South African battery manufacturer Eveready’s Kestrel Renewable Energy subsidiary had its e400nb 3.5 kW wind turbine approved and certified in August as part of the UK government’s Microgeneration Certification Scheme (MCS).

The MCS is a British Standards EN45011 scheme aimed at ensuring the quality of renewable technology installations and products. Kestrel was awarded certification following rigorous testing between July 2011 and March this year at independent testing and assessment services provider TÜV’s NEL wind- turbine test facility, in Scotland, in the UK.

The tests involved mainly safety, performance, durability and acoustic analyses. All design calculations were verified to comply with the British Wind Energy Association (BWEA) Small Wind Turbine Performance and Safety standard.

The tests showed that the small wind turbine is able to withstand winds of up to 252 km/h.

Kestrel technical director and e400nb designer James Carpy says a team of quality engineers was sent out from the TÜV NEL facility to Eveready’s Port Elizabeth-based factory to appraise the Kestrel factory production control.

Carpy notes that the Kestrel e400 range was developed in Johannesburg by Kestrel from 2004.

Since 2006, the range has been improved and perfected under the ownership of Eveready and the first version went into production in 2010.

After seven years of design and quality improvement, the current e400nb was fully developed in 2011.

Carpy says, as a designer, his goal was to realise a fully South African wind turbine that would successfully compete in the global market, while offering an African solution to supply energy to rural areas.

“The Kestrel e400nb 3.5 kW turbine is manufactured in standard voltages for remote battery charging, borehole water delivery and grid-tie applications. The battery-charging version connects to a sophisticated charge controller and is used at remote sites to supply energy to telecommunications operations, farms and households. The borehole solution is matched to a high-quality borehole pump, while a grid-tie inverter that connects directly to the existing mains supply optimises the grid-tie solution,” he explains.

The building then runs preferentially on wind power, with any shortfall in energy being supplied by the mains. This results in a reduced electricity bill.

Further, in the UK, users are able to participate in the Department of Energy and Climate Change’s Feed-In Tariff (FIT) scheme, with government paying participants for the electricity they produce.

The current rate paid to the owner is R3.70/kWh produced by the Kestrel e400nb.

Kestrel director Leon Gouws says solid returns from renewable energy, new technology and improved government incentives make it easier to become less reliant on fossil fuels.
“The UK government’s target [to produce 20% of its energy] from renewable sources by 2020, combined with the certification process, means that people can support this vision, knowing their turbine is robust enough to withstand the toughest of winds and is reliable enough to ensure consistent energy production,” he assures.

Turbine Specifications
The e400nb turbine has a mass of 250 kg, with a blade rotor diameter of 4 m and an overall length of 3 m. The peak power output is independently verified at 3.5 kW and the BWEA-rated yearly energy production at a wind speed of 5 m/s is 3.92 MWh/y.

Carpy notes that all Kestrel turbines use an axial flux multipole permanent magnet alternator.

The Kestrel e400nb is fitted with the 120-pole version, which exhibits a low starting torque and good power density. A fully patented pitch control hub limits the wind turbine and, when the blade rotor reaches the maximum speed, the pitch control adjusts the blade angle of attack to the wind, causing each blade to lose lift and increase drag.

“Therefore, the turbine maintains maximum power at the rated wind speed of 11 m/s or more. The lateral thrust on the turbine also reduces with pitch control, which greatly diminishes the stress on the supporting tower. Many existing Kestrel turbines are operational in all climates – from the heat of the African desert to freezing temperatures in Alaska,” Carpy highlights.

As a result of the MCS certification, the Kestrel wind turbine has also been conditionally registered for a scheme in the US with the North American Small Wind Certification Council. US government and state incentives to install wind energy in the US include tax credits, interest-free loans and FIT schemes.

The Kestrel e400nb 3.5 kW turbines are suitable for homes or small businesses, as they require less space than other installations.

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