Vertical-Axis Wind Turbine Product

Overview

A vertical-axis wind turbine (VAWT) spins about a vertical shaft, so it accepts wind from any compass direction without a yaw mechanism. The type described here is the H-rotor Darrieus, or giromill: three straight airfoil blades held parallel to the shaft by radial struts, driven by aerodynamic lift rather than drag. Small machines of this class produce 1–5 kW and serve off-grid homes, telecom sites, and rooftops where the wind shifts constantly and a horizontal-axis machine would spend much of its life hunting.

The layout puts everything heavy at the bottom. The Rotor is the only thing aloft on the Mast; the PM Generator, Brake System, and shaft bearings sit on the Top Frame just below it, and the Turbine Controller is at ground level. There is no gearbox — the permanent-magnet generator is direct-coupled and its output frequency simply follows rotor speed.

Aerodynamics

Each Rotor Blade uses a symmetric airfoil, typically NACA 0018 or similar, because the blade sees flow from alternating sides as it orbits. On the upwind half of the circle, the vector sum of wind speed and blade motion presents the airfoil with a positive angle of attack, generating lift with a forward component; on the downwind half the geometry mirrors and the blade still pulls forward. Torque therefore pulses twice per blade per revolution, which is why three blades are standard — the pulses overlap into nearly smooth torque.

A Darrieus rotor runs at a tip-speed ratio of 2.5–4, roughly half that of a horizontal-axis machine, which keeps blade noise below about 45 dB(A) at 10 m. The cost is efficiency: peak power coefficient is 0.30–0.38 against 0.45+ for a good HAWT, because each blade wastes part of its orbit at unfavourable angles and passes through its own wake. A second consequence is poor self-starting — at standstill the symmetric blades make little torque, so the controller motors the rotor briefly or relies on gusts to spin it past the dead band.

The Blade Clamp sets a fixed pitch of 0–3° toe-out at the Blade Strut tips; there is no pitch mechanism. Struts are faired because they orbit at blade speed and their drag comes straight off the power curve.

Drivetrain

Rotor torque passes through the Rotor Hub into the Main Shaft, a solid 40–60 mm steel shaft running in two widely spaced Ball Bearing sets inside Bearing Housing castings. The spacing matters: wind side-load on the rotor becomes a bending moment, and the two-bearing stance reacts it without loading the generator. A Shaft Coupling below the lower bearing drives the generator through a flexible jaw element.

The PM Generator is a three-phase axial- or radial-flux permanent-magnet machine with 16 or more Neodymium Magnet poles, wound to reach charging voltage at low RPM. Its output is "wild" AC — voltage and frequency proportional to wind — which the controller's Rectifier Bridge converts to DC before MPPT conversion.

Overspeed protection

A wind rotor with no pitch control must be stoppable two independent ways. The first layer is electrical: a Relay contactor shorts the three generator phases together, and the resulting near-short-circuit current produces heavy braking torque that holds the rotor to a crawl in winds up to about 25 m/s. The second layer is mechanical: a spring-applied Brake Caliper grips the Brake Disc keyed to the shaft. Because the spring applies the brake and electricity releases it, loss of control power parks the rotor — the fail-safe direction. The Overspeed Sensor triggers both layers if RPM exceeds the ceiling, and the Brake Pad Set are sized to hold the parked rotor through a 60 m/s survival gust per IEC 61400-2.

Tower and erection

The Tower Mount is a guyed tilt-up design: the Mast hinges on its Base Plate and is raised with a gin pole and winch, so all rotor service happens at ground level. Four Guy Wire sets with turnbuckles anchor at 60–80% of mast height in radius, tensioned to keep mast deflection small under rotor thrust. The Anchor Kit and Lightning Earth complete the civil work; the mast itself is the lightning down-conductor.

Power conversion

At the mast base, the Turbine Controller rectifies, then tracks the rotor's cube-law power curve: for each RPM it loads the generator to the current that holds the optimum tip-speed ratio. When the battery is full or the grid tie is offline, the controller cannot simply unload the generator — an unloaded rotor accelerates — so it diverts power into the Dump Load Resistor, typically an air heater sized for full rated output. The Microcontroller also supervises the brake contactor and displays RPM and power on the LCD Panel.

Siting

VAWTs tolerate turbulent, shifting wind better than HAWTs, which is their main case for rooftops and tree-broken sites. They still obey the energy in the wind: at a 4 m/s average site a 3 m rotor yields only 1,000–1,500 kWh/year, and raising the mast from 6 m to 12 m typically adds 20–40% annual energy for modest cost.