Page 287 - Handbook of Energy Engineering Calculations

has much less land area for wind farms. Hence, designers have installed large
quantities of wind capacity offshore.
Wind power has a promising future throughout the world. As wind-turbine
capacity rises, these machines will go a long way toward reducing
greenhouse gases worldwide.

Two minor problems facing wind farms are birds and noise. In some areas
birds have flown into wind turbines and been killed. But with more wind
turbines being installed, bird killings appear to have declined. Perhaps the

birds have learned to stay away from wind turbines, or their migration routes
have changed. It is enough to say that birders have been complaining less
vocally in recent years.
Noise complaints about wind turbines have been voiced when wind farms
are set up close to populated areas. Some wind farms in the United States

reduce the rotational speed of their turbines after 7 p.m. to avoid complaints
from nearby residents. And various states set a nighttime noise limit to 45
decibels. In Europe, some wind farms stop their turbines at 10 p.m., rotation

resuming at 6 or 7 a.m. Perhaps the easiest “fix” for noise complaints is to
locate wind farms at least 2 or more miles (3.2 km) from populated areas.
Then, there will not be any noise complaints. While noise and bird injury
complaints occur, proponents of wind power do not believe such claims will
deter the future installation of more wind turbines throughout the world.

At this writing (2011), Denmark is testing a combined wind-power/wave-
power platform that generates power from wind turbines and wave action
using a piston pump that delivers pressurized water to a turbine-generator.

The growing need for clean power worldwide is increasing the number of
wind- and wave-power schemes being tested.

ANALYSIS OF A WIND TURBINE’S POWER-GENERATING

CAPACITY

A 10-m/s wind is at 1 standard atm pressure and 15°C temperature. Calculate
(1) the total power density in the wind stream, (2) the maximum obtainable

2
power density, (3) a reasonably obtainable power density, all in W/m , (4) the
total power (in kW) produced if the turbine diameter is 120 m, and (5) the