How to Harvest Energy From Your Own Body Heat

How to Harvest Energy From Your Own Body Heat

The human body is an incredible source of thermal energy that is constantly being generated and radiated out into the surrounding environment. With advancements in thermoelectric technology, it is now possible to harness some of this waste body heat and convert it into usable electrical energy to power small devices.

What is Thermoelectric Power Generation?

Thermoelectric power generation utilizes something called the Seebeck effect. This describes how an electrical voltage can be produced by creating a temperature difference across the junctions of two different conducting materials.

Devices that leverage the Seebeck effect are called thermoelectric generators (TEGs) or thermoelectric devices. They are made up of thermocouples containing a semiconductor material like bismuth telluride that generates electricity when one side is heated and the other is cooled.

The greater the temperature difference, the more electricity is produced. Even small temperature gradients are enough to produce usable amounts of power due to advancements in materials and device efficiency.

Wearable TEGs to Harvest Body Heat

Wearable thermoelectric generators are designed to leverage the natural temperature difference between the human body (~37°C / 98.6°F) and ambient air to produce electricity. They can be embedded into clothing, watches, fitness trackers, and other accessories that are in direct contact with the skin.

Some key benefits of using body heat powered wearables include:

  • Sustainable power source – Generates electricity from body warmth, no batteries required.
  • Compact and lightweight – Thin, flexible form factors that don’t restrict movement.
  • Always available – Produces power whenever worn against the skin.
  • Self-powering – Can eliminate need for charging devices.

How Much Power Can They Produce?

The amount of power produced depends on several factors:

  • Temperature gradient – Larger gradient = more power. Skin temp vs air temp produces ~15-30°C difference.
  • Thermoelectric material – Bismuth telluride optimal for low-temp body heat apps.
  • Device surface area – More skin contact = more heat transfer and power.
  • TEG efficiency – 5-10% is typical. New materials increasing to 15%.

Under ideal conditions, a small TEG ~1-4 cm^2 in size directly against the skin can generate around 10-100 milliwatts of power. With a large enough surface area covering substantial skin real estate, some prototypes have demonstrated up to 5-10 watts of power generation.

Potential Applications

Some potential uses for body heat harvesting technology include:

Charging Wearable Electronics

  • Smart watches
  • Fitness trackers and biosensors
  • AR/VR headsets
  • Hearing aids
  • E-textiles

The low power output is sufficient to trickle charge tiny wearable devices so they rarely need plugging in.

Powering Implants and Sensors

Internal body sensors and medical implants could be powered by harnessing body heat:

  • Cardiac pacemakers
  • Glucose monitors
  • Neurostimulators
  • Intraocular pressure sensors

This provides a self-sustaining internal power source to eliminate battery replacement surgeries.

Charging Mobile Phones

Larger form factor TEGs embedded in backpacks, laptop sleeves, phone cases can passively charge mobile devices:

  • Slowly recharge phone battery when worn close against body
  • Extend battery life and time between charges
  • Useful as emergency backup charger

Key Players and Products

Some companies developing thermoelectric generators for human energy harvesting:

  • Komodo – Smart straps and wristbands with embedded TEGs
  • Matrix Industries – PowerWatch series smartwatches
  • Hello Energy – Wearable TEGs for industrial workers
  • GreenTEG – Thin, flexible TEGs integrated into garments

Consumer products like the PowerWatch 2 smartwatch rely entirely on body heat to continuously recharge themselves. No external charging required!

The technology is still in early stages but offers exciting possibilities for self-powered electronics through harnessing our bodies’ natural thermal energy. With further materials improvements, body heat harvesting could become a mainstream way to eliminate batteries and charging for mobile tech.