Hot pot vs microwave

[gar]

110802-1005 EDT

I ran an experiment on the input energy to heat 1 quart of 75 F tap water to 200 F in a hot pot, with direct heater contact to the water, vs a GE microwave oven.

The hot pot was almost 100 % efficient in heating the water. This means the input electrical energy was just slightly more that the theoretical energy to heat the water. The microwave required about 2.25 times as much energy as the hot pot. Cost was less than $ 0.01 for the hot pot and about $ 0.02 for the microwave.

Does this mean you should use the hot pot instead of the microwave? Probably not.

This was just an interesting experiment and probably does not extrapolate to a roast in the microwave vs a standard oven.

.

 

[K8MHZ]

110802-1005 EDT

I ran an experiment on the input energy to heat 1 quart of 75 F tap water to 200 F in a hot pot, with direct heater contact to the water, vs a GE microwave oven.

The hot pot was almost 100 % efficient in heating the water. This means the input electrical energy was just slightly more that the theoretical energy to heat the water. The microwave required about 2.25 times as much energy as the hot pot. Cost was less than $ 0.01 for the hot pot and about $ 0.02 for the microwave.

Does this mean you should use the hot pot instead of the microwave? Probably not.

This was just an interesting experiment and probably does not extrapolate to a roast in the microwave vs a standard oven.

.

Very cool experiment!

Now try the same with just a pan of water on an electric stove. I'll bet you fall far short of 100 percent efficiency using that method.

When it comes to microwave vs. convection oven, I'll bet the microwave wins by several margins.

 

[Npstewart]

I would say that the hot pot is just more effective at heating the water just due to the design. The microwave is made for food with water molecules inside, the hot pot is made for liquid. No mater what, it always takes the same amount of energy to increase water temperature because:

q = m(DT)Cp
where:
Energy=mass X temp difference X Specific Heat

As seen above, nor microwave (or) hot pot is a variable in the equation, but efficiency is always a variable.

 

[zog]

Gar, you have too much time on your hands my friend

 

[John120/240]

Yes he does have too much time, but the results are interesting.

 

[gar]

110802-1317 EDT

zog:

This is one of a number of experiments I am including in notes I am writing on Energy Measurement and Ways to Reduce Your Electric Bill.


K8MHZ:

I think your guess about a pan on the stove is correct. It should be somewhere between the hot pot and the microwave.


Npstewart:

The thermal capacity of the water was the one constant between the two tests. The heating element is in direct contact with the water in the hot pot. This does two things. It provides direct thermal contact between the heating element and the water, and provides a lot of agitation of the water.

The microwave does not need agitation because it more or less simultaneously interacts with all the water molecules.

The microwave has poor efficiency between input AC power and RF power output, and also poor coupling of the RF energy to the water.


New subject:

Last night's event. Clear sky (no storm), and a hot day for us (90s). At 1930 the power failed. After a few minutes it was clear it would be off for a while. Setup my generator to keep the freezers, refrigerator, and a few other things working. Called the DTE automated system and entered my report. An hour or more later I went out to see if DTE was at the substation. No, but the phone company was setting up portable generators. Drove to the shop and connected to the Internet to view the outage area. 1500 houses or business were out. Found some DTE trucks in one area. It is now very dark. What I noticed was that practically no houses had generator capability. I doubt that in this area there are more than 100 generators. House prices range from about 150,000 to over 3,000,000.

About 2345 after the news I drove by the substation again and there was some activity. Obviously no big (heavy --- transformer) failure. When I got back home I was going to shutdown the generator (very noisy), but just at that time power was restored. So I did shutdown the generator, and could sleep the remainder of the night. Normally I don't like the freezers off more than about 3 hours.

The DTE automated system and outage map is quite good. The map provides a very easy way to see the extent of the problem and thus from that you can make some judgement on timing of a solution.

One point of this discussion is that you electricians that are looking for work might start a major effort to sell generators to the masses that lack this capability. I think my 7% guess on how many generators are in my area is probably high.

.

 

[glene77is]

GAR,
I am so glad I checked in today.
It is good to see that you can start something interesting. :lol:

 

[marti smith]

Gar,

I think this is a great experiment, although my thoughts go to the time variable. If I cook a roast in the oven for 3 hours vs. the crock pot for 6 hours, I suspect the crocker will win, which is good, as I want it ready when I walk in the door. But if you really want a challenge, prepare a two meals, identical, without time to be factored in, and determine which is the least consuming of electrical energy. You will end some some serious debates that have occurred in my kitchen.

 

[K8MHZ]

Gar,

I think this is a great experiment, although my thoughts go to the time variable. If I cook a roast in the oven for 3 hours vs. the crock pot for 6 hours, I suspect the crocker will win, which is good, as I want it ready when I walk in the door. But if you really want a challenge, prepare a two meals, identical, without time to be factored in, and determine which is the least consuming of electrical energy. You will end some some serious debates that have occurred in my kitchen.

I

I have a small crock pot that I can run on low off a 75 watt inverter plugged into the acc (cigarette style) 12 volt receptacle in my Caravan.

On high it uses twice as much, so I can't keep it on high with the tiny inverter.

So, plugged into the house, it will use 150 watts, or .15kwh per hour. Keeping it running on high for 6 hours will use .9 kwh of energy. At my rate of 12.4 cents per kwh, 6 hours would cost 11.16 cents.

Of course, larger crock pots will use more energy, but all of them seem to be very energy efficient as they don't heat much of anything but the food. A regular oven has to heat about a cubic yard of air and several pounds of metal in addition to the food.

On edit:

I finally came across a website from a power corporation in New Zealand that gave a chart of appliances and the power they use. According to their chart a crock pot has a wattage of approximately 220 while both an electric oven and stove have a wattage of 3,000. I guess that answers my question. I cook with gas, so I'm not really sure where that leaves me.

http://planetgreen.discovery.com/food-health/try-using-a-crock-pot-for-ener.html

 

[dereckbc]

Well the Hot Pot uses a resistive element right? It is also deigned to not loose much heat in the exchange right? A resistive heating element is pretty close to if not 100% efficient at converting electric energy to heat energy. About the only wasted heat would be in the wiring and cord.

Microwave on the other hand is a radio transmitter, and the best efficiency you can have is a Class C amplifier of about 75%, plus the power supply and control circuitry losses.

Now what would be interesting is the efficiency of an Induction Stove Top. I hear they approach 80% or better. I mean who can live off boiled water. Man has to have something fried in grease to survive.:lol:

 

[gar]

110802-2002 EDT

K8MHZ:

For a long heating period the internal contents of a heating device is not the major factor in the energy consumed. Rather it is the external surface area, insulation between inside and out, and the heat transfer coefficient of the exterior of the heating device enclosure.

The crock pot is smaller than an ordinary oven. Thus, the crock pot thermal resistance inside to outside is probably much greater than the oven. Lower thermal resistance means more input energy for the same internal temperature.

Both devices will be thermostatically controlled. Thus, average power used for steady state conditions may be much less than predicted by the power rating of the device.

.

 

[Open Neutral]

A) For more phun, calculate the power output of the microwave by the temperature rise of the water. Contrast to the Kill-a-Watt reading of input power consumed.

B) Three hours, Gar? Are those the freezers with the corpses from Area 51? Please do keep them cold as if they thaw....

C) The only generator it makes sense for Jill Winecooler and spouse to install is natural gas fueled. It might work when needed, and is not the fire hazard of 10 gal of gasoline in the garage, etc.

D) Which telco showed ASAP up with generators? I assume these are for remotes aka SLC's or more pedantically DLC's. Around here, Verizontal would think about doing so after folks were down for a day or two.

 

[gar]

110803-1621 EDT

Open Neutral:

A) That is how the experiment was run.

B) The internal air temperature rises about 20 F in three hours. Too much valuable food to let it get much warmer. The internal temperature within a frozen item will be lower, but why allow the surface of these items start to thaw? These are not new efficient freezers, but are reliable (work even when their ambient is 0 F). One of the two is about 40 years old. The other is a used one for $35 of unknown age. Neither has ever been serviced. The energy consumption is about twice that of a new efficient unit, but they run with no problem. No Chinese parts.

C) Typically I have 15 or more gallons of gasoline. The generator is a portable and can be moved to keep different locations functioning with heat and refrigeration.

D) Comcast were the ones near the substation. AT&T is the POTS supplier. Neither of these companies provide good service. Probably getting worse.

.

 

[Open Neutral]

C) Storing that much gas may get you in a conflict with the fire marshal. I hope you have an outdoor shed for such. It's also a PITA since it has a low shelf life.

I'd get worried at ~90% of the homeowners doing so.


D) [Rotten Service] No, really? I'm shocked, just shocked. Six sigma is now, if anything, a paint color. The only thing I can say is Verizontal is up there in the same crowd. Many a day I dream of Ahrnold and his Minigun making an office visit for me.