Typing Recharges Laptops?

TwoSticks writes "Compaq patents a keyboard that captures your kinetic energy. Magnets and coils on each key charge a small battery to augment the big one in your laptop. Standard NYTimes deal: requires free registration. " I'm a bit suspicious but it looks interesting. It might give me an incentive to fix typos anyway ;)

view the patent

you can view the patent here [ibm.com]

http://www.patents.ibm.com/cgi-bin/viewpat.cmd/U S05911529__

- MbM

Re:How much energy is there in your fingers?

Anyone care to hazard a guess how much energy can be extracted from your typing fingers, relative to how much energy the laptop consumes?

Sure. This is actually pretty easy.

• Assume that the force required to press a key is at most 1 N (roughly the force exerted by a 100g weght). More than this and I'm not using the keyboard :).
  
  
• Assume that the keys move at most 1 cm (0.01 m) down when you press them. More than this gets silly.
  
  
• Assume that I hit at most 10 keys per second sustained typing rate.
  
  

Energy per keystroke is force * distance, or 0.01 J. Keystrokes per second times energy per keystroke gives energy per second (or power), which is 0.1 W.

So, it doesn't look like this is viable unless we have *really* low power notebooks :).

Lo battery?

WARNING: Battery power is low.
Save all your work now.

Oh crap!!!

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Power has been restored. You may now resume work normally.
- - -

Estimation

I'm not going to use a keyboard that requires
me to apply more than 5 newtons to a key.
Let's say the key course length is about 2mm.

That's 10^-2 J per keypress, neglecting the losses
in transformation from mechanical to electric
energy.

You need 10 keypresses to get 0.1W of power for
1 second.

Forget about having your notebook run on that
alone. Keyboard power is somewhere between
"little influence" and "neglectable".

Could be more practical for a PDA without a
hard drive, but then the trend for these things
is not to have a keyboard at all.