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Comment by deftnerd | Hacker News Reader

This is an interesting alternative to residential induction stoves that use AC to create the magnetic fields.

I wonder what the power usage difference is. This style of heating up the metal instead of using AC current to generate electromagnetic fields could be better for "off-grid" scenarios.

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> This is an interesting alternative to residential induction stoves that use AC to create the magnetic fields.

No, it is not an alternative. It is an inferior method to create the same effect/current with additional losses. As an educational experiment it is very impressive though.

The experiment is not the least bit impressive. If your stove behaved like that, you would throw it out. For the cost of the components, you can buy a new, low-end stove at Home Depot or Lowes. That actually works.

Thus missing the point.

Induction cooker doesn't work on grid AC frequency (50-60Hz), it converts grid AC to DC then converts it to high frequency (24 kHz), so possibly induction cooker can be modified to run straight from DC power

so possibly induction cooker can be modified to run straight from DC power

I ass-u-me that's how the induction stoves in modern RVs/caravans work, rather than wasting house battery inverting DC only to convert it to something else.

EDIT: well, I guess that's why "assume" is hyphenated. According to the company that makes stoves for Winnebago, from their manual: "1. Plug into standard 110 outlet."

most RV's don't have all that hefty of house battery capacity (my parent's house battery is 2 deep cycle lead acid batteries). Heating things takes a lot of power, probably run those batteries down before you got much more than a single kettle of water hot. Anything that's going to use an electric stove is most likely going to have a generator.

Or gets plugged into an outlet at a campground.

That's because running #0 copper gauge is expensive. You use the inverter to go from 24 (or 12)V to 110 or 240, run your standard wiring and then wherever you need power you step back down again. It's far more cost effective that way, and much safer as well because the connections do not carry nearly as much current. Even a small resistance will cause a lot of heat at currents in the 10's or even 100's of amps.

Might be very noisy though, and you're spending extra energy moving the magnets.

You are spending the same energy, plus a few percent loss on the motor's friction/inefficiency.

mind showing the math on this? i really can't see how converting energy twice (ac -> motor -> magnets) can only be a few percent difference in efficiency instead of converting it once (ac -> electric stove).

Using the electric induction stove and rotating magnets achieve the same effect: alternating magnetic field in a ferrous mass. Electric motors have efficiency up to 95%, and there's no further loss in this system.

If you are truly off the grid, you'd come about even using the rotating magnets from mechanical power (say, an ICE) vs converting that power via generator and powering a stove.

I wonder a) if this would "pull" more energy with a traditional steel induction ready pan (not sure about the rate of spin/frequency) - but more importantly b) would this make sense as a pure movement to heat system, using a bike, water wheel or windmill?

How fast, hard and long does one have to pedal to boil a litre of water? :)

I'd prefer a regular wood-burning stove for that. Those can also double for providing heat.

Better not leave your phone in your pocket while you cook breakfast, though.

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