Estimating Number and Dwell Time of Visitors from CO2 Concentration using Partial Modeling with Variable Time Window

Abstract

The aim of this paper is to estimate the number and dwell time of visitors in a large room or space with existing sensors such as CO2 sensors included in a building energy management system (BEMS) system. Previous studies tried to estimate the number and dwell time of visitors from CO2 concentration in small rooms without large air-conditioning and ventilation systems. However, in a large room with large air-conditioning and ventilation systems, the number and dwell time of visitors are difficult to estimate for two reasons: 1) CO2 concentration changes much more slowly than the number and dwell time of visitors and with a delay, and 2) the difference in changes is affected by the amount of ventilation. To solve these problems, we propose partial modeling with a variable time window. This method can make a partial estimation model that automatically corresponds to differences in the change speed between two variables: visitors and CO2 concentration. We demonstrate the effectiveness of our proposal using measured sensor data.