Fraunhofer Institute for Silicon Technology
Fraunhofer Institute for Silicon Technology

Energy harvesting

 

 

 



 

 

 

 

In contrast to conventional MEMS energy harvesting systems that use a passive silicon tip mass, Fraunhofer's patented PowderMEMS technology allows to integrate meaterials with higher density like tungsten or NdFeB. This leads to a higher energy yield and, in addition, rotational or translational movements, for example, can be converted into electrical energy. This allows the harvesters developed at Fraunhofer ISIT to be used as a versatile
energy source that can be adapted depending on the application.

 

In the Fraunhofer lighthouse project ZePowEl - towards zero power electronics, a corresponding energy harvesting module was developed, which rectifies, regulates and stores the generated electrical energy. Further applications for the MEMS energy harvesting chips are an event-controlled, powerless standby, as well as magnetic field sensors for current monitoring.

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Energy harvesting: MEMS µW power source

Our solution:

  •  Piezoelectric energy harvester with integrated micromagnets
  •  Integration of high density materials increases performance
  •  Contactless excitation by magnetic forces
  •  Broadband excitation far outside resonance 

PowderMEMS makes it possible to use significantly denser materials as flywheel mass compared to the conventionally used silicon mass. This results in particularly high power densities under mechanical excitation compared to conventional systems.

In addition, the integration of micromagnets makes it possible to induce high forces without contact, and thus higher deflections of the bending beam. Thus, rotational or translational movements can be used for contactless energy harvesting by means of externally mounted magnets. If the initial deflection is sufficiently strong, the bending beam oscillates. This circumstance makes it possible to achieve high energy yields over a broad band of frequencies, i.e. frequencies well below the resonance frequency, which is extremely difficult to achieve with conventional systems. Outputs of more than 85 µW at about 45 Hz and more than 150 µW when operating in resonance have been achieved. 

 

Application:

  •  Energy self-sufficient sensor technology in hard-to-reach places e.g. gearboxes,
     starter generators, crankshafts, drill heads

Powerless standby

Our solution:

  •  Event controlled powerless standby
  •  Wake up by mechanical or magnetic pulses

One application for the MEMS energy harvesters developed at Fraunhofer ISIT is powerless standby. The generated voltage by a magnetic or a mechanical pulses is used to wake up an externally operated microcontroller. In standby mode, energy consumption is virtually zero. Such a system makes it possible to significantly increase the service life of electronic devices, especially if they are in standby for a long time between their actual use. 
 

Application:

  •  Extending the battery life of IoT nodes
  •  Machine Monitoring

Harvesting module

Our solution:

  •  Generate, regulate and store energy
  •  Variable module

As part of the Fraunhofer lighthouse project ZePowEl - Towards Zero Power Electronics, a complete harvesting module was developed. The individual components of the harvesting module are a MEMS energy harvester developed at Fraunhofer ISIT, which can be magnetically excited using PowderMEMS technology. In addition, there is an integrated circuit developed at Fraunhofer IPMS for suitable energy regulation as well as capacities for storage. The harvesting module can thus contribute to extending the lifetime of IoT sensor nodes or even operate them autonomously.
 

Applications:

  •  Supply of IoT nodes in the context of smart cities, condition monitoring, etc.

Contactless current sensing / magnetic field sensing

Our solution:

  •  Contactless power sensor
  •  In resonance detection limit up to 7.2 pT/ Hz0.5
  •  Amplitude modulation enables detection outside the resonance frequency

By integrating magnetic structures into a MEMS oscillator, it is possible to detect changes in the magnetic field. The magnetic field strength of a current-carrying conductor is proportional to the force acting on the bending beam and thus allows the current strength to be determined. In resonance, sensitivities of 34.6 kV/T and a detection limit of 7.2 pT/Hz0.5 are achieved. When the bending beam is operated in resonance, the external magnetic field leads to an amplitude modulation, which makes it possible to detect magnetic fields outside the resonance frequency of the bending beam.
 

Application:

  •  Power monitoring in aircraft and underwater vehicles
  •  Smart grid applications