Batteries Will Only Get You So Far

“Roads? Where we’re going, we don’t need roads…”

Alasdair Allan
2 years ago

Moore’s Law has driven our computing to a place where we all walk around with black rectangles in our pockets, each with more computing power than was available to a major government only a few years before. When you talk about them you generally mention the glass, aluminium, and sometimes even the silicon. What you don’t mention is Lithium, the Lithium polymer battery that now makes up the bulk of the weigh of your magic computing device.

If you’re reading this on a laptop, rather than a phone, things are pretty much the same. While most of the cost is the silicon, most of the weight is Lithium. The size and weight of our modern computing is fundamentally constrained by the power-density of our modern batteries.

As the phones and laptops get smaller and weigh less, the batteries make up more and more of the product. Open up any phone or laptop today and it’s mostly just battery. Which is why many of carry around a battery pack, which makes a bit of a joke of our phones and laptops being the lightest, and thinnest, of their kind in the first place.

But batteries will only get you so far, which is why if you’re expecting an especially long day on the road, you might be bringing along something to charge the battery that’s going to be charging your phone. While for most of us that’s going to be an AC adaptor, if you’re going a bit further a field you might also have a solar battery charger. Sometimes, however, that isn’t going to be enough. Sometimes, if you’re intended to go way off the grid, you need something else.

If so, this year’s Hackaday Prize may well have you covered with its Power Harvesting Challenge, one of the five challenges that make up the prize competition. One project that caught my attention in this category is a project to build a series of Power Generation Modules, which includes both a water and wind turbine, along with a hand crank generator.

Portable water generators aren’t new, we’ve seen them before, but the simplicity and rugged nature of the design here is pretty interesting.

If you have a 3D printer to and a soldering iron you can probably source, or scavenge, all the parts you’ll need to build it, and of the modules in this entry it’s probably the most practical—generating a peak power of just under 25W—beating many of the portable solar panels on the market.

Alongside the water turbine is a hand crank module. Normally seen in low-powered applications like emergency radio and lanterns, the module performs much much more poorly than the water turbine, generating under 5W of power at peak, that a factor of ×5 less power.

While the final module in the entry is a tiny desk top wind turbine based on the Savonious turbine design. Perhaps unsurprisingly, this performed the poorest, generating only 0.5W at peak. That’s a factor of ×10 worse than the hand-crank module, and a factor ×50 worse than the water turbine.

Even for a mini-turbine this module is incredibly small, probably below the practical threshold, as you generally need to scale up a wind turbine to get usable amounts of power.

Smaller wind turbine designs are possible, although there is a minimum size below which they’re not useful anywhere even in the sorts of heavy and sustained wind you only get in a limited number of places — like a ship at sea, or an exposed mountain top. But if you are looking for a good example of a useful small turbine, another entry in the Power Harvesting category in this year’s Hackaday Prize competition, the Portal Point Generator, is probably a good example of a field tested design.

I’m going to be keeping a weather eye on this category, and will be interested in seeing the final outcome. Because I think experimentation around portable, or even just “removable” alternative power, is going to become increasingly more applicable as we continue to push our battery technology, and our computing becomes more mobile.

Submissions to the Power Harvesting category of this year’s Hackaday prize closed today. But if you’ve been thinking of submitting something to the prize there’s still time to enter the Computer Interface and Musical Instrument Challenges ahead of the Hackaday Superconference in November when the winners will be announced. If previous years winners are anything to go by — a satellite ground station, an eye-controlled wheelchair, a modular robot, and autonomous underwater glider — the results should be interesting.

Alasdair Allan
Scientist, author, hacker, maker, and journalist. Building, breaking, and writing. For hire. You can reach me at 📫 alasdair@babilim.co.uk.
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