Hydroponics - the technique of cultivating plants in water containing dissolved nutrients in a controlled environment without soil.

Hydroponics is not something new, 600 BC, the hanging gardens of Babylon are the first signs of horticulture using water. The reason I became interested in hydroponics started when I was in the Caribbean, I noticed the island of Aruba has a hot dry tropical dessert climate with a constant western wind blowing, few natural resources, and everything has to be imported from external countries.

Agriculture on Aruba is very limit due to climate and scarcity of natural water. However what it does have going for it is a tropical temperature, permanent wind and year long nearly constant daylight hours. I thought this could be a good starting point on the grounds that the missing components, mainly water can be overcome.

It became very clear that hydroponics, due to the fact that it can save more than 90% of water usage in comparison to open field agriculture in this dessert tropical climate was the way to go.

Cultivation

Propogating tomato suckers

Cultivation and propagation can take place in two ways. Sprouting seeds, or using cuttings.
Using cuttings from an existing plant is faster and ensures the genetic material of the new plant is the same as the parent.

Fruit

Hydroponic tomatoes

Hydroponic plants in a controlled environment generally grow faster and produce more plant material than the same plants in open soil. They produce more fruit and are less prone to disease and infections from insects and the likes.

Compact

Indoor hydroponics

More and better quality produce can be obtained from a much smaller area as opposed to growing the same plants in ope ground. By ensuring ideal conditions like light, temperature, humidity and water nutrients.

Controlled

Hydroponics controller prototype

Using a network connected MCU (ESP32) not only can we measure, monitor and register environmental parameters like temperature, humidity, light, water level, EC and PH and send this as telemetry to a database for analysis, but we can also control these parameters.

Does it actually work? was my first question. Thus to prove I have the capability an environment to test it was set up. To mimic tropical day/night cycles, 200Watt full spectrum LED light modules were obtained. For test purposes, heaters and Peltier elements are used to heat the environment and nutrient solution to mimic tropical conditions. Obviously once in such environment, the opposite will be applicable, thus cooling the environment and water.
Being a wildlife enthusiast it should not surprise you that there are several reptiles that share what I call home. The love warmth and as such the tropical hydroponics proof of concept was setup in the same room. It is a win/win situation for flora and fauna.

Challenges

  • Low water consumption
  • Optimal space use
  • Large produce volume
  • Constant produce
  • Gather data
  • Learn
  • Gain experience

What form of hydroponics to use: I considered NFT (nutrient film technology), but this involves 24/7 pumps running and any cooling of the nutrient solution will soon be lost as it flows through the piping system to feed the plants. The initial setup was using empty buckets from a local snack bar. Here sweat peppers (capsicums) were placed in a flower pot with loads of small holes for the roots and then hydroton (expanded clay pellets) were used to hold the actual plant. Bucket nearly filled with nutrient solution and added an airstone powered by a small solar panel.

Babylon did intrigue me, so a small vertical wall with 18 pods for leafy green like salad was also added to hydroponics setup. Here a small pump (aquarium 12V) is used to pump the nutrient solution from a container at the base to the top of the wall where it flows down towards the reservoir at the base of the wall. On its way down it flow through cupped containers and replenishes the water for each container.

Vertical hydroponics

Vertical hydroponics wall

Different hydroponics setup

Two types of hydroponics systems are tested. One the 'Kratky" method, in basics, a bucket of nutrient rich water with the plants roots submerged in the fluid. And secondly a vertical "Ducht bucket" system. This comprises of multiple rows of containers stacked on top of each other. Water from a higher elevation reservoir is allowed to flow into the top row of containers and as these fill up, they overflow into the containers below. At the base is a receiving reservoir that collects the water. When full uses a 12V solar powered water pump to refill the top container.

Hydroponics and Technology

Many points of concern are on the table when engineering for low power (read ECO friendly) semi-self operational hydroponics systems. This not even taking the mechanical end environmental engineering into full account. The concept is to have one or more low power functional units that monitors and manages the different aspects needed for an optimal hydroponics environment for the plants that are grown in it.

  • Air temperature
  • Air humidity
  • Water level
  • Water temperature
  • Water PH
  • Water ORP
  • Water DTS
  • Light (sun)

Hydroponics KPI's

Key points of interest is the environment that the plants are in. The purpose of automation and AI is to monitor the environment using sensors, register this information and observe plant behavior with as goal to determine the most optimal growing environment for the plants.

Researching sensors for the key points of interest, choices were made to make a proof of concept. Main concern were precision and durability in relation to cost. This left a lot to be desired. Most affordable sensors were not suitable for continuous use.

Sensor choice was based on absolute need and cost. This did result in certain sensors being changed during development as they were just not accurate at all.

Sensors for hydroponics POC

Hydroponic sensors

Hydroponics and Telemetry

Measuring important parameters like time of day temperature, light intensity and nutritional water parameters are vital to determine and maintain ideal conditions for plant growth. The requirement is to automate sampling these parameters and registering the results in a database for smart analysis and eventual automated control.

Low cost, low energy, low maintenance, fault tolerance (possible fail over) are the main criteria when looking at possible automation systems and platforms. At present the Espressif Systems ESP32 range of products is capable of very low power operations when needed and is powerful enough for AIoT implementations when wanted with integrated WiFi and BlueThooth BLE implementation at an amazing low price. This is my GoTo as it intrinsically runs on RTOS allowing for smart energy efficient programs running simultaneously.