Birgitte Rugaard Furevik

Wind energy mapping using synthetic aperture radar

Offshore and coastal wind farms are becoming important sources of renewable energy. The energy production of a wind farm is closely connected to its location, and the expected outcome is traditionally calculated from at least 1 year of accurate wind measurements. Satellite synthetic aperture radar (SAR) wind mapping may become a useful tool in the process of selecting the optimal site for these measurements and may therefore increase the cost-effectiveness when planning wind farms. The study described in this paper is based on 28 SAR scenes from the Norwegian west coast near the town of Bergen. The wind fields retrieved from these images have been compared with in situ wind data from the Hellisøy lighthouse and modelled wind from the European Centre for Medium-range Weather Forecasts. Based on long-term wind information from the lighthouse, the SAR scenes that show the most representative wind conditions for the site were chosen for the study. The data give an overview of the spatial distribution of the wind field in this coastal region. According to the SAR data, the area with the highest wind energy potential lies in the area north of Hellisøy in the mouth of Sognefjord, as this area is open to most wind directions.

On offshore wind energy mapping using satellite SAR

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. Currently wind observations at meteorological masts positioned in the sea or along the coastline are collected for a minimum of one year and then used in atmospheric models at local scales, for example in the Wind Atlas Analysis and Application Program (WASP) and at regional scales, for example in the Karlsruhe Atmospheric Mesoscale Model (KAMM). Satellite synthetic aperture radar (SAR) imagery provides spatial patterns of wind speed, yet only as snapshots of various atmospheric situations. Regardless, SAR wind speed data may offer new possibilities for mapping offshore wind resources. SAR-derived sea wind maps may be estimated from empirical scatterometer algorithms that are valid for open sea conditions. Scatterometer wind retrieval algorithms are based upon statistical analysis of open-sea wind observations; medium-range forecast winds from weather models; and scatterometer data. Conventional scatterometers measure the normalized radar cross-section at several different aspect angles to infer wind speed and direction. Backscatter coefficients are physically related to wind speed through the roughness of the open sea. Sea roughness is generated by wind-wave interactions in the capillary and short gravity wave spectrum and additional parameters in fetch-limited seas may influence sea roughness compared to the open sea. Hence, SAR-derived wind maps may be biased in fetch-limited seas. Because SAR data provides only one backscatter value in each resolution cell, wind direction must be known a priori. A simple comparison of meteorological observations at a Danish offshore site and from an European Remote Sensing (ERS) SAR wind speed map retrieved using the CMOD4 algorithm shows promising results for wind retrieval from SAR images in coastal regions.

Waves in polar lows

In a rather stationary fetch, one would not expect large waves in polar low situations. However, the picture changes when one considers a moving fetch. The significant wave heights that may be associated with the recorded polar lows on the Norwegian continental shelf from December 1999 to October 2015 are estimated using a one-dimensional parametric wave model. A comparison of the measured and the forecasted significant wave heights in two recent polar low cases in the Barents Sea is presented. The estimated significant wave heights show that the values could have been up to and above 9 m. The forecasted significant wave heights considerably underestimated the measured significant wave heights in the two recent polar low cases that are considered. Furthermore, a generalization of the fetch-limited wave equation in polar lows is proposed, which allows the wind field to vary in space and time, and is shown to give results that are consistent with the one-dimensional parametric model. This article is protected by copyright. All rights reserved.

Mapping Offshore Winds Around Iceland Using Satellite Synthetic Aperture Radar and Mesoscale Model Simulations

The offshore wind climate in Iceland is examined based on satellite synthetic aperture radar (SAR), coastal meteorological station measurements, and results from two atmospheric model data sets, HARMONIE and NORA10. The offshore winds in Iceland are highly influenced by the rugged coastline. Lee effects, gap flow, coastal barrier jets, and atmospheric gravity waves are not only observed in SAR, but are also modeled well from HARMONIE. Offshore meteorological observations are not available, but wind speed and wind direction measurements from coastal meteorological masts are found to compare well to nearby offshore locations observed by SAR. More than 2500 SAR scenes from the Envisat ASAR wide swath mode are used for wind energy resource estimation. The wind energy potential observed from satellite SAR shows high values above

Offshore wind maps from ERS-2 SAR and wind resource modelling

{1000}\;{Wm}^{ - {2}}

WEMSAR-wind energy mapping using synthetic aperture radar

in coastal regions in the south, east, and west, with lower values in the north. The most promising region for wind energy production is the southwestern coastal region.

A high‐resolution hindcast of wind and waves for the North Sea, the Norwegian Sea, and the Barents Sea

ERS-2 SAR satellite scenes in PRI format are calibrated and processed into offshore wind maps for a site in the North Sea. The wind direction is retrieved by the two-dimensional Fast Fourier transform method, and the wind direction is used as input to the CMOD-IFR and CMOD-4 scatterometer algorithms for the calculation of wind speed maps. The wind speed maps are regridded to 400 m by 400 m in order to reduce noise. Each of the wind maps are compared to high-quality meteorological in-situ observations collected from a 62 m tall mast located 14 km offshore. The development of offshore wind farms is in rapid growth. In the planning phase of such wind farms, it is important to asses the wind resources. A new wind resource mapping method based on satellite SAR images may prove useful. A pc-software has been developed for applied use and is presented here.

Offshore wind resource estimation from satellite SAR wind field maps

Satellite-measured wind speed data may offer new possibilities for off-shore wind resource assessment. Currently a minimum of one year wind observations at meteorological masts positioned in the sea or at the coastline are used in atmospheric models at local and regional scale to predict the off-shore wind resources. Satellite SAR imagery from the ERS satellites provide ocean wind speed maps at a local scale of 400 m spatial resolution covering areas of 100 km /spl times/100 km as snap-shots several times a month. New SAR systems (Radarsat, Envisat) will increase the spatial and temporal data coverage at lower cost. The SAR wind speed maps may provide new and useful information relevant for planning optimal siting of off-shore wind parks. A possible future application is thus to use satellite data in combination with numerical modeling in order to get a better indication of where to place a test site.