The Internet of Things is expected to incorporate billions of devices in the future. That's a lot—far too many to all run on battery energy alone. For this reason, the harvesting of energy, or deriving energy from external sources, is growing in importance and being done with more ingenuity every day. Research firm IDTechEx expects the annual global sales of energy harvesting products, which is currently at $300 million, to reach $2.6 billion by 2024. Heat generated from the human body, leg movement, and finger tapping are just a few ways mobile devices are beginning to harness kinetic energy. Experts predict that walking and running could one day be used to power buildings—a sign of what's to come for Smart Cities across the globe.
Taking wearables to a new level, a pair of smart shoes developed by a team of German designers may one day power wireless devices as the wearer walks. But the harvesting of energy to fuel technology is already moving beyond wearables. For example, the consumer electronics company Phillips sells a switch that wirelessly operates room lights, powered by the tap of a finger.
Dr. Wald Siskens, CEO of EnOcean, says finger tap energy will be the most popular energy source for gadgets in the near future for two reasons. One is that people are fascinated by having wireless control with just the small force of their finger press. The second reason is how easily kinetic energy can be transferred to a number of applications. Siskens says the same principle enables wireless and maintenance-free bus stop actions. The act of pressing the bell push generates enough electrical power for a wireless module to activate the stop display and audible stop signal. This energy harvesting wireless solution saves up to 100 meters of cabling in the bus.
"Being batteryless, and therefore maintenance-free, energy harvesting wireless sensors and switches are the assistants we need to collect and transmit the first data bit in an IoT system," says Siskens. "The intelligence to make use of the data can and will be implemented anywhere, but the systems that collect the initial information need to be reliable and perpetual so that we can "install and forget" this. Energy harvesting sensors will be the "Things" in the Internet of Things.'"
What can harvested energy do for Smart Cities?
If the idea of walking and running motion being used to energize buildings and wireless bus stop actions becoming more prevalent are any indication, intelligent data collection and control will also be used to coordinate the lives of people in cities, and may ultimately prevent a city from collapsing. "This can only be realized with millions of sensor nodes collecting and delivering the data needed," says Siskens. "Malfunctions of battery-powered sensors could cause chaos in such a deeply connected system. But cables are no alternative either, as they are too complex and costly to install. In contrast, energy harvesting-powered devices can overcome both issues. Solar-powered occupancy sensors, for example, notify when somebody is walking a street and send a signal to activate the street light. The same can function with motion-powered sensors in the streets' surface when a vehicle passes."
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