With my resolution for weekly updates over, I’ve really let this slide but here’s the status report. I did get tomatoes throughout the winter, but very few in January. More importantly, the modelica simulation of tomato yield diverged from the greenhouse actual experimental yield in about mid Dec. There are two likely possibilities.
First, the weekly light absorbed by the plants may have fallen to such a low level that the model could not accurately predict the yield. The model was not designed for environments were the plants are barely surviving. Second, I found this spring that the co2 sensor was consistently reading 300-400 ppm too high. That means the plants could have been starved for co2 once cold weather hit and the vents were almost always closed. I think the low light scenario is more likely.
The greenhouse has been revamped with new plant trays and highly reflective wall coverings. From the data we did get last winter we can see how much light is absorbed by one row of plants and this new arrangement with a lower plant density and taller plants should put the plants into a parameter regime where the modelica simulation can accurately predict their yield even during the darkest part of the year. I also got a new co2 sensor which will be tested / calibrated outside the greenhouse weekly, and the control system is setup for adding co2 if the level gets too low.
So now all that’s left to do is plant tomatoes of July 1st and run the experiment again through the winter. In the meantime, I’ve got some other smaller projects that I’ll hopefully relate on this blog as well.
Sun Aquasystems 