Development and experiment of movable solar aerator

Abstract: Dissolved oxygen (DO) is the most important factor in pond aquaculture. In order to reduce "oxygen debt" of water in the bottom and prevent fish from hypoxia in the next morning, aerators usually need to run which can stir the water in pond. However, this method consumes a lot of electrical energy and is of low efficiency. A movable solar aerator was designed by the software of Solidworks to solve these problems. It mainly consisted of solar power mechanism, water walking mechanism, aerator and working control system, which could move upon the water, generate waves and exchange amount of water from bottom to surface, etc. The solar power mechanism provided energy for the entire machine, while the water walking mechanism drives the whole machine to move on the water surface. The aerator orbits of the equipment could affect a large area of the pond. In order to verify the reliability of the system, the reliability of walking performance was tested under both idling and load situation by the experiment in which the walking test platform was separately proceeded on the ground and in the pond. First, to deploy the reliability test on the ground, the steel cable was fixed with the stainless steel stem with the diameter of 6 mm, and the locked position was located outside the stop block, so as to ensure there was sufficient gap between stainless steel stem and steel cable. Based on that, it would ensure the synchronous motion of steel cable and stainless steel stem while no interference issue between them. Additionally, to perform the reliability test in the pond, the 2 ends of the steel cable were fixed through the wooden stake. When the moving distance was separately set as 2, 3 and 4 m, after setting the parameters in the control system, the running time and the odometer of single track could be recorded separately. The test duration was 1 day, running 5 h per day with 3 replications, and the illumination intensity of movable solar aerator start-up was 1 7000 lx. In order to test the stirring water capacity of the movable aerator, the aerator was mounted in the center of the round pond with depth of 1.8 m and diameter of 9 m, to get the relevant parameters, such as rotation speed, wave height located at 0, 3 and 6 m away from the device center, wave velocity and wave length. Results of a series of tests on the mechanical properties revealed that the minimum illumination intensity of movable solar aerator start-up was 1 7000 lx; the idle running noise was 75.3 dB; the moving speed upon the water was between 0.027 and 0.041 m/s; the remote-controlled distance was 44.2 m; the maximum wave height was 0.44 m in the aerator position. When the illumination intensity got stronger, the value of oxygen transfer efficiency and the capacity of stirring water were getting higher. The maximum mechanical aeration capacity was 1.24 kg/h, with dynamic efficiency of 2.59 kg/(kW·h); the maximum stirring water capacity was 1254.4 m3/h, with stirring dynamic efficiency of 2613.3 m3/(kW·h). The movable solar aerator utilized solar power, which had the advantages of large operational area and long running time, which was about from 5 to 6 h per day. According to the test result of the water walking mechanism, it performed well with high stability and reliability, which overcame the traditional problems of limited operation area and large energy consumption. It could effectively accelerate to exchange water of the upper and lower layer by machinery disturbing in the whole pond, which could be up to 60%-80% of the pond area. Thus, this process corresponds to the concept of environmental friendly, energy saving, high efficiency and low-carbon emission.