Thermoelectric generators (TEG) is the device that can directly convert heat into electricity by the Seebeck effect, which is fascinated for waste heat recovery. An experiment was setup to study the influence of heat flux through the thermoelectric module on the power output and efficiency of a commercial Bi2Te3-based thermoelectric modules. The experimental result indicated that the power output evidently increased with the increasing heat flux through the thermoelectric module (TEM), while the conversion efficiency increased significantly at first then the tendency became mild with the increasing heat flux for a given air flow velocity and flow temperature. The temperature differences across the thermoelectric module are almost identical with various air velocity, while the power output and efficiency increased with the increase of cooling flow velocity with a fixed heat flux through the TEM. The power output and efficiency almost linearly decreased with the increase of cooling flow temperature with a fixed heat flux through the TEM and a fixed cooling flow velocity. The maximum output power can be obtained by maximization heat flux without exceeding the upper temperature limit of thermoelectric module.
Providing electricity for isolated areas or emergencies (snowstorms, earthquakes, hurricanes, etc.) is an important challenge. In this study, a prototype of a self-powered fan based on a thermoelectric system was built to enhance the heat dissipation of the thermoelectric generator (TEG) systems using household stoves as heat sources. To improve output performance of the system, a heat collector consisting of a heat-conducting flat plate and a heat sink with fan cooling was designed to integrate several thermoelectric modules (TEM). The effects of the fan operating conditions (airflow velocity), number of thermoelectric modules, electrical connection mode under different heat flux among the performance of the TEG system are studied. The data obtained showed a higher heat flux and lower flow velocity are required to realize self-sustained cooling of the system. The maximum electric power is more sensitive to the heat flux than the fan operation conditions. It is also observed that more modules provide a higher power output but lower efficiency. The maximum power of four modules in series is larger than that in parallel, and the difference between them increases with increasing heat flux of the heat collector. In the case of self-sufficiency: the maximum output power and maximum net power with four thermoelectric modules are 10.92 W and 5.26 W, respectively, at a heat flux of 30,000 W/m2. Additionally, the maximum conversion efficiency of 1.8% is achieved for two modules at a heat flux of 14,000 W/m2, providing an effective strategy for the installation of TEMs and cooling fans in TEG.
Although the Chinese government encourages using clean fuels for heating, many households in remote areas still rely on coal as their energy, especially in the Qinghai Tibet Plateau. An updraft coal heating stove was modified to preheat secondary air. The performance of the modified stove was studied compared with a baseline stove. The temperatures in the combustion chamber and near the chimney exit are measured, and the undiluted exhaust concentrations of CO, NO x , and SO2 are obtained. The results indicated that the temperatures and exhaust gas concentrations varied periodically with the coal addition. The oxygen concentration in the flue gas for the modified stove is higher than that for the baseline stove, and the O2 concentration was decreased with the increase in fuel feed rate. The CO concentration peaked 5–15 min after fuel addition and descended quickly toward a baseline with the higher fuel feed rates. It remained almost unchanged at the beginning and then slightly increased when the combustion began to fade with a lower fuel feed rate for the modified stove. The NO x emission for the modified stove is generally lower than that for the baseline stove. The NO x formation during coal combustion mainly comes from prompt NO and fuel NO, while the SO2 emission is mainly related to the sulfur element in the raw coal in the present work. The modified stove is effective in reducing NO x and SO2 emissions. However, the CO emission of the modified stove is higher than that of the baseline stove, especially at the end of the batch.
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