Showing papers by "Zichen Chen published in 2018"

Design and Fabrication of Wearable Thermoelectric Generator Device for Heat Harvesting

Abstract: This letter presents a novel wearable thermoelectric generator (TEG) device for powering electronics by harvesting human body heat. The structural design of the TEG device consists of 12 thermoelectric modules, which are connected by copper strips electrically in series and thermally in parallel. A flexible printed circuit board with special hollows’ design is utilized as the bottom electrodes and substrate to enhance the flexibility of the device. The fabrication procedure to make this TEG device is then described. The hot- and cold-sides of TEG are soldered by a thin layer of Sn96.5Ag3Cu0.5 and Sn42Bi58, respectively. Therefore, the developed TEG device features both high flexibility and excellent performance for heat harvesting. Experimental characterization results demonstrated that the TEG device can achieve 23 μ W power and 4.75 μ W/cm2 power density at a temperature difference of 35 K. After wearing on human wrist, this TEG device can generate an open-circuit voltage of 10.5 mV, and the ability of using this TEG for powering a light emitting diode has been demonstrated. Results indicated that the developed wearable TEG device could be used for powering of wearable electronics and/or sensors.

Wearable Thermoelectric Generator With Copper Foam as the Heat Sink for Body Heat Harvesting

Abstract: Wearable thermoelectric generator (TEG) is an attractive technology to enable self-powered electronics and sensors for healthcare and the Internet of Things through its ability to convert body heat into electricity. However, the actual inner temperature gradient in the thermoelectric legs is relatively small when a TEG is worn on the body, which leads to a low voltage and power generation. To enhance the output performance, the structural design of a wearable TEG with copper foam as the heat sink is proposed. A thermal resistance model was developed to investigate the effects of using copper foam heat sink on the heat transfer and performance of the TEG. In addition, for comparison, the inner temperature gradients and open-circuit voltages of the TEGs with and without plate-fin heat sink were analyzed. Then, these different TEGs were fabricated and tested using an experimental setup. The results showed that TEGs with heat sinks could generate greater open-circuit voltage and output power values, while the TEG with copper-foam heat sink achieved the highest power-to-weight ratio. Finally, a wearable TEG with copper-foam heat sink was connected to a step-up circuit and worn on the wrist to power a miniaturized accelerometer for body motion detection. The results demonstrated that the wearable TEG with the copper-foam heat sink design provided a potential pathway for the realization of electronics powered by harvesting the human body heat.

Numerical modeling of the performance of thermoelectric module with polydimethylsiloxane encapsulation

Abstract: Summary This paper presents a 2-dimensional finite volume model to investigate the performance of thermoelectric module (TEM) with polydimethylsiloxane (PDMS) encapsulation. The voltage and temperature distributions of the TEM under 2 kinds of boundary conditions (constant cold-side temperature and fixed convection heat transfer coefficient) are studied. To validate the developed model, 2 TEMs with or without PDMS encapsulation are fabricated, and the experimental tests are carried out. Both model predicted and experimentally measured results showed that using flexible PDMS as the encapsulation material for the TEM can lead majority heat flowing through thermoelectric legs and is beneficial for heat harvesting. The geometrical parameters' effects of the PDMS encapsulation and thermoelectric legs are analyzed. Results demonstrated that the usage of larger thermoelectric legs and smaller width of the PDMS encapsulation can generate greater temperature difference and hence improve the voltage of the TEM. Thus, the developed model could be applied for optimal structural design of the flexible TEM with highest performance for heat harvesting.