The rapid growth in the field of wireless sensor systems has highlighted the issue of powering remote sensor nodes. The requirement to change batteries, or recharge other power sources, places an unwanted additional maintenance and cost burden on such wireless networks. In certain applications where environmental vibrations are present, there is the opportunity to harvest the kinetic energy of these vibrations and use this to power the remote sensor node. The focus of the researchers now consists of design, modeling and development of vibration based electromagnetic/hybrid micropower generators using MEMS/NEMS structures on Silicon.
Meanwhile, powering wireless sensor network nodes and security management using energy harvesters in Oil and Gas industry may have receive a boost if sensor nodes can be wirelessly powered from thin air using electromagnetic harvester as demonstrated by Dennis Siegel a Digital Media student, skilled in 3D design, physical computing and rapid prototyping at the University of the Arts in Bremen, Germany.
According to Dennis “The omnipresence of electromagnetic fields is implied just by simple current flow. We are surrounded by electromagnetic fields which we are producing for information transfer or as a byproduct”. Many of those fields are very capacitive and can be harvested with coils and high frequency diodes. Accordingly, he asserted “I built special harvesting devices that are able to tap into several electromagnetic fields to exploit them”. The energy is stored in a usual battery possibly a super capacitor. So you can for example gain redundant energy from the power supply of a coffee machine, a cell phone or the catenaries of a train by holding the harvester directly into the electromagnetic field whose strength is indicated by an associated LED on the top of the harvester.
He demonstrated that depending on the strength of the electromagnetic field it seems possible to charge a small battery within one day. The system is meant to be an alternative for granting access to already existing but unheeded energy sources, most of which may be in hazardous places. Therefore, by exploring these sources it can create a new awareness of the invisible electromagnetic spaces.
There are two types of harvester for different electromagnetic fields: a smaller harvester that is suitable for lower frequencies below 100Hz which you can find in the general mains (50/60Hz, 16,7Hz) and a bigger one that is suitable for lower and higher frequencies like radio broadcast (~100MHz), GSM (900/1800MHz) up to Bluetooth and WLAN (2,4GHz).
Energy consumption and prolonging the lifetime of the batteries still remains one of the biggest challenges facing the applicability of wireless sensor networks. It’s clear this technology has some way to go before we’re all charging our mobiles by waving them at the nearest fridge. Even so, it’s a compelling concept as we move into a future where energy conservation is going to become more and more important.