Renewable Energy - Energy and the Environment - page 186

Problem 7.15
Calculate the mechanical power produced by a wind turbine with rotor diameter 40 m when the
wind speed is 8 m/s, assuming a power coefficient C p of 0.3 and an air density of 1.2 kg/m 3 .
How many households can this wind turbine supply, assuming an average power requirement of 3
kW/household? How many wind turbines would be needed for a city of 100,000 population with
four people per household? Calculate the land area for this population, in m 2 and acres, needed for
the wind turbine farm, assuming that the wind turbines should be placed 2.5 rotor diameters apart
perpendicular to the wind, and 8 rotor diameters apart parallel to the wind. Place 10 windmills
perpendicular to the wind, the rest parallel. Compare the wind farm area to that of a typical city of
100,000 (single-family homes, no high rises).

Problem 7.16
An inventor proposes to utilize a surplus ship's propellor, of diameter equal to 2 m, as an underwater
“wind turbine” at a location where a tidal current is 2 m/s. Calculate the maximum power that this
turbine could produce from the underwater flow.

Problem 7.17
For the Annapolis Royal tidal power plant, Table 7.6 lists the pool area A = 4.8 km 2 , tidal range
H

321. (a) Using equa-
tions (7.16) and (7.17) and these values, calculate the ideal tidal energy and ideal tidal power.
[You may assume that the tidal period equals 4.46E(4) s.] (b) Calculate the average power and the
effectiveness

= 6 . 3 m, rated electric power P el = 17 . 8 MW, and capacity factor η = 0 .

= (average power)/(ideal power), and compare it with the value of Table 7.6.

Problem 7.18
A wave energy system is being evaluated for a site where the design wind speed V is 20 knots.

Using equations (7 .22), (7.23), and (7.25), calculate the expected mean wave height H 2 , mean
wave frequency f , and the wave power per unit length.

BIBLIOGRAPHY

Avery, William H., and Chih Wu, 1994. Renewable Energy from the Ocean. Oxford: Oxford University Press.
Armstead, H., and H. Cristopher, 1978. Geothermal Energy . London: E. F. N. Spon.
Baker, A. C., 1991. Tidal Power. London: Peter Peregrinus.
Boyle, Godfrey, Ed., 1996. Renewable Energy. Power for a Sustainable Future. Oxford: Oxford University
Press.
Dickson, Mary H., and Mario Fanelli, Eds., 1995. Geothermal Energy. Chichester: John Wiley & Sons.
Duffie, John A., and William A. Beckman, 1991. Solar Engineering of Thermal Processes, 2nd edition.
New York: John Wiley & Sons.