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Small wind reaches new heights

Substantial growth is forecast for the small wind sector, but until now it has been largely dominated by the use of horizontal axis machines. With its latest vertical axis design, quietrevolution hopes to change that.

Vertical axis wind turbines thrive in very strong winds
Vertical axis wind turbines thrive in very strong winds

The use of small wind turbines is growing, according to UK trade association RenewableUK. It reports a 65% rise in annual capacity additions for 2010, with 14.23MW installed compared to 8.62MW in 2009. The market is shifting, however, away from micro-turbines (0-1.5kW) towards larger, grid-connected ones.

“The annual capacity growth during 2010 came predominantly from the 10-20kW and 50-100kW market segments,” it says in its April Small Wind Systems market report.

With 42.97MW of renewable energy capacity now generated through small and micro- wind systems in the UK, providing an estimated 55.75 GWh in 2010, the association believes this can rise to 1,700 GWh (1.7TWh) generated from an installed capacity of 1.3 GW by 2020.

“The industry anticipates that future technology cost reductions coupled with increases in the consumer price of fossil fuels will result in substantial future growth,” it says. “RenewableUK estimates that there is potential for over 600,000 small wind systems to have been installed in the UK alone.”

The bulk of these, it continues, are likely to be grid-connected while “free standing turbines, rather than building mounted turbines, will continue to make up the predominant share of existing installations in the foreseeable future”.

Horizontal axis wind turbines (HAWTs) are the most common types of units installed and likely to stay so for some time, but vertical axis wind turbines (VAWTs) are making inroads. One VAWT turbine making its mark is quietrevolution’s qr5. With power outputs ranging from 6.5-8.5kW (which puts it squarely in the small wind bracket of units in the 1.5-15kW range), its use is growing in the UK, Germany, Scandinavia, and Australia.

The first small VAWT to gain certification under the Microgeneration Certification Scheme – which means it complies with the criteria required for eligibility to access financial incentives such as the UK’s feed-in tariff – the qr5 “delivers low noise and low vibration output along with an active control system with integral remote monitoring,” says the firm. Manufactured in Wales, it has “a strong visual aesthetic and delivers improved performance in turbulent and gusty conditions.”

Great in gusts

Indeed, according to Jose Carlos Damas, quietrevolution’s Sales & Marketing Director: “While companies with conventional turbines might avoid high levels of turbulence, our vertical axis wind turbines thrive on gusty conditions.” The unit, tested and certified by TUV NEL, is especially suited for generating power on-site while its compact rotor design –measuring 5 metres high x 3 metres wide – enables it to be easily installed either on buildings or as a stand-alone turbine, the firm adds.

The helical (twisted) design of the qr5 is responsible for its robust performance, even in turbulent winds, as well as helping to virtually eliminate noise and vibration, according to the firm. Three ‘S’ shaped blades are tapered to shed noise. The blades, spars and torque tube are made of carbon fibre, while all moving parts are sealed to minimise maintenance. Indeed, “with just one moving part, maintenance can be limited to an annual inspection”, says the company.

The machine adopts a direct-drive, mechanically integrated, weather sealed permanent magnet generator, while “peak power tracking constantly optimises output for all sites and wind speeds”. Its projected peak power at 16m/s is 8.5kw aerodynamic; 7.0kW DC; and 6.5kW grid. Annual energy yield comes is 4197 kWh at 5 m/s rising to 12,729 kWh at 7 m/s. And there is “no reduction in power output at up to 40% turbulence intensity”.

With well over 100 turbines installed, “we have measured data from field installations that show even in high turbulence environment [FTI 45%+] we maintain and in some cases exceed the power curve as measured in the NRC Canada wind tunnel,” says the company. “Using real wind data, our modelling shows that QR produces 20-40% more energy than a conventional similar sized-HAWT in a typical location near buildings, where the wind is turbulent.”

The cut-in wind speed for a qr5 is a sustained wind speed of 5m/s and it will shut down in the event of sustained wind speeds over 26m/s. “The quietrevolution turbines are approximately half the weight of the equivalent rated horizontal axis design, and have much lighter loads,” adds the company. “In the case of the qr5 the turbine weighs approximately 450kg.”

Another key feature is the unit’s gust tracking active control system which “allows us to record the wind and turbine behaviour in detail and use this information to optimize the control system’s response to turbulent conditions”. As the company explains: “A high proportion of power harnessed is located in high speed gusts of wind. In an urban environment, with erratic wind conditions, accessing this power can make a big difference (between 20-40%) to the overall energy generated.”

Smart thinking

Notably, the turbine is being used in the European Smart Control of Demand for Consumption and Supply (SmartCoDe) research project, a three-year project funded by the European Commission under the 7th Framework Program (FP7).

A qr5 turbine was installed in a location outside Vienna, Austria, in September as part of a project to understand the wind resource available for small wind applications. “The aim is to provide energy forecasting between 10 minutes and 48 hours ahead,” explains the company. “This knowledge is critical to making the best decisions on when and how to coordinate the local energy use with local energy production,” says Tamás Bertényi, Innovation and Research director at quietrevolution.

SmartCoDe’s primary mission is to balance and reduce the energy consumption of small buildings and neighbourhoods and pave the way for energy-neutral/energy-positive local grids. The programme is unique in looking at demand side management issues. It is focused on how the local energy end user can maximise the benefit of local energy production and decentralized renewable energy sources, such as the qr5.

As part of the project, low-cost wireless nodes, implemented as highly- integrated microelectronic devices, are being designed. These SmartCoDe nodes use wireless mesh networking and will provide the central Energy Management Unit with the information needed to make decisions on use of locally produced energy.

“Coming up with the theory is one thing, but the SmartCoDe project will actually put these ideas into practice with this installation,” says Bertényi.

“This demonstrator will include typical local energy using devices (such as appliances, heating, and lighting) equipped with the SmartCoDe wireless nodes, together with this qr5 vertical-axis wind turbine as the local energy provider.”

He expects that two years of on-site testing will lead to implementation of new wind energy forecasting software, using the qr5 turbine. “We will know a lot more about our turbine’s effectiveness in maximizing the site's energy use.”