Microwave heating

[Ehouse]

While participating in the below thread on electric resistance heat, I happened across a mint condition Amana Radar Range microwave oven from the 50's in a junk shop and it got me thinking. A quick google search turned up industrial apps. and some heating pads and pet beds, but nothing on domestic heating. Does anyone know of any attempts to use this technology for home heating?

Ehouse

 

[Adabiviak]

I don't, but I'm thinking that's because it's a little inefficient? You get quick localized heating at the cost of some of this efficiency, so applying it to one's entire house seems like it'd be a little wasteful over the long term. That said, I have never designed a system like that, so I suppose it could be done? Run sub-floor water through a microwave system instead of some other heat exchanger? Those heating pads and pet beds were meant to be put in the microwave and then be taken out while hot, no? They weren't using live microwaves, correct?

 

[jimbom]

Imagine a very well insulated box. Water pipe passes through the box. The water is heated in the box. Electric is supplied to the box. So we have cool water and electricity entering the box and warm water exiting. Since the box is well insulated, there is little loss. So the problem becomes the lowest life cycle cost of changing electrical energy into thermal energy.

 

[begreen]

Oh heck, we're organic. Just nuke the interior for 15 second intervals. That will keep you warm. lol But be sure to wear a nylon belt and remove all rings, watches, etc.

PS: don't do this if you have metal fillings, pacemaker, etc.

 

[Ehouse]

I went to Wikipedia and found this breakdown; at 1100 watts input 700watts of energy is transferred to the food (water) for an efficiency of 64%. 400 watts is dissipated as heat. A Scientific American article lists different efficiency nos. and says an electric stove top burner is slightly more efficient at bringing water to a boil. If some or all of that waste heat could be returned to the system it should improve matters. So, here's a hypothetical system:

water enters microwave
microwave heats water /waste heat is used to preheat water supply.
water is moved to holding tank
water is circulated through slab for radiant heating
water returns to microwave being preheated before arrival
repeat.

I suspect this would not be as efficient as a regular electric water heater, however there might be other benefits such as faster recovery time.

I know, I know, I'm looking for a free lunch again. Can't help it.

Ehouse

 

[peakbagger]

I heard that the workers at the defense early warning stations in the artic used to stand in front of the dishes to warm up.

Realistically the Bio-coal plant being built in Maine supposedly uses microwaves to cook the wood

 

[Delta-T]

I heard that the workers at the defense early warning stations in the artic used to stand in front of the dishes to warm up.

Realistically the Bio-coal plant being built in Maine supposedly uses microwaves to cook the wood

there is a tv show my wife likes ...1000 ways to die, who had a story of a gent who would do that, and fell asleep in the dish...woke up dead.

 

[Armoured]

I believe microwaves work very efficiently and quickly with modest concentrations of water, because they excite those molecules in preference to others. This just happens to coincide with many types of food.

Once you switch to things that are pure water or mostly water, they're still quick (because fairly powerful) but not especially efficient. As I understand it...