In the modern world, people are widely surrounded by communication devices, digital sensors and cameras sending data cloud-based analysis services.
Those devices require power, and designers are discovering new ways to achieve it from ambient sources instead of depending on hard-wired grid connections or batteries. Chemical & Engineering News (C&EN), the news magazine of the American Chemical Society, describes energy harvesters and their role in the growing internet of things.
Marc S. Reisch, C&EN Senior Correspondent, describes that even though the majority of digital sensors can be wired easily to existing electrical grids, this is not always convenient for certain locations like the undersides of trains or the insides of air ducts. Batteries, which have to be periodically recharged or replaced, may also be inappropriate for hard-to-reach places. In order to meet this requirement for more versatile power sources, device makers are moving to energy harvesters, which extract trickles of free power from ambient motion, heat or light.
Designs approaching the market include everything from comparatively simple solar cells to a wall switch that, instead of being hard-wired to a light fixture, uses the energy from pressing the switch to send a wireless signal to turn a light on or off.
However, wired connections and batteries are not likely to become extinct any time soon. Since the ambient energy that harvesters depend on may not always be available, they cannot fulfill the demand for 100% reliability that some applications need. As an alternative, energy harvesters can be used together with batteries to extend charge life and offer passive recharging. Yet, those in the energy-harvesting business remain optimistic. They believe the technology is improving, and that it will soon become viable.