The temperatures in the biomeiler pile are measured with thermocouples buried in several locations. Nine of them are found at three heights (1’, 2’, and 3’ above the ground) in the inner core, outer core, and mantle of the pile. The graph shown in today’s post shows the temperatures measured by thermocouples at 3’ height. These sensors are buried 1’ below the upper surface of the pile. A sheet of Reflectix, a tarp, and some snow lie above the top of the pile.
In general, the trend of the pile temperatures (at all three heights) is the inverse of the air temperature. That trend is a puzzle to me. My first thought was that there was something wrong with the measurement techniques, but there are notable exceptions to the trend. The air vent temperatures seem relatively independent of the outdoor air temperature and the temperatures at the 3’ height behaved differently than the general trend at the end of the month. All of these temperatures are measured in the same way. So, I will continue to trust the readings, but will continue thinking about this trend.
The trend with aeration seems to be that no aeration caused temperatures to drop, some aeration caused temperatures to rise, and increased aeration caused the temperatures to drop, again. This trend was the reason I decided to add fresh manure slurry and warm water to the pile. The slurry and water were added on the afternoons of January 26 and 27. The next pile temperature measurements were made in the evenings of the 26th, 29th, and 31st. After the treatment, temperatures rose in the inner core and outer core. Equally importantly, there was no change in the mantle, where I did not apply any slurry or water. That contrast is an indication that the improvement was due to the treatment and not just a coincidence.
The internal temperatures have not risen to a point at which it would be sensible to try extracting heat with water in the PEX pipe. So, I have not progressed with assembling the apparatus needed to do that. Warmer outdoor temperatures or warmer biomeiler temperatures will be required to provide me the motivation to accomplish that work.
To better investigate the connection between aeration and pile temperatures, this month I will begin recording the amount of time the compressor is running each day. In general, it runs for 6-10 minutes during morning chores and 10-15 minutes during the evening chores. Collecting more data is undoubtedly the key to improving matters.
