On the Importance of Blocking Diodes in Thermoelectric Generator Arrays and Their Effect on MPPs Under Temperature Mismatch Conditions

Most of the research studies have reported that series connection of thermoelectric modules (TEMs) performs better under non-uniform temperature distribution (NTD) conditions. However, connecting all the system's modules in series is not a suitable configuration in industrial applications since when one TEM in an array fails, the performance of the entire series string is affected. It is, therefore apparent that industries demand parallel connections that need further research. This study investigates technical issues when connecting TEMs in parallel under NTD. The results show that there are reverse current flows through the thermoelectric generator (TEG) parallel strings when there is slight temperature mismatch between TEMs. This study reveals that blocking diodes are essential in TEG array configurations with parallel strings to protect the modules from reverse currents. Additionally, it has been found that temperature mismatch causes several maximum power points (MPPs) on the power-voltage curve of TEG because of the presence of blocking diodes. Subsequently, the critical value of temperature gradient ratios between mismatched modules is derived, below which multiple MPPs do not exist. This paper introduces a boundary condition which is suitable for real TEG systems with
$n$
number of mismatched modules and is validated by simulation and test results.