Structural design of water-air hybrid cooling for enhancing the net output power of thermoelectric generators

Thermoelectric generators (TEGs) can directly convert low grade waste heat into electrical energy. However, conventional water-cooling methods often lead to non-uniform temperature distributions inside thermoelectric modules (TEMs), which limits heat transfer performance and reduces actual power generation capability. In addition, the parasitic power consumption introduced by hybrid cooling systems has not been sufficiently considered in previous studies. To address these issues, this study proposes a water-air hybrid cooling thermoelectric generator (WAHCTEG) with air inlets integrated into the cooling plate and TEMs to enhance internal convective heat transfer and improve temperature uniformity. Three cooling configurations, including a conventional TEG without air inlets, a WAHCTEG with continuous air inlets, and a WAHCTEG with spaced air inlets, were investigated. The effects of TEM air inlet diameter, water velocity, and air velocity on the flow field, thermal field, output power, and net output power were analyzed. The results show that introducing air inlets significantly enhances internal airflow and local heat transfer inside the TEMs. The spaced air inlet arrangement exhibited superior performance due to lower airflow resistance and more effective airflow distribution. At a TEM air inlet diameter of 5 mm, the total output power of the WAHCTEG with spaced air inlets reached 15.58 W, over 12% higher than the conventional TEG. In addition, the net output power increased by more than 16% due to lower parasitic power consumption. The results demonstrate that the proposed hybrid cooling strategy can effectively improve heat transfer, temperature uniformity, and net power generation capability.