Indirect Solar Dryer
Development of a novel and economical Indirect Solar Dryer for food preservation.
Methodology & Design
Problem Statement
The objective of this study is the development of a novel and economical Indirect Solar Dryer for Food Preservation. The system aims to improve the shelf life and quality of dried foods such as bananas, potatoes, etc., by effectively reducing their moisture content.
System Design
Exhaust Air Flow
The exhaust fan is placed at the back of the drying chamber to release additional air and excess heat efficiently.
Cold Airflow
The inlet fan is placed at the front to intake fresh ambient air while maintaining the desired inner chamber temperature.
Conventional Trays
Custom wooden trays were integrated to hold and arrange agricultural products neatly during the drying process, optimizing air distribution.
Air Circulation & Sensors
Selected fans capable of providing the ideal airflow rates for efficient drying, paired with a DHT11 temperature and humidity sensor to continuously monitor the drying environment.
Arduino Microcontroller Integration
- Connected the DHT11 sensor to measure and monitor temperature and humidity levels inside the dryer.
- Connected the motor driver to control the air circulation fan, adjusting the fan speed dynamically based on desired drying conditions.
- Integrated an I2C module with the display to reduce overall wiring complexity and ensure reliable readings are shown in real-time.
Hardware Requirements
- Sealed box built to precise dimensions
- Polycarbonate top sheet cover
- Air circulation fans (exhaust and intake)
- Zeolite Bed (drying medium)
- Arduino Uno Microcontroller board
- L298N Motor Driver
- DHT11 Temperature & Humidity Sensor
- 16x2 LCD Display with I2C Module
- 12V DC Adapter & connection wires
Arduino & Programming
Arduino serves as the central control unit that allows us to automate and regulate the drying process. Arduino's flexibility, reliability, and extensibility make it an ideal choice for this project. It enables us to precisely regulate temperature, humidity, and airflow by collecting sensor data and driving actuators dynamically.
Wiring and Pin Configuration
- DHT11 Sensor: Data pin connected to Arduino Digital Pin 12.
- L298N Motor Driver: Input pins IN1, IN2, IN3, and IN4 connected to Digital Pins 2, 3, 4, and 5 respectively. Enable pins ENA and ENB connected to Pins 9 and 10 to regulate speed.
- I2C Display Module: SDA connected to Analog Pin A4 and SCL connected to Analog Pin A5 for simplified interface.
Programming Steps
1. Read & Verify
Collect raw readings from the DHT11 sensor and display them on the 16x2 LCD screen.
2. Dynamic Logic
Process temperature readings and compute pulse-width modulation (PWM) to step up or down fan speed.
3. System Safety
Add thresholds to prevent overheating, shutting off fans if the environment stabilizes.
4. Serial Monitoring
Relay metrics back to compile and trace logs, fine-tuning variables for different crop configurations.
Design Consideration
SolidWorks was utilized as a primary tool to design, simulate, visualize, and analyze individual components of the solar dryer. This allowed for precise 3D modeling and structural integrity testing prior to fabrication.
Key CAD Focus Areas
- 3D Modeling & Assembly: High fidelity modeling of the zeolite bed chamber, collector body, polycarbonate sheets, and fans.
- Thermal & Airflow Simulation: Simulated thermal behavior to locate heat traps and maximize convection currents inside the drying chamber.
Structural Integrity
- Insulation Design: Insulated walls to prevent energy loss and maintain a balanced, stable drying environment.
- Polycarbonate Angle: Slanted design optimized to capture the maximum angle of solar radiation during peak hours.
Construction Phases
Angle Cutting & Framework Preparation
The angles required for constructing the solar dryer framework were cut to size according to the CAD drawing dimensions. Marks were measured carefully and cut using an angle grinder.
Arc Welding Assembly
The cut metal angles were joined securely using electric arc welding. Arc welding creates a strong, load-bearing bond essential for structural stability, ensuring the framework remains rigid.
Boundary Structure Formation
Connecting the welded angles formed the main boundary structure of the dryer, acting as the structural cage for internal trays, sheets, and electronic installations.
Steel Sheet Cutting & Enclosure Welding
Steel sheets were cut to precise dimensions and welded onto the inner boundary structure of the solar dryer, forming airtight insulated walls for the heating channel.
Body Priming
Applied an even layer of anti-corrosion primer on all metal surfaces to promote proper paint adhesion and extend the overall lifespan of the system.
Applying Solar-Absorptive Coatings
The outer body was painted black to maximize solar radiation absorption. The interior was painted grey to aid in even distribution of heat and light across drying trays.
Finishing & Component Integration
Once painting was complete, self-groove screws were used to securely fasten the polycarbonate sheet to the top frame. Hot glue was utilized to mount the Arduino microcontrollers, drivers, and displays within insulated cavities, protecting the electronics from the heat of the main drying chamber before all jumper wire paths were routed and tested.