Simulation and Analysis of Microclimate Optimal Control in Subtropical Greenhouse-Lettuce Cultivation as Example
| Autor: | Ching-Fu Yang, 楊清富 |
|---|---|
| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 In recent years, many greenhouses have been built in Taiwan to cultivate crops. In subtropical areas, controlling temperature and humidity in a greenhouse is very challenging. In particular, the temperature in summer has a crucial effect on annual crop production. To reduce the cost of environmental control, ventilation and cooling must be designed carefully in greenhouses. Common techniques for greenhouse cooling include ventilation, evaporative cooling (fan and pad or fogging), and shading. Through suitable environmental control, a better microclimate can be achieved in the greenhouse, thereby improving the crop growth conditions. However, this can lead to excessive energy consumption; this is a major issue in greenhouses. Therefore, environmental control in greenhouses has continually attracted considerable research attention. In recent years, many foreign environmental control systems have been introduced to Taiwan. However, the differences in climate and environment between these regions and Taiwan, these systems did not perform well as expected, and the promotion of economic benefits is limited. Through the mathematical model of the greenhouse under different climatic conditions of simulation, and then developing the best design has become the trend of research greenhouse environment control. This method requires the establishment of a dynamic model to accurately simulate various states of the greenhouse. In this study, a dynamic model containing plant dry matter weight, CO2 concentration, temperature and humidity was established based on subtropical climatic conditions. Through historical climate data and control trajectory with the crop growth model for simulation, the simulation results and the measured values are very close. Taiwan''s agricultural facilities are booming and a large amount of money is invested in the construction of greenhouses, using environment control technology to improve the environment and adversity has gradually been received more attention. However, too much investment in environmental control may cause a negative impact on economic benefits. Therefore, the greatest economic benefit can be obtained by controlling expenditure and benefits; this is a typical optimization control problem. In this study, the maximum net income from lettuce production in greenhouse was defined as the main performance index. By using a climate and crop growth model based on historical climate data, we applied the theory of optimal control to estimate the best control strategy. A comparison was performed with an existing environmental control strategy. The results showed that the proposed control strategy could increase the net income of lettuce production by approximately 8%. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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