Axial Permanent Magnet Generator for Wearable Energy Harvesting

Stig Högberg, Jakob Wagner Sødahl, Nenad Mijatovic, Johan Pedersen, Dushan Vuckovic, Bogi Bech Jensen, Joachim Holbøll

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


An increasing demand for battery-free electronics is evident by the rapid increase of wearable devices, and the design of wearable energy harvesters follows accordingly. An axial permanent magnet generator was designed to harvest energy from human body motion and supplying it to a wearable application. The design was approached from an lectromagnetic point of view in this article. Two types of axial flux permanent magnet generators were designed: one with an iron yoke, which is commonly used to reduce the machine volume and demand of permanent magnets, and a second without the iron yoke in order to reduce the rotor inertia and to reduce losses. Analytical models and finite element simulations were employed for the analyses of both generator types, and verified experimentally by prototypes. The results suggested that a generator of this size and power rating (20 mm radius, and 5 mW, respectively) with an iron yoke is subject to losses that exceed the realistic input power, and was therefore deemed infeasible. A generator without the iron yoke was concluded to perform well as a wearable energy harvester. An experimental investigation of a prototype revealed an output power of almost 1 mW at a voltage close to 1 V, yielding a power density of 13 μW · cm−3.
Original languageEnglish
Title of host publicationProceedings of 2016 XXII International Conference on Electrical Machines
Publication date2016
Publication statusPublished - 2016
Event2016 XXII International Conference on Electrical Machines - SwissTech Convention Center, Lausanne, Switzerland
Duration: 4 Sep 20167 Sep 2016


Conference2016 XXII International Conference on Electrical Machines
LocationSwissTech Convention Center


  • Axial flux
  • Coreless generator
  • Electromagnet energy harvester
  • Internet of Things
  • Permanent Magnet
  • Prototype

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