Ideas for collecting back energy

[OAQfirst]

While cooking, I noticed how much heat energy is lost using the grill. Isn't there some way to rig up the stove so that the heat from the coils on their underside is collected? Can't stoves be made more efficient this way? If I could, I'd have numerous collectors throughout my apartment. Heck, even the heat from some bulbs should be transferred.

It looks like there is so much energy lost all around us.

 

[Pythagorean]

While cooking, I noticed how much heat energy is lost using the grill. Isn't there some way to rig up the stove so that the heat from the coils on their underside is collected? Can't stoves be made more efficient this way? If I could, I'd have numerous collectors throughout my apartment. Heck, even the heat from some bulbs should be transferred.

It looks like there is so much energy lost all around us.

thermocoupling, I guess... which is terribly inefficient itself.

sterling engine would be expensive to build/buy, don't think it would be worth it (don't know if the gradient is enough, even)

I don't think it would really be that much energy because you lose a lot converting it from thermal to electrical and it's not a lot to start with.

Up here in Alaska, it may as well stay heat :P it will just reduce (ever so slightly) your heating bill. Might as well not convert it over and back, losing a bunch of the power.

 

[turbo]

Up here in Alaska, it may as well stay heat :P it will just reduce (ever so slightly) your heating bill. Might as well not convert it over and back, losing a bunch of the power.

My wife and I do a lot of baking in the winter. Baked beans, biscuits, roasts and turkeys... We need to make meals, anyway, and the waste heat from the oven can get this little cabin toasty on a mild day.

 

[Ivan Seeking]

My wife and I do a lot of baking in the winter. Baked beans, biscuits, roasts and turkeys... We need to make meals, anyway, and the waste heat from the oven can get this little cabin toasty on a mild day.

I realized that here in Oregon, CF lightbulbs make little sense as we can use the excess heat anyway. In reality, we are only saving energy about 3 months out of the year. The rest of the time, the incandescent bulbs help to heat the house.

 

[Pythagorean]

My wife and I do a lot of baking in the winter. Baked beans, biscuits, roasts and turkeys... We need to make meals, anyway, and the waste heat from the oven can get this little cabin toasty on a mild day.

It's surprising how much an oven (or incandescent lights in Ivan's case) can contribute to heat in the long-term. I have a friend who turns on his burners and his oven when he runs out of heating fuel!

 

[turbo]

I realized that here in Oregon, CF lightbulbs make little sense as we can use the excess heat anyway. In reality, we are only saving energy about 3 months out of the year. The rest of the time, the incandescent bulbs help to heat the house.

We use CF bulbs here, in part because electricity is so expensive. It's a racket. The dams that supply our electricity were all built many years ago, and hydro-power is very cheap. Maine is an exporter of electrical power because of these dams, but somehow the Public Utilities Commission let's the utilities charge us 'way more than people elsewhere on the grid.

 

[Pythagorean]

In my hometown, we all "own shares" in our electric company (it's also hydro)

 

[Ivan Seeking]

We use CF bulbs here, in part because electricity is so expensive. It's a racket. The dams that supply our electricity were all built many years ago, and hydro-power is very cheap. Maine is an exporter of electrical power because of these dams, but somehow the Public Utilities Commission let's the utilities charge us 'way more than people elsewhere on the grid.

We have cheap hydro power here in Oregon. Even given your arguments that wood heat is environmentally acceptable, it isn't worth it for us, so we're all electric anyway [less emergencies].

We used wood heat for about twelve years, but what a dangerous pain in the butt! We've had a couple of close calls.

 

[Ivan Seeking]

I think the short answer to the op is that it would be too inefficient to try to capture that heat in some usable fashion. It would be cost prohibitive.

 

[OAQfirst]

:rofl: Yeah, so I see. Thanks everyone.

 

[turbo]

We have cheap hydro power here in Oregon. Even given your arguments that wood heat is environmentally acceptable, it isn't worth it for us, so we're all electric anyway [less emergencies].

We used wood heat for about twelve years, but what a dangerous pain in the butt! We've had a couple of close calls.

I have gotten ahead of my firewood to the point that I have about a whole year in reserve. Burn short, hot fires with very dry hardwood in a clean-burning stove, and you can't see smoke coming out of our chimney - just a shimmer of heat-based refraction. I haven't had to clean the chimney since we bought this place. I shovel a bit of creosote out of the cellar clean-out every year and look up the chimney with a mirror - I can see the mortar-joints of every flue-tile all the way up. I can't imagine heating with any other fuel at this point. I have an oil furnace in the cellar, but it's only used if I am going to be away for the day in bitterly cold weather. I have used less than 1/4 tank in three years.

 

[Ivan Seeking]

If we burn the excess wood from our property, then we would burn a lot of fir. Hardwoods can cost $130 a chord, so at that price, electricity is competitive. And since we don't have a stove with an exterior intake, then we are just sucking cold air into the house when we use the woodstove.

I must say though, a load of dry oak can produce an amazing amount of power. I once estimated that we were producing about 100,000 watts of heat at full throttle. When we first moved here, before we learned to control the "thermal momentum", we about ran ourselves out of the house one day. It was twenty degrees F outside, we had the windows wide open, and it still was something like eighty degrees in the house!

 

[Proton Soup]

While cooking, I noticed how much heat energy is lost using the grill. Isn't there some way to rig up the stove so that the heat from the coils on their underside is collected? Can't stoves be made more efficient this way? If I could, I'd have numerous collectors throughout my apartment. Heck, even the heat from some bulbs should be transferred.

It looks like there is so much energy lost all around us.

do you live on a farm?

http://www.hedon.info/FuelEfficientCookstovesUsingCowDungCakes
http://www.repp.org/discussiongroups/resources/stoves/apro/dung/Aprodung.htm

 

[JasonRox]

I think the short answer to the op is that it would be too inefficient to try to capture that heat in some usable fashion. It would be cost prohibitive.

It's not about costs! It's about being green!

Kidding.

 

[turbo]

I pay $65/cord for good-quality hardwood, cut to length, split, and delivered. I have a hydraulic splitter, and I split the wood even finer than it was delivered because we have a really small stove, and it's easier to control the fires with smaller chunks of wood. Small, efficient fires in a well-insulated house keep us comfortable. I don't tighten my house to ridiculous extents - we have to have some air infiltration to keep the place healthy. I insulate the windows to reduce heat losses, but leave gaps around doors, sills, etc, so that the wood fires can draw in fresh air from the outside. It's a balance.

 

[Ivan Seeking]

It's not about costs! It's about being green!

Kidding.

It is ALWAYS about the cost. If it's not practical and cost effective, then almost no one will use it.

Also, dollar cost equates in some fashion to energy cost of production. Many technologies are challenged because the energy input to produce the technology or product rivals the liftetime energy production or savings. This is particularly true of ethanol fuel production, for example. It may take more energy to make ethanol [from corn] than we get back from it as a fuel.

If something isn't cost effective, that can be an indicator that it is not energy effective either. Ethanol production is heavily subsidized.

 

[Proton Soup]

It is ALWAYS about the cost. If it's not practical and cost effective, then almost no one will use it.

Also, dollar cost equates in some fashion to energy cost of production. Many technologies are challenged because the energy input to produce the technology or product rivals the liftetime energy production or savings. This is particularly true of ethanol fuel production, for example. It may take more energy to make ethanol that we get back from it as a fuel.

yes, but have you included taxes on the income for wood you sell? if the biomass on your property has enough turnover to provide your heat, you may be better off to burn it.

 

[Ivan Seeking]

Heh, Jason, I obviously didn't see your hidden "kidding". But the point is still worth making,

 

[Ivan Seeking]

yes, but have you included taxes on the income for wood you sell? if the biomass on your property has enough turnover to provide your heat, you may be better off to burn it.

I don't sell wood. And it takes so much work to get the wood off the hill, I can't even give it away. I have about six chords of uncut fir [from two diseased old-growth trees that we had to drop] laying around now. No one will take it.


When we first bought the place, I liked the exercise, but my feelings about that have changed.

 

[OAQfirst]

do you live on a farm?

http://www.hedon.info/FuelEfficientCookstovesUsingCowDungCakes
http://www.repp.org/discussiongroups/resources/stoves/apro/dung/Aprodung.htm

No. And after reading those sites, I hope it never comes to that. :tongue:

 

[Cyrus]

While cooking, I noticed how much heat energy is lost using the grill. Isn't there some way to rig up the stove so that the heat from the coils on their underside is collected? Can't stoves be made more efficient this way? If I could, I'd have numerous collectors throughout my apartment. Heck, even the heat from some bulbs should be transferred.

It looks like there is so much energy lost all around us.

No. Not even close. You cook on the stove for perhaps an hour, max. The amount of heat lost in that process is trivial.

Probably upwards of 99.99% of the heat goes straight into your pan.

 

[turbo]

No. Not even close. You cook on the stove for perhaps an hour, max. The amount of heat lost in that process is trivial.

Probably upwards of 99.99% of the heat goes straight into your pan.

Not physically possible, nor even plausible.

 

[Cyrus]

Not physically possible, nor even plausible.

Counter argument?

Obviously, 99.99% was tongue-in-cheek. But it would probably be upwards of 80+% transfer.

 

[Gokul43201]

If you are using a standard electric stove, I think the pan only gets about 50% of the heat produced - I haven't noticed any special treatment to the underside of the coils.

 

[Cyrus]

If you are using a standard electric stove, I think the pan only gets about 50% of the heat produced - I haven't noticed any special treatment to the underside of the coils.

Why only 50%?

 

[Gokul43201]

Why only 50%?

The actual thermal contact between the coils and the pan is only a very thin ring at best. Most of the heat transfer from the coils is radiative. The coils radiate about as much heat upwards as they do downwards.

 

[Cyrus]

The actual thermal contact between the coils and the pan is only a very thin ring at best. Most of the heat transfer from the coils is radiative. The coils radiate about as much heat upwards as they do downwards.

The three primary modes of heat transfer are conduction, convetion and radation.

Convection...ehhh. I wouldn't expect the losses to be high. The air near the pan isn't that hot unless you're very close to the pan.

I would expect conduction to be the primary mover of heat.

Radiation...ehhhhhhh. I am not so sure either. If you let the coils get hot and put your hand over it you can get pretty close. And this is both radiation and convection.

 

[Evo]

The actual thermal contact between the coils and the pan is only a very thin ring at best. Most of the heat transfer from the coils is radiative. The coils radiate about as much heat upwards as they do downwards.

What about the reflector pans under the coils?

 

[turbo]

What about the reflector pans under the coils?

Window-dressing mostly. Direct contact between pan and coil is key.

 

[russ_watters]

Hold on a minute here: I think the discussion started with an outdoor cooking device - a grill. Quite obviously, an indoor, unvented cooking device (gas or electric is irrelevant) sends 100% of it's heat into the house. This represents a substantial amount of heat.

 

[Proton Soup]

Hold on a minute here: I think the discussion started with an outdoor cooking device - a grill. Quite obviously, an indoor, unvented cooking device (gas or electric is irrelevant) sends 100% of it's heat into the house. This represents a substantial amount of heat.

yup, if you can't stand the heat, get out of the kitchen

 

[russ_watters]

Now, regarding an electric stove's ability to deliver it's heat to the pan, I suspect the efficiency is above 75%, possibly above 90%. As others have said, conduction is 100% to the pan and represents the vast majority of the heat of the stove. Radiation, due to the reflector plate, is a high fraction (my guess: 75%+). Convection would be considerably lower, certainly below 50%.

 

[OAQfirst]

Eh I'm not too good with words. I did mean a stove - indoor stove. Sorry for the misunderstanding.

 

[russ_watters]

From sears.com, a typical electric range has standard burners of 2500 W (8,500 BTU), gas 9000 BTU. That surprises me - I would think that a gas burner would lose much more due to convection.

 

[russ_watters]

Eh I'm not too good with words. I did mean a stove - indoor stove. Sorry for the misunderstanding.

In that case, the answer's easy: you're already recovering all the heat from cooking and using it to heat your house.