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Old 03 March 2012, 17:51   #11
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If you were running a Yammie V6... then I take your point about alternative fuel... but sh*t you could run your 30hp flat out for a day for 35... cheap at half the price.
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Old 04 March 2012, 03:29   #12
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LPG is popular round here for taxis. Simple enough to convert. Wonder what the power would be like? Harder to fill up as you would not be able to take the fuel to boat in a can?
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Old 04 March 2012, 03:35   #13
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Now we are cooking until the government get their hands on it.

http://crave.cnet.co.uk/cartech/uk-r...itre-50002478/
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Old 04 March 2012, 03:38   #14
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Originally Posted by spartacus
If you were running a Yammie V6... then I take your point about alternative fuel... but sh*t you could run your 30hp flat out for a day for 35... cheap at half the price.
Yes agreed. But even at 35 it's a rip off. Fuel at 20p a gallon has a lot more appeal :-)
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Old 04 March 2012, 03:40   #15
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Originally Posted by Leapy
Wonder how much the cost of producing ethanol in low volumes compares to the cost of buying petrol?

S'pose it depends on whether you have a still?
A still can be built for 10 to produce ethanol
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Old 04 March 2012, 04:25   #16
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A still can be built for 10 to produce ethanol
Perhaps it can but I'm struggling with the notion of having to distill a highly volatile compound in a most probably domestic environment every time I want to take my boat out. Too much hassle and risk...boating is about boating for me not playing with a chemistry set.
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Old 04 March 2012, 04:38   #17
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A still can be built for 10 to produce ethanol
I'd be surprised if a 10 still can produce enough ethanol (relatively dry) to be of use as a fuel. A 10 still also will be relatively unsafe device and potentially a good way to kill yourself or at the very least destroy your garage!

I don't know if you can distill fuel without appropriate licenses but I assume the Irish tax man is sensitive about stills that could be used for making drinkable spirit without paying tax.

Assuming you can convert all the energy in raw potatoes into energy stored in ethanol (probably unlikely - but lets assume you could) then 1 kg of raw potatoes has about 3350 kJ or energy. This is roughly about the amount of energy in 140 mL of Ethanol. i.e. it will take at least 7 kg of tatties to make a litre of "pure" ethanol. So unless you are going to grow them yourself (and have a very big field and enough time to do that) or have access to some ridiculously cheap source of tatties I think you will not be able to do it cheaper than petrol.

Worse than that (even if you could find a farmer with half a tonne of tatties to get rid of) is that first you normally boil the tatties. That takes energy. Then you let it cool down (that wastes that energy) so the yeast can do its work, Then you heat it all back up again to boil off (and condense) the ethanol. Now if your giant vat of tatties was perfectly insulated and efficiently heated (and for simplicity assuming the heat capacity of tatties is similar to water) then for each kg of water/tatties it is going to take about 0.1 kWhr to bring it up to boiling. Assuming you have equal quantities (by mass) of water to tatties that would be 1.4 kWh just to do the first stage of bringing the tatties to the boil. I'd guess you need at least the same amount of energy to keep them boiling until cooked. Then after the yeast has done its magic (you will have about 10% ethanol) you'll need roughly the same energy again to bring it to the boil again, plus another 2.4 kWh to vaporize the ethanol. So the energy requirements will be at the very least 6.6 kWh per litre of ethanol (and even an "efficient" system is probably 2x that - and a hombuilt system probably 4x it). Domestic electricity costs something around 15p per kWh. So its going to cost 1/L in energy absolute minimum to distill your ethanol... and potentially way more.
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Old 04 March 2012, 04:43   #18
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BBC News - Signs of alcohol-making at Boston fatal explosion site
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Old 04 March 2012, 05:14   #19
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I'd be surprised if a 10 still can produce enough ethanol (relatively dry) to be of use as a fuel. A 10 still also will be relatively unsafe device and potentially a good way to kill yourself or at the very least destroy your garage!

I don't know if you can distill fuel without appropriate licenses but I assume the Irish tax man is sensitive about stills that could be used for making drinkable spirit without paying tax.

Assuming you can convert all the energy in raw potatoes into energy stored in ethanol (probably unlikely - but lets assume you could) then 1 kg of raw potatoes has about 3350 kJ or energy. This is roughly about the amount of energy in 140 mL of Ethanol. i.e. it will take at least 7 kg of tatties to make a litre of "pure" ethanol. So unless you are going to grow them yourself (and have a very big field and enough time to do that) or have access to some ridiculously cheap source of tatties I think you will not be able to do it cheaper than petrol.

Worse than that (even if you could find a farmer with half a tonne of tatties to get rid of) is that first you normally boil the tatties. That takes energy. Then you let it cool down (that wastes that energy) so the yeast can do its work, Then you heat it all back up again to boil off (and condense) the ethanol. Now if your giant vat of tatties was perfectly insulated and efficiently heated (and for simplicity assuming the heat capacity of tatties is similar to water) then for each kg of water/tatties it is going to take about 0.1 kWhr to bring it up to boiling. Assuming you have equal quantities (by mass) of water to tatties that would be 1.4 kWh just to do the first stage of bringing the tatties to the boil. I'd guess you need at least the same amount of energy to keep them boiling until cooked. Then after the yeast has done its magic (you will have about 10% ethanol) you'll need roughly the same energy again to bring it to the boil again, plus another 2.4 kWh to vaporize the ethanol. So the energy requirements will be at the very least 6.6 kWh per litre of ethanol (and even an "efficient" system is probably 2x that - and a hombuilt system probably 4x it). Domestic electricity costs something around 15p per kWh. So its going to cost 1/L in energy absolute minimum to distill your ethanol... and potentially way more.
Lovely story...in fact, one of your best researched and presented efforts and almost worthy of a PhD Only your lack of academic referencing contributes a demerit.

But, you either have way too much time or you're a practising or wannabe ethanol distiller
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Old 04 March 2012, 05:21   #20
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and almost worthy of a PhD
He already has one - bit of a lab-rat as it happens...

That said, he knows very little about real world fermentation
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