Effect of pulsed heat power on the thermal and electrical performances of a thermoelectric generator

This paper presents a transient simulation model based on the coupling of electric conduction and heat transfer in order to (1) quantify the conversion efficiency enhancement of a thermoelectric generator (TEG) under periodic heating and (2) predict the thermal and electrical performances of a TEG. Joule heating, the Peltier effect, and the Thomson effect are included in the transient model, which is experimentally validated using a commercial bismuth-telluride-based thermoelectric device under both steady state and transient conditions. In contrast to an alternate temperature gradient (ATG), which has been adopted in previous studies and is difficult to maintain in a regular square form, pulsed input power is considered herein as an effective parameter for investigating its influence on the thermal and electrical performances of a TEG. In particular, the output power and temperature difference across a TEG under pulsed input power are compared with those under constant input power, where the time average of a pulsed heat source is equivalent to the heat flux under a constant heat source. In the case of periodic heating, a rectangular input heat flux with 10% duty cycle is applied to the TEG system, with average values of 40,000 W/m(2), 30,000 W/m(2), 20,000 W/m(2), and 10,000 W/m(2); its time period ranges from 60 s to 2000 s. It is found that pulsed heat power yields better results than an ATG in terms of improving the conversion efficiency under the same input power condition; specifically, a maximum efficiency enhancement of 8.6x is achieved. In addition, it is found that the ratio of the maximum input heat flux to the minimum input heat flux under periodic heating, a/b, plays an important role in improving the conversion efficiency. For a given time period and average input power, a larger a/b value leads to higher efficiency enhancement. Moreover, it is observed that the efficiency enhancement is independent of the average input power under a given a/b value and fixed time period. Finally, we show that the efficiency under steady state heating is linearly proportional to the input heat flux, and the linear coefficient is 2.05 x 10(-7) [1/(W/m(2))]; this result can facilitate the prediction of TEG performance. (C) 2015 Elsevier Ltd. All rights reserved.