Experimental assessment of thermoelectric generator package properties: Simulated results validation and real gradient capabilities

• Optimized design of a flexible thermoelectric generator (μTEG) for self-powered wearable devices.
• Finite element analysis on a 3D generator on wavy-shaped PDMS/Kapton assembly.
• Experimentally measured thermal gradient ranges between 0.20 K and 0.64 K higher than the simulated value.
• The warm-up time of 500 s for 4 mm thick package to completely thermalize the generator.
• Good matching of stabilization times between the experimental and simulated results, error <4.2% for 4 mm package.

The optimized design of a flexible micro thermoelectric generator (TEG) suitable for self-powered wearable devices and its real temperature gradient performance is proposed and discussed in this paper. Finite element analysis was performed on a three-dimensional p-n thermocouple on wavy-shaped poly-dimethylsiloxane (PDMS)/Kapton assembly using COMSOL Multiphysics software. Electrical and thermal simulations were carried out to determine the geometric effects of the single thermocouple (length and width of the thermoelements, deposition procedure of junction between p- and n-type legs) on output power and efficiency performance of the TEG. The experimental results confirmed that the experimentally measured thermal gradient ranges between 0.20 and 0.64 K higher than the simulated value and such a result has great importance for correct generator design and determination of effective thermal gradient which can be recovered using the proposed package solution. Heat transfer analysis was performed to optimize the proposed package solution and maximize the thermal gradient that can be recovered between the thermocouples junctions. Experimental results confirmed that the thicker package ensures better insulation, with a real gradient about 0.11 K lower that the simulated one. The warm-up time for 4 mm package to completely thermalize the Kapton upper surface is about 500 s; good matching on thermal response times has been found between the experimental and simulated results for all investigated package thicknesses.