The Alcohol Stove “Efficiency Percentage” Test Thread
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 Delmar O'Donnell (Bolster) Locale: Between Jacinto & Gorgonio The Efficiency Percentage Calculation on 03/30/2014 18:33:39 MDT [EDIT: Much of the following discussion refers to creating spreadsheets that have been significantly updated and improved. To find the most recent versions, follow the links in the first post of this thread, or you can find Glenn's latest spreadsheet via the direct hyperlink in his post, just two posts following this one.] Edited by Bolster on 04/26/2014 08:57:47 MDT.
 Greg Mihalik (greg23) - M Locale: Colorado Re: The Efficiency Percentage Calculation on 03/30/2014 19:16:28 MDT Delmar,In english (versus the equation), what is the Efficiency Percentage number?
 Glenn S (Glenn64) Locale: Snowhere, MN Re: The Alcohol Stove “Efficiency Percentage” Test Thread on 03/30/2014 19:17:40 MDT Until we get a few more players, I'll keep posting my results in the original spot back on my Foster's thread, then if we get more involved, I can easily move them directly onto this post. But for now, here's a direct link to my test results post (not just the general thread) for a quick hyperlink reference.Greg:I know you posed the question at Delmar, but here's my take on it...I see it as a quantifiable number that reflects the amount of energy absorbed by the water in relation to the output energy of the fuel used. It's somewhat arbitrary, being a rather crude assessment of our limited parameters, but lacking a better system, it's something that provides a somewhat level playing field for testing different systems, rather than a single facet such as boil time alone. I see it as being used similarly to a furnace, or woodstove, in terms of "Energy Efficiency Ratings". Edited by Glenn64 on 03/30/2014 19:47:53 MDT.
 Delmar O'Donnell (Bolster) Locale: Between Jacinto & Gorgonio What It Is on 03/30/2014 20:14:44 MDT ^ That's my understanding also. Ben explained the Efficiency Percentage to me as: Efficiency = Energy Absorbed (by the water) ÷ Energy Released (by the fuel). Ergo, a more efficient stove setup (it tests the whole system, not just the stove) uses less fuel to heat the water. Much of the guts of the formula concerns itself with joules (units of energy) but Ben H. converted a lot of the variables into a constant specific to His estimate of the energy in obtainable denatured alcohol (the 25kJ/g in the formula). The formula only works for denatured alcohol, not other fuels. (If you had access to pure ethanol, that number would go up to 26.8 kJ/g.) To really grok the formula in detail, you'd have to contact Ben H, and possibly take some classes on thermodynamics. What this gives us (for the first time that I'm aware of) is a communal way we can compare stove setups that goes beyond just "I got MM:ss to boil" or "I used XX ml ethanol to achieve boil." It "boils down" comparisons to one easy-to-understand number. Edited by Bolster on 04/22/2014 22:01:36 MDT.
 Bob Gross (--B.G.--) - F Locale: Silicon Valley Re: The Efficiency Percentage Calculation on 03/30/2014 21:06:33 MDT I see your initial water temperature. Where is the final water temperature?The final water temperature will vary for altitude. I've seen water boil at 175*F.--B.G.--
 Delmar O'Donnell (Bolster) Locale: Between Jacinto & Gorgonio Altitude on 03/30/2014 21:07:58 MDT > 6) Tell us your altitude (altitude at this point is not factored into the efficiency formula, but might be later) and anything else that might be affecting your results.If you (or anyone reading) knows how to factor altitude into the formula, please do so! I would be most gratified to see that variable added. As I understand the formula, it is calibrated to sea level. Edited by Bolster on 03/30/2014 21:28:19 MDT.
 Bob Gross (--B.G.--) - F Locale: Silicon Valley Re: Altitude on 03/30/2014 21:12:53 MDT There are charts which show the boiling point of water for different altitudes.I mean, if you are going to make this, then make it right. Or, put a disclaimer up front that it only applies to sea level pressure.--B.G.--
 Delmar O'Donnell (Bolster) Locale: Between Jacinto & Gorgonio Thanks. on 03/30/2014 21:15:48 MDT I will beef up the disclaimer. I should not be the person "making this" (ie, the formulas -- it's not my field of expertise) but perhaps someone out there can modify the formula to account for altitude. Kudos if they can. Edited by Bolster on 03/30/2014 22:39:03 MDT.