HVAC System for Maintaining Pleasant Sleep during Warm Nights in Japan

Global warming has deconditioned people to rapid changes in temperature. Further, recently the incidence of warm nights has increased. In Japan, warm nights are often observed in the middle of August in Japan and cause loss of sleep and deconditioning. This problem is being discussed in Japan because such nights make it difficult for people to sleep well and consequently, they fall sick. In particular, people with heart disease fall sick easily and this could lead to serious medical conditions. A heating, ventilation, and air conditioning (HAVC) control system, which enables people to have pleasant sleep during summer nights, effectively addresses this problem. In this paper, a new HVAC control system, which focuses on providing better environmental conditions for ensuring pleasant sleep by the use of air conditioning, is presented. The system collects environmental data and calculates Predicted Mean Vote (PMV), which indicates comfort in a room, and then controls the air to maintain a normal temperature. PMV is a value used for expressing the people's comfort and is calculated using environmental and physical data. To collect the PMV value, at intervals of 1min, the proposed HAVC control system has a data collection function; the system then generates a signal to control the air conditioning. When the PMV value is over or under the comfort region, the air conditioning is turned out and this helps create a better environment for the better sleep. To confirm the effectiveness of the proposed HAVC control system, the system was installed in a bedroom of a house where two people lived and an experiment was conducted for 10-days by using this system. Further, to evaluate the proposed system, sleeping condition data collected by wearable devices were utilized. A comparison of the data of 5 days when the proposed system was not used and those of 5 days when the proposed system was used revealed a 13.6% improvement in the sleeping conditions. Moreover, answers to a web-based questionnaire revealed that the participants' comfort level was higher than usual on nights when the proposed system was used.