GEARS & GEARBOXES FEATURE
The tide is turning on renewable energy
Magnetic gear technology has been selected for a new project expected to offer a practical solution to the challenge of affordable tidal energy. Magnomatics explains
M
agnetic gear technology provider, Magnomatics, is turning its
attention to the tidal renewable sector. It has joined offshore engineering specialists, Seaplace, in a 32-month collaborative development project that is being supported by the Eurostars-2 programme. The project aims to minimise the
environmental impact as well as providing a turbine that needs little civil engineering infrastructure (many tidal energy approaches need engineering works such as tidal barriers), meaning it will be relatively simple to install and commission. The initial programme will see the
design and construction of a 5kW scaled demonstration machine which, following extensive testing, will lead to the design of a full scale, 750kW generator. The PDD generator is expected to offer greater efficiency, a more compact generator nacelle and better reliability, all achieved through the integration of a magnetic gear and a permanent magnet into a single assembly. In the arrangement the relatively low speed turbine is connected to the pole piece rotor of a magnetic gear. The outer
array of magnets is attached to the inside of a stator, which provides the reaction torque to drive a high-speed magnetic rotor. This induces current into the stator that is then connected to the grid through a three-phase inverter, resulting in a very efficient and compact generator. Of particular significance is the efficiency of the generator when operating at part loads. Measurements on demonstration programmes have shown machine efficiencies in excess of 97%, even when operating at 15% of peak load. Moreover, the direct drive PDD generator is expected to be more reliable than other solutions
Magnomatics has been developing solutions for wind turbines for several years. This is supported by European funding via the Inn Wind Project, with other project partners including Siemens, TU Delft, DNV GL (formerly Garrad Hassan) and the University of Sheffield (for a full list of participants see
www.innwind.eu/). The project demonstrated that Magnomatics’ Pseudo
Direct Drive (PDD) generator has the potential to provide a more reliable direct drive, delivering electricity at a lower unit cost. Following a small-scale demonstration machine, a future project is now planned that will produce a 500kW demonstration unit. Testing the demonstrator paves the way to building a full size multi-megawatt unit.
Static permanent magnets Wound stator
Low speed rotor with ferromagnetic segments
Permanent magnet poles High speed rotor
Magnomatics’ Pseudo Direct Drive (PDD) generator
DEVELOPING AN INTELLIGENT GEAR HOBBING MACHINE
An intelligent CNC gear hobbing machine – with an advanced electronic gearbox that eliminates the need to change mechanical gears on traditional machine tools – has been developed by NUM Taiwan and Feng Chia University. For the project, NUM donated a series of CNC controllers. The machine is based on an upgrade to an NC gear hobbing machine that featured a mechanism provided by Chang Feng Gear Machinery Co. Developed under the Industry 4.0 planning and design concept, it offers powerful expansion capabilities through use of a CNC-PC communication framework. Not only does it have facilities for monitoring parameters such as spindle speed, temperature and motor current, but transmission of network data, calculation of cloud data, analysis and prediction can be performed via tool wear monitoring systems. This facilitates online compensation and product measurement, for optimal cutting parameters and precision. NUM Taiwan offers a variety of special machining software for gear applications, including an
electronic gearbox function (five-axis synchronisation transmission) and an automatic tooth alignment function, which are essential for CNC gear hobbing applications. Professor Ruihong Xu at the University’s College of Engineering said: “The electronic gearbox system
included in the Flexium+ CNC system is superior to the traditional tooth matching gearboxes. It can achieve high precision and output without spending time on changing gears, and without the back clearance problems that occur in gears with traditional tooth matching.”
NUM (UK) T: 0871 750 4020
www.num.com
that utilise a gearbox, which is important for applications where the costs associated with lost operation, removal and re-installation are extremely high.
ACCESSING TIDAL FLOWS Seaplace will provide its FTMC turbine, resulting in a tethered and self-steering turbine that can harness energy from 2-3m/second of tidal flow, generating 750kW of power from a relatively compact 20m diameter machine. The turbine consists of a diffuser that also functions as a floatation device. Inside the diffuser is a fixed impellor turbine that drives the generator. The whole assembly is tethered to the seabed with a mooring tendon that also provides the connection to an inverter. The machine will be able to access
tidal flows of below 60m while giving access to tidal flow resources that would be uneconomic for fixed turbines. As tidal flows change, the design of the turbine naturally weathercocks to capture the tidal flow, without any active control. As well as offering minimal installation costs, these turbines can be installed in arrays that are designed to not affect shipping or fishing activities.
Magnomatics
www.magnomatics.com
DESIGN SOLUTIONS | SEPTEMBER 2016 21
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