Using an Electric Tea Kettle to Save Propane ?

[MarkSF]

Originally Posted by kombivan

and so is diesel hair shampoo petrol vasoline wd40 thinners paint sinkers everything around us has issues but I like a warm shower and I like clean dishes. I also don't drink hot water. But if you have to boil it to purify it for drinking I am sure the impurities will seperate.

The boiling point of DEHP is 385C, so all that boiling the water will do is RAISE the concentration, by boiling off some of the water as steam.

[northwestsailor]

We bought a cheap induction hot plate from China and wife loves it. Now wants a spare.

[zboss]

Originally Posted by northwestsailor

We bought a cheap induction hot plate from China and wife loves it. Now wants a spare.

I've looked at those - 1500 watts. Do you find you run them at 1500 watts or a lot less? About how many Ah do you pull a day from using it?

[zeehag]

btw--has anyone said yet that propane is actually cheap fuel??
doesnt cost much.
"3rd world" runs on propane so availability is not problem.

[sailorchic34]

Propane has a heat rating of 21,600 btu's per pound of fuel (91,000 btu per gallon). It actually varies a bit from location to location. Butane is 21,300 btu per pound, which is pretty close to propane.

The typical galley stove burner is rated at 6500 or 7000 btuh. The energy required to heat one quart (~liter) of water from 45 degrees to 212 degrees is roughly 347 BTU's or 0.101 KWh.

The nitty gritty is a resistive immersion heating element will give you right near 100% eff. That is all the heat goes to the water. A kettle on the stove is probably only capturing 40% ( my WAG or wild a$$ guess of heat transfer efficiency) of the heat of the burner. It could be less then that, probably not much more. Most of it is going around the kettle, heating the stove top, etc.

So right off the top, the propane will need about 868 BTU's per quart (~liter), which with propane being $3.50 a gallon here would be roughly 3.48 cents of propane.

Electrical cost in California at 0.16 cents per kw would be 1.61 cents if your paying for electric use. Of course an electric stove would have similar efficiency's of a gas stove. So if your heating the kettle on an electric stove the cost rises to 13.8 cents (ouch).

But a kettle with an immersion heating coil would be very efficient.

[barnakiel]

If your inverter is big enough, it can be done. Also at sea, on a less rolly day. Make sure you build a gimballed holder if you want to boil water at sea or in a rolly anchorage.

There are 12 / 24 Volt kettles too. (e.g. WAECO)

PS Mind the initial power of the kettle that can be way higher than its specs at the very start.

b.

[northwestsailor]

Originally Posted by zboss

I've looked at those - 1500 watts. Do you find you run them at 1500 watts or a lot less? About how many Ah do you pull a day from using it?

Since my wife does most of the cooking, I would have to ask her for specifics but I don't think she runs it at full tilt, and if so not for long. We do have an electric kettle for boiling hot water which is great to have. But for all other cooking we use the induction stove.

I don't know how many Ah we use because we have a large 960 w solar panel array which keeps the batteries at full charge all day.

[northwestsailor]

Originally Posted by zboss

I've looked at those - 1500 watts. Do you find you run them at 1500 watts or a lot less? About how many Ah do you pull a day from using it?

Since my wife does most of the cooking, I would have to ask her for specifics but I don't think she runs it at full tilt, and if so not for long. We do have an electric kettle for boiling hot water which is great to have. But for all other cooking we use the induction stove.

I don't know how many Ah we use because we have a large 960 w solar panel array which keeps the batteries at full charge all day.

[barnakiel]

You will find Watts / degrees / time calculators online.

If I remember well, a 200W kettle boils 1 liter of water in about 30 minutes. Water 0 degs at the start 100 degs at boil. Scalable too.

Scale it up (you can) and a 2000W kettle will do this in 3 minutes. (Again from zero degs centg)

2000W will take out some 8 Ah out of a 12 Volt battery in same time. More if small battery (Peukhert)

Etc. Get the exact formulas from the web to make accurate calcs. The above very rough and from the top of the battered head.

Cheers,
b.

[barnakiel]

OK.

I have right now boiled 0.5 liter of 25 degs cent water (to the boiling point at the water level, press 1024). 1 minute and 30 seconds.

5Ah out 12 Volt battery, 0.5 liter over 75 degs cent. Conversion losses included.

b.

[hpeer]

Originally Posted by sailorchic34

Propane has a heat rating of 21,600 btu's per pound of fuel (91,000 btu per gallon). It actually varies a bit from location to location. Butane is 21,300 btu per pound, which is pretty close to propane.

The typical galley stove burner is rated at 6500 or 7000 btuh. The energy required to heat one quart (~liter) of water from 45 degrees to 212 degrees is roughly 347 BTU's or 0.101 KWh.

The nitty gritty is a resistive immersion heating element will give you right near 100% eff. That is all the heat goes to the water. A kettle on the stove is probably only capturing 40% ( my WAG or wild a$$ guess of heat transfer efficiency) of the heat of the burner. It could be less then that, probably not much more. Most of it is going around the kettle, heating the stove top, etc.

So right off the top, the propane will need about 868 BTU's per quart (~liter), which with propane being $3.50 a gallon here would be roughly 3.48 cents of propane.

Electrical cost in California at 0.16 cents per kw would be 1.61 cents if your paying for electric use. Of course an electric stove would have similar efficiency's of a gas stove. So if your heating the kettle on an electric stove the cost rises to 13.8 cents (ouch).

But a kettle with an immersion heating coil would be very efficient.

A thread elsewhere measured it empirically at something less than 40% Say about 35%.

[StuM]

Originally Posted by barnakiel

2000W will take out some 8 Ah out of a 12 Volt battery in same time. More if small battery (Peukhert)

<Pedant mode>
Strictly speaking, it will be the same Ah out regardless of battery size. But since you are drawing at a higher "discharge rate", the reduction of capacity remaining in the battery will be greater for the smaller battery because of the Peukert effect.
</Pedant mode>

But the result is the same, the smaller the battery the bigger the reduction in remaining capacity whichever way you look at it

[StuM]

Originally Posted by sailorchic34

Propane has a heat rating of 21,600 btu's per pound of fuel (91,000 btu per gallon). It actually varies a bit from location to location. Butane is 21,300 btu per pound, which is pretty close to propane.

The typical galley stove burner is rated at 6500 or 7000 btuh. The energy required to heat one quart (~liter) of water from 45 degrees to 212 degrees is roughly 347 BTU's or 0.101 KWh.

The nitty gritty is a resistive immersion heating element will give you right near 100% eff. That is all the heat goes to the water. A kettle on the stove is probably only capturing 40% ( my WAG or wild a$$ guess of heat transfer efficiency) of the heat of the burner. It could be less then that, probably not much more. Most of it is going around the kettle, heating the stove top, etc.

So right off the top, the propane will need about 868 BTU's per quart (~liter), which with propane being $3.50 a gallon here would be roughly 3.48 cents of propane.

Electrical cost in California at 0.16 cents per kw would be 1.61 cents if your paying for electric use. Of course an electric stove would have similar efficiency's of a gas stove. So if your heating the kettle on an electric stove the cost rises to 13.8 cents (ouch).

But a kettle with an immersion heating coil would be very efficient.

Absolutely spot on!

[StuM]

Originally Posted by barnakiel

If your inverter is big enough, it can be done. Also at sea, on a less rolly day. Make sure you build a gimballed holder if you want to boil water at sea or in a rolly anchorage.

There are 12 / 24 Volt kettles too. (e.g. WAECO)

PS Mind the initial power of the kettle that can be way higher than its specs at the very start.

b.

But I'd stay away from those 12V "trucker" mug immersion heaters that you see on Ebay for a couple of bucks. Every review that I've seen of them is that they are a cr*p and take forever to heat a mug of water.


(As an aside, none of my cooking appliances are gimballed )

[sailorchic34]

Originally Posted by hpeer

A thread elsewhere measured it empirically at something less than 40% Say about 35%.

That sounds like a nice number. I used 40% as a WAG just from experience with burner efficiency etc. Close enough. Of course, it will vary a bit depending on burner width,flame spread, o2 mix, pan support material and width and the shape of the kettle.

I suspect an inductive griddle on electric might get the efficiency up a bit. But an electric kettle with immersion element probably gives the best efficiency.

Of course, if one had to run the genny to boil water, then your loosing engine efficiency, generator efficiency before you even get to the stove or kettle. So that would factor into diesel or gas usage.

A pretty fun little question.