Operation of Wearable Thermoelectric Generators Using Dual Sources of Heat and Light

Abstract

A wearable thermoelectric generator (WTEG) that utilizes human body heat can be a promising candidate for the wearable power generators. The temperature difference (Δ T ) between the body and the environment is a stable source driving the WTEG, but this driving force is limited by the ambient temperature itself at the same time. Here, a novel WTEG that can be operated using the dual source of body heat and light with exceptionally high driving force is fabricated. The printable solar absorbing layer attached to the bottom of the WTEG absorbs ≈95% of the light from ultraviolet to far infrared and converts it into heat. To optimize the power density of WTEGs, the fill factor of the thermoelectric (TE) leg/electrode is considered through finite‐difference time‐domain (FDTD) simulation. When operated by the dual sources, the WTEG exhibits a power density of 15.33 µW cm −2 , which is the highest under “actual operating conditions” among all kinds of WTEGs. In addition, unlike conventional WTEGs, the WTEG retains 83.1% of its output power at an ambient temperature of 35 °C compared to its output power at room temperature. This study will accelerate the commercialization of WTEGs by introducing a novel method to overcome their limitations.

An Emerging Energy Technology: Self‐Uninterrupted Electricity Power Harvesting from the Sun and Cold Space

“…Jeong developed an optimized millimeter-scale vertical TEG to harvest the dual-source of body heat and sunlight to achieve enhanced temperature difference and power density of TEG (Figure 5d). [45] Another strategy is to use human body as the hot end of the TEG and the radiative cooler as the cold end. Chen developed a wearable TEG with wavy film structure to improve the directional matching of heat flow from human body and thermal resistance of TEG and to minimize the parasitic heat loss of substrate (Figure 5e).…”

“…Reproduced with permission. [45] Copyright 2022, Wiley-VCH. e) Wavy structured, Reproduced with permission.…”

“…d) Wearable TEG using dual source of solar and body heat of the wrist. Reproduced with permission [45]. Copyright 2022, Wiley-VCH.…”

Photolithographic p–n patterning of single-walled carbon nanotube sheets using photobase generators

“…Typical TEG devices adopt a “π-type” structure with alternating p- and n-type semiconductor regions in a zigzag arrangement, connected using metal or conductive paste. 11–16 This series structure produces an open-circuit voltage ( V OC ): V OC = n ( S p − S n )Δ T where n is the number of p–n units, S p and S n are the p- and n-type Seebeck coefficients, respectively, and Δ T is the temperature gradient across the material. Therefore, employing materials with high Seebeck coefficients and increasing the number of p–n units is advantageous for achieving high open-circuit voltages as well as a high power factor (PF):PF = S 2 σ where σ is the electrical conductivity.…”

Optimization of the Thermoelectric Properties of 2D-PEDOT Derivative Chains Using Electrochemical Control

“…Therefore, an urgent need exists for alternative technologies that can increase the conversion efficiency of fossil fuels used for generating electricity or, alternatively, to produce electricity without them. Among the alternatives, thermoelectric generation (TEG) is an attractive technology due to its ability to generate power using industrial waste heat via the Seebeck effect. − The Seebeck effect can convert temperature differences directly into electrical voltages and is an important element of thermoelectric (TE) materials. − The efficiency of TE materials is expressed as the figure of merit ZT = S 2 σ T /κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. − From this definition, TE materials have to show large values for S and σ, with low κ, at low temperatures. − However, there are insufficient thermoelectric materials composed of high natural abundance elements that can work in the low-temperature region (<250 °C). − This limitation has triggered studies on conducting polymers as TE materials. These conducting polymers are relatively less expensive than inorganic materials because of the natural abundance of their component atoms and low toxicities. , Furthermore, these conducting polymers are easy to use in TEG devices as they utilize a solution process and a low-temperature annealing step. − …”