No-Load Performance Testing of an Arduino-Primed Hybrid Solar-Electric Crop Dryer

Abstract

Abstract. This work presents the performance testing of an arduino-controlled hybrid solar-electric cabinet dryer under no-load condition. The integral hybrid system mainly consists of solar and electric heat components which are connected to a programmable circuit board (micro-controller) with a piece of software (integrated development environment, IDE) known as arduino micro-processor which controls and automates the overall operation of the dryer system through its relay and receives signals from transducer sensors (a capacitive humidity and thermistor sensors) placed at different locations on the dryer. Through the use of a 4 X 4 matrix keypad, preset chamber temperature threshold and chamber air flow rates were inputted; relative humidities of the different locations, tray and chamber temperatures and energy consumption from both solar and electric energy sources were measured, recorded, displayed on the liquid crystal display (LCD) and transferred to a micro-computer via a universal serial board (USB) cord. With the arduino platform, the quantity of moisture loss per given time and energy required for drying as well as other basic drying parameters can be effectively measured with minimum human supervision, thus making the entire operation automated and efficient. No-load tests were conducted to evaluate the thermal profile of the dryer, which involved running the dryer at five different air velocities (0.1, 0.5, 1.0, 1.5, and 2.0 m/s) in order to determine the required time to reach the preset optimum drying temperatures of 50, 55, 60, 65, 70oC. Results obtained show that an average minimum drying chamber heat-up times of 9.8 and 6.2 minutes were required by the electrical and hybrid heat sources at a temperature and air velocity of 70oC and 2m/s respectively. Ambient air temperature, relative humidity and air velocity were observed to have significant influence on the dryer heat-up time and tray temperatures. Drying time had significant effect on the energy consumption of the dryer mainly due to hourly solar heat. The hybrid and electric heat sources developed a maximum chamber temperature of about 92.5 and 84oC respectively after 210 minutes. Peak energy of 1946 and 1485kW-hr were developed by the hybrid and electric heat units respectively and 784kW/m2 was developed by the solar collector. The solar component contributed a maximum drying chamber temperature of 30 to 31.7oC which is about 50 to 55% of the required drying chamber temperature. Energy regression equation models were developed in terms of time for each heat source as well as the hybrid with an average R2-value of 0.99. The general performance of the dryer was attributed to the heat contribution of the solar collector and that of the electric heater as well as its negligible thermal losses. Good prospects for future applications as well as recommendations were stated.