Yet there still appears to be a perception that efficiency of fuel is the only issue. The BTU is a bit of a red herring as well. You have to assess the total fuel, stove, pots and other accessories as a whole for each trip if weight is your priority.
I think that BTU being a red herring is a bit of wishful thinking or an inconvenient truth when it comes to meths stoves and pop can stoves in particular.
Ive made a few meths 'pop can' stoves and used the Trangia and Clickstand and optimus trapper all of which I like a lot. Meths leaves a lot to be desired as a fuel and if youre chasing grams in the Bergen I dont see how it makes sense TBH.
Lets compare 2 lightweight stove setups. Lightweight gas and Pop Can meths.
Ok system weights:
LW Gas
TI Crux = 48g ( weighed myself)
Alpkit MyTi cup / pot = 110g ( from Alpkit website including lid)
230g 80/20 butane propane gas canister = 336g
System weight = 494g
Pop can
Stove= 20g basic 2 piece construction holes in rim.
Pot support wire type= 15g ( you could use tent pegs or nails but 15g is representative I feel)
Alpkit MyTi cup pot = 110g
System weight = 145g
But the above does not include the fuel for the meths stove. So lets do some work on that.
Ok Methanol has a energy value of 23mj per kg and Butane ( the main constituent of a LPG canister) has an energy value of 118mj per kg
For our LW gas stove set up above we have a canister with 230g of LPG (lets use butanes value for this)
So 118 divide 1000 = 0.118 mj/gram x 230 = 27.14 mj of potential energy in the canister of 230g of butane.
What quantity of methanol do we need to equal this energy output?
So 23 divide by 1000 = 0.023 mj / gram I want to equal 27.14 mj so 27.14 divided by 0.023 = 1180 grams of meths required to give 27.14 mj or the same energy as is in 230g of butane.
The SG of meths is pretty much the same as water so thats over a Ltr of meths.
So the LW gas set up total weight 494g with 27mj of potential energy
Pop can set up total weight 1325g with 27mj of potential energy
Based on that calculation would you use a meths stove to reduce your pack weight?
The above is hypothetical in as much as it talks about potential energy in a given fuel. To release that energy we need to burn the fuel. That is where the efficiency of the burner comes into play. Most decent quality gas stoves will run at 90+% efficiency. Ive made a few pop cans and Id predict the efficiency to be at best 70% the yellowing on the flame is soot ( hence black pots on your Trangia) particles this is called incandesance and the soot is unburnt fuel so not all the fuel is getting converted to heat energy.
Then youve got to take the stove out into the real world and get it to perform. We could call this effectiveness. Its no use creating lots of heat energy if its lost or wasted. The Alpkit TI mug is to a degree a poor choice if were chasing joules ( opposed to grams) as Ti is not a good conductor of heat when compared to Aluminium for example so perhaps the grams we save on pot weight are lost in fuel weight carried and not conducted to useable heat. Then you have to factor in wind performance and heat transfer. So a good idea would be a stove that used an aluminium pot with a heat exchanger and was adequately shielded from the wind
with gas as a fuel source.
food for thought....