Model-Based Monitoring of Occupant’s Thermal State for Adaptive HVAC Predictive Controlling

Youssef Youssef,Aerts Aerts,Caballero Caballero

doi:10.3390/pr7100720

Abstract

Conventional indoor climate design and control approaches are based on static thermal comfort/sensation models that view the building occupants as passive recipients of their thermal environment. Recent advances in wearable sensing technologies and their generated streaming data are providing a unique opportunity to understand the user’s behaviour and to predict future needs. Estimation of thermal comfort is a challenging task given the subjectivity of human perception; this subjectivity is reflected in the statistical nature of comfort models, as well as the plethora of comfort models available. Additionally, such models are using not-easily or invasively measured variables (e.g., core temperatures and metabolic rate), which are often not practical and undesirable measurements. The main goal of this paper was to develop dynamic model-based monitoring system of the occupant’s thermal state and their thermoregulation responses under two different activity levels. In total, 25 participants were subjected to three different environmental temperatures at two different activity levels. The results have shown that a reduced-ordered (second-order) multi-inputs-single-output discrete-time transfer function (MISO-DTF), including three input variables (wearables), namely, aural temperature, heart rate, and average skin heat-flux, is best to estimate the individual’s metabolic rate (non-wearable) with a mean absolute percentage error of 8.7%. A general classification model based on a least squares support vector machine (LS-SVM) technique is developed to predict the individual’s thermal sensation. For a seven-class classification problem, the results have shown that the overall model accuracy of the developed classifier is 76% with an F1-score value of 84%. The developed LS-SVM classification model for prediction of occupant’s thermal sensation can be integrated in the heating, ventilation and air conditioning (HVAC) system to provide an occupant thermal state-based climate controller. In this paper, we introduced an adaptive occupant-based HVAC predictive controller using the developed LS-SVM predictive classification model.

Highlights

Thermal comfort (TC) is an ergonomic aspect determining the satisfaction about the surrounding environment and is defined as “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation” [1]
The results have shown that a reduced-ordered multi-inputs-single-output discrete-time transfer function (MISO-DTF), including three input variables, namely, aural temperature, heart rate, and average skin heat-flux, is best to estimate the individual’s metabolic rate with a mean absolute percentage error of 8.7%
25 participants are subjected to three different environmental temperatures, namely 5 ◦ C, 20 ◦ C and 37 ◦ C, at two different activity levels, namely, at low level and high level

Summary

Introduction

Thermal comfort (TC) is an ergonomic aspect determining the satisfaction about the surrounding environment and is defined as “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation” [1]. Thermal sensation mathematical models have been developed in order to overcome the difficulties of direct enquiry of subjects The development of such models is mostly dependent on statistical approaches that correlates experimental conditions (i.e., environmental and person-related variables) data to thermal sensation votes obtained from human subjects [3,5]. Most of these models (e.g., predicted mean vote, PMV) are static in the sense that they predict the average vote of a large group of people based on the seven-point thermal sensation scale. The idea behind adaptive model is that occupants and individuals are no longer regarded as passive recipients of the thermal environment but, rather, play an active role in creating their own thermal preferences [8]

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Conclusion