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00261 Analysis of height variations of sodar-derived wind speeds in Northern Spain
07 Alternative energy sources (wind energy) The thermal emittance of infrared reflectors, deposited by DCmagnetron sputtering on glass substrates of spectraUy selective solar absorbers was studied. The deposition process was optimized in order to decrease the thermal emittance of the absorber. The sputter deposition process was optimized with regard to applied power and argon pressure for nickel-vanadium, copper-nickel and copper. The results show that the thermal emittance of the infrared reflector in a tandem solar absorber can be reduced from 0.12 to 0.06 by replacing nickel-chromium by copper-nickel. The copper-nickel alloy has a higher deposition rate and is less sensitive to the sputtering conditions, which is also favourable in large-scale industrial production.
Wind energy 05•00261 Analysis of height variations of sodar-derived wind speeds in Northern Spain P6rez, I. A. et al. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (10), 875 894. The Weibull distribution has been widely used in wind speed analysis. Ten-min averages from a sodar placed in an extensive plateau in the North of Spain were considered. The measuring period was April 2001. Daily wind speed evolution has been analysed and a sharp contrast between day and night has been obtained. Contrasting behaviour between surface and more distant levels has also been seen. The strong convection during the day and the stratification stability during the night were responsible for this well-defined pattern. Four wind speed intervals for a typical wind turbine were considered. Low wind speeds showed no directional character, although moderate winds came from two prevailing directions due to the synoptic weather systems affecting the Iberian Peninsula with a 5-6 day period. Ground influence was present only at lowest levels. As a result, the behaviour of wind speed derived from surface data must be avoided. Although moderate winds were frequent, a persistence analysis revealed the low number of lasting runs. The wind speed power law was also analysed and the usual one-seventh expression was proved not to be valid. The Weibull parameters were calculated by four methods: linear regression by cumulative frequency, moments, maximum likelihood and quartiles. The equivalence was in general clear. Finally, height analysis revealed that the shape parameter was around two whereas major differences were reached for the scale factor. A successful fit with the height was proved for the latter. Finally, a well-defined daily evolution was obtained, indicating that selection of a site for energy generation purposes must be preceded by a temporal study based on direct height measurements.
05•00262 Assessment of wind energy potential for coastal locations of the Kingdom of Saudi Arabia Rehman, S. and Ahmad, A. Energy, 2004, 29, (8), 1105-1115. This paper presents the wind data analysis for five coastal locations of the Kingdom of Saudi Arabia, namely Dhahran, Yanbo, A1-Wajh, Jeddah, and Gizan. The data analysis utilized hourly mean values of wind speed and wind direction covering a period of almost 14 years between 1970 and 1983. The data were validated in terms of completeness, continuity, erroneous values, etc. The analyses include seasonal and diurnal changes in wind speed values. Energy calculations and capacity factors were also determined for wind machines of different sizes between 150 and 2500 kW. It was found that Yanbo is the best location, among the sites analysed, for harnessing the power of wind, while Dhahran is the next best location. The other three locations were found to have more or less the same results.
05•00263 Determination of the wind energy potential for Maden-Elazig, Turkey Akpinar, E. K. and Akpinar, S. Energy Conversion and Management, 2004, 45, (18 19), 2901 2914. The Weibull density function has been used to determine the wind energy potential in Maden-Elazig, Turkey. A long-term data source, consisting of five years (1998-2002) of hourly mean wind data, was adopted and analysed. Based on these data, it was found that the numerical values of the shape and scale parameters for the MadenElazig meteorological station varied over a wide range. The yearly values of k range from 1.51 to 1.70 with a mean value of 1.60, while those of c are in the range of 5.54 6.12 with a mean value of 5.83. However, the yearly mean wind speed and mean power density of Maden-Elazig are found as 5.63 m/s and 244.65 W/m 2, respectively. The results show that Maden-Elazig has an available district for wind energy potential.
36
Fuel and Energy Abstracts January 2005
05•00264 Efficient models for wind turbine extreme loads using inverse reliability Saranyasoontorn, K. and Manuel, L. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (10), 789 804. The reliability of wind turbines against extreme loads is the focus of this study. A procedure to establish nominal loads for use in a conventional load-and-resistance-factor-design format is presented. The procedure, based on an inverse reliability approach, permits inclusion of randomness in the gross wind environment as well as in the extreme response given wind conditions. A detailed example is presented where three alternative nominal load definitions are used to estimate extreme bending loads for a 600 kW three-bladed horizontal-axis wind turbine. Only operating loads - here, flapwise (out-of-plane) bending moments - at a blade root are considered but the procedure described may be applied to estimate other loads and response measures of interest in wind turbine design. Results suggest that a full random characterization of both wind conditions and shortterm maximum response (given wind conditions) will yield extreme design loads that might be approximated reasonably well by simpler models that include only the randomness in the wind environment but that account for response variability by employing appropriately derived 'higher-than-median' fractiles of the extreme bending load conditional on inflow parameter values.
05•00265 Evolution of local citizen participation schemes in the German wind market Enzensberger, N. et al. International Journal of Global Energy Issues, 2003, 20, (2), 191 207. Local citizen participation schemes like the German 'Biirgerwindparks' (citizen wind farm) have been an important vehicle to develop the wind energy business to its present state of market maturity. This article discusses ownership as an integrated part of the economic project design for renewable energy projects. Different forms of local citizen participation are differentiated and strategic aspects related to the entrepreneurial decision of involving local citizens are highlighted. Then, the focus will be on a description of different role models for local citizen-financed wind energy projects. The paper also explains the evolution of two new role models: the merger of existing project companies to larger citizen-owned project portfolio companies and the role of closed-end wind funds as a new equity provision approach. Finally, the role of local citizen participation schemes in different market phases is discussed.
05•00266 turbine
Hysteretic flow characteristics of biplane Wells
Mamun, M. et al. Ocean Engineering, 2004, 31, (l 1-12), 1423-1435. In order to investigate the hysteretic flow characteristics of the biplane Wells turbine in detail, an incompressible unsteady three-dimensional numerical simulation was carried out with LES model. For the monoplane Wells turbine, the hysteretic loop is opposite to the wellknown dynamic stall of an airfoil. For the biplane Wells turbine, the hysteretic behaviour was similar to the monoplane at lower attack angles. But the hysteretic loop similar to the dynamic stall was observed at higher attack angles, which was attributed to the unsteady flow separation near the hub and the trailing edge of the suction surface of the upstream blade.
05•00267 Importance of thermal effects and sea surface roughness for offshore wind resource assessment Lange, B. et al. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (11), 959 988. The economic feasibility of offshore wind power utilization depends on the favourable wind conditions offshore as compared to sites on land. The higher wind speeds have to compensate the additional cost of offshore developments. However, not only is the mean wind speed different, but the whole flow regime, as can, for example, be seen in the vertical wind speed profile. The commonly used models to describe this profile have been developed mainly for land sites. Their applicability for wind power prediction at offshore sites is investigated using data from the measurement program Rcdsand, located in the Danish Baltic Sea. Monin-Obukhov theory is often used for the description of the wind speed profile. From a given wind speed at one height, the profile is predicted using two parameters, Obukhov length and sea surface roughness. Different methods to estimate these parameters are discussed and compared. Significant deviations to the Monin-Obukhov theory are found for near-neutral and stable conditions when warmer air is advected from land with a fetch of more than 30 km. The measured wind shear is larger than predicted. As a test application, the wind speed measured at 10 m height is extrapolated to 50 m height and the power production of a wind turbine at this height is predicted with the different models. The predicted wind speed is compared to the measured one and the predicted power output to the one using the measured wind speed. To be able to quantify the importance of the deviations from Monin-Obukhov theory, a simple correction method to account for this effect has been developed and is tested in the same
Wind energy 05•00261 Analysis of height variations of sodar-derived wind speeds in Northern Spain P6rez, I. A. et al. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (10), 875 894. The Weibull distribution has been widely used in wind speed analysis. Ten-min averages from a sodar placed in an extensive plateau in the North of Spain were considered. The measuring period was April 2001. Daily wind speed evolution has been analysed and a sharp contrast between day and night has been obtained. Contrasting behaviour between surface and more distant levels has also been seen. The strong convection during the day and the stratification stability during the night were responsible for this well-defined pattern. Four wind speed intervals for a typical wind turbine were considered. Low wind speeds showed no directional character, although moderate winds came from two prevailing directions due to the synoptic weather systems affecting the Iberian Peninsula with a 5-6 day period. Ground influence was present only at lowest levels. As a result, the behaviour of wind speed derived from surface data must be avoided. Although moderate winds were frequent, a persistence analysis revealed the low number of lasting runs. The wind speed power law was also analysed and the usual one-seventh expression was proved not to be valid. The Weibull parameters were calculated by four methods: linear regression by cumulative frequency, moments, maximum likelihood and quartiles. The equivalence was in general clear. Finally, height analysis revealed that the shape parameter was around two whereas major differences were reached for the scale factor. A successful fit with the height was proved for the latter. Finally, a well-defined daily evolution was obtained, indicating that selection of a site for energy generation purposes must be preceded by a temporal study based on direct height measurements.
05•00262 Assessment of wind energy potential for coastal locations of the Kingdom of Saudi Arabia Rehman, S. and Ahmad, A. Energy, 2004, 29, (8), 1105-1115. This paper presents the wind data analysis for five coastal locations of the Kingdom of Saudi Arabia, namely Dhahran, Yanbo, A1-Wajh, Jeddah, and Gizan. The data analysis utilized hourly mean values of wind speed and wind direction covering a period of almost 14 years between 1970 and 1983. The data were validated in terms of completeness, continuity, erroneous values, etc. The analyses include seasonal and diurnal changes in wind speed values. Energy calculations and capacity factors were also determined for wind machines of different sizes between 150 and 2500 kW. It was found that Yanbo is the best location, among the sites analysed, for harnessing the power of wind, while Dhahran is the next best location. The other three locations were found to have more or less the same results.
05•00263 Determination of the wind energy potential for Maden-Elazig, Turkey Akpinar, E. K. and Akpinar, S. Energy Conversion and Management, 2004, 45, (18 19), 2901 2914. The Weibull density function has been used to determine the wind energy potential in Maden-Elazig, Turkey. A long-term data source, consisting of five years (1998-2002) of hourly mean wind data, was adopted and analysed. Based on these data, it was found that the numerical values of the shape and scale parameters for the MadenElazig meteorological station varied over a wide range. The yearly values of k range from 1.51 to 1.70 with a mean value of 1.60, while those of c are in the range of 5.54 6.12 with a mean value of 5.83. However, the yearly mean wind speed and mean power density of Maden-Elazig are found as 5.63 m/s and 244.65 W/m 2, respectively. The results show that Maden-Elazig has an available district for wind energy potential.
36
Fuel and Energy Abstracts January 2005
05•00264 Efficient models for wind turbine extreme loads using inverse reliability Saranyasoontorn, K. and Manuel, L. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (10), 789 804. The reliability of wind turbines against extreme loads is the focus of this study. A procedure to establish nominal loads for use in a conventional load-and-resistance-factor-design format is presented. The procedure, based on an inverse reliability approach, permits inclusion of randomness in the gross wind environment as well as in the extreme response given wind conditions. A detailed example is presented where three alternative nominal load definitions are used to estimate extreme bending loads for a 600 kW three-bladed horizontal-axis wind turbine. Only operating loads - here, flapwise (out-of-plane) bending moments - at a blade root are considered but the procedure described may be applied to estimate other loads and response measures of interest in wind turbine design. Results suggest that a full random characterization of both wind conditions and shortterm maximum response (given wind conditions) will yield extreme design loads that might be approximated reasonably well by simpler models that include only the randomness in the wind environment but that account for response variability by employing appropriately derived 'higher-than-median' fractiles of the extreme bending load conditional on inflow parameter values.
05•00265 Evolution of local citizen participation schemes in the German wind market Enzensberger, N. et al. International Journal of Global Energy Issues, 2003, 20, (2), 191 207. Local citizen participation schemes like the German 'Biirgerwindparks' (citizen wind farm) have been an important vehicle to develop the wind energy business to its present state of market maturity. This article discusses ownership as an integrated part of the economic project design for renewable energy projects. Different forms of local citizen participation are differentiated and strategic aspects related to the entrepreneurial decision of involving local citizens are highlighted. Then, the focus will be on a description of different role models for local citizen-financed wind energy projects. The paper also explains the evolution of two new role models: the merger of existing project companies to larger citizen-owned project portfolio companies and the role of closed-end wind funds as a new equity provision approach. Finally, the role of local citizen participation schemes in different market phases is discussed.
05•00266 turbine
Hysteretic flow characteristics of biplane Wells
Mamun, M. et al. Ocean Engineering, 2004, 31, (l 1-12), 1423-1435. In order to investigate the hysteretic flow characteristics of the biplane Wells turbine in detail, an incompressible unsteady three-dimensional numerical simulation was carried out with LES model. For the monoplane Wells turbine, the hysteretic loop is opposite to the wellknown dynamic stall of an airfoil. For the biplane Wells turbine, the hysteretic behaviour was similar to the monoplane at lower attack angles. But the hysteretic loop similar to the dynamic stall was observed at higher attack angles, which was attributed to the unsteady flow separation near the hub and the trailing edge of the suction surface of the upstream blade.
05•00267 Importance of thermal effects and sea surface roughness for offshore wind resource assessment Lange, B. et al. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (11), 959 988. The economic feasibility of offshore wind power utilization depends on the favourable wind conditions offshore as compared to sites on land. The higher wind speeds have to compensate the additional cost of offshore developments. However, not only is the mean wind speed different, but the whole flow regime, as can, for example, be seen in the vertical wind speed profile. The commonly used models to describe this profile have been developed mainly for land sites. Their applicability for wind power prediction at offshore sites is investigated using data from the measurement program Rcdsand, located in the Danish Baltic Sea. Monin-Obukhov theory is often used for the description of the wind speed profile. From a given wind speed at one height, the profile is predicted using two parameters, Obukhov length and sea surface roughness. Different methods to estimate these parameters are discussed and compared. Significant deviations to the Monin-Obukhov theory are found for near-neutral and stable conditions when warmer air is advected from land with a fetch of more than 30 km. The measured wind shear is larger than predicted. As a test application, the wind speed measured at 10 m height is extrapolated to 50 m height and the power production of a wind turbine at this height is predicted with the different models. The predicted wind speed is compared to the measured one and the predicted power output to the one using the measured wind speed. To be able to quantify the importance of the deviations from Monin-Obukhov theory, a simple correction method to account for this effect has been developed and is tested in the same