Energy Harvesting – Thermoelectric

Energy production through temperature differences.

Thermoelectric Power Supply

What is thermoelectric Energy Harvesting?

It's the use of heat or cold sources to supply electrical appliances with energy.

The so-called Seebeck effect is used to generate energy from temperature differences. In this case, an electric current flows between two contact points of two electrical conductors, which have a different temperature. Since the voltages generated by the Seebeck effect are extremely small (a few microvolts per degree of temperature difference), Fraunhofer IIS has been researching for several years to use very small voltages and energy quantities through electrical circuitry and to reduce the energy requirements of electrical systems. Our current developments can already be operated permanently with 2 degrees Kelvin.

Fraunhofer IIS on IDTechEX TV

Dr. Peter Spies explains how the thermoelectric wristband from Fraunhofer IIS works on IDTechEX TV during the congress.

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Challenges

The realization of an efficient thermal harvesting system faces different challenges. First, a good thermal conductivity from the heat source to the thermoelectric generator (TEG) and from the TEG to the heat sink and the environment must be realized. Thermal simulations take into account the properties and dimensions of the materials and components involved and calculate the optimal configuration for the best heat flow. In addition, a good electrical matching between the TEG and the electronic power management must be ensured. Optimized voltage regulators are used for this purpose which, if necessary, also use maximum power point adjustment (MPPT) techniques when the temperature gradient has some variability. To use even the smallest amounts of energy from the environment, such as on the human body or on buildings, ultra-low voltage start-up voltage boosters can be used to operate with the lowest voltage levels of TEGs. Finally, a highly efficient charge controller must be developed to store the energy in an application-specific energy store.

Taking into account the challenges outlined above, a multidisciplinary approach, including materials science, physics and electrical engineering, is required to arrive at an energy and cost-efficient energy supply.

Our developments with thermoelectric power supply

We develop generators, power management circuits and complete power supply systems consisting of converter, memory and power management.

 

Sensor module BlueTEG

The sensor module BlueTEG from Fraunhofer IIS has an integrated power supply and communicates via a Bluetooth Low Energy radio link. It completely recovers its energy via thermoelectric generators and a special voltage converter from Fraunhofer IIS. The sensor data for temperature and acceleration are transmitted via bluethooth.

 

BlueTEG Pipe

Fraunhofer IIS has developed the sensor BlueTEG Pipe with thermoelectric power supply for industrial applications. BlueTEG Pipe uses temperature differences on pipes, supply lines or energy supply machines. The sensor measures values such as temperature, humidity or gravitational acceleration and sends them to a tablet via Bluetooth Low Energy. With this form of energy generation, sensors and radio electronics supply themselves autonomously from the environment. Elaborate power cables or regular battery replacement are a thing of the past.

 

DC-DC converter ASIC

Thanks to our high-efficiency voltage transformer, even the smallest amount of energy from the environment can be used efficiently. It works with a minimum input voltage and converts it into a higher output voltage. As a result, e.g. thermoelectrically supplied wireless sensors can be operated with energy from a small temperature difference and thus do without annoying battery change or complicated wiring.

Maximum Power Point Tracker

The Maximum Power Point Tracker ensures optimum adaptation between energy converters such as thermal generators or solar cells and energy storage. This system thus guarantees a maximum energy yield with minimum own energy consumption.

 

Energy self-sufficient tracking system

Consistent and energy-efficient localization of goods, people and animals is made possible by the modular, energy-independent tracking system. Satellite navigation was combined with localization in wireless sensor networks and energy supply through Energy Harvesting.

Our offer

  • Highly integrated voltage transformers: starting voltages below 20 mV and high efficiency up to 90%
  • Charge Controllers and Battery Management Circuits: Efficient charging of various types of energy storage with optional charge state estimation
  • Maximum power point tracker for voltage transformers for automatic impedance matching
  • Characterization of thermoelectric harvesters: Laboratory equipment for the generation of defined thermal differences and for the measurement of the output power depending on various parameters
  • Thermal Modeling and Simulation: Software tools for modeling thermoelectric generators, heat sinks and interface structures to optimize heat flow and power output