Friday Hack Chat: Energy Harvesting

Think about an Internet-connected device that never needs charging, never plugs into an outlet, and will never run out of power. With just a small solar cell, an Internet of Thing module can run for decades. This is the promise of energy harvesting, and it opens the doors to a lot of interesting questions.

Joining us for this week’s Hack Chat will be [John Tillema], CTO and co-founder of TWTG. They’re working on removing batteries completely from the IoT equation. They have a small device that operates on just 200 lux — the same amount of light that can be found on a desktop. That’s a device that can connect to the Internet without batteries, wall warts, or the black magic wizardry of RF harvesting. How do you design a device that will run for a century? Are caps even rated for that? Are you really going to download firmware updates several decades down the line?

For this week’s Hack Chat, we’ll be discussing what energy harvesting actually is, what TWTG’s ‘light energy’ technology is all about, and the capabilities of this technology. Going further, we’ll be discussing how to design a circuit for low-power usage, how to select components that will last for decades, and how to measure and test the entire system so it lives up to the promise of being always on, forever, without needing a new battery.

This is a community Hack Chat, so of course we’ll be taking questions from the community. If you have a question, add it to the discussion sheet

join-hack-chatOur Hack Chats are live community events on the Hack Chat group messaging. This Hack Chat will be going down noon, Pacific time on Friday, October 20th. Is it always five o’clock somewhere? Yes, so here’s a time zone converter!

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

23 thoughts on “Friday Hack Chat: Energy Harvesting

        1. I kept trying to get one of theses panels from calculators a few years back. Never found a real one in the 10 or so cheap and old calculators I have opened.
          Or maybe it is a survivor bias and I only get my hands on the ones with dead batteries.

    1. Wasn’t there a group putting Stirling engines on the end of the focal point of old satellite dishes after increasing their reflectivity. I can’t seem to find where i saw it.

    2. You can NOT generate any power from the earths magnetic field without motion. It is a quasi static field, even if you want to wait for a pole shift, that would be too slow. :-) And with motion you can use an inertia based device, like the generator of some auto-“winding” electronic watches.

  1. The spy world has got to have some insight into this. What’s an IoT device if not a bug you place around your own home/property. Burst transmission, radio powered transmiters (the great seal bug, RFID, etc), directional antennae. Does the standard 802.x protocol really need to be the standard for IoT if low power is the goal. Do you really need to poll your toaster or weather station every 5 minutes if you only use it 10 minutes a day?

    It seems most of the problems have already been solved but IoT devices are sloppily designed because the focus is being first to market.

    1. Not all ceramic caps. Only class I dielectrics (NP0/C0G) don’t age, and they’re typically too small to be the *only* kind of caps in the circuit. Class II and higher dielectrics age due to crystalline relaxation. It’s small for the more stable dielectrics (e.g. X7R) but it can be very significant for the less-stable ones (e.g. Y5V/Z5U). On the scale of a decade (1E6 years) you’d be looking at about a 30% or so decrease in capacitance, which could be fatal to the device depending on the design.

      Of course if the temperature isn’t stable as well, ceramics would eventually fail due to thermal expansion/contraction.

      1. A decade is 10 (1E1) years, not a million.

        But I would avoid Y and Z dielectrics at all. If you really need them, double up the capacitance. thermal exp. is not that big a problem, but it is better to avoid bigger physical sizes as they are more sensitive to mechanical damage.
        Tantalum caps are also very durable if used properly – that means 30% to 50% voltage derating and avoiding the possibility of current surges.

  2. Yep, sounds like solar cells and a good boost/MPPT circuit to me. Did a feasibility study a few years ago about putting “IoT” (RF mesh) sensor networks on submarines. Turns out you can run a Dust mote on ~40 lux indefinitely with a modest sized amorphous cell and a well-known COTS boost chip. Supercap or coincell needed to bootstrap for the first half minute or so (peer discovery).

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