# Electric by Stretching Action

Discussion in 'Electric Propulsion' started by RonL, May 23, 2019.

### Help Support HomeBuiltAirplanes Forum by donating:

1. May 23, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
2. May 23, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina
Sound like a generator to me. Which means you'd need to wind it in flight. A motor to wind it so it can run a motor?

3. May 23, 2019

### Aerowerx

#### Well-Known Member

Joined:
Dec 1, 2011
Messages:
4,697
1,243
Location:
Marion, Ohio
Uh, no.

The way I read it is that all you need is a bottle of water and some table salt.

4. May 23, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
I would think the motor could be built into the prop hub, or between the prop and band, continually keeping a tension between two values. It would cycle in the same way a shop air compressor works between two air pressure set points.

250 watts per Kg seems impressive, but I'm not sure how 30 stretch cycles per second would work, or how expensive it will be.
A sealed tube with about 200 pounds of yarn and enough salt water to saturate it?

5. May 23, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina
But where are you getting the power to stretch it?

6. May 23, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
"In order to generate electricity, the yarns must be either submerged in or coated with an ionically conducting material, or electrolyte, which can be as simple as a mixture of ordinary table salt and water. Fundamentally, the yarns are supercapacitors. In a normal capacitor, energy — like from a battery — is used to add charges to the capacitor. In the new method, when the carbon nanotube yarn is inserted into an electrolyte bath, the yarns are charged by the electrolyte itself; no external battery or voltage is needed.

When a harvester yarn is twisted or stretched, the volume of the carbon nanotube yarn decreases, bringing the electric charges on the yarn closer together and increasing their energy. This increases the voltage associated with the charge stored in the yarn, enabling the harvesting of electricity. Stretching the coiled twistron yarns 30 times a second generated 250 Watts per kilogram of peak electrical power when normalized to the harvester’s weight.

Tests showed that a twistron yarn weighing less than a housefly could power a small LED, which lit up each time the yarn was stretched. To show that twistrons can harvest waste thermal energy from the environment, a twistron yarn was connected to a polymer artificial muscle that contracts and expands when heated and cooled. The twistron harvester converted the mechanical energy generated by the polymer muscle to electrical energy. The researchers also sewed twistron harvesters into a shirt. Normal breathing stretched the yarn and generated an electrical signal, demonstrating its potential as a self-powered respiration sensor."

I have always indicated the need for some battery capacity to be able to receive, store, and release energy at different rates.

7. May 24, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina
But where would you get the power to stretch the yarn?

If you want 250W of electricity out of the yarn, you are going to need to put a minimum of 250W of mechanical power into the yarn.

This is the first law of thermodynamics. It is inviolable.

8. May 24, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina

Inviolable except for one day each April...

Last edited: May 24, 2019
9. May 24, 2019

### proppastie

#### Well-Known Member

Joined:
Feb 19, 2012
Messages:
3,606
1,027
Location:
NJ
I am stuck on the long "nanotubes" the rap is these are incredibly strong, perhaps strong enough for the "sky hook" or elevator to orbit.

10. May 24, 2019

### Dan Thomas

#### Well-Known Member

Joined:
Sep 18, 2008
Messages:
4,724
1,954
I am in my '60s and have been reading about all the "revolutionary" engines proposed since the 1950s. The Wankel rotary is one. In fact, AFAIK, it's the only one that ever made it to commercial viablility. All the others were what is known now as vaporware. I call them wishful thinking or investment scams, and don't put any faith at all in such claims until I see it in action, doing actual work and performing as predicted.

pictsidhe and proppastie like this.
11. May 24, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina
Many 'revolutionary' engines worked fine. They just failed to create a revolt. The Napier Deltic comes to mind. It lived up to claimed performance and worked very well in service once teething problems had been fixed. But, it never caught on.

12. May 24, 2019

### Dan Thomas

#### Well-Known Member

Joined:
Sep 18, 2008
Messages:
4,724
1,954
If it didn't catch on, there had to be some disadvantages to the design. If there's a better design than the typical V or inline or opposed engine it would take over. Capitalist economics and competition dictates that sort of thing. "Better" would mean, for a given HP output, a lighter, smaller, stronger, longer-lasting, better SFC, and cheaper-to-build engine. Not meeting any one of those factors can doom a design.

13. May 24, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
Going back over the article, it seems that the yarn stretches up to 25%, a question would be..... how much of that stretch would be needed to produce maximum power?
Would stretch action over 30 cycles per second cause the nano-fibers to break down?

I'm changing my mind about long twisted bands because that would be a slow cycle. However special design sections of wing spars and longerons might offer the capacitor-like workings they talk about.

If their hype is anywhere near correct it looks like very good potential. I would think of the possible cam action or air flutter actuation of what could be thousands or even tens of thousands of strands inside structural parts of wing and fuselage of an aircraft.

Someone has to speculate

14. May 25, 2019

### bmcj

#### Well-Known MemberHBA Supporter

Joined:
Apr 10, 2007
Messages:
12,634
4,651
Location:
Fresno, California
Is it merely a coincidence that an article about yarn that can be knitted into electricity-generating clothing is published by “Tech BRIEFS”?

I think not.

BJC and pictsidhe like this.
15. May 25, 2019

### pictsidhe

#### Well-Known Member

Joined:
Jul 15, 2014
Messages:
6,203
1,592
Location:
North Carolina
Anything new also has to overcome the inertia of the status quo. Incremental improvements are far easier to accept. Anything radically different is going to be viewed with suspicion by most people. It really doesn't help that many radical inventions aren't viable. Few consumers have the technical acumen to properly assess a new concept, so they stick to what they know. A revolution means significant change. That requires significant motivation.
I'm currently reading a book about the Rolls Royce Crécy. RR came to the conclusion that for the design to be accepted, they would be best off developing it as marine engine until they had the knowledge and experience for it to be a superlative aero engine. It was another revolution, the jet engine, that actually killed the concept.

16. May 25, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
I did find this link that gives a little better coverage.

“Although numerous alternative harvesters have been investigated for many decades, no other reported harvester provides such high electrical power or energy output per cycle as ours for stretching rates between a few cycles per second and 600 cycles per second.”

https://www.utdallas.edu/news/2017/...-Energy-Harvesting-Yarns-Gene_story-wide.html

600 cycles per second, this speed would work well with airflow somewhere around a plane to activate a flutter condition that would cause the stretching of the "Twistron".
I'm thinking the most expensive batteries today would be cheap by comparison, but it might work out that all the power needed would come at the expense of a little extra drag.
Not sure what conditions produced 250 Watts per Kg?

Just spotted the answer.... 30 cycles

Maybe someone can make this clear to me......
Stretching the coiled twistron yarns 30 times a second generated 250 watts per kilogram of peak electrical power when normalized to the harvester’s weight,

Last edited: May 25, 2019
17. May 25, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
18. May 25, 2019

### proppastie

#### Well-Known Member

Joined:
Feb 19, 2012
Messages:
3,606
1,027
Location:
NJ
You forgot "not invented here"

pictsidhe likes this.
19. May 26, 2019

### RonL

#### Well-Known Member

Joined:
Jan 9, 2007
Messages:
449
26
Location:
Texas
Looks like Carbon Nanotubes ("Twistron") is a little above my price range.

"A group of researchers from Universiti Sains Malaysia (USM) have successfully created a new method for producing carbon nanotubes. The new method is capable of reducing the price of carbon nanotubes from $100 -$700 US to just $15 to$35 US for each gram, much lower than world market prices.

The method known as the Continuous Production Method of Carbon Nanotubes using Rotation Reactor is the first ever created in Southeast Asia.

Carbon nanotubes are widely used in the production of end products such as memory chips, rechargeable batteries, tennis rackets, badminton rackets, bicycles, composite to manufacture cars, airplanes and so forth.

The research team leader, Assoc. Dr. Abdul Rahman Mohamed said, a new rotation of the reactor system is designed to enable the continuous production of carbon nanotubes without compromising the quality and authenticity.

"The system is capable of producing up to 1000 grams of carbon nanotubes a day,'' he said.

He added that the developed system is also environmentally friendly as it operates at atmospheric conditions, cost effective and does not require a large space to operate the reactor."