N.M. Nielsen’s scientific contributions

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Publications (1)


TABLE 1. Characteristics of the Aeroenvironment 4000 minisodar operated during the Vindeby experiment. 
FIG. 8. Relative velocity deficit profiles for each of the 13 experiments grouped by distance of the measurements to the turbine (expressed as number of rotor diameters). Numbers shown refer to the experiment designations given in Table 3.  
FIG. 10. Relative velocity deficit and transport time calculated for two different roughnesses [representing onshore (0.05 m) and offshore (0.0002 m) and from the sodar data]. Numbers shown refer to the experiment designations given in Table 3.  
Offshore wind turbine wakes measured by SODAR
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April 2003

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382 Reads

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110 Citations

Journal of Atmospheric and Oceanic Technology

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L. Folkerts

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N.M. Nielsen

A ship-mounted sodar was used to measure wind turbine wakes in an offshore wind farm in Denmark. The wake magnitude and vertical extent were determined by measuring the wind speed profile behind an operating turbine, then shutting down the turbine and measuring the freestream wind profile. These measurements were compared with meteorological measurements on two offshore and one coastal mast at the same site. The main purposes of the experiment were to evaluate the utility of sodar for determining wind speed profiles offshore and to provide the first offshore wake measurements with varying distance from a wind turbine. Over the course of a week, 36 experiments were conducted in total. After quality control of the data (mainly to exclude rain periods), 13 turbine-on, turbine-off pairs were analyzed to provide the velocity deficit at hub height as a function of the distance from the turbine. The results are presented in the context of wake measurements at other coastal locations. The velocity deficit is predicted with an empirical model derived from onshore measurements based on transport time dependent on surface roughness. The measurements are closer to those predicted using an onshore rather than an offshore roughness despite the relatively low turbulence experienced during the experiments.

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Citations (1)


... Shallower coastal waters allowed an earlier expansion of offshore wind energy in Europe, where the first installations were in 1993 and installed capacity now exceeds 30 GW, including more than 100 MW of floating offshore wind turbine installed capacity [3,4]. The rated capacity of offshore wind turbines increased over 20 times from the 0.5 MW turbines installed in 1993 at Vindeby [5] to 13 MW (and larger) turbines planned for deployment off the US East Coast. Offshore wind turbine hub-heights increased from 37 m in 1991 to 100 m in 2021 and rotor diameters from 38 m to over 156 m [6]. ...

Reference:

Modeling Annual Electricity Production and Levelized Cost of Energy from the US East Coast Offshore Wind Energy Lease Areas
Offshore wind turbine wakes measured by SODAR

Journal of Atmospheric and Oceanic Technology