Tiny Solar Can Embed Power Generation in Clothing

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Clothing embedded with tiny solar cells the size of a flea will allow wearers to generate electricity on the move and charge items like mobile phones and smartwatches.

Nottingham Trent University has developed a way to embed miniaturized solar cells into yarn that can then be knitted and woven into textiles. The technology has been tested and proven to charge a mobile phone and a Fitbit.

The cells are encapsulated in a resin which allows the textile fabric to be washed and worn like any other form of clothing.

Measuring only three millimeters in length and 1.5 millimeters in width, the cells are almost invisible to the naked eye and cannot be felt by the wearer.

For all intents and purposes, garments appear exactly the same as any other form of clothing despite having the capability to generate electricity.

Up to 200 miniaturised cells can generate 2.5-10 volts and up to 80 miliwatts in power. The university’s Advanced Textiles Research Group made a proof of concept textile of 5cm by 5cm size with 200 cells.

This proved powerful enough to charge a mobile phone and a Fitbit. Researchers say if 2,000 solar cells were incorporated into a textile it would generate enough power to charge a smart phone.

Nextbigfuture Commenter Goatguy Feels This Work Has Problems

Of course, in the end its mostly bbb-bb-b-bûllsnot:
1. The teeny-tiny solar cells need to be connected together quite specifically in series-parallel to generate power that is USEFUL for recharging one’s smartphone.
2. The little things need to be ‘normal’ oriented to the light source.
3. The specific output … 89 watts per square meter (thank you Excel) is only attained when the cells are illuminated by full Noon sunlight (8.9% efficiency with 1,000 W/m² illumination).

It needs to be remembered that if one were — per the suggestion of the article — to have these things woven into the yarn of a sweater (hoodies, jacket, windbreaker…), that ONLY the cells on top of one’s shoulders would be oriented normal to noon illumination. The rest would be pointed the wrong way. If the wearer were prone (laying down), then again, only half point the right way. The rest are shadowed by the body.

Moreover, being materials-science savvy, what about all those series-parallel wiring connections between the cells? How to collect the electricity from thousands of rather disorganized distribution flea-sized solar cells? Establishing good connections between them, ORGANIZED connections (to get useful power) between them, all the little + terminals and — terminals hooked up the right way to aggregate power delivery, wow… that’s asking a lot for things ‘woven’ into a yarn.

And of course the real-world, “how then do these exquisitely dainty cells, woven into clothing, ‘survive’ being repeatedly washed in washing machines and tumble-dried in home dryers?” All those precious connections, tumbled along with other soggy clothing, mmm…. mmm… nope, I can’t see ‘em surviving. I can’t even see a “cell phone recharging cable” surviving. Let alone the tens of thousands of connections.

Anyway,
More grad school GoatStuff.

7 thoughts on “Tiny Solar Can Embed Power Generation in Clothing”

  2. What GoatGuy says. I read the paper. The power output described above only refers to the “naked” diodes lying perpendicular to extreme sunlight. Once you weave the PDs into the special-made PD yarn (that resembles “cable sweater” thickness), the effect drops quite a lot (because the yarn hides and scatters the light….). From 80 milliwatts to about 20. That is, when using a very high intensity UV lamp (they had to cool the material or it would have melted under the lamp).

    In real life, the power output would be quite disappointing. Particularly at night.

    Also, the washing tests were normalized conditions but the PD yarn lasted only about 25 washes. The copper wires embedded in the yarn broke down pretty quickly. Water+electrical wiring are usually not the best companions.

    I don’t think this material will hit the shelves anytime soon. I think the flexible thin-filmed PVs have much better application (not for clothing).

  3. But that just points to the next+2 generation Fitbit needing to be a lot more energy efficient. Which was probably desirable and on the roadmap anyway.

    Jim’s got it. Self winding watches solved the “recharge by wearing it” problem decades ago. Any new solution needs to be significantly better than the existing solution, which a mesh of power cables strung through your [wet? damaged? ] clothing that you then have to hook up to your devices… not going to be an improvement.

  4. Oh, heck – what Goat Guy said. He got it first…

    That said – Seiko has their Kinetic line, with an unbalanced rotary mass that powers a tiny generator. No real idea of the electrical output on one, however.

    Here’s an overview on the system…

    https://forums.watchuseek.com/f281/look-into-seiko-kinetic-watch-technology-254265.html

    Apparently some Seiko Kinetics us the TC920S rechargeable battery which has a nominal discharge rate of 100 microamps. Which ain’t a whole heck of a lot.

    http://biz.maxell.com/en/rechargeable_batteries/pdf/TC_15e.pdf

  5. ⊕1 … because I like it.  

    However, if you recall, the “perpetual watch” concept of a self-winder depends on an unbalanced rotary mass that wobbles around the interior in a circular sort of fashion. Its geared quite aggressively to the main spring, so that it takes about 10 minutes of concerted wiggling to re-tighten one’s spring entirely. Per day.  But over the course of a day, even the least jiggly corporate bench warmer will get those 10 minutes of wiggles in.  

    Apparently a FitBit (6 mo. on a CR2025 ½ watt-hour battery) is drawing about 113 µW average. Figuring that one might do what, 500 arm-swings worth anything per day? 113 µW × 60 × 60 × 24 = 9.78 joules/day.  Divided by 500 = 20 mJ per swing. Hard to quantify what that’d feel like. One should assume over 75% mechanical-to-electrical efficiency tho.  

    Putting 10 J/day into perspective: I think that that is substantially more than what a wind-up watch spring holds. So, from that point, then the dead-weight in the fitbit watch would fell like a sloppy mass.  Not sure if people’d cotton to it. 

    Just saying,
    GoatGuy

  6. The technology for charging an electronic watch by the wearers movement has existed for decades. I think the fitbit would be the best tech to be recharged by the wearers movement. If it runs out of charge you are *definitely* not moving enough.

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