| 1. |
- Möllerström, Erik, 1984-, et al.
(författare)
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Improvement of AEP Predictions with Time for Swedish Wind Farms
- 2021
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Ingår i: Energies. - Basel : MDPI. - 1996-1073. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Based on data from 2083 wind turbines installed in Sweden from 1988 onwards, the accuracy of the predictions of the annual energy production (AEP) from the project planning phases has been compared to the actual wind-index-corrected production. Both the electricity production and the predicted AEP come from Vindstat, a database that collects information directly from wind turbine owners. The mean error for all analyzed wind turbines was 13.0%, which means that, overall, the predicted AEP has been overestimated. There has been an improvement of accuracy with time with an overestimation of 8.2% for wind turbines installed in the 2010s, however, the continuous improvement seems to have stagnated around 2005 despite better data availability and continuous refinement of methods. Dividing the results by terrain, the error is larger for wind turbines in open and flat terrain than in forest areas, indicating that the reason behind the error is not the higher complexity of the forest terrain. Also, there is no apparent increase of error with wind farm size which could have been expected if wind farm blockage effect was a main reason for the overestimations. Besides inaccurate AEP predictions, a higher-than-expected performance decline due to inadequate maintenance of the wind turbines may be a reason behind the AEP overestimations. The main sources of error are insecurity regarding the source of AEP predictions and the omission of mid-life alterations of rated power. © 2021 by the authors.
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| 2. |
- Möllerström, Erik, 1984-, et al.
(författare)
-
Noise Emission of a 200 kW Vertical Axis Wind Turbine
- 2016
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Ingår i: Energies. - Basel : MDPI. - 1996-1073. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The noise emission from a vertical axis wind turbine (VAWT) has been investigated. A noisemeasurement campaign on a 200 kW straight-bladed VAWT has been conducted, and the result hasbeen compared to a semi-empirical model for turbulent-boundary-layer trailing edge (TBL-TE) noise.The noise emission from the wind turbine was measured, at wind speed 8 m/s, 10 m above ground, to96.2 dBA. At this wind speed, the turbine was stalling as it was run at a tip speed lower than optimaldue to constructional constraints. The noise emission at a wind speed of 6 m/s, 10 m above groundwas measured while operating at optimum tip speed and was found to be 94.1 dBA. A comparisonwith similar size horizontal axis wind turbines (HAWTs) indicates a noise emission at the absolutebottom of the range. Furthermore, it is clear from the analysis that the turbulent-boundary-layertrailing-edge noise, as modeled here, is much lower than the measured levels, which suggests thatother mechanisms are likely to be important, such as inflow turbulence.
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| 3. |
- Möllerström, Erik, 1984-
(författare)
-
Wind Turbines from the Swedish Wind Energy Program and the Subsequent Commercialization Attempts – A Historical Review
- 2019
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Ingår i: Energies. - Basel : MDPI. - 1996-1073. ; 12:4
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Forskningsöversikt (refereegranskat)abstract
- This paper summarizes wind turbines of Swedish origin, 50 kW and above. Both the large governmental-funded prototypes from the early 1980s and following attempts to build commercial turbines are covered. After the 1973 oil crisis, a development program for wind turbine technology was initiated in Sweden, culminating in the early 1980s with the 2 and 3-MW machines at Maglarp and Näsudden. However, government interest declined, and Sweden soon lost its position as one of the leading countries regarding wind turbine development. Nevertheless, several attempts to build commercial wind turbines in Sweden were made in the following decades. Most attempts have, like the earlier prototypes, used a two-bladed rotor, which has become synonymous with the Swedish wind turbine development line. The current ongoing Swedish endeavors primarily focus on the niche-concept of vertical axis wind turbines (VAWTs), which is a demonstration of how far from the broad commercial market of Sweden has moved. Thus far, none of the Swedish attempts have been commercially successful, and unlike countries like Denmark or Germany, Sweden currently has no large wind turbine producer. Suggested reasons include early government interventions focusing on two-bladed prototypes and political disinterest, with wind power grants cut in half by 1985, and the domestic industry not being favored in government policies for deploying wind power.
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| 4. |
- Negash, Teklebrhan, et al.
(författare)
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An Assessment of Wind Energy Potential for the Three Topographic Regions of Eritrea
- 2020
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Ingår i: Energies. - Basel : MDPI. - 1996-1073. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the wind energy potential and wind characteristics for 25 wind sites in Eritrea, based on wind data from the years 2000–2005. The studied sites are distributed all over Eritrea, but can roughly be divided into three regions: coastal region, western lowlands, and central highlands. The coastal region sites have the highest potential for wind power. An uncertainty, due to extrapolating the wind speed from the 10-m measurements, should be noted. The year to year variations are typically small and, for the sites deemed as suitable for wind power, the seasonal variations are most prominent in the coastal region with a peak during the period November–March. Moreover, Weibull parameters, prevailing wind direction, and wind power density recalculated for 100 m above ground are presented for all 25 sites. Comparing the results to values from the web-based, large-scale dataset, the Global Wind Atlas (GWA), both mean wind speed and wind power density are typically higher for the measurements. The difference is especially large for the more complex-terrain central highland sites where GWA results are also likely to be more uncertain. The result of this study can be used to make preliminary assessments on possible power production potential at the given sites. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 5. |
- Möllerström, Erik, 1984-
(författare)
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Energy—History and Time Trends : Special Issue Editorial
- 2022
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Ingår i: Energies. - Basel : MDPI. - 1996-1073. ; 15:15
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Energy is essential to human survival, and with increasing concerns regarding the global warming caused by greenhouse emissions, the energy field has become a global focal point [...]
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