When I was younger, the dynamo flashlight was a fairly common product. Usually it would consist of an electromagnetic generator, a lightbulb, a flywheel for energy storage and a lever with some sort of clutching mechanism. One would squeeze the lever into the body of the device to add power, then allow it to extend again. This could easily be operated with one hand, even wearing mittens, as one simply closes and opens the gripping hand.
Nowadays, I’d be vaguely annoyed at any generator that didn’t provide an outlet. I’ve been on the lookout for a handheld generator, and while lots are available, most are simply hand cranked. Those require much finer manipulations, and tend to end up with obvious inefficiency as our arms just aren’t unlimited rotary joints. Besides that, frequently the device itself it downright fragile, which doesn’t mesh well with the concept of applying force to get it to work at all. I’d like something different.
I finally found one; the Revolve xeMicro. It looks like a decent enough product, but I’d prefer a european plug if the device is to have AC input. I’ll keep looking a bit.
A nice little article on hackaday pointed out this possibility. A commenter linked to a commercial offering of the same thing called Manual Power. This has a configuration which appeals to me; there’s no crank, in fact no externally moving parts, and it doubles as a decent training device. I’ve had the opportunity to test one without the power harvesting feature. One for the wishlist, or perhaps when I have money to spare.
I heard of the Potenco pull-cord generator through the One Laptop Per Child project. It has a rather impressive power output, at the cost of requiring two attachment points; though one could allow one to be static, say, tied to the backpack or held underfoot. Unfortunately, it isn’t available for purchase – and I’m not inspired with much hope when the FAQ hopes for this to change mid-2009, over a year ago.
Linear motion harvesters
Kinetic energy harvesters like nPower PEG rely on some internal moving weight, typically a magnet sliding through a coil. I’ve seen flashlights of such design, and while most of them are rather inefficient, it could have the advantage of being passively usable. The suggested example is attaching it to a backpack, thus converting a little energy from each step. Again, however, this particular model doesn’t seem available to purchase.
As usual, I would dearly love suggestions of further options!