Wind Energy Resources Assessment in the Coastal Zones Based on Spatial Information Techniques
空间信息技术支持下的沿海风能资源评价

Coastal zones play a very important role in wind energy resources exploration in China. Offshore wind is an attractive energy source due to the potential of very high wind power as a result of relatively low sea surface roughness. The great variation of wind field near the ground baffles wind energy resources assessment. Synthetic aperture radar (SAR) images from remote sensing satellites have been achieved over the oceans on a continuous basis. Their unique characters, including independence on daylight, uninfluenced from clouds, high spatial resolution and large spatial coverage, make them a very useful tool for acquiring main parameters of wind fields in ocean areas. Main data sources are ERS-1 and ERS-2 satellites of Eu rope, the RADARSAT-1 satellite of Canada, and the latest European satellite ENVISAT. SAR-derived sea wind maps may be estimated from empirical scatter meter algorithms that are valid for open sea conditions. With recent development of spatial information techniques, methodology and algorithm for retrieving wind vectors from SAR onboard satellite become mature. The physical principle is that capillary waves and short gravity waves at the sea surface created by the instantaneous wind field backscatters electromagnetic radiation in the C-band as emitted and received by the SAR instrument. Relationship between backscatter coefficient and sea surface wind field was established based on Bragg mechanism, and key factors such as wind direction and speed were derived. Empirical algorithms, the so-called scatterometer models CMOD-4 and CMOD-IFR, relate the backscattered signal to wind speed. The paper gave a brief review in this area. Means for wind field retrieval and validation were presented in detail. Problems and application prospect in China were also discussed.