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By Sensible
#5690
Hot water pumped through radiators is how many houses are heated, right? The water is heated in a boiler using electric or gas burners.... Well how about heating the water using microwave... if it's cheaper to heat a cup of water in a kitchen microwave oven, rather than on a gas or electric stove, then surely it's cheaper to heat the house boiler with a specialy designed microwave thing.

Reward: Fame and fortune.
By DirtpatchSmacky
#10385
well when heating a cup of water, the water is inside the microwave, and everything outside is sheilded, so in order to heat the amount of water used to make a home temperate, would require quite a large microwave unit. Also, im not sure about what effect this would have,, but the particles in microwaved elements degrade after microwaving,, so i would assume that constant microwaving might make the water degrade molecularly to the point that energy)heat) tranfer might be compromised as far as effeciency goes. Its certainlly worth a small mock up trial tho.
By andysmee
#11672
I don't quite understand your reply. Microwaves cause the water to heat by exciting the molecules, I don't remember any degrading going on.

If the microwave generator is as efficient as a metal heating element in converting the electricity to heat in the water then this idea should work.

However, boiling a kettle full of water is still quicker than microwaving a bowl of water so I reckon the gains will be marginal (obviously the power used in a kettle is much more than in a microwave, but it is a smaller package too - no fans, shielding, and generators)

How much energy is lost in heating the element of a kettle itself and never gets conducted to the water (i.e. the kettle is still hot after you pour out the water
By Rishi
#11688
Microwave ovens have an overall efficiency of about 66%. An oven delivering 700 watts microwave energy consumes about 1100 watts input power. On the other hand, an immersion heater delivers 100% energy into the water.

Microwave cannot dissociate water molecules. A simpler solution is to use a radiant heater to heat a room as all the energy will have to be delivered into the room. The disadvantage is that the heat distribution tends to be directional.

rishi
By imadvd
#13117
the magnatron i looked into has an effeciency rating of about 70%. i would like to know weather resistance heating has a greater or lesser value. Hmmm? how would this compare to the cost of kw/hr or cubic foot/hr of natural gas...
By Rishi
#13146
imadvd wrote:the magnatron i looked into has an effeciency rating of about 70%. i would like to know weather resistance heating has a greater or lesser value. Hmmm? how would this compare to the cost of kw/hr or cubic foot/hr of natural gas...

If the heating is by using electricity, the cheapest way is to use a heat pump. In effect a refrigerator in reverse. Have the evaporator outside the house (in the cold) The fluid picks up the latent heat of vapourization, cooling the atmosphere a little more.
The condenser is inside the house where the picked up heat is delivered. Since one is only moving heat and not creating it, a 1 kw heat pump can deliver about 3 kw heat.

There is no violation of the first law, since the energy is used to move the heat from a lower temperature level to a higher temperature one and not for creating heat.

rishi
By BernardII
#23229
I am not sure exactly how you are thinking of utilising microwaves to any advantage here. Microwaves, when used for cooking, are basically radio waves around 2.4GHz, which is a good absorption frequency for water molecules. This is why it is good for cooking. It penetrates objects and heats the water within them throughout the object. Like any radio wave it will not pass through metal and will not heat objects that are not electrical conductors. Of course it can cook humans as well as any other meat so these high energy radio wave need to be "contained" in a metal box.

As it uses electrical energy to make microwaves, and not with 100% efficiency, it would not seem practical to use them for heating water (say) as it is much more efficient, and less hazardous, to simply use an immersion heater.
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