Magnetic gearbox for the hydroelectric plant

As energy security for the campus is a major priority at Kadagaya, we have constructed a gravitational vortex hydroelectric plant on our river. In addition to providing electricity, extensive testing of the system has been performed to evaluate it as an appropriate technology. The results of the initial testing of the system were published in the scientific literature in 2019 (get the paper here or contact us for a copy). We showed that the system is economically and technically feasible for application in developing countries, and has many environmental advantages as an off-grid distributed energy system compared to other renewable energy sources and conventional large-scale hydroelectric.

As the turbine speed is very slow, a gearbox with a high gearing ratio is required. As the turbine speed in inversely proportional to the torque, a slow turbine results in a system with very high torque. This high force is a challenging condition for standard gearboxes. Most heavy-duty gearboxes, such as those used for trucks, have a long lifetime as they operate only several hours per day. In the case of a hydropower plant running 24 h/d, such a gearbox will only last a year or two before needing to be replaced. Hence, we spent several years investigating different gearbox options for this system. We evalauted several generations of magnetic gearboxes (as shown in detail in the video). Although this new gearbox technology is an interesting solution for many renewable energy systems, we concluded that it was not suitable for our hydroelectric plant as it requires precise machining, specialized materials, and an external power supply and motor to resynchronise the gearbox during startup. Hence, we decided to redesign the turbine to increase its speed and reduce the torque to allow the use of more conventional gearboxes.