In this post, we will go through designing and building a pressurized nutrient supply.

But first, lets study why we use high-pressure aeroponics, and understand the key aspects of this method. Then we design and build according to the findings.

Why Aeroponics?

There is lots of information about what is high-pressure aeroponics and why it is better. Check the article from Maximumyield.com: Growing on Air: How Aeroponics Turns Less into More

There is also a YouTube video showing the difference, even the aeroponics systems in the video are just Low-Pressure Aeroponics.

And here from academic authority: (The benefit list is too long that you have to read by yourself)

Aeroponics systems can reduce water usage by 98 percent, fertilizer usage by 60 percent, and pesticide usage by 100 percent, all while maximizing crop yields. Plants grown in the aeroponics systems have also been shown to uptake more minerals and vitamins … American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 27, No 1, pp 247–255

High-Pressure Aeroponics Benefits

Here is the list of experts from Wikipedia: Aeroponics.

Oxygen (O2) in the rhizosphere (root zone) is necessary for healthy plant growth. The increased aeration of nutrient solution delivers more oxygen to plant roots, stimulating growth and helping to prevent pathogen (virus, bacterial and fungus) formation. Aeroponics can limit disease transmission since plant-to-plant contact is reduced and each spray pulse can be sterile. Due to the disease-free environment that is unique to aeroponics, many plants can grow at higher density (plants per square meter) when compared to more traditional forms of cultivation. Less nutrient solution is needed throughout. It allows greater control of plant environment and improved nutrient feeding.

Key Factors

The key factor of root development in an aeroponic environment is the size of the water droplet. Based on researches, NASA has determined that high pressure hydro-atomized mist of 5–50 micrometres micro-droplets is necessary for long-term aeroponic growing. Atomization (>65 pounds per square inch (450 kPa)), increases bioavailability of nutrients. When an accumulator system is incorporated, the spray pressure is more stable. And by skipping the phase of activating pump to apply pressure, the cycle times can be further reduced to < ~1 second on, ~1 minute pause. Maintaining a higher pressure when the nutrient is atomized will reduce the chances of nutrient salt accumulated on atomizing sprayers, thus lower the maintenance cost.

Goal and Design of Pressure Regulating Unit

In a typical closed-loop high-pressure aeroponics system, the nutrient delivery function can be demonstrated in the graphic below.

So, in the above diagram, the nutrient is sucked in to a booster pump and pressurized. The accumulator tank stores the pressurized nutrient and maintain the pressure in the delivery tubes. An optional pressure sensor monitors the nutrient pressure to prevent over/under pressurization. Solenoids control the nutrient delivery timing. The release valve is used to drain the system, normally in maintenance phases.

The design goal is to create a device that

is safe to use, portable to fit indoor household spaces, can boost the nutrient pressure, can maintain the pressure without pump running all the time, do not alter characteristics of nutrient, can deliver nutrient with precise timing, is modularized and easy to use.

Encapsulate the Implementation

Well, if you have read my previous blog posts, you would know that I like to modularize functions and encapsulate the detailed internal implementation. The result is simplified unit interface. And, this is important, it allows future upgrade of the unit without causing dependency issues, as long as the interface compatibility are maintained properly.

In this case, the unit is simplified as a box with one nutrient intake from reservoir, two pressurized nutrient outputs to nozzles, one recycle output back to reservoir, one folded drain tube, along with power/signal wires. It is much easier to maintain and operate.

Here it is the simulated rendering of the nutrient pressure control assembly:

Internal Component View

Packaged View

View of a unit In Operation Mode

Sourcing and Building

The design process seems pretty straight forward. Based on the design, I chose to use the following components:

a quiet boost pump that can pressurize nutrient to 100psi, 24vdc, a small 2 liter accumulator tank. A bigger tank will make changing nutrient a slower, less agile process, though it would reduce the pump running frequency and provide more stable pressure too. non-rust and food-grade material through out the nutrient system, including tank and pump. two 24vdc solenoids. You can get by with just one solenoid for all atomizers. However, one-solenoid-for-each-atomizer-nozzle approach allows more stable pressure, especially when the tubes connected to atomizer is long. Also, in some cases, it would reduce dripping effects on nozzles of low closing threshold. After all, we want atomized nutrient mist, not streams. Also, by isolating sprayers to solenoids, it is easier to identify a specific sprayer having a pressure anomalies. a manual drain valve, and other various tubing fixtures. an insulated box to protect the components and maintain nutrient temperature.

The main challenge was to find compatible parts. After all, we want to build things at reasonable cost and with good performance.

First, the accumulator tank of a suitable size is difficult to find. Most of accumulator tank are for RO system, ranging from $30–$50 dollars alone. And they are pretty big.

Eventually, I found a 2–3 liter accumulator tank. Then I had to deal with manufacturer to change connector material from copper to stainless steel, and to add internal liners inside of the tank to prevent rust and corrosion.

I also went through various pumps of different brands, including Aquatec 8800 made in USA. Eventually, I settled down to a pump made in Taiwan. It handles max pressure of 120psi, though we use it at around 100psi. It meets all my requirement. It is quiet. And it is less expensive.

Last major piece is the pressure sensing and controlling components. Instead of using analog switches to control pump and clamp the pressure, I opted for digital pressure sensor, because it gives the system an option to change working-pressure-range settings via APIs on the fly. In addition, the pressure reading can provide vital clues of system operation status, such as whether atomizers are jammed, or if the pump has failed. The log of the pressure with time-series is also very useful in data analysis later on.

After talking so long, did I actually make a prototype after all?

Yes, with great help from friends. Here it is.

And here is a photo of atomized mists generated by the high pressure.

Thank you very much for the positive feedbacks and comments. In fact, I have received a request to build small batch of high-pressure aeroponics kits.

It is a core HPA kit that you can drop in your existing grow settings, like tents, cabinates, etc. Besides its core fuctions, it can also do live camera views, and control your grow-lights, if available.

Here is the photo of Aeroponics Kit in the Making (Our latest unit AeroXPS is now available) sent by our manufacturing partner:

High-Pressure Aeroponics Kit in the Making

So stay tuned for the next post: High-Pressure Aeroponics Kit