# is a hand-powered/wind-up food warmer possible???

#### jsca

Joined Apr 30, 2007
6
i'm currently working on a project whereby i'm trying to make a food warmer more eco-friendly. i thought of using a dynamo to power a heating element hot enough to warm up food. i was just wondering whether this is possible? i've seen a lot of wind-up torches, bicycle lights, battery/phone chargers etc...but i doubt the same dynamo used in those applications would be able to power a heating element...or would it?

also...is a spring-driven generator which uses a high carbon tensile steel spring similar to a dynamo?

i'm open to any suggestions!

#### beenthere

Joined Apr 20, 2004
15,819
It may not be practical from the demands on the user. Say that to heat some quantity of food - not cook it - takes 10 minutes with 100 watts of power. That would require the user to input that amount of energy, plus the loss due to storage and conversion inefficiency.

I haven't run any numbers, but it sounds like the bulk of any spring large enough to store that amount of power plus the generator would make the device pretty massive. Take a look at the springs needed to rotate a lighthouse beacon or the ones that run the clockwork in Big Ben. Neither require anything like 100 watts of output, although the run time is something like 24 hours.

#### SgtWookie

Joined Jul 17, 2007
22,210
1 hp = 745.7 Watts = 550 ft lb/Sec = 33,000 ft lb/min
So, 100 W per minute for ten minutes would be 44253.7 foot lbs of energy.
Making it more manageble, 88.5 lbs lifted 500 feet or 44.25 lbs lifted 1000 feet would be equivalent.
But then, you have the conversion losses beenthere mentioned - and then there's the nagging problem of thermal loss by radiation, convection and conduction that will cool the food while you're trying to heat it up.

#### Cornelius

Joined Mar 17, 2008
19
If you want to go with power that matters, a windgenerator would be the way to go; say, with a propeller at least 4 feet. Making the generator from scratch, DIY like, would be the best way to go. (Get some NeoDyn magnets, wind coils, cast the stator in epoxy, carve the blades out of wood etc.)

Not very portable though, but eco-friendly...

(Sorry, i misunderstood the original question... )

#### Caveman

Joined Apr 15, 2008
471
i'm currently working on a project whereby i'm trying to make a food warmer more eco-friendly. i thought of using a dynamo to power a heating element hot enough to warm up food. i was just wondering whether this is possible? i've seen a lot of wind-up torches, bicycle lights, battery/phone chargers etc...but i doubt the same dynamo used in those applications would be able to power a heating element...or would it?

also...is a spring-driven generator which uses a high carbon tensile steel spring similar to a dynamo?

i'm open to any suggestions!
Think more basically here. You want to heat stuff in a more eco-friendly manner. I'm assuming you mean in an energy conservation sense as opposed to just using natural materials to build it. Fortunately all processes that convert energy from any form back to heat work 100% efficiently. But they are the only ones that do so. However, the other forms of energy conversion generally lose the energy as heat.

So, you really just want to convert the energy directly to heat. That is most efficient. But if you want to go through the electrical route, you can get the same energy efficiency by collecting the excess heat from the dynamo as well. Also, you need to insulate well so that the heat is not lost during the cooking process as well.

#### jsca

Joined Apr 30, 2007
6
you lost me there when the numbers kicked in! but it sounds like where i'm headed with this hand-powered heating element doesn't seem quite doable. what i was actually thinking of was to design a portable container (mainly to be used in the kitchen) of some sort that would have a heating element in it. it would be sealed and insulated well so that no heat gets lost. what i had in mind was that you put the food you want heated up into the container and then hopefully get the food warmed up by winding up the dynamo which produces a current to get the heating element working.

i also thought of using a heat lamp powered by a hand-driven dynamo to heat up the food (again the heat lamp would be enclosed in a container). but then heat lamps aren't exactly very eco friendly cos they're still a form of incandescent light bulbs!

so do you guys reckon what i've proposed won't work? i guess what i'm trying ask is if any hand-driven dynamo would be able to power any heating device (heating elements, heat lamps, etc)?

p.s. would it help if there was a battery or capacitor that stored the energy generated by the dynamo?

#### beenthere

Joined Apr 20, 2004
15,819
Solar energy might hold more promise. There is at least one energy farm in the desert (perhaps Arizona) the uses arrays of parabolic troughs to heat some working fluid enough to make steam in a heat exchanger. The thought is to be able to store solar heat at a high enough temperature and in sufficient quantity to heat food.

Make a breakthrough and maybe you can cook with it. Really good insulation would help.

#### jpanhalt

Joined Jan 18, 2008
10,063
What's wrong with eating cold soup, bread, or whatever? Even a windmill has eco costs, when all costs are considered. John

#### mrmeval

Joined Jun 30, 2006
833
http://solarcooking.org/plans/

What's wrong with cold is that you cannot kill the germs, the taste is not as good and it is not as satisfying. Solar cookers and ovens are used in poor countries with good results.