Development and Evaluation of Environmental / Growth Observation Sensor Network System for Aquaponics

An aquaponics is attracting attention to achieve a new type of primary industry where workers can get a stable income. The aquaponics is a system that combines aquaculture and hydroponic cultivation equipment where the excrement of fishes is broken down by bacteria into nutrients utilized by plants. In the system, optimization of activity of the bacteria is an important problem to maximize the harvest amount from both aquaculture and cultivation, but an automatic control system that can keep the activity in an optimal state has not been achieved.Therefore, in this study, a new sensor network system that remotely monitors various environmental information of water (e.g., water temperature, pH, dissolved oxygen) affecting the growing conditions of aquaculture and cultivation, and that quantitatively estimates the degree of plant/fish growth is proposed. In the proposed system, a depth camera module is utilized to grasp a detailed shape of each plant, and an area of each part (i.e., leaf, stem) of the plant is estimated by analyzing both RGB and depth images to quantify a growth condition of the plant automatically. Also, measurement results of the environmental information are automatically collected from each sensor through a low-power short-range wireless communication (i.e., Bluetooth Low Energy (BLE)). Furthermore, the obtained information is analyzed to specify the correlation between the growth condition and the environmental information. Based on the correlation, the proposed system controls the water quality so that the activity of the bacteria becomes optimal for each kind of plant/fish. Through the performance evaluation, it is clarified that the use of BLE is suitable for constructing a sensor network for collecting the environmental information, and the growth condition of the plant can be estimated at a high accuracy.