I see many threads here asking about alcohol stoves vs canister stoves. From the posts it seems there are many myths about alcohol stoves, especially about cold weather performance. I thought that since we were in the midst of a polar vortex, it would be a good night for some testing. I ran two tests - one in my kitchen on one on my deck. For those not interested in all the technical data below, the executive summary is as follows. At room temperature, my system boiled 2 cups of room temperature water in 4 minutes using about 14 mL of alcohol. Outside with the air, fuel, and stove all at 2 degrees below zero F, the power and efficiency of the stove was unchanged. The only effect of the cold was that it was hard to light (I just dropped the match into the stove) and it took about 50 seconds longer to get started).
Technical Stuff:
The system is a DIY easy Capillary Hoop Stove (1.5" tall), an Olicamp XTS pot with lid, an aluminum flashing cylinder wind screen (4.5" tall with radius 1/4" larger than pot, lots of air holes around the bottom), a stainless steel hardware cloth pot stand (3 1/8" tall - bottom of pot is 1/2" higher due to the pot's heat exchanger), everything sets on aluminum foil (for protection) and a plastic cutting board a table. The volume of fuel to boil the water was calculated from the formula: mL to boil=total mL fuel x time to boil/time to flame out. Both tests used 2 cups of water and 25.0 mL of fuel (50:50 ethanol/methanol). For the outside test, the stove and fuel temperature was -2 F. At this temp, alcohol doesn't "poof" into flames when you light it, so I just dropped the match into the alcohol which worked fine. I can't see the flame during the test, but based on the sound and the water condensing at the top of the wind screen, it seemed to take about 10 seconds for the stove to get going in the kitchen and about 60 seconds outside. The volume of fuel to boil calculation assumes a linear burn rate which I know to be a reasonable approximation inside, but it probably isn't for the outside test due to the delay in priming. Since the time to flame out, the time to boil, and the time to prime were all delayed by about the same amount, I conclude that the power of the stove (inversely proportional to boil time) and the efficiency of the stove (inversely proportional to volume of fuel to boil) for both tests were about the same once the stove got going. If I subtract 10 seconds from the inside times and 60 seconds from the outside times to adjust for the time to prime, then the power and efficiency of the stove running outside were both 96% of the inside test. Thus the only effect of the cold (72 degrees F colder than room temperature) was a 50 second delay in starting the stove.
Here are the data.
Test Kitchen Outside Ambient Temp (deg F) 70.0 -2.0 Wind Speed (Furlongs/Fortnight) zero negligible Initial Water Temp (deg F) 70.0 68.0 Initial Fuel Temp (deg F) 70.0 -2.0 Time to Boil (Min:Sec) 4:00 5:00 Time to Flame Out (Min:Sec) 7:15 8:05 Volume of Fuel Needed to Boil (mL) 13.8 15.5 Sanity of Tester Questionable