Risoe mapping wind resources in China
The work has been carried out within the framework of the Sino-Danish Wind Energy Development Programme (WED). The fundamental idea behind this bilateral development programme is to share with China the experience which Denmark has at incorporating a record share of wind power in the Danish energy system.
The Dongbei region covers approx. 780,000 square kilometres. Dongbei means East-North and is the Chinese name for this northern Chinese plateau which is also where the Chinese provinces of Liaoning (145,000 square kilometres), Jilin (180,000 square kilometres) and Heilongjiang (454,000 square kilometres) are found. By comparison, Denmark covers an area of 43,094 square kilometres or approximately one eighteenth of the area being mapped.
The activities have been carried out under the Sino-Chinese Wind Energy Development Programme (WED), which will help China introduce wind power into the Chinese electricity system.
The study was carried out between December 2007 and June 2010 by China's Meteorological Administration (CMA) and Risø DTU and financed by the governments in China and Denmark through WED.
The purpose of the project was to map the wind resources in Dongbei based on reliable wind data from a number of measuring masts which had been erected for the purpose and equipped with measuring equipment from Risø. Based on the measurements, calculations of the wind resources were to be made using Risø's advanced calculation models. Moreover, the project aimed to provide the Chinese authorities with better methods for using wind data and the calculations needed to evaluate wind resources and the optimum siting of wind turbines in Dongbei.
The wind resources were mapped for 5x5-kilometre tracts of land by means of mesoscale models. The resolution of the mesoscale models enables modelling for areas of between 5 and 500 km. This provides an overall picture of the wind resources. As an example, Figure 4 shows calculated average wind speeds 100 metres above ground. The calculations were made using the Karlsruhe Atmospheric Mesoscale Model (KAMM). These calculations can be included directly in subsequent microscale calculations. Microscale modelling is used for land areas from 10 to 5,000 metres with a resolution which can be used for the siting of wind turbines. This combination of mesoscale and microscale modelling has been developed by Risø and provides very detailed knowledge about wind conditions.
Specific measurements for verifying model calculations
For the purpose of carrying out specific measurements of the wind conditions in Dongbei, twelve 70-metre meteorological masts were erected, and measurements were then made for a whole year. The siting of the masts is shown in Figure 4. Both wind speeds and turbulence were measured at heights of 10, 30, 50 and 70 metres above ground. Moreover, the wind direction was measured at 30 and 70 metres above ground. Finally, the masts were used to measure temperature, humidity, changes in temperature and air pressure.
All in all, the measurements provide a reliable picture of the wind conditions over a twelve-month period at each of the twelve sites. The data are used to check the accuracy of the mesoscale model calculations with a view to making any necessary adjustments. Using the masts, it was also possible to test and adjust the microscale calculations, thereby ensuring the best possible basis for mapping the wind resources and for calculating the potential for generating wind power in Dongbei.
Specific wind farm calculations
The last step in the process is to carry out microscale calculations for specific wind farms. These calculations serve two important purposes. In addition to the twelve meteorological masts being used to provide data for verifying the mesoscale calculations, the microscale calculations are used to provide a detailed and reliable evaluation of the wind resources and where the wind resources are in the area surrounding the masts. Based on this knowledge, they can start planning a wind farm with the best possible siting in the area.
Enough results to plan first wind farms in Dongbei
The project in China which has now been completed makes it possible to map wind resources in Dongbei and establish how much wind power a given wind farm will be able to generate. The results will thus make it possible to prepare and implement wind power projects in the area. Around the twelve measuring masts, the project results can be used directly to plan wind farms.
"We hope that the project can be used as a model for wind resource mapping in the rest of China," says Jens Carsten Hansen, Head of Programme at Risø's Wind Energy Division.
The project in China was divided into four subprojects:
- Mesoscale modelling
- Measurements using twelve measuring masts
- Microscale modelling