I just posted this over at Donkey's board, but wanted to put it up here for those of your that are interested in the nuts and bolts of the thing. Here's what I wrote over there:
"Finally home, 7100 miles on the odometer for this trip! I'm tired.
Those box stoves were very impressive, and I'd be delighted if all of my neighbors chose those stoves. They were amazingly clean, no visible smoke, exceptional numbers on the testing machines, and they threw out a ton of heat. I still think that a constant burn is going to be far dirtier than our short burn/long heat cycle heaters, but they are really something and gave me a lot of hope, truly.
As Sandy mentioned, our heaters are probably not ever going to do very well in the particulate measurements of the small particles. We just have too much turbulence and a lot of air moving through the ash bed. The particles we are concerned about are inorganic, so cannot be burned out, and are so small and light that once they are in the gas flow they act like gas. Short of an electrostatic filter or a physical filter, we are probably going to have high particulate emissions, which is kind of a bummer. To be fair, my heater had no secondary mass or chambers, which surely would reduce particulate somewhat. Also, again, the short burn/long heat cycle goes a long way to mitigate this, so overall I'd say we are still right down there with the best of them in real world applications.
The testing followed either the EPA test method 28 or the Masonry Heater ASTM testing method. In the former the box stoves were tested after 30 minutes of loading a warm stove, for 15 minutes. Using the latter the masonry heaters were tested 15 minutes after lighting from cold.
Neither was appropriate for testing a rocket stove. I tried to get them to change but things were hectic and I may have been a bit too passive, however they were very gracious and I never felt that things were unfair on purpose. We all learned a lot about how these burn and how we might set up a testing protocol specifically for these devices. Obviously, after 15 minutes the fuel load is on the downhill run, and the machine didn't actually get numbers until 3 minutes after official start, so 17 minutes into a burn. Not only that, but a 15 minute "snapshot" of our burn cycle is like 80% of the total burn, where as with the box stoves it is truly a snapshot of a 6 hour burn.
On Monday, I did succeed in getting the head testing judge and one other judge to oversee an unofficial run, with the first numbers coming at 6 minutes after loading. That run had CO running from under 10ppm and occasional drops to 0ppm over the following 10 minutes before coaling stage started and CO started to rise. My 02 levels were high (10%) since I gave it plenty of air to allow for the tall stack and no load (mass) on the stove. Likewise exhaust temps were high which hurt the efficiency calculations. The judging pool was so very experienced, they all understood all of those factors better than I, and were overall impressed with our technology.
Like I said, we did a whole lot of good at the event. Had some great conversations with the actual individuals who are the regulators, decision makers, test protocol writers, and so on. Sandy and I together did some ground work on the path to getting through the maze of regulation and I think there is a clear path to getting these devices recognized as safe and legal to install. It's going to take a lot of work and quite a bit of investment, but the path is there.
As for the event overall, man, I gotta say, it made me very optimistic about wood heat in general. Pretty much all of the entries were impressive, and I learned that there are other very clean burning heaters out there for folks to choose from. Conversely, the wood stove world has now had first hand experience with a decent rocket stove, and I think as a whole we made a good impression on the industry and regulation folks."
And, as an aside for you all, my friends, I'd like to elaborate a bit on the part of the trip that was not the wood stove challenge. I had the opportunity to get to know and have some quality time with some decision makers in DC with regards to stuff we care about. Water, fracking, wildlands and wilderness, air quality, Big Ag and practices, and so on. I don't do politics, and never have, but I gotta say, without exception every one I met there who is working on this stuff was amazing. They were informed, and truly caring. I was really inspired and have a ton of hope and optimism for the future. Those were exactly the people I'd like to be making decisions about the things that matter to me. They would all fit right in here with us.