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A small British energy company has developed a vertical-axis wind turbine for onshore applications.
4Navitas Green Energy Solutions’ concept was created to avoid fatigue, an ongoing issue with horizontal-axis designs, with wind coming from all directions, creating bearing and gearbox stress due to yaw/pitch requirements.
The vertical-axis turbine is designed with low drag airfoils and a low rotor speed of 32rpm. There is no need for a blade pitch control system, and, with power, electronics, motor and gearbox at ground level for easy maintenance, wear is considerably reduced and performance improved beyond the 20-year predicted life. 4Navitas has worked with Siemens over a period of 18 months to refine the design.
Drive, motor, coupling and gearbox use the Siemens integrated drive system for performance and extended life. Output is now rated at up to 75kW with plans for a 1MW version already in the pipeline.
The turbine houses a Siemens FZG helical bevel gear unit at its base, and the IE3-rated motor is close-coupled with the gearbox. The shaft is supported by bearings down the mast so gearbox load is significantly reduced. These factors are designed to extend the lifespan of the turbine and improve reliability, said the firm.
The power from the wind is controlled by a Siemens S7-1200 PLC and a Siemens Sinamics S120 system. The S120 harnesses the wind power, even in turbulent conditions, and, by using Active Front End technology connected and synchronised to the supply, transmits power back to the 415V three-phase grid.
Another advantage of the vertical turbine is that by effectively earthing through the 4Navitas-designed tower, two buttress legs and grillages, resonance and noise is reduced to just 40dB. The 4Navitas turbine has a height of 37m, less than horizontal counterparts, taking up a smaller footprint with no need for a large concrete base.
Dominic M’Benga, director of 4Navitas, said: “Our vertical-axis model represents the next generation of wind turbines for micro-generation. It can take wind from any direction without suffering the vibration and wear issues of horizontal-axis turbines, because it’s designed to turn rather than to hold a hub; there’s no weight transfer onto the gearbox and fewer moving parts."