The Future of Wearable Power Is Energy Harvesting

One of the many challenges the wearable market faces has to do with battery limitations and physical size. The simple fact is batteries require a relatively large amount of space and that’s not likely to change soon.

In fact, the proportion of space batteries take up inside our devices continues to increase. Look into the guts of today’s notebooks, smartphones, tablets or any other mobile devices and you’ll quickly discover the vast majority of the volume inside them is devoted to batteries.

The new Apple MacBook is a great example. While the motherboard has shrunk down to a tiny size, the battery has expanded to fill all the new space the shrinkage of the actual computing electronics has enabled. It’s essentially a big, cleverly designed battery that comes with a screen.

In the case of wearables, of course, you have the challenge of needing to fit batteries into a relatively small space. It’s a classic tradeoff exercise for engineers—the more battery they build in, the bigger and bulkier the device, but the bigger and bulkier the device is, the less likely people are to want to wear it.

Some wearable makers are addressing the issue by designing devices with an extremely low power screen or even no screen at all because the screen is the largest consumer of battery power in most devices—particularly wearables. By doing so, they can build a device with a modest size battery (and, therefore, a modest-sized device) and still get days, weeks or even months and years of battery life.

Others, like Apple, are choosing to put in a high quality screen on their wearable but require people to charge their device every night because they could only build in a battery big enough to last a day without making the device too large and cumbersome.

This dilemma and these compromises are leading engineers and product designers to search for new ways to power their devices while living within the realistic physical constraints of where battery technology is, and likely will be, for several more years. The trick won’t necessarily be how to fit a bigger battery in but rather figuring out how to continually charge the battery that is there so it can last longer between recharges.[pullquote]The trick won’t necessarily be how to fit a bigger battery in but rather figuring out how to continually charge the battery that is there so it can last longer between recharges.”[/pullquote]

Ironically, one of the ways being investigated actually comes from the world of traditional, mechanical watches. Essentially, all the mechanisms used inside high quality Swiss watches leverage the kinetic motion of your body. As you move your arms throughout the day, that motion is used to both power the intricate collection of interconnected parts that make up the mechanism and to “store” enough energy to keep the watch ticking when it’s not moving. This “storage” is commonly referred to as the watch’s power reserve and is often measured in the range of 30-70 hours (though it can vary widely). If a mechanical watch’s power reserve is depleted, it stops running and you have to manually wind the watch to get the process started again.

Applying the same principle to wearables, you could recharge the battery inside a wearable from your own kinetic motion, thereby extending the life of relatively small physical battery without needing to recharge quite as often. Of course, as with many things, the devil is in the details and the amount of energy that can be harvested from kinetic motion is often very small. Plus, translating motion to electrical power to charge a battery isn’t always super efficient. That’s why we don’t see a lot of wearables on the market that currently use energy harvesting.

There are a number of companies who are investigating both this and many other more sophisticated types of energy harvesting, however, and I believe these technologies are going to play a critical role in future wearables. As I understand it, the technology is likely going to involve combining together a number of potential energy sources, each of which harvests a tiny amount of energy either from your own body’s kinetic motion, the heat your body generates, the physical environment around you (sunlight, air temperature, etc.) and other sources, into a total that starts to become meaningful. And who knows? What’s to say there’s anything wrong with winding a smartwatch every now and then and harvesting energy that way?

The physical size constraints and power demands of wearables are likely to be in conflict for some time to come, but with some clever engineering and adaption of old world ideas, solving some of the challenges of battery life on wearables could arrive sooner than we think. Let’s hope so.

Published by

Bob O'Donnell

Bob O’Donnell is the president and chief analyst of TECHnalysis Research, LLC a technology consulting and market research firm that provides strategic consulting and market research services to the technology industry and professional financial community. You can follow him on Twitter @bobodtech.

9 thoughts on “The Future of Wearable Power Is Energy Harvesting”

  1. I’m amazed that you wrote this whole article without ever mentioning the words “Seiko Kinetic” at all.

    Even though quartz watches give you accuracy on the cheap, I stayed with automatic watches because I did not want to deal with the hassle of going to a store just to get the batteries replaced. My interest perked up when Seiko announced it’s Kinetic line of self-charging quartz watches, but the first few generations were really thick and bulky. That was until about a couple of years ago when they were able to shrink the charging mechanism (is it a dynamo?) to the point that they didn’t look much bigger than an automatic. So I’ve ditched my trusty Seiko automatic (about $150, online) in favor of the kinetic (about $150 too).

    Perhaps a few more generations and the technology might be compact enough for a smart watch. As it is now, under normal use (and charge), if I then leave my watch sitting idle, Seiko says it has enough juice to keep running for about 4-6 months. Wonder if that’s enough to keep an
    AppleWatch running overnight. Point is, kinetic self-charging is way more advanced than what the relatively sparse info in the article seemed to imply.

    1. Thanks for the note. I hadn’t heard of the Seiko Kinetic, but I appreciate the info. There are a number of developments going on in this area and the point of the article was to make people aware of some of the concepts and ideas.

  2. I’m wondering if removable batteries wouldn’t be a nice stop-gap solution: design you watch to work 36 hours on a charge (that’s 24 hours + safety), ship it with 2 batteries so charging it up only takes 10s to swap the depleted battery with the one that’s been charging up, and week-end trips can be taken without the charger/charging hassle.
    Sounds better than having to take off the watch 2-3 hours per day, either waking hours when you’re supposed to need it, or sleeping hours were the sleep phases analysis thing is supposed to be a life-changer.

    1. Removable batteries are even less likely in a watch than in an iPhone (or a svelte SGS6). Compromises in design, let alone waterproofing are unacceptable. People will find their own usage patterns and drive their own charging patterns depending on their priorities. Sleep monitoring will be a useful but minority sport.
      As the article says, new battery and charging tech is the chase that is on…

      1. I’m not sure either consideration is relevant: for example, the removable-battery SGS5 was splash-proof, the fixed-battery SGS6 isn’t. As for aesthetics, it’s not as if even the iWatch’s backplate were good looking.

  3. Traditional watches require minuscule amounts of power, which is the reason kinetic energy recovery systems work well. If all you need is the time, then it is a good solution to the problem, though a battery that lasts years is a good (better?) alternative.

    It is almost unimaginable that these systems would be able to power a smart watch, however, which requires perhaps a thousand or ten thousand times more power.

    My guess is the gap is more likely to be closed by advances in processor and screen tech, which are still advancing quickly, than advances in the mechanical recovery systems, which are unlikely to have all that much room for improvement.

    For a long time, watches had to be wound every day. People put up with this because it was a small price to pay for the convenience of having the time available to you at a glance. Having to charge a watch daily probably involved less effort than winding it. If daily charging remains necessary for smart watches, then again, it is a very small price to pay for the capabilities the device brings.

  4. How about an Apple Watch band that is mostly a battery (easily swappable), or even sucks up solar energy through the day? I would think this isn’t too far off.

      1. Well, perhaps it can’t be done, but I tend to think in terms of what can be done, rather than what can’t. Otherwise how do you move forward?

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