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Papers by Undarmaa Tumenbayar

Research paper thumbnail of Characteristics of Wind Turbine Power Production Variation with Wind Veer Direction Using Nacelle Lidar measurements

Journal of power system engineering/Dongnyeok siseutem gonghakoeji, Feb 29, 2024

Research paper thumbnail of Investigation of wind veer characteristics on complex terrain using ground-based lidar

International Journal of Renewable Energy Development, Oct 25, 2023

The wind direction shift with height significantly influences wind turbine performance, particula... more The wind direction shift with height significantly influences wind turbine performance, particularly in relation to terrain conditions. In this work, wind conditions at 12 measurement heights ranging from 40 m to 200 m using a ground lidar, Windcube V2, installed on a 16 m tall building were analysed to examine the characteristics of wind veer angles in complex terrain. The measurement campaign was carried out from January 1 st to December 31 st , 2022, in the southeastern part of South Korea. The terrain complexity around the ground lidar system was evaluated using the ruggedness index (RIX), whose result was 14.06 percent corresponding to complex terrain. The ground lidar measurements were compared with mesoscale data, EMD-WRF South Korea, for the data accuracy check. Wind veer frequencies and wind roses were derived to identify directional shifts with height. Furthermore, diurnal, monthly, and seasonal variations of wind veer characteristics were analysed. Wind shear exponent factor (WSE) and turbulence kinetic energy (TKE) were calculated, and wind veer profiles were constructed based on these parameters. The relative errors of wind speeds were analysed for rotor equivalent wind speed (REWS) and hub height wind speed (HHWS), with REWS with wind veer correction, REWSveer, as a reference. Additionally, atmospheric stability conditions were classified using WSE and TKE, and the vertical changes in wind veering were analysed according to the stability conditions. The findings reveal lower wind speeds exhibited larger wind veer values and fluctuations. The relative errors for the REWS and the HHWS were 0.04 % and 0.20 % on average, respectively. The study demonstrates that terrain conditions significantly impacted wind veer angles at heights below 100 m, whereas the influence diminished with increasing height above 100 m. The results could be helpful for wind farm developers to make decisions on the siting as well as the hub height of wind turbines on complex terrain.

Research paper thumbnail of An Effect of Wind Veer on Wind Turbine Performance

International Journal of Renewable Energy Development, Oct 25, 2022

An investigation was performed to identify the wind veer impact on wind turbine power performance... more An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the frequencies of the types, VV, VB, BB and BV were 62.7 %, 4.9 %, 9.2 % and 23.1 %, respectively. The PDCs for the types VV and BV were 3.0 % and 4.2 %, respectively, meaning a power gain while those for the types VB and BB were-2.9 % and-3.9 %, respectively, meaning a power loss.

Research paper thumbnail of Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm

International Journal of Renewable Energy Research, 2018

In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terr... more In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the actual wind data from the SCADA system. Then, the wake effect was analyzed with the distance between the wind turbines. As a result, the wake effect predicted by the WindModeller simulation was greater than the actual wake effect. The actual wind speed ratio decreased by 22% and 35% when the turbines were separated with the distances of 3.1 and 5.8 times rotor diameters, respectively. The wake effect behind multiple wind turbines is revealed in this paper.

Research paper thumbnail of An analysis of wake loss and atmospheric stability on a wind farm situated on complex terrain

The trend from the actual wind data analysis was the same as that from the WindModeller analysis.

Research paper thumbnail of Experimental investigation on power performance testing using nacelle lidar measurements over excavated terrain

Journal of Wind Engineering and Industrial Aerodynamics, Jul 1, 2021

Abstract In order to find out the usability of the nacelle mounted light detection and ranging (l... more Abstract In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for power performance testing under the condition of excavated terrain, an experimental investigation was carried out at the DBK wind farm on Jeju Island, South Korea. A nacelle lidar installed on a 2 MW test wind turbine was used with an 80 m tall met mast and a ground-based lidar for measuring wind conditions. The measurement sector was calculated for the site, which was reduced to the analysed sector for finding out the influence of the excavated landfill. Since the excavated landfill was located near the test wind turbine, the excavated terrain was evaluated according to International Electrotechnical Commission (IEC) 61400-12-1, 2nd edition and the power curve was drawn using met mast wind speeds at the hub height, which was compared with that from the turbine manufacturer. The excavated terrain was further analysed using the Computational Fluid Dynamics (CFD) technique to determine whether it has an influence on wind flow. Then, the wind speed data measured by cup anemometers on the met mast, the ground-based lidar and the nacelle mounted lidar were compared through the linear regression method. The rotor equivalent wind speed (REWS) was calculated using met mast and ground lidar wind speeds according to the IEC 61400-12-1, 2nd edition. The power curves were obtained by applying the REWS and the nacelle lidar measurements. In addition, the relative errors of the power outputs were estimated and further annual energy productions (AEPs) were analysed by applying the Rayleigh wind speed distribution to the power curves. As a result, the effect of the excavated terrain on the power curve was very small. The power curves using the nacelle lidar measurements were mostly the same as the power curve using the REWS.

Research paper thumbnail of Wind power variation by wind veer characteristics with two wind farms

Scientific Reports

To clarify the wind veer characteristics with height and their effect on the wind turbine power o... more To clarify the wind veer characteristics with height and their effect on the wind turbine power outputs, an investigation was carried out at the wind farms with complex and simple terrains. A 2 MW and a 1.5 MW wind turbine were tested, each having an 80 m tall met mast and a ground lidar to capture wind veering. Wind veer conditions were divided into four types based on wind direction changes with height. The power deviation coefficient (PDC) and the revenue differences for the four types were derived from the estimated electric productions. As a result, the wind veer angle across turbine rotors were more significant at the complex site than at the simple site. For the two sites, the PDC values ranged from − 3.90 to 4.21% depending on the four types, which led to a 20-year revenue variation of − 274,750–423,670 USD/MW.

Research paper thumbnail of An Effect of Wind Veer on Wind Turbine Performance

International Journal of Renewable Energy Development

An investigation was performed to identify the wind veer impact on wind turbine power performance... more An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the...

Research paper thumbnail of Experimental investigation on power performance testing using nacelle lidar measurements over excavated terrain

Journal of Wind Engineering and Industrial Aerodynamics, 2021

In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for... more In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for power performance testing under the condition of excavated terrain, an experimental investigation was carried out at the DBK wind farm on Jeju Island, South Korea. A nacelle lidar installed on a 2 MW test wind turbine was used with an 80 m tall met mast and a ground-based lidar for measuring wind conditions. The measurement sector was calculated for the site, which was reduced to the analysed sector for finding out the influence of the excavated landfill. Since the excavated landfill was located near the test wind turbine, the excavated terrain was evaluated according to International Electrotechnical Commission (IEC) 61400-12-1, 2nd edition and the power curve was drawn using met mast wind speeds at the hub height, which was compared with that from the turbine manufacturer. The excavated terrain was further analysed using the Computational Fluid Dynamics (CFD) technique to determine wh...

Research paper thumbnail of Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm

International Journal of Renewable Energy Research, 2018

In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terr... more In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the ac...

Research paper thumbnail of Characteristics of Wind Turbine Power Production Variation with Wind Veer Direction Using Nacelle Lidar measurements

Journal of power system engineering/Dongnyeok siseutem gonghakoeji, Feb 29, 2024

Research paper thumbnail of Investigation of wind veer characteristics on complex terrain using ground-based lidar

International Journal of Renewable Energy Development, Oct 25, 2023

The wind direction shift with height significantly influences wind turbine performance, particula... more The wind direction shift with height significantly influences wind turbine performance, particularly in relation to terrain conditions. In this work, wind conditions at 12 measurement heights ranging from 40 m to 200 m using a ground lidar, Windcube V2, installed on a 16 m tall building were analysed to examine the characteristics of wind veer angles in complex terrain. The measurement campaign was carried out from January 1 st to December 31 st , 2022, in the southeastern part of South Korea. The terrain complexity around the ground lidar system was evaluated using the ruggedness index (RIX), whose result was 14.06 percent corresponding to complex terrain. The ground lidar measurements were compared with mesoscale data, EMD-WRF South Korea, for the data accuracy check. Wind veer frequencies and wind roses were derived to identify directional shifts with height. Furthermore, diurnal, monthly, and seasonal variations of wind veer characteristics were analysed. Wind shear exponent factor (WSE) and turbulence kinetic energy (TKE) were calculated, and wind veer profiles were constructed based on these parameters. The relative errors of wind speeds were analysed for rotor equivalent wind speed (REWS) and hub height wind speed (HHWS), with REWS with wind veer correction, REWSveer, as a reference. Additionally, atmospheric stability conditions were classified using WSE and TKE, and the vertical changes in wind veering were analysed according to the stability conditions. The findings reveal lower wind speeds exhibited larger wind veer values and fluctuations. The relative errors for the REWS and the HHWS were 0.04 % and 0.20 % on average, respectively. The study demonstrates that terrain conditions significantly impacted wind veer angles at heights below 100 m, whereas the influence diminished with increasing height above 100 m. The results could be helpful for wind farm developers to make decisions on the siting as well as the hub height of wind turbines on complex terrain.

Research paper thumbnail of An Effect of Wind Veer on Wind Turbine Performance

International Journal of Renewable Energy Development, Oct 25, 2022

An investigation was performed to identify the wind veer impact on wind turbine power performance... more An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the frequencies of the types, VV, VB, BB and BV were 62.7 %, 4.9 %, 9.2 % and 23.1 %, respectively. The PDCs for the types VV and BV were 3.0 % and 4.2 %, respectively, meaning a power gain while those for the types VB and BB were-2.9 % and-3.9 %, respectively, meaning a power loss.

Research paper thumbnail of Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm

International Journal of Renewable Energy Research, 2018

In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terr... more In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the actual wind data from the SCADA system. Then, the wake effect was analyzed with the distance between the wind turbines. As a result, the wake effect predicted by the WindModeller simulation was greater than the actual wake effect. The actual wind speed ratio decreased by 22% and 35% when the turbines were separated with the distances of 3.1 and 5.8 times rotor diameters, respectively. The wake effect behind multiple wind turbines is revealed in this paper.

Research paper thumbnail of An analysis of wake loss and atmospheric stability on a wind farm situated on complex terrain

The trend from the actual wind data analysis was the same as that from the WindModeller analysis.

Research paper thumbnail of Experimental investigation on power performance testing using nacelle lidar measurements over excavated terrain

Journal of Wind Engineering and Industrial Aerodynamics, Jul 1, 2021

Abstract In order to find out the usability of the nacelle mounted light detection and ranging (l... more Abstract In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for power performance testing under the condition of excavated terrain, an experimental investigation was carried out at the DBK wind farm on Jeju Island, South Korea. A nacelle lidar installed on a 2 MW test wind turbine was used with an 80 m tall met mast and a ground-based lidar for measuring wind conditions. The measurement sector was calculated for the site, which was reduced to the analysed sector for finding out the influence of the excavated landfill. Since the excavated landfill was located near the test wind turbine, the excavated terrain was evaluated according to International Electrotechnical Commission (IEC) 61400-12-1, 2nd edition and the power curve was drawn using met mast wind speeds at the hub height, which was compared with that from the turbine manufacturer. The excavated terrain was further analysed using the Computational Fluid Dynamics (CFD) technique to determine whether it has an influence on wind flow. Then, the wind speed data measured by cup anemometers on the met mast, the ground-based lidar and the nacelle mounted lidar were compared through the linear regression method. The rotor equivalent wind speed (REWS) was calculated using met mast and ground lidar wind speeds according to the IEC 61400-12-1, 2nd edition. The power curves were obtained by applying the REWS and the nacelle lidar measurements. In addition, the relative errors of the power outputs were estimated and further annual energy productions (AEPs) were analysed by applying the Rayleigh wind speed distribution to the power curves. As a result, the effect of the excavated terrain on the power curve was very small. The power curves using the nacelle lidar measurements were mostly the same as the power curve using the REWS.

Research paper thumbnail of Wind power variation by wind veer characteristics with two wind farms

Scientific Reports

To clarify the wind veer characteristics with height and their effect on the wind turbine power o... more To clarify the wind veer characteristics with height and their effect on the wind turbine power outputs, an investigation was carried out at the wind farms with complex and simple terrains. A 2 MW and a 1.5 MW wind turbine were tested, each having an 80 m tall met mast and a ground lidar to capture wind veering. Wind veer conditions were divided into four types based on wind direction changes with height. The power deviation coefficient (PDC) and the revenue differences for the four types were derived from the estimated electric productions. As a result, the wind veer angle across turbine rotors were more significant at the complex site than at the simple site. For the two sites, the PDC values ranged from − 3.90 to 4.21% depending on the four types, which led to a 20-year revenue variation of − 274,750–423,670 USD/MW.

Research paper thumbnail of An Effect of Wind Veer on Wind Turbine Performance

International Journal of Renewable Energy Development

An investigation was performed to identify the wind veer impact on wind turbine power performance... more An investigation was performed to identify the wind veer impact on wind turbine power performance at a wind farm located on Jeju Island, South Korea. A 2 MW wind turbine was used as a test turbine. An 80 m-tall met mast was located 220 m away from the test wind turbine and a ground lidar was installed close to the met mast. The wind veer conditions were divided into four types: veering in upper and lower rotor (VV), veering in upper and backing in lower rotor (VB), backing in upper and lower rotor (BB) and backing in upper and veering in lower rotor (BV). The frequency of the four types was identified at the wind farm. The characteristics of wind veer was analysed in terms of diurnal variation and wind speed. In addition, the power curves of the four types were compared with that under no veer condition. Also, the power deviation coefficient (PDC) derived from the power outputs was calculated to identify the effect of the four types on the turbine power performance. As a result, the...

Research paper thumbnail of Experimental investigation on power performance testing using nacelle lidar measurements over excavated terrain

Journal of Wind Engineering and Industrial Aerodynamics, 2021

In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for... more In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for power performance testing under the condition of excavated terrain, an experimental investigation was carried out at the DBK wind farm on Jeju Island, South Korea. A nacelle lidar installed on a 2 MW test wind turbine was used with an 80 m tall met mast and a ground-based lidar for measuring wind conditions. The measurement sector was calculated for the site, which was reduced to the analysed sector for finding out the influence of the excavated landfill. Since the excavated landfill was located near the test wind turbine, the excavated terrain was evaluated according to International Electrotechnical Commission (IEC) 61400-12-1, 2nd edition and the power curve was drawn using met mast wind speeds at the hub height, which was compared with that from the turbine manufacturer. The excavated terrain was further analysed using the Computational Fluid Dynamics (CFD) technique to determine wh...

Research paper thumbnail of Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm

International Journal of Renewable Energy Research, 2018

In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terr... more In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the ac...