Although claims about utility-scale wind farms causing “wind turbine syndrome” have been scientifically debunked, there’s no question that small wind turbines - the ones used for residential-scale - are pretty noisy. The noise from a turbine is proportional to its rotational speed, and small turbines rotate faster than large turbines. Engineers at Renewable Energy Solutions Australia (RESA) think they have a solution: Eco Whisper Turbines, two models of wind turbines designed for the residential market. RESA claims that their turbines are not only quiet, but up to 30% more efficient than traditional three-blade turbines. As an added bonus, they have lower start-up speeds, allowing them to produce electricity at wind speeds as low as 1.7 m/s (3.8 mph), roughly half the start-up speed of typical three-blade small wind turbines.
The Eco Whisper comes in two sizes: a 6.5 meter diameter that generates up to 20 kW, and a 3.25 meter diameter that generates up to 5 kW. The former stands 21 meters tall, while the latter is 18 meters tall.
Eco Whisper turbines have a unique 30-blade design that provides more surface area to capture the wind. This allows the turbine to extract more energy at lower rotational speeds, which partly reduces the noise that it produces. The Eco Whisper has a cowl along the circumference to reduce blade tip noise and power loss caused by turbulence at the blade tips. Another cowl located halfway between the blade tips and the hub improves mechanical stability. The hub includes a direct-drive axial flux permanent magnet alternator; the lack of gears helps reduce cost, complexity, and mechanical noise. The “wild-frequency” AC is rectified. An inverter converts the DC to grid-compatible AC.
A sensor above the turbine measures wind speed and direction.
The Eco Whisper includes sensors that measure wind speed and direction. Sensor data is fed to a digital signal processor that runs a maximum power point tracking (MPPT) algorithm, which is part of an active slew control system that turns the turbine towards the wind for optimal production. If the wind speed exceeds 50 m/s (111 mph), the active slew control turns the blades away from the wind to prevent damage. And if you’re expecting a hurricane, the tower is hinged, so it can be tilted down temporarily. (Also handy for performing maintenance.)
Want to listen to it in action? Turn up your speakers and start the video. I can hear wind and traffic, but not much else.
Images and video: RESA
In general my feeling on wind power has been "go big or go home." While I think utility-scale wind farms are a significant player in renewable energy, most small wind (i.e. residential) options are very expensive and require high wind speeds in order to produce a substantial amount of energy. And yes, small turbines tend to be noisy. The Eco Whisper might be an innovation that silences my skepticism about small wind.