Page 104 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

Offshore Wind Chapter | 4 97

Eq. (4.15), and using the properties of the Gamma function, we can write
3
3
¯ u = E(u) = cΓ(1 + 1/k) → E(u ) = c Γ(1 + 3/k) (4.17)
Consequently, the expected value or mean power density is given by

1 3 1 3
E(P) = E ρu = ρc Γ(1 + 3/k) (4.18)
2 2
4.3.3 Block Island Wind Farm
In this section, the resource assessment for a real offshore wind farm in the
United States is performed using the methodology that was described in the
previous section. The Block Island Wind Farm (see Fig. 4.12) is the first offshore
wind farm in the United States and was constructed in 2016 by Deepwater Wind
as a demonstration project. The farm includes five turbines, each with a rated
power of 6 MW (Haliade-150 6 MW), and therefore the total capacity of the
project is 30 MW.
Long-time series (e.g. covering a decade) of hourly wind data should be used
for wind resource assessment to capture interannual and seasonal variability of
wind energy for a location. In some cases, wind data are collected at the project
site, but if the period of data collection is not long, other datasets should be
combined. For instance, collected data at a site can be used to find the correlation
of wind speed with other nearby stations that have longer records. Then, long-
time series of wind data can be generated using those stations.
In order to conduct the resource assessment for the Block Island Wind
Farm, the hindcast wind data provided by Wave Information Studies (WIS)

FIG. 4.12 An aerial photograph of Block Island, RI, United States, and the five wind turbines
(each 6 MW) that have been installed about 6 km from this island. The turbine hub-height is about
100 m. (Photograph courtesy of Deepwater Wind.)