Hackaday Prize 2022: Drying Clothes With Ultrasound

Clothes dryers are great, and a key part of modern life, but they do use a lot of energy. [Mike Rigsby] decided to see if there was a more efficient method of drying clothes that could compete with resistive heating for efficiency. Thus, he started work on an ultrasonic clothes dryer.

In early testing, he found ultrasonic transducers could indeed blast droplets of moisture away from fabric, effectively drying it. However, unlike heat, the ultrasonic field doesn’t effectively permeate through a pile of clothes, nor can it readily be used with a spinning drum to dry many garments at once.

[Mike]’s current experiments are centered around using a basket-type system, with a bed of ultrasonic transducers at the bottom. The idea is that the basket will shake back and forth, agitating the load of clothing and allowing the different garments to effectively contact the transducers. It’s still a work in progress, but it’s an interesting approach to the problem. We’d love to see a comparison of the energy use of a full-scale build versus a regular dryer.

We’ve heard of the ultrasonic drying concept before, too, with the Department of Energy researching the matter. It could just be that we’ll all be using ultrasonic dryers in decades to come!

28 thoughts on “Hackaday Prize 2022: Drying Clothes With Ultrasound

  1. Interesting idea! There are couple other clever tacks on drying out there, folks have filed patents on vacuum-assisted dryers to lower the water’s boiling point (EP3102730A1) and dryers that use microwaves to heat the water in the clothing (US4250628A). Another approach to washing is to forego water completely and use supercritical CO2 to wash away the dirt (WO1994001613A1)

    1. OR, you could just use cheap paracord like a sane person. If you habeba covered porch, even better, can dry without fade. If not, turn clothes inside out to reduce fade. Or hang inside and let the air conditioner donits job all while keeping your sinuses from drying out.

  2. From the linked page: “Traditional dryers (heat pump or resistance heat) utilize a spinning drum. A rotating drum is not the best solution for an ultrasonic system. Because transducer/cloth contact is necessary, a rotating drum requires roughly twice as many transducers as needed (half the drum is not in contact with clothing at any time). Rotating electrical connections (slip rings) and control (turning off the unused transducers) represent cost and complexity that can be avoided.”

    Maybe so, but if a drum shaped prototype turns out to be easier to make than the other basket pivot thiny then it might still be a good first practical shot at the idea.

    1. I’d be amazed if you can generate that amount of hot dry air in the size of a regular dryer with a heat pump compared to the cheap simple ~3kW heating element plus fan that’s in every dryer I’ve ever seen.

      1. It was hot enough to melt some full color decals in my t-shirts when I visited France. The same shirts had been dried in conventional dryers in the USA many times. Plus heat pump dryers don’t need an exhaust vent so they don’t suck conditioned air out of your home. And the vacuum conventional dryers create sucks air into your home from outside. All contributing to energy usage so a heat pump dryer uses less than 1/3rd the energy of a conventional dryer. And you could probably use the condensate water for your plants.

      2. Our heat pump based dryer consumes 25% of it’s resistive replacement to run. As a bonus, it also produces distilled water as a by product, which is convenient for topping up lead acid batteries.

      3. Part of the reason why it works is because a condensing dryer keeps recirculating the air and the heat. The damp air condenses on the evaporator and becomes dry air that is immediately heated back up, which returns almost all of the heat back through the heat pump and keeps it running at a very high CoP. It’s a closed loop – unlike regular tumble driers which just keep venting the hot air out.

        The minimum energy requirement to evaporate water is about 600 Watts per liter per hour. Regular driers are somewhere around 20% efficient in doing that.

        1. A window air conditioner and fan only use about 500w according to my kill-a-watt, and keeps my house cool at the same time, energy i already would be using. So zero energy loss minus the 10 calories i burn hanging them up.

    1. There was one years ago announced. It was like a ball with a power lead on it. To put into a bucket of “clothes” along with soap and water. Apparently you didn’t need much detergent.

  3. Centrifuge drying is the way to go. I’ve used one at a laundromat, it was great. As a bonus it also pulls out the left behind detergent, which is left behind if the water evaporates in place. Gotta be careful loading or it will shred your clothes.

  4. Wouldn’t this work better with a very low frequency transducer that would literally vibrate and push the water out of clothes via air pressure? Like a subwoofer essentially?

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