Page 4 - Avolio_Ferrara_2000

‡standard· orographic situations can be found, The data acquisition of wind velocity and
where the wind resource decreases as far as we direction, on an hourly basis, covers a period of
move inland out of the coast. 21 months, from July '96 to April '98, April.
The results of the raw data analysis (Figure 3)
It is a fact that historical windmills existed in reveal a prevailing wind blowing Northward
the western part of Sicily. and Southward, with an annual mean speed of
5.0 m/s at 10 m. above the ground level, where
The availability of wind data recorded by a met the sensors are positioned.
station onshore located in the "Salt Ponds" area North
of Trapani (very near to the coastline) has given
the cue to a study to assess the level of wind 20
energy resources on the sea.

THE STUDY 10

The development of offshore wind power plants
needs a complete integration of several kinds of West 0 10% 20% East
0 10 20
activities. Among this the analysis of the wind
field has a special relevance, as can be seen from
the various studies on the subject. It must be
pointed out that the various computer codes
achieve offshore a degree of reliability higher
than the one for on shore complex orography
areas. Legend
South wind speed [m/s]
frequency of occurrence [%]
In these cases it is possible to extrapolate
offshore the anemometric data acquired
onshore, applying recognised models and SITE commune Trapani
utilising the several met stations useful for the location "Le Saline"
0 m agl
altitude
purpose. MET code 0027
STATION sensor height h=0 mast
st
st
DATA time period selected Nov 1 , 96 - Oct 31 , 97
A preliminary study concerning the feasibility acquisition frequency Hourly
of an Offshore Wind Energy plant in the data availability 100%
annual mean wind speed
5.03 m/s
coastal area of Trapani has been performed. Weibull k 1.61
Weibull c 5.7 m/s
Figure 3: The data
A digital orographic model has been created
digitizing both the terrain height and sea depth
contour lines, the last ones till to 50 m below
the sea level and with the purpose of
identifying the allowable sea zone for the
possible installation of an offshore wind plant.

The wind resources calculation has been
performed running a session of WasP by RIS±
over an area covering a surface of about 70 km 2
(23 km x 31 km). The estimated wind velocity
Figure 2: Trapani and the Egadi Islands
values, calculated at each point of a 125 m
regular grid, at an height of 80 m above the
The available data, used for the generation of ground (sea) level, are interpolated to generate a
the wind atlas over the sea zone between the
eastern Egadi Islands, Levanzo and Favignana, filled wind speed contour map.
and the western territory of Trapani's Province, The wind potential map so obtained, together
were measured by a met station onshore located with the sea depth and constraints boundary
at "Le Saline", a flat site very close to the map (including interdiction zones for fishing
Trapani coastline.
activities, minimum distance from the