Powering the Internet of Stuff – by sucking electricity from TREES
Where are my generating wellies?
Feel the vibe
Advanced Cerametrics makes wireless sensors with magnets on the back. The magnets are used to hold the sensor in place – slap them onto a big machine and they'll start transmitting performance information powered entirely by piezoelectricity, generated from the vibrations of the machine. That vibration is also the information transmitted, as changes to the frequency or amplitude can indicate developing faults, so the sensors take their power and data from the same source.
Perpetuum's Rail Solutions do much the same thing with rolling stock, and can spot worn bearings, failing gearboxes and anything else which turns. The sensors gather data while the carriage is vibrating in motion, while a capacitor stores enough charge to upload the information on arrival at the station.
Perpetuum wireless sensor node: Place in the most inaccessible of places, the sensor needs no maintenance
Southeastern Trains, the Govia-owned operator of the Kent rail franchise, has fitted Perpetuum sensors to its fleet of 618 Bombardier Electrostar carriages, convinced that early identification of faults will pay off in reduced maintenance costs.
The devices being made by Advanced Cerametrics, and its competitors, are a perfect example of how the Internet of Things is so much more than wrist watches and smart glasses, and energy harvesting is a key element in making it work. Batteries would probably be cheaper, and certainly provide more power, but having to replace them can be prohibitive when the working environment is the underside of a train, or an industrial generator.
Sensors powered by wasted energy – in this case the vibrations of the equipment – can run indefinitely without worrying about their operational life, so owners can build up a knowledge of what constitutes "normal" behaviour which makes spotting anomalies so much easier.
Yet vibrations aren't the only source of ambient energy, and piezoelectrics aren't the only way to harvest power.
Going hot and cold on the alternatives
Any temperature difference can be harnessed to create electricity, based on the Seebeck effect which utilises two metals placed side by side with conductors above and below. As the metals react differently to the heat differential between the top and the bottom, current is created. Manufacturers vie to create metal alloys which generate the greatest current in the widest range of temperatures.
Tellurex Enviro-Light: just light a candle and before you know it you'll have light enough to see!
The technique scales quite well, enabling the BioLite Stove to run a fan. That improves combustion, and charge an iPhone too, while Enviro-Light gathers the heat of a candle to power a light, which is, we have to assume, brighter than the candle whose heat it consumes. Several companies are creating much smaller thermal generators for use in less-headline-grabbing Things.
Thermo Life, for example, has a charger the size of a ha'penny which (the company claims) can put out 3 volts of electricity (at 10 microamps), while Perpetua will sell you the delightfully-named Power Puck, which uses an array of fins to create a temperature difference when magnetically affixed to something hot. The 'puck is designed to power pressure sensors from GE, Honeywell and Rosemount, but the company also sells a Power Tile which will – when slapped onto a pipe 90°C hotter than the surrounding air – supply 24 volts topping out at 20mA.
Perpertua Power: Surely the best-looking of the harvesting technologies
So attractive is the Seebeck effect that it's even available for in-home use, thanks to Micropelt: maker of the wireless radiator valve which turns boring old (manual) valves into intelligent Things powered by the heat of the water running past them. The "intelligent Thermostatic Radiator Valve" uses EnOcean's highly-efficient (but proprietary) radio protocol to integrate with other kit from EnOcean, providing truly-wireless home automation.