The human body is an incredible source of thermal energy that can be tapped into to produce electricity. With the right materials and techniques, you can harness your own body heat to power small devices and gadgets. This renewable energy source is always available, portable, and eco-friendly.
How Body Heat Energy Works
The human body produces a constant flow of thermal energy as a byproduct of metabolic processes. This can be captured through thermoelectric generators (TEGs) that convert heat differentials into electrical energy via the Seebeck effect.
TEGs contain semiconductor materials such as bismuth telluride that generate a small voltage when one side is heated up relative to the other side. The greater the temperature difference, the more electricity is produced.
Your body heat provides an abundant source of waste heat that can be leveraged by TEGs to produce usable electricity. A small TEG device can generate up to a few milliwatts of power from body heat alone.
Wearable Harvesters to Capture Body Heat
Specialized wearable devices can be designed to harvest electricity from your body’s thermal radiation. These thermoelectric harvesters are equipped with TEGs and strategically placed on the body to leverage areas with the most heat dissipation.
Some example designs include:
- Wristbands – Placed on the wrist over the radial artery to capture heat from blood circulation. Can produce up to 5-10 mW.
- Socks – Worn as normal socks but with embedded TEGs to capture dissipated heat from the feet. Output around 2-4 mW.
- Patches – Flexible patches with TEGs that stick to high heat areas like the neck, head, or chest. Generate 1-5 mW each.
These wearable harvesters use the same TEG technology but are optimized to efficiently capture your body’s thermal radiation through intelligent placement and design.
How Much Power Can You Produce?
The amount of power that can be harvested from your body heat depends on:
- Surface area – More TEG surface area exposed to the body equals more power output.
- Contact area – Better contact with the skin improves heat transfer to the TEGs.
- Location – Areas with lots of blood flow (wrists, neck, etc) produce more energy.
- Activity level – More body heat is generated during exercise and movement.
Under normal indoor conditions, the average person can produce roughly 10-30 milliwatts using a practical wearable setup with TEGs on the wrist, neck, and feet. With a larger coverage area, output can potentially reach over 100 mW.
Vigorous activity like exercise or working outdoors can boost power generation significantly. A maximal theoretical value is around 1 Watt per person, but that would require nearly full body coverage of high efficiency TEGs.
Applications Powered by Body Heat
The amount of electricity that can be produced from body heat alone is relatively modest. But it’s enough to trickle charge small wearable electronics like:
- Smart watches – Requires just 5-10 mW for charging.
- Fitness trackers – Can operate on 10-20 mW of power.
- Wireless earbuds – Low power models may work with 30-50 mW input.
- Smart glasses – Augmented reality heads-up displays only use around 100 mW.
With sufficient TEG coverage, you could potentially power handheld gadgets like smartphones and tablets too. However, the ergonomics are less convenient compared to dedicated wearables.
Body heat alone can’t run high power devices, but it can help extend battery life by slowly topping up your gadgets throughout the day. The key is pairing energy harvesting technology with ultralow power components.
Tips for Harvesting Maximum Body Heat
Here are some tips to get the most out of a body heat harvesting setup:
- Choose TEGs with a high figure of merit (ZT value) for optimal efficiency. Values above 1 are preferred.
- Focus TEG placement on areas with lots of blood flow – neck, wrists, upper back, chest.
- Good skin contact and thermal coupling improves heat transfer to the TEGs.
- Exercise and physical activity will boost power generation significantly.
- Outdoor use produces more heat versus indoor ambient temperatures.
- Combine multiple TEGs together to increase total coverage area.
- Look for TEGs designed and optimized specifically for body heat harvesting.
With smart harvesting techniques, your body can become an endless source of renewable energy to power next generation wearable electronics. The key is creating ergonomic and convenient TEG devices that seamlessly capture waste heat you already produce.