Powering the Internet of Stuff – by sucking electricity from TREES
Where are my generating wellies?
If a tree falls in the woods, will it still recharge my iPhone?
Such proprietary protocols permit even tiny amounts of power to be usefully harvested. The standards (ZigBee Green, Dust Networks, Weightless, etc.) are catching up, but when the power is being squeezed out of the trees then every smidgen has to be utilised to achieve something worthwhile.
Voltree: Big bit of kit, but a very small amount of power
Getting electricity out of a tree might seem a small step from getting blood from a stone, but in fact it's surprisingly easy, though using that energy is harder. A nail driven into the tree a few feet from the ground, with another in the ground nearby and a circuit between them to collect the voltage, was demonstrated by researchers at MIT in 2009. Doing anything useful with that power has been a challenge.
Voltree was born from that research, and wants to run a wireless mesh capable of detecting forest fires. The company has been running trials with the US forestry service: tree-powered sensors could, in theory, be easily deployed and forgotten about, until they get hot enough. The company also sells an educational kit for schools who want to see how much power their local trees can produce (we're talking microwatts here), with a view to understanding more about the process.
The power, apparently, comes from the pH difference between the inside of the tree and the ground. The tree has to maintain that difference to grow, so the mechanism really is tapping the tree (as opposed to drawing energy from the degradation of one of the nails, as a potato battery does) and will provide energy indefinitely - though, again, only in very small quantities.
Detecting fires is no-doubt useful, but it's not immediately obvious what other applications will be found for Voltree's technology, and the company is still struggling to turn what is has into a sustainable business as it's right at the edge of what's possible with ambient energy harvesting.
But in that respect Voltree is far from alone. There are many more companies making harvesters than companies making products which use them, for the moment at least. Numerous suppliers will deliver evaluation kits, often featuring multiple harvesting techniques, to enable the entrepreneur or inventor to find out what is possible. When Things become self-powered it opens up a huge range of possibilities, but we're only just starting to understand how to exploit them.
Wurth is one of many offering multiple techniques on a PCB: this device has solar, thermal, vibrational and magnetic energy harvesting
Energy harvesting is only one part of the IoT puzzle - printed electronics, highly efficient MOSFET chips, greater intelligence, and better radio technologies, are all playing their part in making better Things to manage our lives. Few people can reasonably justify spending ninety quid on a Nest smoke alarm just because it can talk to Google, but we can all see the value is knowing a train is going to fall apart before it happens.
Bringing it back to the Things around us
The popular press keeps banging on about smart thermostats and wearable technology, as though that were the Internet of Things, but such applications are already in the minority compared to the devices which proliferate wherever there is enough energy to run them. The Internet of Things isn't a buzz of unmitigated hype, it's just that one has to wade through a shitload of nonsense to see that the proliferation of self-powered Things really is going to change the world. ®
* Thanks to all the commentards and emailers who pointed out the original sums were wrong, stating 1cm instead of 20cm. Vulture Central's backroom gremlins have revised their very rusty knowledge of geometry and amended the story accordingly.