This week I finished the modelica simulation for tomato yield. It seems to give reasonable results with the calibration parameters used by B H E vanthoors, but I have not yet built up a simulation for my growth chamber to calibrate it against that. The main difficult variable is determining how much light is absorbed by the tomato plants, hence the other project of scanning the tomato plants and ray tracing.
Unfortunately, the tomatoes are now so large that I cannot get the scanner in around them. When I planned the experiment I did not realize how far back the scanner needed to be, nor how wide the plants would get. They have pretty well covered all the floor area of the growth chamber now. Fortunately, it’s pretty obvious that the plants adapt their leaf angle according to the available light. Cultivar is Maxxis from axia seeds. The plants along the south wall have leaves that are almost vertical on the south side, and then almost perfectly horizontal on the north side. These are also the plants that have the most immature tomatoes. So while not as quantitative as I was aiming for, it does look like tomatoes can use light coming from the side just fine.
I measured the albedo outside my greenhouse, which was low, 0.2 – 0.4 depending on snow cover. It will be interesting to see the how much light can be added by adjusting the albedo in the ray tracing simulation. I realized that I can validate my ray tracer against the solTrace program, which is a similar solar power ray tracer. I initially was going to use solTrace instead of my own program, but it was so difficult to build depending on many libraries and with a complicated GUI that I gave up and made my own. My program uses only header files and has command line interface only. So I will aim to get some of this validation done next week.
The rest of this week was spent trying to sort out the night time insulation. I feel like that’s best explained in pictures so I’ll wait til next week when the testing rigs are complete. Everything looks plausible for next winter though, so the tentative plan is to plant in the test greenhouse July 2022 for harvest through next fall, winter, and spring. I was adding plywood panels to the test greenhouse this week and insulating the soil between the greenhouse part and storage section. The non-glazed greenhouse walls will be insulated with blown in fiberglass or cellulose to R-40 so the heat loss there is minimal.
Sun Aquasystems 