Wind Power – New Development Areas in Commercial Forests a report by Peter Herbert Meier Wind Cert Services, TÜV SÜD Industrie Service GmbH, Regensburg
With >25 gigawatts of installed wind capacity, Germany is the leading producer of wind power in Europe and plans to increase its capacities further in the future. Commercial forests, which account for around eleven million hectares and thus 30 per cent of the land in Germany, offer a particular source of new development areas. Today's technology makes numerous decentralised locations suitable for harnessing wind power. TÜV SÜD surveyed several sites planned in commercial forests and calculated their wind profiles and potential yields.
According to the latest forecast of the European Wind Energy Association (EWEA), onshore wind energy capacity is to be extended from 75 to 190 gigawatts over the next ten years. By 2020, onshore wind farms will thus provide the largest share of electricity from renewable sources. To reach this goal, new inland sites must be developed. However, future wind farm sites must also fulfil the requirements of cost-effectiveness, safety and social and environmental compatibility. High-wind regions in commercial forests in particular present a host of suitable locations, offering the additional advantage that existing infrastructure, including national roads, forest roads or overhead power lines, can be used.
More Powerful Turbines Open up New Site Options The use of forest areas as locations for wind farms only became economically feasible some years ago as rapid progress was made in wind-turbine technology. Hub heights and rotor diameters are particularly crucial in this context. Wind turbines with hub heights of >100 metres enable energy from high-wind but low-turbulence layers of air to be harnessed (see Figure 1). Even inland sites in Southern Germany offer wind speeds of between 5.8 and 6.7 metres per second. At higher altitudes, wind speeds tend to be both higher and more consistent. In combination with larger rotor diameters, modern wind turbines can thus achieve yields even at average inland sites that until a few years ago were only feasible in coastal regions. TÜV SÜD Industrie Service has successfully supported a host of wind-energy projects at numerous sites across the world, assisting operators, investors and local administrations in planning, installation and operation.
Peter Herbert Meier has been Head of Wind Cert Services at TÜV SÜD Industrie Service GmbH since 2009. As a Project Manager and Leading Project Engineer, Meier has worked in the areas of wind site assessment and measurements at various well-known German companies. The optimisation of wind farm layout and extreme wind calculation are among his key areas of focus. He has managed several challenging projects throughout Europe and overseas. He studied
Environmental Engineering, with a focus on energy technology. E:
windenergy@tuev-sued.de
Interdisciplinary Assessment of Sites
The assessment of a forest site requires interdisciplinary know-how in plant engineering, measurement systems, landscape and nature conservation, logistics and air-pollution control. A reliable assessment of the potential site first necessitates a survey of the forest stand structure with a focus on diversity, average stand height, tree density and tree crown width. German forests consist mainly of spruce, pine, beech, oak and Douglas fir, with average stand heights of between 15 and 30 metres and a density of between 400 and 1,000 trees per hectare (see Figure 2). The tree crowns are between four and 20 metres wide and the trees have a mean age of between 45 and 65 years. Wind-relevant parameters are measured with the help of modern laser technology. In this context, regional differences between and within the forest areas should be taken into consideration.
Comprehensive wind measurements deliver indispensable data for preparing reliable expert opinions. The data are determined in wind measurement campaigns based on one or several measurement stations. In this context, TÜV SÜD experts rely on empirical and comparative data from an extensive range of wind measurements across the world. Using a quasi-3D model, the experts can predict mean energy generation per year and the wind speeds for various project configurations. These data form the basis of 'bankable wind reports' and detailed analyses of wind potential on the one hand and on the other hand, they can also be used for determining the most suitable type of wind turbine for a specific site as well as ideal hub heights and distances.
Sustainable Energy Production
Today's wind turbines permit the cost-effective development of forestry areas. Thanks to the remote locations of these sites, wind farms built there will avoid the adverse effects on residential areas caused by sound emissions and shadow flicker. Prior consultation with forestry authorities and forest wardens helps to prevent negative impacts on the regional fauna. In addition, third-party partners such as TÜV SÜD can provide impartial support throughout the realisation of planned projects. In this case, the many different interests of operators, investors, nature conservationists, residents, forest owners and forest authorities need to be taken into consideration.
Although forest areas across Germany are growing year by year, the issue of the scope and impact of the required deforestation must always be addressed for every forest site. Plant safety and sustainability must hold the balance. Generally, the foundations, the crane and the assembly require a total free area of 1,350 to 2,400 square metres per turbine. The required deforestation can be offset by subsequent dismantling and reforestation, as well as compensatory measures. Deforestation exceeding the required areas does not provide any energy benefits because wind speed only increases near ground level and not at the turbine's hub height.
10 © TOUCH BRIEFINGS 2011
Regional Focus – Germany
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