The main topic of this discussion is "efficiency" and the perception of it for heating systems. I believe, with my limited research skills, enough anecdotal data and scientific research exists to "prove" or at least empirically define what efficiency actually means in this case and what people have mistakenly think it means.
"Design efficiency" is defined as the efficiency of the wood burning device to turn the chemical energy in the wood fuel into heat energy. "Transport Efficiency" is defined as the ability of the wood burning device to transport the heat generated in the device, to the room which it is heating. "System Efficiency" is the total of or combination (product) of the two other efficiencies (SE = DE X TE). In my estimation, wood burning manufacturers specify the "design efficiency" and people perceive that at the "system efficiency". This causes large confusion and "heated" debates (pun intended) based on misinformation (or incomplete information).
While that may be the case, the estimates of efficiency may also be flawed by the testing instrumentation or procedures causing major inaccuracies (uncertainties). Also, "design" efficiency is usually compared to what theoretical limit of the design, not the theoretical limit of the energy stored in the wood fuel. Likewise, most people embroiled in this type of argument fail to analyse the wood fuel and waste of the wood burning device and ignore this portion of the efficiency calculation. This wood fuel does not magically appear next to the wood burning device and the ash/waste does not magically disappear from the device.
My limited knowledge of thermodynamics and the barriers the wood device industry places on transparency have hindered some of these effort but I feel I have made a reasonable effort for the time constraint (do not want to do more) and limited resources (I have never even touched a rocket stove). I am reasonably assured, without further investigation, that a "rocket" - "mass" stove (compare to wood or pellet) IS the most efficient heating alternative of the three. That is, from the standpoint of conversion of chemical energy into heat energy filling a room. Likewise, it is my opinion that it also is the most efficient from a fuel gathering and waste minimization perspective in the parameters of labor, transport fuel, garbage created and money spent. While I did not do a complete analysis, I believe the initial creation and end of life environmental considerations also point to the "rocket" - "mass" stove being the most advantageous.
I compared the three systems and gave a rank for many factors for the "wood stove", the "pellet stove" and the "rocket-mass stove". I submit Figure 1 as a table of that ranking. Likewise, I tried to come up with estimate of actual numbers corresponding to the issues raised in the Executive Summary. I submit Figure 2 as a table of those number. I would like to point out, these are best efforts numbers based on the investigations of the previous chapters. In the end, these are just (educated) guesses. I assume in the first line of "design" efficiency the numbers are compared to 8,600 BTU/lb for the wood fuel.
Notice, I do give a "system efficiency" estimate for the three. I would like someone else to provide some rigger into verifying some of these estimates. Since these are guesses, I do not want people to state the number to others as if they were gospel. If there is at least a little consensus with the people that work with the stuff, that would be good.