Plant Fitting Box

What it does

By installing the smart farm instead of using shading nets for cultivating shade plants, we can reduce the environmental pollution caused by incinerating shading nets and recycle the solar energy that would otherwise be wasted.

Your inspiration

I came across an article about the cost of disposing of used ginseng shading nets in Cheongju (source: Dong-A Ilbo). Farmers face costs of 250 million KRW for disposal, leading many to resort to illegal incineration. These nets do not decompose, and illegal burning releases toxic gases, causing air pollution. To address these environmental issues and recycle sunlight wasted on shading nets, we chose transparent solar panels that allow light to reach the plants. Using PDLC film and LEDs controlled by PWM, we maintain a consistent light saturation point, ensuring a stable light environment regardless of weather conditions

How it works

Energy Harvesting Process A transparent solar panel converts sunlight into electrical energy to charge a 12.3V (3S) battery. The panel maintains approximately 26.3V under sufficient sunlight, and a step-down buck converter lowers the voltage. A battery protection circuit prevents damage from reverse voltage. LUX Adjustment Process A transparent solar panel with 40% transparency and 60% power generation adjusts the LUX reaching the plants using film and LEDs. Example: Target LUX is 550 External light at 100 LUX: Internal light is 100 * 0.4 * 0.8 = 32 LUX; LED adds 518 LUX. External light at 2000 LUX: Internal light is 2000 * 0.4 * 0.8 = 640 LUX; film blocks 90 LUX. A light sensor measures LUX. ATmega128 uses ADC and PWM to adjust LED brightness and film transparency. MOSFET connects 12V LEDs to the battery, controlled via PWM. An LCD screen displays real-time LUX inside the smart farm.

Design process

1. Charging Process A step-down buck converter and battery protection circuit were used to charge a 12.3V lithium-ion battery from a 26.3V solar panel. Mandatory Protection Circuit: When the solar panel doesn't output voltage (due to insufficient sunlight), reverse voltage can flow to the battery and damage the converter. Hence, the protection circuit is essential. Correct Connection Order: The proper sequence (Panel → Converter → Protection Circuit → Battery) must be followed for proper charging. Incorrect sequencing can cause reverse voltage, leading to damage. 2. LUX Adjustment Process Control Sensor Positioning: Initially, both control and internal sensors were inside the smart farm. The control sensor was affected by film and LEDs. Repositioning it to rely only on sunlight stabilized the internal sensor, maintaining target LUX. Real-time Data Correction: Sensor discrepancies caused instability in maintaining target LUX. Using a moving average filter in the ATmega128 to correct external sensor data stabilized the internal sensor, enabling consistent control of LED and film. LED Voltage Rating Issue: Due to the ATmega128's voltage limit, the battery used for charging was connected to the LED via MOSFETs, with PWM control from the ATmega128 managing the LED.

How it is different

In traditional shading plant cultivation, the main component is covered with a light shield made of plastic in order to block sunlight. The shading net is classified as a household waste, and the manpower, budget, and system to handle it are not properly established. After all, long and thick waste mining networks are either neglected or illegally incinerated because there is no other way to do anything about them. Neglected waste mining networks do not decompose in nature, and during illegal incineration, they emit a lot of toxic gases, causing air pollution. Our idea can solve the environmental problems caused by waste mining networks. Additionally, the remaining light reaches the plant, which uses renewable energy to operate the smart farm by producing solar power. As a result, it is possible to contribute to environmental protection by building a self-contained system and reducing carbon emissions.

Future plans

Traditional shading nets are designed to allow air and moisture to pass through freely. In contrast, the proposed model consists of solar panels and film, which do not allow air and moisture to pass through, potentially causing heat or moisture buildup that can harm the plants. To address this issue, the model includes temperature and humidity sensors inside to monitor the internal environment in real-time and automatically adjust it. Based on the sensor data, fans, heat exchangers, and temperature and humidity control devices will operate to maintain the optimal environment for plant growth.

Awards

Grand Prize at the 55th Korean Institute of Electrical Engineers Summer Conference 2024 (15th Smart Energy Competition)