Offshore wind energy resources Gaetano Gaudiosi 21 MARCH 2007

1. After the introductory session of the Offshore Wind Energy on the 1st March 2007 today How to choose the offshore wind farm areas and evaluate the offshore potential Offshore wind energy resourcesGaetano Gaudiosi21 MARCH 2007

2. Offshore Wind Resources Technical , economic, environmental limit Constraints of the sea space utilizations Waves Currents Bathimetry Sea bed morphology and geology Offshore wind potential Offshore wind farm approuved areas An application Offshore wind farm Siting and energy potential

3. A typical offshore wind farm Offshore turbines are mounted on a tower, in turn mounted on a platform connected to the foundations. The foundations may be a monopile sunk into the seabed, an anchored tripod, or a caisson (basket) filled with aggregate. Foundations may be surrounded by rocks for protection from scouring action of currents. A network of cables connects individual turbines to a separate platform with electrical switchgear and transformers which condition the power ready for transmission, along a cable to an onshore substation. From the sub-station the power is conveyed directly into the onshore network. Other marine renewables may share similar electrical infrastructure as shown

4. Offshore Wind Farm Piles (1) are driven into the seabed . Erosion protection, similar to sea defences, are placed at the base to prevent damage to the sea floor. The top of the foundation is painted a bright colour to make it visible to ships and has an access platform to allow maintenance teams to dock. Once the turbine is assembled, sensors on the turbine detect the wind direction and turn the head, known as the nacelle , to face into the wind, so that the blades can collect the maximum amount of energy. The movement of the wind over the aerodynamically shaped blades (2) makes them rotate around a horizontal hub, which is connected to a shaft inside the nacelle (3). This shaft, via a gearbox, powers a generator to convert the energy into electricity. Subsea cables (4) take the power to an offshore transformer (5) which converts the electricity to a high voltage (33kV) before running it back 5 -10 miles to connect to the grid at a substation on land (6)

5. Foundation of turbines in various water depths

6. Floating turbine Platform and ocean environmental parameters

7. Larger water depth is a technical and economic limit to wind farm installation due to the foundation increasing cost . -Small distance from the coast is a landscape limit for visual impact of the offshore wind farm, large distance is an economic limit for the cable connection to the onshore electric grid. Technical , economic, environmental limit

8. . The current global satellite network

9. Cup anemometer with vane

10. Offshore wind measurements Weather stations aboard buoys in the Atlantic Ocean,

11. Wind measurements –Meteo Mast Offshore Meteorology- The instrumentation of the meteorological mast consists of cup and ultrasonic anemometers and wind vanes in all heights ranging from 33 m up to 100 m above sea level. The arrangement of the instruments can be seen on the photo.

12. Offshore Wind Resources-Surface pressure forecast

13. Offshore wind characteristics

14. European Offshore Wind Map

15. The size of the offshore wind resource is impressive. A study carefully examined all the relevant offshore constraints excluded all the following areas from the resource assessment: everything closer to the shore than 5 km shipping lanes military exercise areas regions where dredging concessions existed known dumping grounds for ammunition, explosives and other hazardous materials areas with sea depth less than 10m or greater than 50m The Offshore Wind Resources and Constraints

16. The last three constraints would be considered less valid in future years. The distance to the shoreline may depend upon the planning classification of the land in question and existing sea uses. Regions with dredging concessions may be considered, depending upon the depth of water and draught of vessels used. Technological development relating to the foundationsupon which turbines stand mean that water depth can now be well under 10 metres. Part of the area of the proposed Scroby Sands wind farm is a sand bank at low tide. The Offshore Resource-a

17. US offshore Wind Resources

18. Oceanographic measurements Oceanographic measurements cover the monitoring of waves, currents, sea level, salinity and oxygen content. Record time series of parameters are measured to document a large number of offshore conditions. Meteorological and oceanographic measurements provide important data for designing offshore foundations and wind turbine constructions as well as for project profitability calculations. Besides, they enable the improvement of atmospheric-physical and oceanographic models and serve the marine environmental monitoring.

19. Wave map as set out by Dr Tom Thorpe (ETSU 1998 ,Wave Energy Commentary). The highest energy waves are concentrated off the western coasts in the 40o–60o latitude range north and south. The power in the wave fronts varies in these areas between 30 and 70 kW/m with peaks to 100kW/m in the Atlantic SW of Ireland, the Southern Ocean and off Cape Horn. Wave

20. Global Distribution of Deep Water Wave Power Resources

21. The circulation of the world's oceans is important in the latitudinal redistribution of energy. Warm ocean currents are corridors of warm water moving from the tropics poleward where they release energy to the air. Cold ocean currents are corridors of cold water moving from higher latitudes toward the equator. They absorb energy received in the of ocean currents and the air circulation above them can be made. The major ocean currents are wind-driven currents, though some ocean currents result from density and salinity tropics thus cooling the air above. A distinct correlation between the pattern variations of water.  The subtropical high pressure cells are responsible for many of the Earth's great ocean currents. Ocean Circulation –Currents-a

22. Examine the location of the subtropical highs and then place their position on the map of world ocean currents. Notice how the position of the subtropical highs and the circulation around them coincide with the circulation of many of the world's ocean currents. Take the Gulf Stream for example. As air blows out of the western side of the subtropical high it flows over a warm pool of subtropical water dragging it northward creating a warm ocean current. Approaching the eastern seaboard of the United States it is deflected toward the northeast flowing towards the north Atlantic and Europe. After crossing the Atlantic it turns into the North Atlantic Current (Drift). The Gulf Stream enhances instability and the likelihood for precipitation as air passes over it. The warmth of the North Atlantic Drift moderates the climate of British Isles. Ocean Circulation –Currents-b

23. Major ocean currents

24. The legal continental shelf Under the law of the sea a nation can extend its territorial claim of the ocean floor if the surrounding continental area extends more than 200 nautical miles offshore. The maximum limit of this additional area is 350 nautical miles offshore. In 2005 New Zealand was preparing a submission to extend its legal jurisdiction to the maximum limit

25. Sea bed morphology and geology Sea bed morphology and structural configuration are very important for the type of foundation tobe used for the support platform of the wind turbine. Water depth is a structural and economic limiting factor for foundation . Increasing the water depth the size of the wind turbine should increase . A geological evaluation should be carried out in the design phase of the wind farm to choose the correct type of foundation

26. Bathimetry

27. Bathimetry and a wind farm

28. Nordsee: Offshore-Windparks

29. Baltic Offshore-Windparks

30. After the identification of all areas of wind farm application according water depth , distance from the coast and other constraints their total gives the usable sea surface. Assuming a surface wind farm power density ( MW/ Kmq) it is possible to evaluate the potential in GW. The surface power density results from the size and mutual distance of turbines according their wind interference. Assuming a mean value of equivalent hours/ year of Electricity generation for the standard turbine nominal power it is possible to evaluate the TWh/year of regions or countries. OFFSHORE WIND POTENTIAL

31. Horns Rev Wind Farm-Denmark

32. Application (Example) An Assessment of Offshore Wind Energy PotentialUsing Mesoscale Model and GIS Atsushi YAMAGUCHI Takeshi ISHIHARA Yozo FUJINO University of Tokyo, Japan

33. Economical criteria

34. Social criteria

35. Mesoscale Model-a

36. Annual mean wind speed

37. Available Potential

38. Available potential for each water depth class-a

39. Available potential for each water depth class-b

40. Most of the available potential is located at the east offshore of Chiba and Ibaraki especially at the offing of Choshi while available area is limited around Sagami Bay because of the sea bed topography. Considering all the economical and social criteria, the total available energy potential in this area is 94TWh/year, accounting for 32% of the annual demand of TEPCO. Available potential for each water depth class-c

41. Weather forecasting Accurate forecasts have the potential for the following benefits: -Improved market trading - Optimised scheduled maintenance- Enhanced plant scheduling by system operators Forecast programs have predicted the long term energy production of wind farms on a commercial basis for more than 20 years, and have analysed more than 50,000 MW of projects. Techniques on short term forecasting have been built on the experience gained from this work.