Energy harvesting
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From: D Yuniskis on 8 Mar 2010 13:08 Marco Trapanese wrote: > Il 07/03/2010 19.58, D Yuniskis ha scritto: > >> New devices use a small Li cell. And, when *that* dies >> (refuses to accept charge) you throw the thing away! > > > So, what's the advantage of the Li cell instead of the supercap? 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) >>> 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. > > Any rough values for sizes of magnet and coil to obtain some hundreds > mW? Just to know how big should be the "torch". 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)
From: Marco Trapanese on 8 Mar 2010 14:19 Il 08/03/2010 19.08, D Yuniskis ha scritto: > 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*! :> Ok, I got it. > No idea. I was pointing you at the shake lights thinking you > could get an idea from them (physical size, etc.). No problem, thank you. Marco
From: Dirk Bruere at NeoPax on 9 Mar 2010 04:07
On 06/03/2010 10:38, Marco Trapanese wrote: > 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 > > 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 http://www.theconsensus.org/ - A UK political party http://www.blogtalkradio.com/onetribe - Occult Talk Show |