Sources - Small Scale Wind Energy

Small scale wind turbine units are a cost-effective solution to the energy needs of a wide range of both residential and industrial centers. Wind turbines are becoming increasingly more attractive with the potential of significantly reducing energy bills and helping to achieve the government's target of reducing greenhouse gas emissions by 10% by 2010.

There are a wide range of turbines available for small scale use; much will depend on the requirements of the client and both the physical and energy needs of the local environment. The following information has been designed as a source of reference for communities, individuals and small scale industries interested in the potential of wind energy.

The basic wind energy conversion device is the wind turbine. Although various designs and configurations exist, these turbines are generally grouped into two types:

Vertical-axis wind turbines, in which the axis of rotation is vertical with respect to the ground (and roughly perpendicular to the wind stream).

Horizontal-axis turbines, in which the axis of rotation is horizontal with respect to the ground (and roughly parallel to the wind stream).

Energy from the wind turns the blades or rotor, this movement turns the shaft which powers a generator for the production of electricity.

There are broadly two types of wind generator available: wind chargers, consisting of smaller units up to 10Kw and wind turbines, consisting of grid connected units from 10Kw upwards. A wind charger will generate electricity at 12v to 48v DC for battery charging. An electricity supply can be achieved from a suitable storage battery bank. A wind turbine will generate electricity at mains voltage and will interface, through a control panel, directly with the regional electricity company.

MKW Engineering - "Gazelle" 20kW Wind Turbine - (www.mkw.co.uk/).

MKW Engineering Ltd have developed and designed a small scale wind turbine for consumers with some land in rural or open areas. Users include dairy, pig and poultry farms, glasshouses, rural industries, water and sewage works, schools, hotels and environmental projects.

The Gazelle turbine generates enough electricity to offset most of the electricity used by a typical farm. When environmental conditions are windy and the energy needs of the site are low, excess power can be sold back to the local power company. The manufacturers estimate that the Gazelle will be most cost effective for consumers who spend between £3,500 and £7,000 annually on electricity bills.

At wind speeds of 6.5 metres per second at hub height, the turbine should produce over 60,000kWh per year.

At 7.5 m/s, the turbine should produce over 72,000 kWh per year.

The turbine has three blades with a diameter of 10.2 metres with a tower measuring 15 metres in height.

A gazelle wind turbine costs approximately £35,000. For examples of other system costs visit www.cholwell.org.uk/.

Proven Wind Turbines - (www.almac.co.uk/proven)

There are three Proven Wind Turbines; the WT600, WT2500 and the WT6000 each designed to provide electricity for a range of energy requirements.

The photograph illustrates a Proven 2.2kW wind turbine in use on Dartmoor. The house was previously powered by a diesel generator but is now supplied with a 240V AC supply of electricity from a bank of batteries charged by the wind turbine. The system was fully installed for £5000, as an alternative to the £60,000 cost to connect the house to the local grid.

Further information can be found here.

Wind charges cost up to £15,000 plus installation and wind turbines upwards of £25,000. Typically, wind energy will cost between 2 pence and 10 pence per kWh depending on project scale and location, comparing favourably with the cost of electricity from conventional sources. Lower cost wind generation can be achieved on the windier sites.

Sites for individual and clusters of wind turbines are carefully assessed for environmental impacts before construction. Some of the main issues considered are listed here.

Aesthetics
The visual impacts of individual wind turbines and wind farms can vary depending on the site and the size of the turbines. They may also appear intrusive to some people, but not to others. Many manufacturers have employed architects and landscape designers to soften the impact a wind farm has on the landscape. Most sites are carefully chosen to minimise the visual impacts as far as possible.

Noise
Noise from wind turbines is less than many other country activities. Two types of noise are generated by a wind turbine; aerodynamic (from the blades) and mechanic (from the rotating machinery). Aerodynamic noise has been likened to the noise of branches of trees during a brisk wind. Mechanical noise can be minimised through well-proven engineering practices. Planning tools are often used before construction to minimise the effects on neighbouring residential areas.

Wildlife
Generally, wildlife lives in harmony with wind turbines. There is a minimal risk to bird life from collision with the wind turbines; however, when compared with other large structures the risk is low.

Safety
There have been a few cases, worldwide, of injuries being caused by wind turbines shedding parts or ice. However, the risk is extremely low and there are no known cases in Europe.

Restoration
Wind turbines are typically designed to last for over 20 years. No wind farm has reached the end of its life in the UK but some have been experimentally taken down. When a wind farm is decommissioned all visible traces of the wind farm are removed, the general infrastructure, including service roads, are all taken away. Foundations are sometimes left in situ as digging them up would cause greater environmental damage than leaving them.

A model showing the potential of architecturally integrated urban wind turbines. (www.urbanturbines.com).

Smaller scale wind turbines can potentially be exploited in urban areas.As well as conventional turbines, architecturally integrated systems are a possibility. At present most small scale wind turbines have the potential to be incorporated into urban design.

However, Strathclyde University recently developed a Duct Wind Turbine which utilises the updraft of the airflow along a building side. The air flows upwards; hugging the building wall then enters the front of the duct. The rotor and generator are hidden inside the duct.

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