Forum Index » Editor's Roundtable » Lightweight Stove Systems for Group Cooking Part 1: Basic Framework for Selecting A Cooking Pot and Predicting Fuel Needs


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Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
Lightweight Stove Systems for Group Cooking Part 1: Basic Framework for Selecting A Cooking Pot and Predicting Fuel Needs on 11/19/2013 22:47:08 MST Print View

Companion forum thread to:

Lightweight Stove Systems for Group Cooking Part 1: Basic Framework for Selecting A Cooking Pot and Predicting Fuel Needs

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Lightweight Stove Systems for Group Cooking Part 1: Basic Framework for Selecting A Cooking Pot and Predicting Fuel Needs on 11/20/2013 08:22:51 MST Print View

It apears that the data may be skewed somewhat. You didn't take into account the number of BTU's produced from a given amount of fuel, nor, the the maximum efficiency at any given temperature. For example, the Reactor seems like it is the most efficient. But, it may simply be burning fuel at a lower rate, and NOT producing as much heat output, hence wasted heat, when you measure the actual BTU output. I would guess around 6000BTU based on what I am seeing. Only the heat exchanger and close fitting pot make it efficient enough to use that small of a stove in cold weather. Typically, a winter stove pumps out 8000-10,000 BTU, some more.

But, measuring a stoves true output can be difficult. Some don't even function in any meanfull way at 0F. Caffin's stove works well with a cone or tight fitting wind screen. The same may not be possible for the Reactor or any upright canister stove. As you say, a lot of questions.

Many still consider melting snow at 0F to be a challange. I never go out when it is that cold,so I cannot say. The physics say that the ice will require more heat to melt betwwen 0F and 32F(water) than 32F(snow) to 32F(water.) Convectional heat loss (wind,) radiative heat losses, and insulating value of the sides and lid, the material the pot is made of (and any coatings,) the actual color of the pot, heat exchanger, etc, all make a measurable difference in fuel consumption when you are making water for groups. Things like this are much easier to measure in large quantities.

A good start Ryan! Looking forward to the rest of the parts to the article whether or not you ever measure the BTU outputs. Thanks!

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Thanks but no thanks on 11/20/2013 13:51:40 MST Print View

I'll stay with my MSR Dragonfly when temps are near or below zero F. I KNOW it will work and even save fuel with its great simmering ability.

Coupled with my 1.5 L. Jet Boil pot (W/ heat exchanger fins on the bottom) and a Backpacker's Pantry oven covering the pot my winter liquid fuel setup is quite efficient.

My "other" winter stove is a Trail Designs Sidewinder with the woodburning Inferno insert that makes it a highly efficient gassifier stove. Even with fast burning evergreen wood it is a reliable stove.

Greg Letts
(gletts) - F - M

Locale: Northern California
GSI pan on 11/20/2013 13:56:18 MST Print View

Hey Ryan - wondering how you're measuring the GSI 5 L pan...typically capacities are measured to the rim. The GSI Base Camper Large 5 L pan is 5 L to the rim. Obviously that's not the useable capacity, just as you can't use the whole liter on a Jet Boil Flash or the .85 L with an MSR Titan Kettle.

Jeff McWilliams
(jjmcwill) - M

Locale: Midwest
Heat Exchanger Pots? on 11/20/2013 17:38:05 MST Print View

Interesting article. I'm slated to spend 4 days in the Adirondack High Peaks the last week of December with 3 or 4 other people. As a result, this series of articles feels particularly relevant to me.

Will you be adding any heat exchanger pots to the mix? I own one of Roger Caffin's new LW invertible remote canister stoves, as well as a Whisperlite. I'm torn on which to take, and I still don't know what pot would be most appropriate.

I have a 2L stainless Steel pot, and I have an MSR clamp-on heat exchanger. It's a very heavy winter system. I would be very interested in whether something like the Primus Etapower HX pot, or something similar but larger, would perform.

Laneha Everett
(leverett) - MLife
Elevation? on 11/21/2013 08:03:09 MST Print View

I'm new to winter and cold weather mountaineering. Wondering how elevation would affect stove performance in addition to the cold temps you plan on testing. Love this article - thanks for posting!

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Elevation? on 11/21/2013 13:58:44 MST Print View

I've used a white gas stove up to nearly 20,000 feet, and I never noticed much of an serious effect of elevation on fuel usage. Obviously it gets colder up there, so you tend to need more snow melting and cooking going on. Also, snow tends to be colder and drier up there, so the entire snow melting process tends to be a little less efficient than at sea level.

--B.G.--

Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
winter cooking systems on 11/22/2013 21:35:05 MST Print View

@jamesdmarco, who wrote: "You didn't take into account the number of BTU's produced from a given amount of fuel, nor, the the maximum efficiency at any given temperature."

I know. Of all the times that I've freezing my butt off trying to get dinner done so I can go to bed, I'm not sure if I have ever, ever, EVER thought about BTU's or E = f (T). ;)

Seriously, though, I'm only interested in trying to collect data that will allow some extrapolation into field scenarios, and then try to validate it as best as possible with some actual field scenarios.

@Danepacker - sounds like you have a good setup here. Do you have a feel for how much fuel your setup consumes per "pot" of water at cold temps?

@gletts - I'm measuring nominal capacity at a volume of 3/4 to 1 inch below the pot rim. This allows for a vigorous boil without a rowdy spillover.

@jjmcwill - I hadn't considered heat exchanger pots yet (other than the MSR Reactor 2.5L being tested in this series) but I certainly would, if it's consistent with the theme (large water volumes). Do you have a recommendation?

@leverett - I won't look at elevation per se in this series because previous tests that I've done don't show a lot of differences at the elevations we have in the US. For example, on any given winter trek I might travel between 7k and 12k, which isn't a lot of change. Note that water boils at a lower temp at higher elevation, so in theory less fuel is required to reach boiling. I've looked at the math, and it doesn't justify much investment of time to consider fuel needs until you get to altitudes frequented by high altitude mountaineers.

I will definitely will look at temperature range - from about 40 deg F down to minus 20 deg F or so. These stoves are more sensitive to temperature differences that we're likely to see in the winter than they are to elevation differences.

Jeff McWilliams
(jjmcwill) - M

Locale: Midwest
Re: winter cooking systems on 11/23/2013 08:09:31 MST Print View

Ryan,

I am personally looking at the Primus Eta heat exchanger pots for my trip. They are the only ones I can find that are offered in larger sizes. They sell 1.0L, 1.8L, and 3.0L sizes.

It would be interesting to know if the cost and weight penalty make HX pots worthwhile over standard aluminum models.

Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
Primus ETA 3L on 11/23/2013 12:06:31 MST Print View

OK, I'll add this pot to some tests, and if the results look promising, we'll investigate further. Do you know if the heat exchanger can be easily removed from the bottom? It would be neat to have one version with and one version without for side by side comparison.

Jeff McWilliams
(jjmcwill) - M

Locale: Midwest
Re: Primus ETA 3L on 11/23/2013 12:52:31 MST Print View

I do not think the heat exchanger is removable. I don't have one yet, so I could be mistaken.

I look forward to the test results! :-D

Anthony Huhn
(anthonyjhuhn) - F - MLife

Locale: Mid West
Carbon Lid on 11/23/2013 16:40:49 MST Print View

Would Ruta Locura make you a carbon fiber lid for that popcorn kettle? ;)

Paul McLaughlin
(paul) - MLife
a few results of my own on 11/23/2013 23:22:23 MST Print View

Some time back I ran some tests of my own that are related to this. I took my 4 qt Open Country pot, filled it with 12 cups of water at 50 degrees starting temp, and at 40 degree air temp, in a garage with the door open but effectively no wind. so very similar there. However, the stoves were White gas stoves. - Whisperlite and Simmerlite. Results: each stove brought the 12 cups to a boil using 43 grams fuel.
The really interesting thing to note is that this number is precisely half of my average fuel usage for solo snowcamping trips where I have to melt snow, and I typically produce about 2 liters twice a day, each time lighting the stove once and running it continuously until I have the water I need and the water for my meal is boiled. So this is an excellent simulation of my actual usage.

Another data point: Analysis of my fuel usage from snowcamping trips where I have tracked both fuel usage and the number of days I found running water yields the info that a melting day consumes 1.5 times the fuel of a non-melting day. Note that these are spring ski trips, where during the day I am able to add snow to my water bottle and it will melt, so that I can start the day with 3/4 of a liter of water in my bottle and drink all day by just adding snow to the bottle every time I drink. So I only need to melt the morning and evening water. For deep winter trips more melting would be required.

Given the numbers you've come up with, it looks like only the Reactor (so far at least, we'll see what the Caffin stove can do) can beat the Simmerlite for weight efficiency for a week-long trip. Fuel usage by weight is the same, and fuel container weight is lower for white gas since I can carry it in plastic bottles. Using a half-liter Sigg bottle for the tank and refilling from plastic, I can carry 21 ounces by weight in 6.3 ounces of container, and as the trip gets longer the average container weight goes down since it's all in plastic after the first 12 ounces by weight.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: a few results of my own on 11/24/2013 00:00:57 MST Print View

Paul, why not just carry the fuel and use it out of the same 1L Sigg bottle?

On ski tours, I never plan my fuel on being able to find running water.

--B.G.--

Jeff McWilliams
(jjmcwill) - M

Locale: Midwest
Fuel Energy Density on 11/24/2013 05:31:24 MST Print View

I'm just doing a personal assumption check.

I recall energy density of various fuels being discussed somewhere in the forums in the past but can't find it, and I couldn't remember how canister fuel compared to White Gas.
Maybe most of those discussions were related to alcohol vs canister fuel.

I DID find a table of fuel energy densities on the Optimus website

http://www.optimusstoves.com/seen/technical-support/faq/fuel-faq/

Does this seem fairly accurate? Is the entry for LP gas good enough when discussing the 80/20 Isobutane/Propane canister and comparing it to white gas?

If there had been a significant difference in the energy density between white gas and alcohol, one might have argued that, despite the weight penalty of a white gas stove, it would have been more weight efficient once you reach a particular quantity of group water to be boiled or snow to be melted. However, the chart referenced above would indicate this would never be true, because canister fuel and white gas should both provide similar energy per weight.

Correct?

If so, the only other advantages of white gas, as I'm sure have been discussed often in the past, are fuel cost and packaging.

Edited by jjmcwill on 11/24/2013 05:32:07 MST.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Fuel Energy Density on 11/24/2013 07:13:35 MST Print View

Jeff, Yes, pretty much.
WG and canister fuel have about the same energy density.
Alcohol has far less.

I usually use a balance of around 20,500 BTU/lb when checking this. WG has around 19,500 per pound (note that it is mostly pentane, hexane, heptane.) Similar.
Alcohol has about 11,000 average (blend of ethanol, methanol.) On long trips in winter, it makes no sense to use alcohol, especialy for group cooking. There just ain't enough heat in the fuel.

However, you cannot have canister gas without a canister. These weigh about 30-40% of the fuel weight, much reducing the fuel overall density. The same applies to WG, of course, but you can carry WG in a 1 ounce container(6,8,10,12,16, 20 or 24oz, or 1 liter & 2 liter) soda bottle for anything up to 69-70 fluid ounces. Note that canisters are already in mass weights. WG is not and WG is in FLUID ounces. Mass/density is close to .78 that of water so to carry 12floz of WG fuel, we multiply by .78 to get 9.36oz of weight. With a 1oz fuel bottle we get around 10.36oz in weight. This is for roughly 11407 BTU's in fuel.
Reiterate:
12oz soda bottle: 1oz
12 floz of WG: 9.36oz
Fuel efficiency: 11407BTU/10.5oz or 1086BTU/oz


For canisters we get a total weight of around 220g + can = 308g or about 11oz for roughly 10067 BTU's in fuel.
Reiterate:
Can: 88g (3.14oz)
Fuel: 220g (7.86oz)
Fuel efficiency: 10071BTU/11oz or 916BTU/oz

Clearly, based on fuel, the WG is superior to take. However, for shorter trips, smaller groups (ie, less fuel used,) you consider the weight of the stove. WG stoves, are heavier, on average, than canister stoves. Usually offsetting the weight of the fuel. So, this is why canisters are so popular, even though they are less efficient, fuel wise. In the above, Ryan was trying to decide on the best performing stove for winter group use, but this can vary based on all the criteria he mentions, eg pot size, wind, etc and the base BTU efficiency of each stove.

Jeff McWilliams
(jjmcwill) - M

Locale: Midwest
Re: Re: Fuel Energy Density on 11/24/2013 08:05:49 MST Print View

James,

Is it safe to carry white gas in soda bottles? I'd never tried that before.

On our mountaineering expedition, we carried spare fuel in metal MSR fuel bottles. We even had two or three big ones: 40oz or 1.5L or something like that. If they were anything like the Primus 1.5L fuel bottles, the bottle alone had to weigh 9.6oz or more.

Paul McLaughlin
(paul) - MLife
Re: Re: a few results of my own on 11/24/2013 09:18:37 MST Print View

Bob - using the smallest sigh bottle I have and then carrying the rest of the fuel in plastic is lighter - my larger bottle weighs more than the small one plus the plastic.

On expecting running water - I don't always, but depending on snowpack and how late in the spring I'm going, I may. If it's mid-May or later, I've found I usually find water even in a big snow year; if it's closer to mid-April it has to be thin snowpack. I keep track of how many days I have to melt, to help with planning future trips. Campsite choices play a big part as well. If I'm going to be up on the ridges then there's much less chance.

Paul McLaughlin
(paul) - MLife
Re: Re: Re: Fuel Energy Density on 11/24/2013 09:24:31 MST Print View

Jeff - I've carried WG in plastic safely on several trips up to 9 days. I do look for more robust bottles. Those really thin wall water bottles seem to flimsy to me. Before I tried it on a trip, I tested by storing gas in a plastic bottle for several months with no effect on the bottle or cap.

Ben Pearre
(fugue137) - MLife
More heat exchanger pot thoughts on 11/24/2013 10:54:26 MST Print View

I would guess that the heat exchanger becomes less important as the pot diameter increases, but that's just a guess.

Heat exchangers on the bottom of the pot probably won't be removable, since there needs to be a good thermal connection to the pot, and I think that a clamping system would be far heavier than welds.

The MSR around-the-pot removable exchanger is 170 grams, and I don't know whether it will fit any of your pots. It obviates that tricky aluminium-titanium weld that's problematic on the Jetboil Al/Ti pots (you don't want a titanium heat exchanger because Ti is such a poor thermal conductor, and the two don't love being welded together).

Jetboil has 2 options that may be of some interest:

3.0 liter heat-exchanger pot: 550 grams, probably usable on non-Jetboil stoves.

1.8 liter sumo heat-exchanger pot: 225 grams for Ti (or 325g for Al). Aspect ratio is probably too high to be useful on non-Jetboil stoves or to be easy to shovel snow into, but you could carry 2 1.8-liter pots at less weight than their 3-liter pot, which may or may not be more versatile. No reason other stoves couldn't clamp Jetboil pots, but AFAIK they don't...