The chart accompanying today’s post shows the temperatures measured in the biomeiler at a height of 4’ above the ground. This height marks the boundary between the existing biomeiler and the recent extension. The data were collected by a thermocouple buried in the pile at that height at the very center of the inner core, another placed halfway between the inner and outer walls of the outer core, and a third similarly placed between the inner and outer walls of the mantle. The air temperature was measured on a thermometer in the open air.
At the beginning of October, the mantle extension had not been completed. That being the case, the thermocouple shows the mantle temperature rising until the 10th. After that day, the mantle temperature is roughly the average between the core temperatures and the outdoor air temperature. It is unlikely that any significant composting will take place in the mantle. Thus, the expectation is that its temperature profile will match the core temperatures at the inner boundary and the air temperature at its surface.
The temperatures in other parts of the pile show the same general trends. A developing problem is the failure of different thermocouples. During the past month, three have malfunctioned and another is working sporadically. Inconveniently, all but one of these thermocouples are buried so deeply that there is no possibility for replacement during the winter. I strongly suspect that the weight of the pile extension has led to increased compression of the materials in the deeper levels and the thermocouple wires were stretched past their limits.
Observation of the top of the pile shows that my efforts to construct a symmetrical conical top have been entirely undone by the uneven settling of the materials. The temperatures in the upper parts of the pile are so high that composting action is likely more to blame than the force of gravity alone.
Enough heat is passing through the Reflectix that snow is melting on the top of the biomeiler and only the puddles around the perimeter are cold enough for ice to form on their surfaces. Even without the data from the thermocouples, the presence of open liquid water in these low areas would be adequate proof of the continuous and substantial generation of heat in the materials below.
The forecast calls for the arrival of cold weather in the next few days. It will be interesting to see how long the biomeiler can preserve these puddles once Mother Nature gets serious about winter.
Looks like success in the function of the pile, just not the thermocouples.
It will be fun to see what Mother Nature does with the puddles, and at what temperature she may freeze them.