April 2, 2008

Cost, space, safety risk, threats to flora and fauna, noise, aesthetic intrusion, shadow flicker: problems with wind energy

Ton van de Wekken, of KEMA Nederland, an energy systems consultancy, writes in the April 1 Renewable Energy World (excerpts):

The costs of onshore wind ranges from €55–100/MWh, depending on the wind resource. For most locations, though, wind energy is not cost-effective and incentives are a prerequisite to make a wind farm profitable.

Inevitably, offshore wind farms are more expensive to develop than onshore farms – requiring about double the initial investment and double the operational costs – due to the extra costs of construction, transport to site and interconnection.

Initiation and feasibility

... Wind farms require large sites. Depending on the rotor diameter the required mutual separation is 300–500 metres with a similar separation distance from dwellings and commercial buildings to limit noise nuisance and provide a safety zone. Even for a medium-sized wind farm, say 5 × 2 MW machines, a substantial land area is required.

Planning requirements of local authorities

The wind farm site has to meet planning and regulatory requirements. In most countries wind turbines may not rotate above roads, railway tracks and waterways, and a minimum clearance from public infrastructure must be observed such as facilities for transport, storage or processing of hazardous goods, and residential, commercial or public buildings.

In northern countries and countries with a continental climate, specific attention has to be paid to the possibility of icing. Ice developed on rotating rotor blades can be thrown long distances, potentially causing injury and damage and planning authorities and regulatory bodies may require an additional risk analysis if the site is subject to icing.

There may also be a zoning plan that prohibits wind turbines or limits the maximum height of structures. Under such circumstances, the relevant authorities should be approached to investigate the possibility of obtaining permission at the earliest possible stage.

In most European countries wind turbines must also be certified according to the relevant national or international safety standards. Manufacturers have to demonstrate conformance by the production of a valid type-certificate.

For any proposed wind farm the following should be considered:
  • Check municipal zoning plan on competing activities and maximum building height
  • Mutual distance between wind turbines 400 metres
  • There are to be no buildings and as few obstacles as possible within 300–500 metres
  • Authorities or concerned parties may request a risk analysis if other activities are to take place within 400–500 metres of the wind turbines.
Planning procedures and environmental issues

The wind farm must comply with all relevant environmental regulations. This may require a number of studies of, for example, the effects on birds, animals and plant life during the construction and use phases. Key parameters include noise, visual impact and safety, and most planning authorities also demand safety and risk assessment studies.

Wind turbines produce noise, mostly caused by the rotor blades and drive train, and the noise impact of wind turbines on the environment is one of the major planning issues. The distance to nearby residential buildings has to be sufficient to ensure that the noise level at the house front is below the statutory limit. The visual impact of a wind farm is also an important planning consideration. Wind farms require open, often elevated, sites and are consequently highly visible from a distance. Many of the potentially most productive sites are in areas of great natural beauty where planning regulation can be very restrictive. Shadow flickering on dwellings and offices due to the periodic – about once per second – passage of the rotating blades across the sun can be very annoying for the occupants, although it is not regulated by law.

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