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- Juhl Andersen, Søren, et al.
(författare)
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Global trends in the performance of large wind farms based on high-fidelity simulations
- 2020
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Ingår i: Wind Energy Science. - : Copernicus GmbH. - 2366-7443 .- 2366-7451. ; 5:4, s. 1689-1703
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Tidskriftsartikel (refereegranskat)abstract
- A total of 18 high-fidelity simulations of large wind farms have been performed by three different institutions using various inflow conditions and simulation setups. The setups differ in how the atmospheric turbulence, wind shear and wind turbine rotors are modeled, encompassing a wide range of commonly used modeling methods within the large eddy simulation (LES) framework. Various turbine spacings, atmospheric turbulence intensity levels and incoming wind velocities are considered. The work performed is part of the International Energy Agency (IEA) wind task Wakebench and is a continuation of previously published results on the subject. This work aims at providing a methodology for studying the general flow behavior in large wind farms in a systematic way. It seeks to investigate and further understand the global trends in wind farm performance, with a focus on variability.Parametric studies first map the effect of various parameters on large aligned wind farms, including wind turbine spacing, wind shear and atmospheric turbulence intensity. The results are then aggregated and compared to engineering models as well as LES results from other investigations to provide an overall picture of how much power can be extracted from large wind farms operating below the rated level. The simple engineering models, although they cannot capture the variability features, capture the general trends well. Response surfaces are constructed based on the large number of aggregated LES data corresponding to a wide range of large wind farm layouts. The response surfaces form a basis for mapping the inherently varying power characteristics inside very large wind farms, including how much the turbines are able to exploit the turbulent fluctuations within the wind farms and estimating the associated uncertainty, which is valuable information useful for risk mitigation.
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- Vidlund, Mårten, et al.
(författare)
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GLUTAMICS : a randomized clinical trial on glutamate infusion in patients operated for acute coronary syndrome
- 2011
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: Glutamate has been claimed to protect the heart from ischemia and to facilitate metabolic and hemodynamic recovery after ischemia. The GLUTAMICS-trial investigated if intravenous glutamate infusion given in association with surgery for acute coronary syndrome can reduce mortality and prevent or mitigate myocardial injury and postoperative heart failure. Methods: In this investigator-initiated prospective, double-blind study 861 patients undergoing surgery for acute coronary syndrome in three Swedish Hospitals were randomly assigned to intravenous infusion of glutamate (n=428) or saline (n=433) perioperatively. The primary endpoint was a composite of postoperative mortality (30 days), perioperative myocardial infarction and left ventricular heart failure on weaning from cardiopulmonary bypass. Results: Thirty-day mortality was 0.9 % in the glutamate group and 1.2% in the control group. Cardiac mortality was 0.2% in the glutamate group and 0.9% the control group. The incidence of the composite primary end point was 7.2% in the glutamate group and 5.8% in the control group. None of these differences were statistically significant. Regarding secondary end points significantly fewer patients in the glutamate group were hemodynamically unstable at completion of surgery (0.3% v 1.8%; p=0.035) or in need of intra-aortic balloon pump on arrival to the intensive care unit (0.0% v 1.2%; p=0.026). In patients with severe unstable angina (CCS class IV; n=475) the incidence of severe circulatory failure according to prespecified criteria was significantly lower in the glutamate group (2.6% v 6.6%; p=0.036). Conclusions: The primary endpoint did not differ significantly between the groups. Regarding secondary end points there were significant differences compatible with a beneficial effect of glutamate on myocardial recovery. (ClinicalTrials.gov Identifier: NCT00489827)
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