Study on Judging Direct Sunlight in Actual Use of Blind Slat Angle Control Systems

In a system that automatically adjusts the slat angles of horizontal blinds, it is possible to allow skylight in while shielding direct sunlight. This can lead to good energy savings since it can reduce the need for artificial lighting without increasing the air-conditioning load. Our research has previously demonstrated this effect of reducing the amount of energy consumed by artificial lighting by controlling the blind slats according to the amount of skylight in an existing office building. However, it was confirmed that the occupants were dissatisfied with the system since it controlled the blinds to shut even though the occupants observed no direct sunlight and they could not clearly see out the windows. Therefore, this study was conducted with the aim of setting threshold values between the existence and non-existence of direct sunlight based on daylight conditions, so that the automatic controlling of blind slat angles would be ceased to allow slats open when they do not need to block direct sunlight.