[DESIGN] - High-Pressure Aeroponics

[JLefebvre55]

@PeaPodTech/mechanical

Completion is tracked in the linked issue.

Design Scope

Design a high-pressure aeroponics system for delivering pH- and temperature-controlled nutrient-rich water mist to the root zone.

Purpose

The purpose of the aeroponic system is to deliver water to the root zone as a fine mist for plant uptake, while controlling the water temperature, pH, and concentrations of various nutrients.

Function

Inputs:

• Reverse osmosis water under positive pressure
• pH up & down solutions
• Various concentrated nutrient solutions
• Pump control (on/off to relay for pump power)
• Nozzle control (on/off to relay for solenoid power)
• pH and nutrient solution ratios as signals (stepper positions/valve open percent)
• Thermoregulation power as signal (PWM to H-bridge polarity switch to MOSFET to Peltier)
• Thermoregulation fan power

Outputs:

• Mist (50 micron mean droplet diameter)

Interfaces with:

• Automation
• Energy systems
• Water input

Assumes:

• Input is under positive pressure
• All solutions are non-empty
• All systems have power

Method

1. Water is pressurized to constant 80PSI
2. Heat is added to or removed from the water
3. Temperature and pressure of the water is read (feeds back)
4. Nutrient and pH solutions are mixed in-line at an adjustable ratio
5. Flow to nozzle is controlled (on/off)
6. Nozzle turns pressurized water into mist, which is 98% more water efficient than traditional farming;
7. Mist runoff is contained by a container, and recycled

Features

Each feature should be added to relevant BoMs and CADs where applicable.

• [x] Water Source: Input for reverse-osmosis water. (#71)
• [ ] Manual Source Shutoff Valve
• [x] Diaphragm Pump: Self-priming, auto-shutoff at 80PSI. Power is controlled by external relay signal. (#71)
• [ ] #73
• [x] Accumulator Tank: Uses an air bladder to create and stabilize pressure.
• [ ] #48
• [ ] Manual Drain Valve: Ball valve. Allows the system to be depressurized and drained.
• [ ] Nutrient and pH Adjustment Solution Tanks
• [ ] #70
• [ ] Solenoid Valve: Enables on-demand misting.
  • [x] Source and test
  • [x] Add to BoM
  • [ ] Add to CAD
• [x] Grow Tray Quick-Disconnect: Connectors between aeroponics supply and nozzles that allow for quick disconnection with auto-shutoff so the trays may be removed.
• [x] Nozzle: Mounted to grow tray, pointed at plant roots. 80PSI water through a 0.4-0.6mm orifice produces 5-50 micron water droplets, optimal for plant growth.
• [ ] Runoff Collection Container: Mounted and sealed to the grow tray. Encapsulates the nozzles and root zone entirely, and provides a runoff water extraction port
• [ ] Runoff recycling pump
• [ ] Tubing to connect everything

Requirements and Validation

What does this design need to accomplish? How do we know it has accomplished this?

List any applicable metrics with criteria/constraints, applicable to purpose, function, method, and each feature, as well as how to test them.

1. System throughput must meet water delivery requirements

More in sub-features

Verification

Each test should be performed and documented, and the testing documentation attached to the PR.

How does this design achieve its method effectively, safely, and reliably? How do we test this?

Specific testing procedure:

1. Temperature, pressure sensors communicate as expected
2. No leaks at any connections under a) source pressure, b) fully pressurized
3. Pump auto-shuts off near 80PSI
4. Tubing and all components withstand full pressurization
5. Solenoid is normally closed, withstands full pressurization, and opens when power is applied
6. Quick-disconnect operates as intended at full pressurization without leaks
7. Nozzles produce full-cone mist
8. Manual and servo-actuated valves operate as intended
9. Runoff container is sealed, and extraction port works

Additional context

Add any other context or screenshots about the prototyping request here.

• [x] Plumbing diagram

[JLefebvre55]

(Potentially) useful resources:

• Aeroponic Spray Nozzles to Use/Buy
• High Pressure Aeroponics System Components Explained

[nchareunsouk]

Potential pump options:

Option 1: Onsen 1L tank + External Pump Onsen 1L tank is rated for 125 psi. Onsen also makes a pump but only rated for 55 psi. https://onsenproducts.ca/products/onsen-1-0l-accumulator-tank

Keeno pump is from Amazon. Is rated for 116 psi - 5L/min. Other similar pumps available. link

Similar pump from SailFlo. link

Option 2: All in one bladder tank + pump. - EDIT: these are just tanks These types of pumps are on Amazon and contain a built-in 0.75L bladder. link or link

[nchareunsouk]

Good resource/overview on HPA: https://www.aeroponicgrowers.com/high-pressure

[JLefebvre55]

Frame/housing problem: how do we a) mount the nozzle hardware under the grow tray, and b) contain the spray?

Potential solutions in existing NASA space aeroponics work?

[nchareunsouk]

Potential solution: Make a bag with ripstop (a zero porosity nylon fabric). Ripstop is used to make everything from raincoats to camping gear and parasailing canopies. It's also cheap.

A square bag could be made to fit underneath the frame and it can be held in place by securing it to the sides of the aluminum extrusion. This would encapsulate the nozzle/mist and have the added benefit of also being flexible (in reference to the accordion idea).

[nchareunsouk]

Top Options: pump bladder tank

Nozzle: potential option Nozzles with orifices of ~0.6mm at 80 psi should produce a mist of 5-50 microns. Most cheap nozzles on Amazon have 0.4mm orifices.

[JLefebvre55]

Just realized this issue should cover testing as well.

[JLefebvre55]

Bought fittings today. Will open a new PR to a) update BoM and b) test.

[JLefebvre55]

@nchareunsouk is gathering a list of nozzle alternatives.

[JLefebvre55]

Ordered new nozzles, fittings from McMaster Carr

[JLefebvre55]

@nchareunsouk Can you find the source where it mentioned the .6mm nozzle opening? Preferrably the NASA document

[JLefebvre55]

Re-opened for remaining tasks