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New Magnetic Gearbox Concept Makes Hydropower Possible in Environmentally Sensitive Applications

Posted: Monday 24th April 2017

Innovative gearbox design enables hydropower to be used safely in drinking water treatment facilities or aqueducts.

Driveline engineering specialist, Drive System Design (DSD), is contributing to two innovative hydropower projects in the USA by developing an existing magnetic gearbox concept for turbine generator applications. Pioneer of the concept, Emrgy Inc., has commissioned DSD to evolve its 10kW proof-of-concept unit into a second generation design engineered for minimal maintenance.

Following the initial success, DSD has been further commissioned to scale up the concept to 100kW in a parallel program, part-funded by the US Department of Energy. The aim is to broaden the range of applications with DSD simulations demonstrating the potential for further enlargement to more than 500kW.

Emrgy is an Atlanta based start-up company with proprietary technologies including an axial flux, cycloidal magnetic gear concept used, in this instance, to connect a water-driven turbine to a generator. The system is able to extract energy that would otherwise be wasted from slow-flowing, low-head applications and is completely carbon-free.

"The magnetic gearbox concept makes environmentally sensitive hydro applications feasible because it significantly reduces the risk of water pollution that could arise from the lubricants used in a conventional gearbox," explained Tony Walsh, VP at DSD Inc., Michigan. "The only lubricant required is for the bearings, and for this we use FDA-approved grease and bearings from the food industry. This allows the system to be used safely, even in drinking water treatment facilities or aqueducts."

The 10kW production unit designed by DSD has a 60 rpm input speed with a 30:1 step-up ratio to the output and uses a 16 inch (0.41m) diameter rotor. The initial concept was determined by the available water flow and channel width of the first intended application.

DSD worked alongside Emrgy to refine and develop the initial concept through to the first production unit. This phase of the project involved a rigorous assessment of the technology's boundaries and the development of innovative magnetic arrangements that enabled the reduction in gearbox size. DSD's simulation led approach facilitated the development of design, analysis and life calculations to a 10 year duty cycle. The DoE-supported program for the 100kW unit began in February 2016 and has successfully met the requirements stipulated in phase 1. Phase 2, build and test, has been approved and is about to commence.

DSD has re-sized the design with a rotor of 39 inches (1.0m) diameter achieving a 10X yield in performance, with a 2X increase in diameter. Because the design has relatively few moving parts, it offers a reliable, low cost solution yet can provide a very long life with limited scheduled maintenance.

"Hydropower already supplies approximately 7% of America's electricity and this could be significantly extended by the use of environmentally friendly technologies such as the magnetic gearbox," said Walsh. "Alternative applications, such as waste water treatment facilities, are already being discussed."

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