Micro Energy Harvesting: From basic research to practical application

Peter Woias

Albert-Ludwigs-University of Freiburg, Dept. of Microsystems Engineering, Laboratory for Design of Microsystems, Freiburg, Germany


Abstract

From today’s perspective, micro energy harvesting has seen a tremendous start in the last decade, concerning basic research, fabrication technologies and the outcome of first products and applications. The main driver of this success is the on-going application of distributed and embedded microsystems in almost every area of our daily living. More and more wireless sensors are used in logistics, environmental and building technologies or automotive applications, with their need of a reliable power supply without batteries or power cords. Also, the “internet of things” is considered as the main future - and ubiquitous - network for signal processing, data transmission and control. Finally, our ever growing infrastructure networks claim for widely distributed sensor and actuator networks, e.g. for the structural integrity monitoring of bridges and tunnels or for a reliable control of our waste water management system.

As a consequence, the phase of early “high-flying” research in energy harvesting is definitely settling down towards a technically and application-oriented approach and towards energy-autonomous embedded systems. Within the process, it is more and more recognized by system designers and potential customers that micro energy harvesting cannot be considered as an isolated technology whose only distinction is the replacement of batteries or wire cords in a modular fashion. In contrary, the embedded system together with its energy harvesting capabilities has to be re-designed in a full system approach as an energy-autonomous embedded system that embraces energy conversion, energy storage, energy management and the system hardware and functionality. Finally, it turns out that conventional and familiar technologies, e.g. for energy storage or power management, do not show an optimal performance in this specific application. This altogether is stimulating research and development towards optimized and application-oriented energy-autonomous embedded system, far beyond the first stage of energy harvesting.

From a more global standpoint it is interesting to see that we do not recognize embedded systems as such, however depend on their reliable operation and seam-less interaction. One might say that our natural and technical environments are enhanced via the embedding of artificial sensors and actuators, as an extension of our current natural or technical sensor and actuator systems. This vision can be carried on even further: Biological systems, the natural models of energy harvesting, generally work by a principle of "function follows energy". This way of thinking takes us to revolutionary new, biologically inspired embedded systems that live a "technical life" in their surroundings. Their design and their operating concept are made "liveable", analogous to biological principles, to maintain the function when the available energy and data vary. Like biological organisms they match their activity to the energy, use different energy sources, know their own resources, and make efficient use of them. This radical change to energy- and data-adaptive design principles promises - beyond energy autonomy - a dramatic enhancement in the operating reliability of embedded systems, and in turn opens up entirely new perspectives.