| Summary: | 博士 === 國立臺灣大學 === 生物產業機電工程學研究所 === 107 === The increase of greenhouse gases, temperatures and sea level on the earth makes food production in jeopardy. The plant factories provide the most favorable growth environment for plants, which is unaffected by the weather and can reach stable mass production. It is considered as a possible solution to the problem of planting food crops. The main problem of plant factories is high cost, so increasing plants growth efficiency and reducing energy consumption can reduce production costs.
Hydroponic systems in plant factories can be categorized into recirculating or noncirculating systems. In this study, the effects of various commercially available circulation pumps, including a centrifugal magnetic drive pump, a regenerative self-priming pump, and a submersible pump, were experimentally explored. In addition, the effects of an ultraviolet sterilization system on the ion concentrations in nutrient solutions were examined. For all three types of pumps, the results indicated that there was no significant effect on the concentrations of the nutrient solution. However, the concentration of Fe3+ ions decreased significantly after the nutrient solution was treated by a ultraviolet sterilization system for 48 hours. In addition, the effects of the three types of pumps on the growth of butterhead lettuce (Lactuca sativa var. capitata L.) were examined. The temperature records during the pump circulation tests showed that the nutrient solution temperature of the regenerative self-priming pump increased by 15.5 oC, which caused yellow seedling, scorching on the leaves, and browning of the roots. The ion concentration in the nutrient solutions and total fresh weight of butterhead lettuce did not show any noticeable difference between the centrifugal magnetic drive pump and the submersible pump.
Using centrifugal magnetic drive pump and regenerative pressure controlled automatic booster as the cycle power of strawberry (Fragaria × ananassa Duch. cv. Toyonoka) hydroponic system. During the experiment of the pressured and magnetic drive circulating systems, the pH value remained constant within the range of 6.2–7.0. However, the pH value of the solution in the noncirculating system decreased to 5.5 in the first 2 days after the solution was changed, and gradually increased to approximately 6.5 over the following days. No significant change was noted in the ion concentration of the nutrient solution in the noncirculating system. The concentration of ions the nutrient solution recirculated by two types of pumps was measured, and the ion content and consumption in the solution was calculated. After the 48-day cultivation period, the aboveground and underground fresh weights of the strawberry plants in the magnetic drive recirculating system were significantly higher than those of plants in the noncirculating system, where no significant difference was observed between the two recirculating systems in this respect. Additionally, the aboveground dry mass of the strawberry plants in the two recirculating systems were significantly higher than that of the plants in the noncirculating system. However, the underground dry mass in the three systems did not exhibit any significant difference.
The thermoelectric cooling kit was used to reduce the temperature of the nutrient solution in the single-layer tray in the plant factory. The cooled nutrient solution with a water cooling radiator was then used to lower the air temperature within the shelf. The use of one to three thermoelectric cooling kits reduces the temperature of the nutrient solution by approximately 4.94 to 9.36 °C, and reduces the air temperature within the shelf by 3.34 to 5.52 °C. SolidWorks Flow Simulation was used to effectively simulate the air temperature distribution within the shelf, and verified by experimental results.
In the first generation of the light fixture board, multi-segment switches and overhead fans have been added. If the light fixture board can be adjusted the height along with the growth of the plant, the number of lights can be reduced to obtain the same enough brightness. The average photosynthetically active radiation (PAR) intensity of 200 μmol m-2s-1 was measured above the polystyrene board. The temperature above the polystyrene board reduced by 2 oC using the overhead fans. Using SolidWorks Flow Simulation to design the displacement of the round openings on the light fixture board, the upward airflow light fixture board was constructed with the cross-flow fans. An Arduino Uno with an ultrasonic sensor is used to control the motor and pulleys, and the light board can be automatically lifted in accordance with the height of plants. The upward airflow produced by the cross-flow fans and the openings on the light fixture board takes away the hot air that is generated by the glowing lamp. The temperature above the polystyrene board reduced by 3 oC.
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