integrated photovoltaic (BIPV) systems have become increasingly popular because they provide increased available space and have great environmental appeal. However, these systems may be adversely affected by shadows of surrounding buildings. In order to reduce the effect of shadows on solar panels, we propose the concept of a PV system with reconnection (smart PV), where PV arrays can be reconnected to minimize the mismatch loss depending on the output of each module measured at regular time intervals. In this study, the effects of minimizing the mismatch loss of a BIPV system by reconnection are evaluated by studying shadow patterns. The PV system with reconnection showed good performance for typical shadow patterns. In the evaluation, the optimized connection is determined by calculating the outputs of several array connection patterns. To analyze the daily impact of the PV system with reconnection, the daily output energy by the BIPV system that is partially shaded by a neighboring building is considered as a case study. The maximum improvement in the daily mismatch loss with the reconnection was 8.1 kWh per day compared with that of conventional array connections. In conclusion, it is shown that the PV system with reconnection shows better performance compared with conventional fixed array connections.