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Table of Contents
Introduction
Introduction
Thermoelectric generators or TEG) work in a similar way to high efficiency heat pumps, but they are less efficient and more expensive.
Potential Benefits of TEG
Potential Benefits of TEG
Independent Energy Generation for Personal Use
Independent Energy Generation for Personal Use
Scientists don't expect this technology to save us from an energy crisis, but they do expect that this technology could help to power small and wearable technology, such as heart monitors and other health-related equipment.
One major benefit of improving and helping to scale up this technology would be the potential freedom and independence for those with medical conditions. People may be able to power important monitors or other devices even in the face of power grid failure, or while traveling into nature.
Simple Technology for Students & Home Labs
Simple Technology for Students & Home Labs
10:56 minute video "Showing how with "off the shelf" TEG/peltier modules (only 5% harvest efficiency) it is possible to generate enough energy to power small devices using ONLY the body heat.
Although, generating 5V requires additional modules or cooling with ice, it is possible to generate it without them. However it requires more complicated circuitry and it would generate much less current (5mA) and even shorter charging spikes when connected to a phone. Therefore, I am using more simpler setup."
Problems with TEG
Problems with TEG
Current Level of Practicality & Efficiency
Current Level of Practicality & Efficiency
Comfort and Output
Comfort and Output
"Optimizing both wearability and device output presents a significant challenge. Wearability (the device’s bending stiffness and bending radius, the body’s perceived temperature, etc.) and output performance (power density:\({P}_{d}\), load resistance:\({R}_{l}\), voltage density:\({V}_{d}\), etc.) are intricately coupled through the device structure, the properties of the thermoelectric (TE) material, and the environment21,22,23. Hence, achieving comfort and high output simultaneously is not straightforward. In essence, maximizing output does not rely only on optimizing TE material performance, but also requires meticulous design of the w-TEG’s structure and thermal management at the system level. However, no general analytical formula for system efficiency and wearability of w-TEGs has been reported to date." - Nature: Comfortable Wearable Thermoelectric Generator with High Output Power
Material Problems
Material Problems
According to this paper, "previous results showed unexpectedly poor TE performances due to the parasitic heat loss in high-thermal-impedance polymer substrates, undesirable air gaps arising from limited mechanical conformability, and low device yield of manual manufacturing. Therefore, implementation of high-performance TEGs that can conform perfectly to arbitrary-shaped heat sources with enhanced heat transfer ability via straightforward manufacturing is highly desirable."
Scalability & Labor Requirements
Scalability & Labor Requirements
"Currently, the thermoelectric fabric and button cannot be mass-produced outside the lab. The material must be made and sewn by hand, which is laborious." - Earth: Silk Thread can Turn Clothes into Electricity Generators
People making clothing or devices with this technology need to have a certain amount of experience and knowledge in order to produce functional devices, without damaging the technology during the manufacturing stage.
Additional Considerations for Wearable TEG
Additional Considerations for Wearable TEG
Variability of Energy Generation from Certain Body Parts
Variability of Energy Generation from Certain Body Parts
Though the following was written in the context of comfort for the wearer and maximizing efficiency:
"Compared to the wrist, the open circuit voltage of the thigh is lower, and the voltage of the device reaches thermal equilibrium and becomes stable after 5 mins, at which time the output power of the device worn on the arm was obtained." - Nature: Comfortable Wearable Thermoelectric Generator with High Output Power
There is another issue to consider. That of patients with various disabilities and medical conditions. For an ambulatory patient, TEG worn on the thigh may make perfect sense for charging their medical devices. However, patients with blood circulation issues, paralysis, or otherwise limited mobility may have to rely on other muscles for daily tasks, or have higher body temperature in areas where blood flow is more consistent. In these cases, alternative wearable designs or even custom designs may be necessary.
Types of Wearable TEG
Types of Wearable TEG
Inorganic TEGs
Inorganic TEGs
Bismuth telluride (Bi2Te3) alloys have been the most favored candidates for TEG for performance reasons. - High-Performance Compliant Thermoelectric Generators with Magnetically Self-Assembled Soft Heat Conductors for Self-Powered Wearable Electronics
"Liquid Wires"
"Liquid Wires"
Gallium is a metal that is liquid at comfortable body temperatures, but when mixed with indium, the two create a eutectic alloy with an even lower melting point. Liquid wires allow wearable technology it be both flexible and
8:45 minute video "Heat is energy, and most of the heat we produce - from our bodies, kitchens and cars - just dissipates into the environment. It’s a huge waste in an energy-strapped world. But University of Washington scientists are looking for ways to turn that waste heat into electricity. They’ve developed a flexible “fabric” that could be worn like a second skin, while helping to power our e-lifestyles."
Organic TEGs
Organic TEGs
"Silk Wire"
"Silk Wire"
Researchers from Chalmers University of Technology "coated the silk thread with a conductive plastic material that has exceptional properties for turning ordinary textiles into electricity generators.
These futuristic fabrics, or thermoelectric textiles as they are called, convert temperature differences between our bodies and the surrounding air into an electrical potential. This technology may bring a significant change to our daily lives and society at large.
When connected to a sensor, these textiles can power devices without batteries. The sensors could help monitor our movements or measure our heartbeat." - Earth: Silk Thread can Turn Clothes into Electricity Generators
Resources
Resources
Wearable TEG Data & Studies
Wearable TEG Data & Studies
High-Performance Wearable Thermoelectric Generator with Self-Healing, Recycling, and Lego-Like Reconfiguring Capabilities "Here, we report a high-performance wearable TEG with superior stretchability, self-healability, recyclability, and Lego-like reconfigurability, by combining modular thermoelectric chips, dynamic covalent polyimine, and flowable liquid-metal electrical wiring in a mechanical architecture design of "soft motherboard-rigid plugin modules." A record-high open-circuit voltage among flexible TEGs is achieved, reaching 1 V/cm2 at a temperature difference of 95 K. Furthermore, this TEG is integrated with a wavelength-selective metamaterial film on the cold side, leading to greatly improved device performance under solar irradiation, which is critically important for wearable energy harvesting during outdoor activities. The optimal properties and design concepts of TEGs reported here can pave the way for delivering the next-generation high-performance, adaptable, customizable, durable, economical, and eco-friendly energy-harvesting devices with wide applications."
Organizations
Organizations
Since this technology is still in its infancy, the organizations listed so far include the universities and labs currently studying new materials.
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