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Documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. These resource documents are provided to assist anyone wishing to research the issue of industrial wind power and the impacts of its development. The information should be evaluated by each reader to come to their own conclusions about the many areas of debate.

Date added:  March 13, 2018
Sweden, TechnologyPrint storyE-mail story

Wind turbine performance decline in Sweden

Author:  Olauson, Jon; Edström, Per; and Rydén, Jesper

[Abstract] We show that Swedish wind turbines constructed before 2007 lose 0.15 capacity factor percentage points per year, corresponding to a lifetime energy loss of 6%. A gradual increase of downtime accounts for around one third of the deterioration and worsened efficiency for the remaining. Although the performance loss in Sweden is considerably smaller than previously reported in the UK, it is statistically significant and calls for a revision of the industry practice for wind energy calculations. The study is based on two partly overlapping datasets, comprising 1,100 monthly and 1,300 hourly time series spanning 5–25 years each.

Jon Olauson, Division of Electricity, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden
Per Edström, Sweco Energuide, Gothenburg, Sweden
Jesper Rydén, Department of Mathematics, Uppsala University, Uppsala, Sweden

Wind Energy 2017; 20(12):2049–2053. DOI: 10.1002/we.2132

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Date added:  March 12, 2018
Denmark, Finland, Grid, Norway, SwedenPrint storyE-mail story

Impact of Hourly Wind Power Variations on the System Operation in the Nordic Countries

Author:  Holttinen, Hannele

[abstract] The variations of wind power production will increase the flexibility needed in the system when significant amounts of load are covered by wind power. When studying the incremental effects that varying wind power production imposes on the power system, it is important to study the system as a whole: only the net imbalances have to be balanced by the system. Large geographical spreading of wind power will reduce variability, increase predictability and decrease the occasions with near zero or peak output. The goal of this work was to estimate the increase in hourly load-following reserve requirements based on real wind power production and synchronous hourly load data in the four Nordic countries. The result is an increasing effect on reserve requirements with increasing wind power penetration. At a 10% penetration level (wind power production of gross demand) this is estimated as 1·5%–4% of installed wind capacity, taking into account that load variations are more predictable than wind power variations.

Hannele Holttinen, Technical Research Centre of Finland

Wind Energy 2005; 8:197–218. DOI: 10.1002/we.143

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Date added:  March 10, 2018
Grid, TechnologyPrint storyE-mail story

Effect of Energy Storage on Variations in Wind Power

Author:  Paatero, Jukka; and Lund, Peter

[abstract] Irregularities in power output are characteristic of intermittent energy, sources such as wind energy, affecting both the power quality and planning of the energy system. In this work the effects of energy storage to reduce wind power fluctuations are investigated. Integration of the energy storage with wind power is modelled using a filter approach in which a time constant corresponds to the energy storage capacity.The analyses show that already a relatively small energy storage capacity of 3 kWh (storage) per MW wind would reduce the short-term power fluctuations of an individual wind turbine by 10%. Smoothing out the power fluctuation of the wind turbine on a yearly level would necessitate large storage, e.g. a 10% reduction requires 2–3 MWh per MW wind.

Jukka V. Paatero and Peter D. Lund
Helsinki University of Technology, Advanced Energy Systems, Espoo, Finland

Wind Energy 2005; 8:421–441. DOI: 10.1002/we.151

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Date added:  March 2, 2018
SafetyPrint storyE-mail story

Analysis of throw distances of detached objects from horizontal-axis wind turbines

Author:  Sarlak, Hamid; and Sørensen, Jens

Figures 4 to 6 show the results for different-size blade pieces from different-size turbines at different wind speeds and blade tip speeds. For normal tip speeds (figs 4 and 5), the potential blade throw distance for a 2.3-MW turbine was calculated to be ~500 m (1,640 ft) and for a 5-MW turbine ~900 m (2,953 ft). At “extreme” tip speeds (fig 6) the corresponding distances were 800 m (2,625 ft) and 1500 m (4,921 ft).

[ABSTRACT] This paper aims at predicting trajectories of the detached fragments from wind turbines, in order to better quantify consequences of wind turbine failures. The trajectories of thrown objects are attained using the solution to equations of motion and rotation, with the external loads and moments obtained using blade element approach. We have extended an earlier work by taking into account dynamic stall and wind variations due to shear, and investigated different scenarios of throw including throw of the entire or a part of blade, as well as throw of accumulated ice on the blade. Trajectories are simulated for modern wind turbines ranging in size from 2 to 20 MW using upscaling laws. Extensive parametric analyses are performed against initial release angle, tip speed ratio, detachment geometry, and blade pitch setting. It is found that, while at tip speeds of about 70 m/s [157 mph] (normal operating conditions), pieces of blade (with weights in the range of approximately 7-16 ton) would be thrown out less than 700 m for the entire range of wind turbines, and turbines operating at the extreme tip speed of 150 m/s [336 mph] may be subject to blade throw of up to 2 km from the turbine. For the ice throw cases, maximum distances of approximately 100 and 600 m are obtained for standstill and normal operating conditions of the wind turbine, respectively, with the ice pieces weighing from 0.4 to 6.5 kg. The simulations can be useful for revision of wind turbine setback standards, especially when combined with risk assessment studies.

Hamid Sarlak and Jens N. Sørensen
Section of Fluid Mechanics, Department of Wind Energy, Technical University of Denmark, Lyngby, Denmark

Wind Energy 2016; 19:151–166. DOI: 10.1002/we.1828

Download original document: “Analysis of throw distances of detached objects from horizontal-axis wind turbines

See also:&nbsp:A method for defining wind turbine setback standards” by Jonathan Rogers, Nathan Slegers, and Mark Costello, Wind Energy 2012; 15:289–303

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