System efficiency and power: the bridge between the device and system of a thermoelectric power generator

Zhu, Kang; Deng, Biao; Zhang, Pengxiang; Kim, Hee Seok; Jiang, Peng; Liu, Weishu

doi:10.1039/d0ee01640c

Cited by 33 publications

(18 citation statements)

References 40 publications

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“…This 1D model fits well with Zhu's general design strategy for matching the external thermal resistance, output power and voltage of TEGs on system level. [ 31 ] As shown in Figure S9 (Supporting Information), the TE‐leaf absorbs heat from the substrate and continuously releases heat at its lateral surface, resulting in a descending temperature profile. By solving the steady‐state governing equation and boundary conditions (Note S3 in the Supporting Information), the temperature distribution along the length of the TE‐leaf was obtained

T = \frac{h_{b}}{h_{normalb} + κ_{normaleff} β \tanh (β L)} \frac{\cosh (β y - β L)}{\cosh (β L)} Δ T + T_{air}

…”

Section: Resultsmentioning

confidence: 99%

Leaf‐Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

Qing

Zhu

et al. 2021

Advanced Science

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The inherently small temperature difference in air environment restricts the applications of thermoelectric generation in the field of Internet of Things and wearable electronics. Here, a leaf‐inspired flexible thermoelectric generator (leaf‐TEG) that makes maximum use of temperature difference by vertically aligning poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate and constantan thin films is demonstrated. Analytical formulae of the performance scales, i.e., temperature difference utilization ratio (φth) and maximum output power (Pmax), are derived to optimize the leaf‐TEG dimensions. In an air duct (substrate: 36 °C, air: 6 °C, air flowing: 1 m s−1), the 10‐leaf‐TEG shows a φth of 73% and Pmax of 0.38 µW per leaf. A proof‐of‐concept wearable 100‐leaf‐TEG (60 cm2) generates 11 µW on an arm at room temperature. Furthermore, the leaf‐TEG is flexible and durable that is confirmed by bending and brushing over 1000 times. The proposed leaf‐TEG is very appropriate for air convection scenarios with limited temperature differences.

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T = \frac{h_{b}}{h_{normalb} + κ_{normaleff} β \tanh (β L)} \frac{\cosh (β y - β L)}{\cosh (β L)} Δ T + T_{air}

…”

Section: Resultsmentioning

confidence: 99%

Leaf‐Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

Qing

Zhu

et al. 2021

Advanced Science

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“…To enable compliance for wearable requirements, rigid TE legs are encapsulated in elastomers such as Polydimethylsiloxane (PDMS), which has low thermal conductivity thus results in high thermal resistance between human skin and TEGs, severely reduces the thermal utilization efficiency. [21][22][23] To address these issues arising with the employing rigid commercial bulk TE legs to build stretchable TEGs, some strategies have recently been adopted. For examples, Lee et al [24] proposed a soft heat conductor where metal particles magnetically self-assembled in elastomeric substrate to significantly enhance the heat transfer to TEGs.…”

Section: Introductionmentioning

confidence: 99%

High‐performance Stretchable Organic Thermoelectric Generator via Rational Thermal Interface Design for Wearable Electronics

Wang

Zhou

et al. 2021

Advanced Energy Materials

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Compliant thermoelectric generators (TEGs) hold great promise in the field of self‐powered wearable electronics. Yet, the low heat transfer efficiency arising from large thermal resistance between elastic encapsulating materials and the contacted objects severely lowers the thermopower. This issue is much more challenging for organic TEG (oTEG) due to the high parasitic heat loss in the whole polymer system. Herein, guided by finite element analyses, a polydimethylsiloxane based composite coated with Cu is developed as a thermal interface without compromising the compliance of the oTEG, which possesses the merits of high thermal conductivity and significantly reduced thermal resistance, thus maximizing the temperature difference utilization ratio to 86%, which is 75.5% higher than for a routine oTEG. As a proof‐of‐concept, 50 pairs of p/n porous polyurethane/single‐wall carbon nanotube TE legs are integrated onto the designed substrate without further encapsulation. Both simulations and experiments on output performance under various thermal conditions are carried out, and show excellent agreement. The in situ output performance tests under various deformation conditions reveal the mechanical robustness of the oTEG. Finally, an oTEG functioning as a body heat harvester and an environment temperature sensor are demonstrated. The outstanding performances unambiguously demonstrate the success of the thermal interface design strategy for promoting oTEGs applied as wearable electronics.

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“…To maximize the output power, ideal external loads are expected to exhibit comparable electrical and thermal resistances to the internal resistances of WTEGs. Recently, Liu et al [196] developed an analytical model for the system level analysis of a TEG, and proposed a set of explicit formulae for quickly evaluating the optimal operating conditions as well as the corresponding system efficiency and power output. More importantly, the dimensionless cold-side thermal resistance had a larger inhibiting effect on system performance than its hot-side counterpart, suggesting that better thermal management is needed on the cold side.…”

Section: Figure 14cmentioning

confidence: 99%

Wearable Thermoelectric Materials and Devices for Self‐Powered Electronic Systems

et al. 2021

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Because of their readiness and high power bandwidth, batteries are the preeminent source of power supply for portable electronics, but are subject to periodic recharging and replacement. Hence, a key challenge is to design suitable and sustainable power sources for portable electronic devices. Harvesting energy from the human body is suitable for providing consistent and uninterrupted energy for wearable electronic devices. The daily activities of a 68-kg adult can generate over 100 W of power, through breathing, heating, blood transport, and walking. [3] Thus, converting 1% of the power generated by the human body may be enough to support the work of most portable electronics. Various energy-harvesting technologies, such as, triboelectric nanogenerators (TENGs), [4][5][6] piezoelectric nanogenerators, [7] and thermoelectric generators (TEGs), [8] have been developed to convert human energy (from human motion and body heat) into electricity. In line with recent developments in wearable electronics and e-skins, the use of a self-powered direct-current (DC) electric power supplier is inevitable for activating human body-adjustable electronic systems. [9] Among the various energy-autonomous devices, [10] only TEGs can permanently produce DC electric power without complex power managing components, and they are maintenance free. Moreover, solar energy and vibration-based energy harvesters areThe emergence of artificial intelligence and the Internet of Things has led to a growing demand for wearable and maintenance-free power sources. The continual push toward lower operating voltages and power consumption in modern integrated circuits has made the development of devices powered by body heat finally feasible. In this context, thermoelectric (TE) materials have emerged as promising candidates for the effective conversion of body heat into electricity to power wearable devices without being limited by environmental conditions. Driven by rapid advances in processing technology and the performance of TE materials over the past two decades, wearable thermoelectric generators (WTEGs) have gradually become more flexible and stretchable so that they can be used on complex and dynamic surfaces. In this review, the functional materials, processing techniques, and strategies for the device design of different types of WTEGs are comprehensively covered. Wearable self-powered systems based on WTEGs are summarized, including multi-function TE modules, hybrid energy harvesting, and all-in-one energy devices. Challenges in organic TE materials, interfacial engineering, and assessments of device performance are discussed, and suggestions for future developments in the area are provided. This review will promote the rapid implementation of wearable TE materials and devices in self-powered electronic systems.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202102990.

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System efficiency and power: the bridge between the device and system of a thermoelectric power generator

Abstract: The thermoelectric efficiency formula (η_max), derived by Ioffe, provides a direct connection between the material dimensionless figure of merit ZT and the maximum efficiency from heat into electricity in an...

Cited by 33 publications

References 40 publications

Leaf‐Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

Leaf‐Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

High‐performance Stretchable Organic Thermoelectric Generator via Rational Thermal Interface Design for Wearable Electronics

Wearable Thermoelectric Materials and Devices for Self‐Powered Electronic Systems

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