Climate and nutrient automation for a hydroponic greenhouse

GreenDune grows lettuce in nutrient film channels inside a 1,200 m² greenhouse. In summer the outside air reaches 45 °C at noon. The greenhouse is cooled by six exhaust fans pulling air through wet cellulose pads on the opposite wall, with a retractable shade screen overhead. A small dosing system adds nutrient concentrate and acid to the recirculating water.

Today a worker switches fans and pumps by hand and checks the water with a handheld meter twice a day. On hot afternoons the greenhouse reaches 33 °C, lettuce bolts and turns bitter, and about 12% of each summer crop is lost. Water EC (nutrient strength) drifts between checks, and pH sometimes goes above 7, which locks out iron. The owner wants a simple, cheap controller the team can maintain.

The targets are: - air temperature at or below 28 °C during the day and 18–22 °C at night; - relative humidity 60–85%; - nutrient EC 1.2–1.8 mS/cm and pH 5.8–6.2.

The controller will run on an ESP32 with a temperature and humidity sensor, an EC probe, a pH probe, a light sensor and relays for the fans, pad pump, shade motor and two dosing pumps. A partner grower in a Nashik polyhouse wants the same design for capsicum.

You will build a simple greenhouse climate model in Python, write and test the control logic against it, add nutrient dosing logic, and then run the firmware on a simulated ESP32 in the free Wokwi simulator. Finally you will estimate water and electricity use.

You need no hardware. If you have an ESP32 or Arduino kit, you may also test on a breadboard.

Done looks like a climate model, control logic that holds the targets through a simulated 45 °C day, dosing that keeps EC and pH in range, firmware that runs in Wokwi, and a short report with water, power and crop-loss estimates in dirhams and rupees.