Does back cooling improve human thermal comfort in warm environments? A device for heat conduction by the semiconductor Peltier effect

The hot environment and the metabolic heat of commuting in summer caused individual overheating and intense thermal discomfort. Local cooling presents huge potential for optimizing thermal comfort. This study investigates the performance of a back cooling device, based on the semiconductor Peltier effect, in improving thermal comfort after summer commuting. We studied one case without cooling, and three cases with surface temperatures of the cooling device of 29, 27, and 25 degrees C using a simulated summer commute at a moderate activity level. The results showed that thermal sensation, perceived sweating rate, and skin temperature decreased markedly in the cooling cases compared to the non-cooling case, with the changes being most notable in the lower back, in contact with the cooling device. The decrease in overall thermal sensation and mean skin temperature was approximately 0.52 score and 0.31 degrees C on average, respectively, with a 1.71 score increase in overall thermal comfort. We contend that the surface temperature of local contact cooling devices should not be lower than 22 degrees C to minimize local overcooling. Back cooling devices present a huge potential for building energy-savings at ambient air temperature exceeding 30 degrees C. Moreover, the functional paradigms for individual comfort predict improved comfort performance in future applications. This study contributes to the understanding on the well-being and physiological recovery of individuals after a summer commuting.