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Charging batteries via multi fuel stove


snaggletooth

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On 20/09/2019 at 10:21, WotEver said:

But we must think outside the box apparently. ;)

 

We all know it’s a dumb idea, which is why no-one does it, but we must discuss it anyway...

 

Quite. Anybody claiming the best way to do something is the, err, tried and tested way lots of people do it already, is by definition a narrow minded and abusive idiot unable to think freely for themselves. 

 

 

 

 

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24 minutes ago, Mike the Boilerman said:

 

Quite. Anybody claiming the best way to do something is the, err, tried and tested way lots of people do it already, is by definition a narrow minded and abusive idiot unable to think freely for themselves. 

 

 

 

 

 

Yes, but at least they have the satisfaction of having something that works reliably and didn't cost an arm and a leg. ?

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If you set up a stove with the back plate clamped to the underwater hull with a TEG sandwiched in between you would have a water cooled generator. It may only be a trickle charge but its silent and requires no maintenance* , no petrol, no engine wear, and produces the most power in the winter as opposed to the opposite for solar.

 

( *though heating the hull plate will cause it to corrode faster ) 

 

The colder it is outside the more you want from your stove and the bigger heat difference there will be on the TEG.

 

 

 

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2 hours ago, CompairHolman said:

If you set up a stove with the back plate clamped to the underwater hull with a TEG sandwiched in between you would have a water cooled generator. It may only be a trickle charge but its silent and requires no maintenance* , no petrol, no engine wear, and produces the most power in the winter as opposed to the opposite for solar.

 

( *though heating the hull plate will cause it to corrode faster ) 

 

The colder it is outside the more you want from your stove and the bigger heat difference there will be on the TEG.

 

 

 

Correct but the teg efficiency is abysmal 5% is good. If you need to circulate water from a skin tank to the teg clamped to the stove, your pump will consume several watts, to get any real charge current say 1 amp at least, you have to transfer about 500 watts of heat through the teg. That is heat lost to the cabin so you burn more fuel which sort of defeats the object. It you pass the heat to a radiator you don't lose the heat but the radiator return is going to be about 30 degrees as opposed to the 10 or so for a skin tank lower temperature difference, lower power out, burn the fire harder to regain the temperature difference back to square one.

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On 20/09/2019 at 16:46, stegra said:

Back to the question. Maybe someone could design a steam turbine that sits on the stove and charges the batteries. The excess steam could be condensed under a dome and provide a nice warm bath full of water. ?

Your behind the time's, They were already around in WW2 for use behind the lines by troops or  used by the SOE (special operations executive). Wartime spies had these dropped behind enemy lines for use in charging and powering wireless sets, My grandfather used one of these when with the 14th Army in Burma. 

 

http://www.royalsignals.org.uk/photos/steam.htm

 

 

 

 

Edited by nbfiresprite
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On 20/09/2019 at 16:59, dmr said:

Just get a really efficient wind generator and put it in front of the ecofan.

That might be a partial solution for the outside the box thread.

 

Stick the bottom of the ecofan in a bath of cold water and spin the fan really quickly with your finger.  The base will then get hot and warm the water.

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On 21/09/2019 at 21:53, nbfiresprite said:

Your behind the time's, They were already around in WW2 for use behind the lines by troops or  used by the SOE (special operations executive). Wartime spies had these dropped behind enemy lines for use in charging and powering wireless sets, My grandfather used one of these when with the 14th Army in Burma. 

 

http://www.royalsignals.org.uk/photos/steam.htm

 

 

 

 

where can i get one. looks great

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On 21/09/2019 at 21:53, nbfiresprite said:

Your behind the time's, They were already around in WW2 for use behind the lines by troops or  used by the SOE (special operations executive). Wartime spies had these dropped behind enemy lines for use in charging and powering wireless sets, My grandfather used one of these when with the 14th Army in Burma. 

 

http://www.royalsignals.org.uk/photos/steam.htm

 

 

 

 

I want one!

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On ‎19‎/‎09‎/‎2019 at 17:53, Chewbacka said:

Having read it again I can see why we all forgot about them - a simple air cooled unit will give at best 45W which is about 3.5A, which is not a lot for the money.

 

On ‎19‎/‎09‎/‎2019 at 18:04, Paul C said:

That's got to be 1% efficiency, maybe 2%?

I fail to understand 'objections' like these.

 

If - and yes it's a big 'if' - there was a gizmo available that could reliably convert 2% of a stove's heat to electricity for battery charging, costing say £500 or less, I'd buy one like a shot. Assuming a stove generated a modest 1.5 kW of heat on average over a 24 hour period (when in constant use over winter), that would be 2% of 36kWh = 720Wh a day. Nobody would question the usefulness of a solar panel generating that amount of power on an average day in summer. And in terms of keeping a battery bank topped up, what could be better than a silent device using essentially 'free' heat to put in a steady 2-3 amps for 12 hours overnight after the engine or generator has to be switched off? (Not that you'd run an engine or generator for an extra 5 hours a day to put in a diminishing 10-8-6-4-2 amps anyway...)

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1 hour ago, magictime said:

Assuming a stove generated a modest 1.5 kW of heat on average over a 24 hour period (when in constant use over winter), that would be 2% of 36kWh = 720Wh a day.

All of that heat being used to power the Teg, with none of it available to heat the boat.  So are you suggesting a second stove just for the Teg?

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42 minutes ago, WotEver said:

All of that heat being used to power the Teg, with none of it available to heat the boat.  So are you suggesting a second stove just for the Teg?

Eh? The 98% of heat not converted to electricity would remain heat.

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8 minutes ago, magictime said:

Eh? The 98% of heat not converted to electricity would remain heat.

Heat transferred to the Teg in order for it to convert an abysmal couple of percent to power. So no, it’s not available to heat the boat as it’s been lost across the Teg. 

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8 minutes ago, WotEver said:

Heat transferred to the Teg in order for it to convert an abysmal couple of percent to power. So no, it’s not available to heat the boat as it’s been lost across the Teg. 

If it’s an air cooled teg then if cooled with boat air you will keep the heat, but as the air temp rises the cooling effect will reduce so the teg output will reduce.  But if water cooling the teg to a skin tank - best for electric generator efficiency - then all that heat is lost.

 

i am ignoring the tiny amount of heat that is converted to electrical energy because (a) it is tiny and (b) you get most of it back as waste heat when using the electrical energy anyway.

Edited by Chewbacka
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7 minutes ago, WotEver said:

Heat transferred to the Teg in order for it to convert an abysmal couple of percent to power. So no, it’s not available to heat the boat as it’s been lost across the Teg. 

Lost to where? Converted from heat to what?

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Just now, Chewbacka said:

If it’s an air cooled teg then if cooled with boat air you will keep the heat, but as the air temp rises the cooling effect will reduce so the teg output will reduce.  But if water cooling the teg to a skin tank - best for electric generator efficiency - then all that heat is lost.

Ah maybe that's what WotEver is picturing then. I was picturing air cooled. I accept it would be bonkers to run a stove just to produce a small amount of electricity while not using the heat.

1 minute ago, WotEver said:

See Chewy’s post above. 

I did! Cross posted.

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2 minutes ago, Chewbacka said:

if water cooling the teg to a skin tank - best for electric generator efficiency - then all that heat is lost.

I assumed we were talking about water cooled as Magictime was referring to 2% of 36kWh. 

2 minutes ago, magictime said:

I was picturing air cooled

Then I’d guess that your 2% would in fact be less than 0.1%. 

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2 minutes ago, WotEver said:

I assumed we were talking about water cooled as Magictime was referring to 2% of 36kWh. 

Then I’d guess that your 2% would in fact be less than 0.1%. 

Really? I don't know, but I was erring on the conservative side of Chewbacka's figure of 45W max from an air cooled unit. 2% of 1.5kW being 30W.

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