Energy harvesting

Hello,

let's say I want to light a led (steady, not flashing) of some hundred mW. I'd like to use a magnetic energy harvesting method, for example the classical strong magnet into a coil (suggestion about other e. harvesting method are welcome; no thermal or solar, though).

Given the following condition (estimated) for the magnet movements:

frequency of oscillation: 1 Hz acceleration: 1 m/s^2 max velocity: 1 m/s

I want to estimate the dimension of the magnet and of the coil to produce the needed energy. I bet they will quite large... but I need just an order of magnitude.

Here another way to see the problem. Given the coil:

length: 50 mm internal diameter: 10 mm # of turns: 300 wire diameter: 0,1 mm

and given the magnet:

material: neodymium shape: cylinder diameter: 10 mm length: 10 mm

and given the information above about its movements, how much energy the system could provide? I'm interested to a rough value: 10 uW, 100 uW, 1 mW, 10 mW etc...

Thanks in advance for any answer Marco

Reply to
Marco Trapanese
Loading thread data ...

google "shake light"

The problem you will have is you *still* need storage of some sort (lest the light blink).

Reply to
D Yuniskis

Il 06/03/2010 18.54, D Yuniskis ha scritto:

Yes, that's true. A supercap for example.

But at the end the energy provided must be enough to power the load even with the storage unit. Otherwise the led will turn off after some time.

Marco

Reply to
Marco Trapanese

New devices use a small Li cell. And, when *that* dies (refuses to accept charge) you throw the thing away!

Reply to
D Yuniskis

Il 07/03/2010 19.58, D Yuniskis ha scritto:

So, what's the advantage of the Li cell instead of the supercap?

Any rough values for sizes of magnet and coil to obtain some hundreds mW? Just to know how big should be the "torch".

Thanks! Marco

Reply to
Marco Trapanese

Marketing! Pick up one of the Li cell shake lights, shake it for a few seconds, turn it on: "WOW! LOOK HOW BRIGHT THAT IS!!!" (Li cell undoubtedly still has a charge from the last person who shook it or from the factory, etc.)

Let it sit, unused, on a shelf for a year (after all, it is just for EMERGENCY USE, right?) and wait for The Big Disappointment when you shake the sh*t out of it and find *nothing*! :>

The same is true of the "crankable" flashlights now en vogue.

I've debated whether replacing their Li cells with supercaps would be a step in the right direction or just a different sort of failure waiting down the road.

(I have a "squeeze" light that works well -- all the energy is stored mechanically -- but it gets tiring to use)

No idea. I was pointing you at the shake lights thinking you could get an idea from them (physical size, etc.). I have seen them in sizes similar to a "2 D-cell" flashlight and a "2 C cell" flashlight. Both used Li cells and both had LED emitters. (seeing one with an incandescent lamp would be more telling)

Reply to
D Yuniskis

Il 08/03/2010 19.08, D Yuniskis ha scritto:

Ok, I got it.

No problem, thank you.

Marco

Reply to
Marco Trapanese

100g Nd magnet dropped through 1 m height. Max energy = mgh = 0.1 x 10(approx) x 1 = 1 Joule Do it once a second and you get 1W
--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
 Click to see the full signature
Reply to
Dirk Bruere at NeoPax

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.