Micro magnetic driven bidirectional turbine used in urban water mains for hydropower generation

H. Yang, J. Du, Z. Shen
The Hong Kong Polytechnic University,
Hong Kong

Keywords: nicro hydropower, magnetic driven, bidirectional turbine, urban water mains


Data collection along water supply pipelines in an urban environment is of vital importance for urban water supply as it can provide timely detection and early warning of water leakage and other information. However, any water monitoring systems are usually composed of a lot of sensors and meters which usually need power supply through batteries, which need to be replaced frequently. To provide constant and reliable power supply for water monitoring system, a micro magnetic driven bidirectional hydro turbine was developed to generate electricity using limited water head inside water mains. The inline turbine consists of a T-joint, two blocks integrated to the pipe inner wall and one cross-flow runner inserted through the T-joint. The blocks are used to accelerate flow velocity and direct more water to flow through the runner, so that the runner can harvest energy from water flow and transfer the energy into electricity. However, unlike traditional micro hydropower, the water mains possess a very high requirement for hydropower harvesting because of water security and complex pipe conditions. Firstly, no water pollution or leakage could be caused by the application of inline turbine. To meet this requirement, all the components that contact with water are made of food grade materials. Besides, a magnetic coupling is used for sealing and transmission. Unlike traditional mechanical seal which achieve sealing by tight fit of two different seal parts, the magnetic coupling seals water by a containment shroud and transfers torque from one shaft to another using a magnetic field rather than a physical mechanical connection, so seal failure and water pollution can be avoided effectively. Secondly, bidirectional water flow may exist in the water mains under the situation of pipe bursting for maintenance or switching of supply sources, so the inline hydro turbine should be capable to generate electricity with bidirectional water flow. To solve this problem, the shape of blocks integrated to pipe inner wall is specially designed. With the developed blocks, the inline turbine could operate under bidirectional water flow without changing the runner rotation direction. A preliminary prototype was manufactured and tested in a lab test rig. Experimental results indicated that the daily electricity generation of the proposed turbine at flow velocity of 1.3m/s is about 600Wh and the water head loss is always within 5m water, which means that the proposed turbine can provide sufficient power for any general water leakage monitoring system without influencing the normal water supply. In conclusion, the developed micro magnetic driven bidirectional turbine is a promising solution for constant and reliable power supply to water monitoring system. Its commercialization potential could be huge because water leakage monitoring has been increasingly important in many countries or regions due to the fact that a considerable length of water mains has approached the end of their service life.