Since bigsleep's anno, below I have been pondering the frictionless conversion of mechanical into heat energy. In lots of places, deforestation is driven by need for cooking fuel. Cooking over wood or charcoal is smoky and slow. If there could be a pedal powered hot plate that would never wear out this would be a huge boon.
This would be a plate affixed to magnets that would spin like a potters wheel. I suspect faster spinning would be better and there would be a pedal or crank. The simplest version would be a stand over the spinning magnets (maybe enclosed in plastic to keep them clean) on which you would put your pan or wok. The pan would be heated via induction and you would cook.
One level up of complexity involves an element designed to be heated well by induction. It seems like people use aluminum. Wouldn't nichrome be better? It is an alloy which heats up a lot with current. The pan would sit atop this.
Third level of complexity would be a heat reservoir. For most cooking the wok or pan is itself the heat reservoir. It cools off fast when you put the food in. This reservoir heats up and then stays hot as you cook, so you don not need to pedal the whole time. You could get one of the kids to spin it up to heat while you prepare ingredients.
Bonus: no flames means no smoke and much less fire risk.
Bonus 2: Moving parts could be bike parts: easy to fix almost anywhere in the world. The magnets could be speaker magnets: easy to replace if the field got weak with age.
Problem: I do not have a good feel for the amount of energy needed to heat a pan vs the amount easily generated by a pedal. If you would need to pedal for hours to get the pan hot that would not be good.
//creating a large drag on the rotor and heating the plate//
A regenerative system could make a nice cup of tea. — bigsleep, May 31 2015 [delete]-- bungston, Jun 07 2015 A hot plate typically draws 1000 to 1400 watts.
A Tour de France cyclist typically generates 300 to 350 watts. Joe Average on a bicycle will go over 150 watts only in short bursts.
(And remember: muscles generate heat, too - and they're only 18-25% efficient. So the power peddler will be heating up, but won't have the cyclist's breeze cooling their body down... )-- lurch, Jun 07 2015 [lurch], a typical hot plate is not an INDUCTION cooker. A lot of those watts get wasted. However, even allowing for greater heating efficiency, the numbers still probably don't work out well enough.-- Vernon, Jun 07 2015 What is needed to really do the math is cost: how much a watt of human work is worth and how much a watts-worth of cooking fuel is worth. Or: how many watts of human work are expended collecting cow chips or branches or other fuel that can be had for free.
Lurch thank you for the math. It makes me thing the heat reservoir type might be better as cumulative work will be stored as heat.
Re peddler heating up: also a problem and it makes me thing more efficient is better. Maybe a full on bike connected as opposed to some puny push pedal.-- bungston, Jun 07 2015 [Vernon] - //a typical hot plate is not an INDUCTION cooker.// A typical house does not contain an induction cooker; [bungston], in his last paragraph, admitted to not being right on top of appliance power requirements, and induction cookers are purchased primarily by people who are very sensitive to such requirements.
An induction cooker will be usually rated at 1300 to 4000 watts; they will commonly operate at 400 to 700. The higher rating is because they exhibit far lower impedence when cold (less resistance to eddy currents), so you have to run them at high power to get the ferropottery warmed up to the efficient low-power temp. The induction cooker requires AC current; it is optimized for the frequency of the power supply on which it will be used.
So, to explain the basic problem in relation to induction cooking would be far more complicated and difficult than using a simple resistive element of similar demands, with no particular benefit.-- lurch, Jun 07 2015 //The induction cooker requires AC current;// and, typically, between 120 and 240 V voltage.-- MaxwellBuchanan, Jun 07 2015 random, halfbakery