QuietStove.com

Monday, January 26, 2015

Fuel Economy (Efficiency) with Stoves

OK, how do I stretch my fuel with my backpacking stove?  I do NOT want to run out of fuel before the end of my trip!  And why carry more than I have to?

What are the tricks to getting good stove fuel economy?  Are some stoves more fuel efficient than others?  Herein, I address this and more.  Read on, dear reader, read on.
A Kovea Supalite in use with a heat exchanger pot.
Heat exchanger pots save fuel.
With most stoves, it's typically more about how you use the stove than it is about which stove you buy – at least with the major stove brands.  In other words, the user usually matters more than the stove.  However, all bets are off with "no name" stoves that one can buy off of eBay or Amazon for shockingly low prices.  Caveat emptor.
An uber cheap stove from Amazon.
Is it fuel efficient?  Who knows?
So, what are the "best practices" for fuel efficiency?  Here's my list.  Items are listed in general order of importance, the most important being listed first.
  • Pick a sheltered spot.  On top of a rock or picnic table might be convenient, but it's going to be windier up there.  Set up your stove on the ground behind a rock or log.  On a windy day, this is absolutely the most important thing to address in terms of efficiency, far more important than how you actually run the stove itself.
  • Turn it down.  High heat = inefficient.  This is the number one mistake of new stove users – they open the valve 100% (i.e. maximum), which is the absolute last thing that you want to do if you want to be efficient.  Running your stove at say 30% of max will be far more efficient.     Lower heat = more efficient. Of course it's going to take a bit longer when you turn down the heat.  Here's where you'll want to experiment.   You need to find the balance between speed and efficiency that works for you.
  • Use a windscreen.  Yes, even on an upright type canister stove (like a Pocket Rocket), just not a full 360 degree windscreen.  If you use a (partial!) windscreen with an upright canister stove, be careful to check the canister frequently with your hand.  If it feels so hot that you can't leave your hand resting on the canister, take immediate steps to cool things down.  See Canister Stoves and Wind before you use a windscreen on a canister stove.
    In general windscreens add to efficiency in two ways.  They a) prevent wind from blowing away the heat and b) focus the heat on the pot.  Because a windscreen focuses heat, it's always good to use a windscreen even on a day where it isn't particularly windy.
  • Use a lid.  A tight fitting lid without a strainer or other openings is best.  Escaping steam = escaping heat = inefficient.
The above can be used with pretty much any stove and pot combination.  There are some additional things that one can do if one is willing to make some additional gear purchases; I list those below.
An MSR Windburner uses a heat exchanger pot to achieve high levels of efficiency.
  • Use a wider pot.  Tall, skinny pots wind up having flames go up the sides, wasting heat.  A wide, squat pot catches that heat better.
  • Use a heat exchanger pot.  A heat exchanger pot (e.g. MSR Reactor, Jetboil Flash, Primus Eta Express, etc) can save a lot of fuel.  Now, you will save fuel with a heat exchanger , but usually the heat exchanger weighs more than the weight of the fuel you save.  In other words, using a heat exchanger is often heavier overall.  However, if on a trip you prevent having to carry a larger or second canister, a heat exchanger can actually save you weight.  See Can a Jetboil Save Weight? for specific examples and a full discussion.
  • Use a darker colored pot.  This is pretty minor compared to the others, but a darker colored pot will absorb more heat than a shiny reflective one.
A windscreen makes any stove more fuel efficient.
Featured in this photo:  A Bobcat system from Flat Cat Gear.
OK, so the general rule is that it's more how you use a stove than what stove you buy, but there are exceptions.  Alcohol and ESBIT stoves are an exception to my general rule that the user matters more than the stove.  With an alcohol or ESBIT stove, you typically have to design the efficiency in.  Most DIY alcohol or ESBIT stoves will not be as efficient as a good commercially produced stove.  However, do your homework.  Just because a stove is commercially produced doesn't mean that it is necessarily efficient.
A Ti-Tri Cone from Trail Designs – efficient by design.

So, there you have it, some basic tips and tricks for stretching your fuel.

I thank you for joining me,

HJ

15 comments:

  1. To me, the number one heat robber is wind. Finding a sheltered spot is the most important thing that you can do. A good windscreen helps, but the less wind that it has to screen, the better it will work. My windscreens are sized to fit the pot and have a 1/4" gap around the pot. This also makes for a snug fit wrapped around the pot and its cozy. I've seen minor gains from using heat exchanger pots, but most of my HE pots are tall and narrow. Mostly for grins, I just got an Alocs HE tea Kettle. It's short and squat and has a protective ring around the heat exchanger. I'm not certain what the capacity is, probably around .7L. I'll be interested in how it compares to my Optimus Terra Weekender HE pot.

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    1. Hi, Bill,

      Well, I won't disagree with you. I put "turn it down" first because that is almost universally applicable. Even on a absolutely still day, you still want to turn down the stove.

      On a windy day though, you are correct. Sheltering the stove properly is #1.

      HJ

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  2. Bill, I was thinking about what you said. I decided to re-order the list pursuant to our conversation.

    HJ

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  3. Jim is keerect, ESBIT stoves require all components to be maximized for their efficiency and work together as a system.

    EX.: My "BEST EXOTIC ESBIT STOVE SYSTEM"
    1. Stove-> Trail designs Sidewinder cone stove (Retains most of the heat with its tight pot seal.)
    2. Open Country 3 cup mating pot for the stove (Max size for ESBIT and good height-to-width ratio.)
    3. Brian Green's Blog "BEGET" ESBIT tablet holder. (It captures all the liquid residue which doubles burn time to 15 minutes! You make it yourself from a template link on his blog.)

    With this system I have cut my fuel use down 55% from any privies ESBIT stove, either DIY or commercial. To me this is THE most efficient ESBIT system available. If there is a better one God is keeping it to Himself.

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    1. Interesting. I'll have to check into that one. Thanks, Eric.

      HJ

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  4. I'd have to disagree with Jim on the use of a heat exchanger pot with ESBIT fuel. Cleaning the exchanger fins would be a nightmare, even with a special cleaning brush - which also adds more weight in addition to the weight of the heat exchanger fins.

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  5. "An uber cheap stove from Amazon. Is it fuel efficient? Who knows?" I DO! I have one of these uber cheap stoves in my collection. I paid $7 including shipping from China. It gets the same fuel efficiency as my pocket rocket: uses 7g (0.25 oz) of MSR fuel to boil 500ml of water.

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    1. Interesting. And were you running it with the valve fully open or were you running it at a lesser setting? If at a lesser setting, do you have a feel for what percentage of a full flame you were running at?

      HJ

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  6. I did 3 timed tests where I measured the weight of the MSR canister each time. The time to boil the water averaged 3min 15sec with a variance max of 5 seconds. I used the same pot for each test. The valve was definitely not wide open. That would have sent the flames up the side of the pot. I'd estimate the flame output I used was ~90% of max output.

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  7. Oh, one more thing... the water I used was straight from the tap. I waited until it got as cold as it would go. Although I did not take a temp reading of the water before I started, I can assure you that tap water gets very cold in Canada in February. Let's just say that if you want a nice cold glass of water you don't need to add ice, and you'd better not have sensitive teeth!

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  8. I see! I have not known there are a wide range of heat exchanger

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  9. I have better luck with my Alcohol stoves when they are vented from the bottom, but the cross wind is blocked. Trangia is a great example of optimizing venting from the bottom up to maximize fuel economy and performance.

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  10. Have you tested an MSR Reactor pot combined with burners such as an MSR Pocket Rocket (or similar) or a Primus Omnifuel (or similar)? Do you know if there's anything particular to the MSR Reactor pots that lend them advantages/disadvantages when combined with other stoves than the Reactor stoves?

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    Replies
    1. I suppose you could use a Reactor pot with a stove other than a Reactor burner, but the bottom of the pot is concave and the Reactor burner is convex. The two parts fit together and for a stable connection. A Reactor pot is pretty unlikely to fall off a Reactor burner. If you use a non-Reactor burner, you won't have that convex burner surface to hold the Reactor pot, so it may not be very stable. It certainly will not be very wind proof.

      HJ

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