Modular Hydroponics System

My sustainable design is a modular hydroponics system utilizing 3D printing in the fabrication process.

As a part of my "Engineering for the Future" class in school, I was tasked to build a hydroponics system (a gardening technique for growing plants in water without soil).

I traveled to a local hydroponics farm, where they incorporated fish tanks with plant growth. They raised the fish, using their excrement as fertilizer for the plants, creating a virtually closed ecosystem.

They showed us how the water was purified of any bacteria or contaminents, then given to the fish, and then transported back up to the upper level of plants with a pump.

I took inspiration from some of their systems, especially their use of water-cycled PVC piping, to use in my own design.

For the project, I used Fusion 360 to design and render everything.

Required:

3D Printer

Filament

PVC Pipe 4", 24"

PVC Pipe 3", 24"

Rockwool

Various Plant Seeds

Plastic adhesive glue (any brand works)

Large 24" basin

Water Pump

Air Pump

Hand Saw

Drill and bits

Optional:

Arduino Oopla Kit

Arduino Temperature Sensor

Hydroponics is a more sustainable technique than traditional agriculture. To ensure a more sustainable future for our world, we need to drastically shift how we make our food.

Hydroponics systems use up to 95% less water than traditional agriculture. Since most systems are completely closed loops where very little water can leave (or erode the local ecosystem), hydroponic growers are very effective when used and managed correctly.

Using a hydroponics system also allows plants to be grown year-round, as opposed to the common growing seasons dictated by the weather. Droughts and weather events also have less of an impact on hydroponics systems because they are usually indoors and carefully temperature controlled. This also allows a bigger variety of plants to be grown wherever the farmer sees fit.

Also, when comparing the square footage of traditional agriculture versus a hydroponics system, the traditional techniques actually grow less food when factoring in the extended growing seasons and multilayer scaling of hydroponics.

Another positive factor of indoor hydroponics facilities is that they can grow in cities because of the reduced environmental requirements to reduce the distance food has to travel. Traditional agriculture needs to be transported hundreds of miles across the country, sometimes thousands, to be flown into a grocery store. This reduces the freshness of the food, increases total costs, and requires more CO2 to transport the food.

All of these positive factors mean that hydroponics is a greener solution that can feed our growing world. By requiring less water, using extended growing seasons. and reducing food travel distances, hydroponics offers an opportunity for the engineers of our future.

For my project, I wanted to explore this field and create my own educational system to judge the feasibility of small-scale aquaponics.

My goal for this project was to design a user-friendly and modular hydroponics system for schools and other educational facilities. Thus, my design considerations focused more on ease of use and education over total efficiency and planting area. 

My first design was an Nutrient Film Technique (NFT) hydroponic system, a large horizontal PVC pipe with smaller pipes extending perpendicular from it, in the shape of an E. I hoped this would allow for different plant types to be grown from each section, and create a compact system that could be stacked (last image shows the system).

I decided against this design because I realized that a system using the same nutrient solution cannot grow many different plants that would require different nutrient concentrations (Hoidal, 2022). Also, I wanted to focus more on ease of use for students, so I traded a super space-efficient system for a tree-like educational model. 

My design contains a large vertical central PVC pipe with a diameter of 4 inches that is filled with water using a flexible pipe attached to a pump at the bottom of the tube. In the most basic form, the design is just a single water tube, with no plants at all. Small holes with quick-disconnect pipes attached on the sides of the tube can hold any pipe module we design. We can insert many of these “branches” (3-inch diameter PVC pipes with planters cut into them) along the central “trunk” to create a tree-like structure with branches of planters. 

The most important aspects of my design are the quick disconnect joints. The complex connection points and 3d printed components need to be sealed very well, and many hours went into 3d modeling to reduce points of contact with the water. I initially looked at mist hydroponics systems, but I thought that would be too complicated for use in such a small-scale product. Since we need the system to fit within a 2x2x2’ cube, excessive weight in water wasn’t a concern. 

Another method of hydroponics I considered was using media, like the large bed systems at Springworks farms. I ultimately decided against this for two main reasons: complexity and cost. Since I wanted to make a simple and easy-to-use system, adding the extra variable of media particles into my product would unnecessarily complicate it with little additional gain. Also, media, whether it’s rocks, clay, or another natural product, is usually rather expensive. 

In my research, I looked into the actual plants that could be grown. Since we want to grow year-round, sensitive plants like strawberries are not a viable option. Lettuce would be the easiest and most efficient crop to grow hydroponically. Almost every lettuce variety can be grown indoors. They can grow well with moderate lighting and in small spaces two inches wide. 

Another aspect of hydroponics that I researched and highlighted in my system was periodic maintenance. It’s important to clean out hydroponics systems every few weeks of sediment and bacteria buildup. My design includes quick detachable arms that can be removed for easy cleaning without creating a mess of water or requiring the whole system to be drained. 

This quick disconnect system also allows for the easier implementation of sensors to monitor water health, nutrients, and pH, which are vital for good plant growth. For example, lettuce prefers a pH of around 6, which must be maintained and checked often to ensure optimal growth. 

The field trip at the local aquaponics garden influenced my decision to use PVC pipe for a closed system. Although this was the medium suggested by Mr. In our design, I saw how such a technology could be implemented in conjunction with other hydroponics methods, and I figured that it would be the most cost-efficient way to create a robust and reliable system. There are some concerns with chemicals used in the PVC manufacturing process like dioxins and Vinyl Chloride, but these substances rarely leach out of PVC made using modern technology, and even if they do leak, they probably wouldn’t be absorbed by the plants 

The branches are the most important part of my system. They are modular and separate pods that can grow two plants each, and can be easily removed or attached to the central pillar.

I started modeling these by creating the 3" pipe that they are based on. These pipes are under a foot long, and have 2.5" holes in them.

The most important part of these branches is the quick disconnect joint that connects the branches to the central trunk. These took many design iterations and testing to get working without slop or leakage. The quick disconnect component is simple in practice: it is a small 1/4" quick disconnect fitting that is glued in, using a special type of plastic bonding hot glue, and sealed with marine sealant.

In the sectional analysis picture, you can see how the parts are seated with the quick disconnect. During preliminary testing, I connected water hoses which were pressurized to both ends of the connection points and was able to easily press the top button to release and stop the flow and reconnect to reestablish flow.

These holes also have small plant pots above them that hold the growing medium—in my case, Rockwool. They are shaped to slot into the pipe perfectly without any rotational freedom.

I initially wanted to use off-the-shelf plant pots, but these were rather expensive, flimsy, and not shaped exactly like the sizing I had previously established.

I designed the slits to be large enough to allow easy water flow but small enough to keep the chunks of rockwool growing medium from falling through into the water circulation system. The top flange also has a sweeping shape to allow it to not rotate when placed tangentially to the branch PVC pipe.

Since the water flow needs to be maintained at a constant rate, the water being pumped up into the branches needs a way to be cycled back into the system.

I initially wanted to put another set of quick disconnect fittings onto each branch joint, but I realized that it would be very hard to route both water in and out outlet in a single middle pipe. I then decided to have the water trickle out the end like a fountain, which would be an aesthetically pleasing way to create circulation.

I worked through a few 3D-printed prototypes until I settled on a longer, curved spout that would direct the water towards the central column to avoid splashing.

The central pipe is filled with water using a small pump and has holes drilled in it from the side to allow water to flow into the branches. It is made of a 4" PVC pipe cut to 24" long. If we look under the top cap of the central pipe, we can see that there is another 2" PVC pipe inside of the larger pipe. This addition serves to reduce the overall water volume from 301.6 cubic inches to 183.8 cubic inches, which is a relatively large reduction given the simplicity of the fix. This small change saves over 4.2 pounds of water from the final design, reducing the overall weight and time needed to fill up the tube.

The top of the pipe has an Arduino Oopla Kit mounted on it, which can be optionally fitted with many sensors to monitor water quality. Our design only has a temperature sensor, but it is possible to attach particulate matter sensors and pH sensors, two indicators that are very important for plant health.

There is also an emergency drainage port in case the water level rises too high and threatens to disturb the electronics.

The basin is where the water is stored. Nutrient solution can be added, and water is pumped up and trickles down to the basin.

I initially planned on 3D printing the basin, but because of the size of the circle (24" in diameter), I opted to buy a cheap plastic plant pot bin instead and screw the 3D printed mount (pictured in green) to it.

The basin also provides structural stability for the whole design. It forms the "roots" of the tree-inspired structure and keeps everything from tipping.

I constructed this project in my school fabrication studio using parts purchased from a local lowes. I cut all PVC pipes to size using band saws, and I drilled the large holes in PVC using hole saw drill bits.

I did encounter some hurdles while completing my design:

The hot glue I initially tested wouldn't bond very well with PVC and the 3D-printed filament I used, PETG. I used a variety of different glues, including epoxy resin and marine adhesive, before settling on a special hot glue stick made for thermoplastics and PVC. I completed the testing for these glues by attaching a prototype curved part onto the central 4-inch PVC and hitting it with a hammer to attempt to dislodge it (first picture). For the successful glue, I couldn't detach the part with a hammer and ended up actually breaking the part while it was still glued to the PVC pipe.

Many parts had small leaks that needed to be identified and fixed. These were sometimes almost microscopic, and I had to fill the whole design with water and wait for hours to see if there were any water spots forming.

1. 3D print all necessary components

The shown tray is only for one single branch; you need to increase the number of 1, 2, 4, 5, 6, 7 parts printed.

Refer to the above numbers in the following steps

1. Cut 24" of 4" PVC
2. Drill 1/4" holes on the side of the 4" PVC where you want the branches to be positioned
3. Drill a small emergency drain hole anywhere on the 4" PVC where the max water level should be

1. Connect 4" PVC to the base mount (part 7) using plastic bonding glue

1. Connect the PVC tube and bas mount to the bottom basin using either glue or screws
2. Press fit the top end cap onto the 4" PVC, a seal is not required

1. Use plastic bonding glue to secure the curved joint (part 2) to the 4" pipe on the locations drilled during the above step
2. Use plastic bonding glue to glue in the white quick disconnect fittings to the component attached above

1. Cut two 12" segments of 3" PVC
2. In each of these segments, drill a 2.5" hole using the circle saw drill bit spaced evenly apart
3. For the water exit spouts, drill a 3/4" hole on the desired maximum water level

1. Use plastic bonding glue to secure the button (part 5) to the branch joiner (part 8)
2. Use plastic bonding glue to secure the female quick disconnect fitting to the branch joiner (part 8)

1. Secure the branch end stand (part 3) and the branch joiner (part 8) to the 3" PVC pipe using plastic bonding glue
2. Ensure that these connections are watertight

1. Slide in the plant pots (part 6) into the previously drilled large holes
2. Insert the water spout (part 4) into the previously drilled side holes

1. Connect the two components made in the above steps
2. The final result should look like the above image; more branches can be made by repeating steps 6 through 9
3. Attach a pump on the outside of the 4" PVC pipe, in the water basin
4. Route the water from the pump up into the central pipe, and ensure water is flowing smoothly

I wanted to conduct various tests to ensure my system was functioning as I intended.

First, I tested the joints to make sure they could reliably be detached and attached without any leaks or too much wiggle room. This testing took the most time, as I found many tiny leaks in the piping and my 3D printed parts where I had forgotten to glue or seal.

I also tested the water circulation by putting red food coloring into the basin. After waiting for 20 or 30 minutes, the pump dispersed the food coloring very evenly across the whole system, which proved the reliability of spreading the nutrient solution.

IT WORKS!

Theres a small plant visible in one of the pods in the photo above. As of right now, the plants each reach around 6 inches up and are growing well, even without nutrient solution.

Challenges

One of the biggest challenges was designing the internal geometry to mate the quick disconnect connectors. It took quite a few 3D-printed prototypes to get just right, but I eventually found a successful design. The initial leaking, which has now been fixed, was caused by relying too much on merely hot glue to seal some components. If I were to do the whole project again, I would have used some other waterproof marine sealant instead of the specialty hot glue, because although the hot glue worked well for our final design prototype, it wouldn’t be usable for a marketable product. 

I also was unsure about the plant pot spacing, as from my research, I discovered that many plants need significantly different spacings when grown hydroponically. Since it was hard to get the spacing and angle of the holes for the baskets on the branch pipes, I decided to switch to single plant baskets from the double ones I had designed in the blueprint.

Conclusions and Future Iterations

I am pleased with the aesthetics of the design. In creating the blueprints, I was attempting to make a tree-like structure that had branches stretching along a central pillar. Although I only finished two branches, more can be added. In designing the hydroponics system, I didn’t focus too much on aesthetics. I prioritized ease of use and creating an aesthetically simple design that wouldn’t be too flashy but could also fit in a school or lab environment. 

If I were to redesign the system, I also would have liked to have done a bit more prototyping with the base of the system that connects the central pipe to the water basin. With some more time on this mechanism, I would have been able to route the water hose inside of the central pipe, improving aesthetics and making the design easier to work with. There are always improvements to be made, and I’m proud of being able to design a finished and working tree water planter prototype.