A method of predicting dynamic thermal sensation for e-bike riders under fluctuating solar radiation in winter

Abstract

Electric bikes (e-bikes) are essential for urban commuting. However, riders face significant challenges in maintaining thermal comfort due to heightened wind speed and fluctuating solar radiation. Urban shading designed for summer can reduce beneficial winter solar exposure, leading to cold discomfort, particularly for e-bike riders. This study aims to investigate the dynamic physiological and perceptual thermal response characteristics and develop a dynamic thermal sensation model for e-bike riders in winter. An experiment simulating fluctuating solar exposure was conducted with 25 participants along a campus road in Nanjing during early winter. Meteorological data, physiological measurements and thermal perception responses were collected. The results show that high wind speeds frequently cause cold discomfort for e-bike riders during winter. Solar radiation can partially counteract this cooling effect, even under strong wind conditions. A pronounced anticipatory effect was observed, which limits the explanatory power of the rate of change in skin temperature for predicting e-bike riders’ thermal sensation. The Universal Thermal Climate Index (UTCI) provides a reliable estimation of thermal sensation but tends to underestimate the coupled effects of wind speed and solar radiation on e-bike riders. To address this limitation, a new dynamic model was developed, integrating a base component derived from UTCI and an offset component incorporating the rate of change in skin temperature, mean radiant temperature, and wind speed. This study advances the understanding of thermal comfort for e-bike riders and contributes to optimizing a health-oriented low-carbon travel system.