Alcohol stove efficiencies, designs and boil times.

[Size12]

Just wondering if anyone has easily made an alcohol stove that is able to boil 500mL of water (2 cups) with under 20mL of methylated spirits, in 5 min or under?

I was looking at the penny stove 2.0 but couldnt find much data on efficiency. And what I did find was wildly conflicting.
Also, it says an old penny is needed, would any coin that is the right size do? I live somewhere where we dont have pennies at all!

I was also looking at the supercat stove but from what I gather it is rather innefficient, although fast boiling.

If anyone has any designs to suggest that would fulfill the above requirements, or can provide data on any designs, then this would be immensely helpful. If a stove fulfilling the above requirements can be easily made, then I am definitely looking to switch to alcohol for some trips, but otherwise I'd stick with my canister stove, which can get me the water for a brew boiled in around 3min.

[Starchild]

Just wondering if anyone has easily made an alcohol stove that is able to boil 500mL of water (2 cups) with under 20mL of methylated spirits, in 5 min or under?

I was looking at the penny stove 2.0 but couldnt find much data on efficiency. And what I did find was wildly conflicting.
Also, it says an old penny is needed, would any coin that is the right size do? I live somewhere where we dont have pennies at all!

I was also looking at the supercat stove but from what I gather it is rather innefficient, although fast boiling.

If anyone has any designs to suggest that would fulfill the above requirements, or can provide data on any designs, then this would be immensely helpful. If a stove fulfilling the above requirements can be easily made, then I am definitely looking to switch to alcohol for some trips, but otherwise I'd stick with my canister stove, which can get me the water for a brew boiled in around 3min.

I'd be willing to sell you a penny .

20mL = 0.67 Oz. Yes it is common to get a boil of 2 cups using under 1/2 a oz of alcohol. However 6 minutes seems to be a more common boil time. The Cadara Cone and their 12/10 stove seems to be a highly efficient set up and also fast.

[Size12]

So the penny stove is a good bet the? Any other designs that can give good boil times while using under 20mL of meths per 500ml of water boiled?

Do you know if its possible to get a supercat to hit that efficiency target? As far as I know, the penny stove and supercat are the two common designs that achieve a boil in a relatively quick time. Id also look into making a caldera clone, but Im going to make a burner first.

I apologise for my use of metric, but Imperial makes my brain hurt

Im sure having to buy a penny would be unnecessary haha. Would another type of coin work? Or a small copper disk perhaps?

Sorry for all the questions, and thanks for the response! I just couldnt seem to get these questions cleared up properly through searching the internet.

[Tuckahoe]

Or rather than using a coin to cover the fill hole, use a set screw.




And ppppppssssss -- we dont use Imperial, its US Customary...

[jimyjam]

The Cadara Cone and their 12/10 stove seems to be a highly efficient set up and also fast.

+1 for the Caldera Cone system
I have been using mine for a couple of years now. It has never failed me and is the most efficient alcohol stove I've come across. The company custom makes the system to fit your cook pot. Here is a link...check it out!

http://www.traildesigns.com/stoves/caldera-cone-system


Life is full of ups and downs! Hike on!

[BirdBrain]

Do not confuse rate with efficiency. In general, the shorter the boil time, the lower the efficiency. As an example, I have built many Capillary Hoop Stoves based on TetKOBA's work. I can boil 2 cups starting at 70° in around 3 minutes using a FREVO version of this stove. However, it will consume close to 20ml of methanol in the process. I can also boil 2 cups of water starting at 70° using close to 10ml of methanol using a mutt version of the eCHS with tiny jets and a small aperture. However, it takes around 10 minutes to get the water to boil. Odd Man Out and I have done extensive testing on the standard design of the eCHS. If done right 15ml of methanol will bring 2 cups of water on the trail to a boil in 4 minutes consistently in all but the most adverse conditions. Trail boiling is all that matters. This assumes you use a good shield. I use a cone. The eCHS also allows for fuel recovery. There is a lot of exaggeration and confusion in stove designs. Odd Man Out can confirm my claims.

[Rocket Jones]

Different strokes for different folks, but I've never understood the obsession with efficiency regarding alcohol stoves. My SuperCat does just fine, and I'm not in such a hurry that I'm going to begrudge an extra minute or two before boil.

[BirdBrain]

Different strokes for different folks, but I've never understood the obsession with efficiency regarding alcohol stoves. My SuperCat does just fine, and I'm not in such a hurry that I'm going to begrudge an extra minute or two before boil.

Rate of fuel consumption or rate of water heating, in and of themselves have nothing to do with efficiency. Efficiency is work done per energy consumed. Time is a preference that has nothing to do with efficiency in this discussion (unless that is your primary focus). Mine is fuel per boil given a duration that is not absurd. Those of us obsessed with efficiencies are that way because we want to carry less fuel. It is logical for those not obsessed with saving 5ml of fuel per boil to build stoves that do not require a machine shop to construct. A Cat stove is a great choice for many. It is all a matter of where you want to focus your energy (all puns intended).

[BirdBrain]

Let me provide a more efficient answer:

A properly constructed CHS (I prefer a customized eCHS) can boil 500ml of water starting at 20° C with about 14ml of yellow HEET in around 4 minutes. You will only suffer marginal efficiency loss on the trail using this stove if you use a properly constructed shield. A cone works great for this purpose. A Caldera Cone is a patented device sold by Trail Designs.

IMG_20140429_192540_081.jpg
This is my stove.

[kevperro]

Efficiency probably has more to do with the windscreen design than it does with the stove. Also... the pot size in relation to the flame pattern so the engineering problem is much bigger than just the stove design.

If you want a fast boil, don't use alcohol.

[atraildreamer]

I took a shot at addressing this question a few years ago:

http://www.whiteblaze.net/forum/show...ncy?highlight=

[Slo-go'en]

The problem with a penny stove or other pressurized stoves is that it is more flame thrower then burner. I tried building one once and had jets shooting out 6" from the stove sideways and it burnt up the fuel in no time.

How long it takes X amount of fuel to boil Y amount of water starting at Z temp is one indication of a stoves efficiency, but what you really want to know is how much fuel does it take to cook a typical Knorr pasta side? For that you need to know how much fuel it takes to boils 2 cups of water and then keep it going for 5 to 6 minutes.

For that it's hard to beat the Caldera cone stove system. Filling the stove between 1/3 to 1/2 full depending on water temp and ambient temp will cook a pasta side. The other thing I like about the Caldera cone is the wide base which makes it very stable. If you've ever lost a meal from the pot falling off the stove due to an unstable picnic table, you'd appreciate that feature.

[BirdBrain]

Efficiency probably has more to do with the windscreen design than it does with the stove. Also... the pot size in relation to the flame pattern so the engineering problem is much bigger than just the stove design.

If you want a fast boil, don't use alcohol.

It is a system. It all has to be in balance. It is like any other item in any other system. If you enjoy having a part in your gear, tinker away. If you don't, buy something made in bulk.

I agree with the last point. If saving 2 minutes is vital, buy a jetboil.

[Size12]

Agreed that if a fast boil is wanted I should stick with my canister stove , but I dont mind waiting a little longer, but anything above say 6mins is a bit slow for me. Im just aiming to strike a balance of fuel consumption vs boil time. Someone had a pattern going around for a copy of a caldera cone, that you could size to fit your pots and all. Im trying to avoid having to ship anything overseas where possible.

Some insightful suggestions.
That eCHS system looks intriguing, particularly if it can boil in 4-5min and use under/around 20ml of methanol. (Id be using methylated spirits, which is mostly ethanol and has a higher energy content and thus less fuel is needed as I understand it.)

Caldera cone definitely seems worth it for both efficiency and stability. Hate having things nearly fall off stoves.

[MuddyWaters]

Efficiency, has to do with heat output of the stove, and heat input area of the vessel, and heat losses.

Heat output of the stove, is determined by vaporization rate, which depends on heat feedback from the flame. This can be affected in different ways. pot to stove distance for one.

A wider shallower pot is better for more heat input area with less wasted heat (up sides)

Windscreen is the real determining factor. Heat losses are HUGE. For instance, to heat 16 oz of water = 2cups from 60-212 F takes 152 Btu. 0.5 oz alcohol burning puts out about 300+ btu depending on fuel type. About half the heat of combustion is lost typically, even in "efficient" sytems.

It is absurd to worry about time from an alcohol stove. You have nothing else to be doing. My simple tealight cup, boils 2 cups on 0.4 oz, in about 7.5 minutes. Its good enough for me. Even when I use a cannister, I heat it on low, and get similar fuel usage as a heavy jetboil. the difference being my stove and pot weigh 2.7 oz.

[BirdBrain]

I have a picture of a pattern for a 2 piece cone with the formulas somewhere. I drew this a while ago for a friend. I will post it if I can find it again. Building a cone is a ton of fun or a royal pain depending on your perspective.

[BirdBrain]

I have noticed another thing about stove efficiency. Whereas in general fast alcohol stoves are less efficient than slow ones, slow ones are more adversely affected by the elements than fast ones. My most efficient eCHS is impractical for the trail. Much of the effeciency savings can be lost due to the duration in fighting the elements. That reality is what made me settle on my current design. 2 minutes or 10 minutes to boil matter little to me.

[Odd Man Out]

OMO is in Istanbul but the hotel has free wifi! BB is correct. I use a standard eCHS stove. Can boil 2 cups in 3 to 4 min with less than 15 ml water. I use a pot stand made of hardware cloth. Light and stable. Wind screen is a cylinder of aluminum flashing. I use an Olicamp XTS pot which has a heat exchanger. The speed you can boil would be best described as power. Efficiency is the amount of fuel used. To get this combination of both power and efficiency you need a high heat output and the ability to capture that heat. If your windscreen gets very hot or you feel much heat coming off the top you are losing heat and power and efficiency both suffer. This is not a function of the stove. It is a function of the whole system working together. There are many variables that need to be optimized. The other thing to consider is ease of use in the field. Fuel recovery as BB pointed out is key to effective efficiency in the field. Ease of use is also key. The eCHS needs no priming. It is not prone to over heating. It won't explode like my Penney stove did. It performs normally at below zero temps. A pot of cold water doesn't affect it's performance.the one parameter I haven't tested yet is win performance. BB's cone should do well. I expect my system will also be ok. BTW the Suleymaniye Mosque is beautiful when lit up at night.
.

[BirdBrain]

BTW the Suleymaniye Mosque is beautiful when lit up at night.

I had to look that up. Wow! That looks beautiful. I cannot imagine what that would be like in person. Forget stoves and enjoy that marvel.

[BirdBrain]

A quick test to see if you have an inefficient stove is to set it on a block of ice after it is lit. If the stove slows then energy is not going where it belongs. Ideally all the energy should go to the water. Of course, that is impossible.

Another test of the system is to feel the windshield. The hotter the shield, the more inefficient the system. Causes of inefficiencies can include improper venting, improper stove to pot gap, improper focus of flame, improper burn rate, and improper pot diameter.

Again, all this is meaningless to the mass produced flame thrower approach. Hopefully they are useful to the tinkerers.