Here’s a short progress report that describes the new learning and thinking I’ve done and the new manufacturing capacity I’ve added over the past few weeks.
Reading and Learning
I spent a little time doing an internet scan of several hydroponics systems that were designed and built by others. I also did a lot of reading about hydroponic systems operations and maintenance. I even downloaded a job description from a production hydroponics greenhouse operator, so I know what the pros do to run their systems.
Some Issues to Factor Into the Design
Each of the next sections highlights an issue that must be factored into the design of my hydroponic system.
Algae and Bacteria
Hydroponic systems feed the plants with a nutrient solution. That nutrient solution makes great food for other less-desirable plants, such as algae. Algae is a plant, and algae uses the same nutrients that lettuce does. Same for bacteria. Algae clogs up the nutrient pump and the plumbing, while bacteria can attack the plant roots and ruin them.
The best way to prevent algae from growing in the system is to prevent light from reaching the nutrient solution. That means that no light can be permitted to enter the supply and return plumbing lines, nor the tower itself.
For bacteria, the best way to address that problem is to change the nutrient solution about every two weeks, and immediately remove any plants that are showing signs of disease.
Root Mass
During my survey of other people’s tower designs, I noted that some towers have significantly more plants growing per tower than others. The main constraint that governs the “how many plants per tower” decision is the diameter of the tower itself. The wider the diameter, of course, the more plant roots that can fit in it while still allowing for nutrient and air flow within the tower. Given that the tower design I’ve tentatively settled upon is only 4.5” in diameter – as compared with at least one other design that has an 8-inch diameter – I’m probably going to limit the number of plants per grow-module section of the tower to 3 plants.
Oxygen
Plant roots need oxygen. I reviewed a few videos that discuss this subject, and one very talented hydroponics practitioner published an excellent video that showed the results of research he did on the subject. If the tower system is very air-permeable, then oxygenation of the nutrient solution is less necessary, but that also suggests that the tower assembly is permitting light to enter, in addition to air. As I mentioned above, that may not be such a good thing. The alternative is to put an aerator, like the one you’d find in a fish tank, into the nutrient reservoir, and have it on all the time. This is likely to be the option I’ll go with, and if you watch the video I linked to above, you’ll see why.
Light
Another major factor that affects plant density in the system is light. How do you get the necessary light to all of the plants in the tower? If you looked at the Survey of Other Designs document, you’ll note that some of the designs don’t lend themselves to delivering light uniformly to each plant in the system. I think I’ve found the right lights for the job, and at the right price, and I’ll detail this in a subsequent Light System Design post.
Usability
As I’ve discussed in the requirements document, this system has to be easy and fast to use. It also has to make the “best use of the operator’s time”. To me, that means that almost all of the operator’s time should be spent grooming plants, and harvesting food, not managing the nutrient solution, nor cleaning the system.
Managing the nutrient solution means periodically topping up the nutrient reservoir and testing the quality of the nutrient solution – what concentration of nutrients it contains, how acidic it is, and how contaminated with algae it is. As I mentioned above, the nutrient solution also has to be completely drained and replaced every two weeks.
Every six months or so, the entire system – towers, supply and return lines, and the reservoir – must be completely disassembled, sterilized, and put back together. Right now, that seems like a big job, and it didn’t seem like the other systems I reviewed were easy to clean. My basic strategy will be to make it really simple and fast to disconnect and connect the components to one another, to make each sub-assembly light and portable, and of course to make each component really easy to sanitize. This subject will also get a lot of attention in the next few posts.
Manufacturability
In addition to the design issues set out above, I’ve got to start preparing to actually build this system once I get the design sorted out. Since I’m committed to this 3D-printed tower design, the fact that I have never done any 3D printing needs to get addressed.
Am I going to be able to actually manufacture this tower system? Questions abound.
Which 3D printer should I get? What type of plastic filament (feed-stock for the printer) should I use? Is it food-safe plastic? What are all the fiddly things I need to learn about the CAD / CAM software, the printer settings, the materials acquisition and preparation, and the idiosyncrasies of the particular components I’ll be printing?
As you can see from the picture I’ve included with this post, I’m making good progress. I have a printer, I’ve selected the right plastic filament, I’ve gotten a few prints done, and at this minute I’m printing what’s likely to be the most complex and largest item I’ll need to 3D-print.
I’ll be talking quite a bit about the CAD/CAM and printing in subsequent posts. Although I was intellectually aware of what 3D printing is, and can do, I must say that I am astonished at what just happened right before my eyes. This is some amazing stuff. The Fun Factor meter just red-lined.
