Modelling Results

KUCHING AIRPORT RESULTS

At Kuching Airport the received mast data is plotted against the 10 m and 150 m TAPM extracted wind speed. The supplied location of Kuching Airport was latitude 01o 29’ N longitude 110o 20’ E  at an elevation above mean sea level (MSL.) of 21.7 m and anemometer height AGL of 12.2 m.

The mean monthly wind speed shows fairly small variations in wind speed over the 2008 year. The general trend of the hourly mean wind speed data is an afternoon peak that could be attributed to an afternoon sea breeze at this location. The wind speed remains flat outside of this afternoon peak. The 10 m TAPM mean wind speed and the actual Kuching airport data exhibit the similar trends as can be seen in the seasonal and daily wind speed profiles. 

The 150 m TAPM record has a dip in the mean wind speed after midday a similar time of day as when a peak occurs in the Kuching airport site data as can be seen in Figure 2.2.3.1 (b). This dip in the 150 m TAPM record may be the result of thermal effects, in particular unstable stratification where surface heating causes warm air near the surface to rise, which can lead to a large boundary layer and a relatively small change in mean wind speed with height. HTC predicts wind speeds from higher elevations 150 m to lower elevations, for further detail refer to section 2.2.2.

Figure 2.2.3.1 (a) : Kuching Airport Monthly Mean Wind Speed

Figure 2.2.3.1 (b) : Kuching Airport Hourly Mean Wind Speed

 

MIRI AIRPORT RESULTS


The Miri Airport supplied location is latitude 04o 20’ N longitude 113o 59’ E at an elevation above MSL of 17 m. The seasonal wind speed profile shows fairly small variations in wind speed over the 2008 year for both the actual and modelled data at 10 m, the extracted wind speeds at 150 m also exhibit a similar trend with peaks in February. The general trend of the hourly mean wind speed data is an afternoon peak, which could be attributed to an afternoon sea breeze at this location. The 10 m TAPM mean wind speed and the actual Miri airport data exhibit similar trends as can be seen in the seasonal wind speed profiles.

The 150 m TAPM record has a dip in the mean wind speed at midday a similar time of day as when a peak occurs in the Miri airport site data as can be seen in Figure 2.2.3.2 (b). This dip in the 150 m TAPM record may be the result of thermal effects, in particular unstable stratification where surface heating causes warm air near the surface to rise, which can lead to a large boundary layer and a relatively small change in mean wind speed with height. HTC predicts wind speeds from higher elevations 150 m to lower elevations, for further detail refer to section 2.2.2.

Figure 2.2.3.2 (a): Miri Airport Hourly Mean Wind Speed

Figure 2.2.3.2 (b): Miri Airport Hourly Mean Wind Speed

 

BINTULU AIRPORT RESULTS

The Bintulu Airport supplied location is latitude 03o 12’ N longitude 113o 02’ E at an elevation above MSL of 3 m. The seasonal wind speed profile shows fairly small variations in wind speed over the 2008 year for the actual Bintulu airport wind speeds. The 10 m TAPM mean wind speed and the actual Bintulu airport data exhibit similar trends as can be seen in the seasonal and daily wind speed profiles. Although the Bintulu airport record has a more pronounced afternoon peak in comparison to the extracted 10 m TAPM wind speeds.

The 150 m TAPM record has a dip in the mean wind speed before midday, a similar time of day as when a peak occurs in the Bintulu airport site data as can be seen in Figure 2.2.3.3 (b). This dip in the 150 m TAPM record may be the result of thermal effects, in particular unstable stratification where surface heating causes warm air near the surface to rise, which can lead to a large boundary layer and a relatively small change in mean wind speed with height. HTC predicts wind speeds from higher elevations 150 m to lower elevations, for further detail refer to section 2.2.2.

 

Figure 2.2.3.3 (a): Bintulu Airport Hourly Mean Wind Speed

 

 

Figure 2.2.3.3 (b): Bintulu Airport Hourly Mean Wind Speed

 

SIBU AIRPORT RESULTS

The Sibu Airport mast for which data was supplied is located at latitude 02o 15’ N longitude 111o 58’ E with height above MSL of 38 m. The seasonal wind speed profile shows very small variations in wind speed over the 2008 year for the Sibu Airport and 10 m extracted TAPM records. These wind speeds are consistent with the low wind speeds generated by the TAPM modelling. The diurnal profile shows a small variation during the middle of the day recorded by the met mast that is not picked up by the TAPM 10 m record. This may be a result of a local temperature increase typical of an inland site that TAPM is not necessarily picking up.

The 150 m TAPM record has a dip in the mean wind speed near midday, a similar time of day as when a peak occurs in the Sibu airport site data as can be seen in Figure 2.2.3.4 (b). This dip in the 150 m TAPM record may be the result of thermal effects, in particular unstable stratification where surface heating causes warm air near the surface to rise, which can lead to a large boundary layer and a relatively small change in mean wind speed with height. HTC predicts wind speeds from higher elevations 150 m to lower elevations, for further detail refer to section 2.2.2.

Figure 2.2.3.4 (a): Sibu Airport Hourly Mean Wind Speed


Figure 2.2.3.4 (b): Sibu Airport Hourly Mean Wind Speed

Correlation between the airport site and the modelled TAPM 10 m data provides confidence in the modelling technique when wind speeds were extracted at 150 m AGL, which was used in the creation of the coarse resolution wind resource map.
The supplied observed airport data from Kuching Airport was from an anemometer at a height above ground of 12.2 m. At this height there are numerous factors that affect the measured wind speed data and its usefulness in relating it to modelled wind speeds at a higher altitude. Some of these limitations may be generated from localised obstructions such as buildings and vegetation, and can result in increased disturbance to the air flow.

Heating of the land’s surface occurs more rapidly in comparison to that of the ocean, this causes a low pressure over the land where the warm air has risen and circulates back over the ocean, and this causes an onshore breeze flowing into the areas of low pressure over the land. Afternoon sea breezes can be observed in some of the airport data. From analysis of TAPM output wind speeds HTC has identified limitations in the model for accurately predicting the effects of sea breezes. Generally the TAPM sea breeze is shallower, weaker and its effects are less prominent when moved a distance inland.

 

COARSE WIND RESOURCE MAP

The results of the 3 km coarse resolution wind resource modelling are presented below. This map displays the mean wind speed for the 2008 year at a nominal height of 75 m AGL. The wind resource map is a combination of 30 separately extracted wind resource grids from TAPM that have been combined to generate a single surface of mean wind speed.

 

DISCUSSION

The wind resource identified in the Sarawak wind resource map can generally be characterised as a relatively low wind resource, which is typical of many regions of this latitude. Areas located at higher elevations along the eastern side of Sarawak display the highest wind resources.

Higher elevations and temperatures can have an effect on air density, which in turn affects the power able to be extracted from the wind. Sarawak contains areas with elevations from sea level up to 1600 m near the Bario site. It must be kept in mind that a reduction in air density affects the energy output of a wind turbine. It is recommended that site specific air density data is collected at each prospective site to determine the effects of air density on energy output of a potential wind turbine.

The power output of a wind turbine is given by the following mathematical relationship:

Power = 0.5 x Swept Area x Air Density x Velocity3
Air density = 1.225 kg/m3 at sea level at 20DE
Air density = 1.003 kg/m3 at 1600 m at 20DE

As power output is proportional to air density, it can be seen that that the elevation will have a significant impact. Based on the above numbers up to an 18% reduction in theoretical energy output may be expected. However the practical power output will only be a portion of power calculated based on physical limits to the amount of wind power able to be extracted.