Environmental Engineering Reference
In-Depth Information
Problem 4.1
From Figure 4.1, estimate the ratio of peak demand/average demand and that of minimum
demand/average demand. If the electricity supply system must have a capacity 20% above the
peak demand, estimate the system capacity factor—that is, the ratio of average demand to system
capacity.
Problem 4.2
A generator armature coil of length
L
=
10 cm and half-width
r
=
2 cm, as shown in Figure 4.3(b),
1 weber/m
2
. If the coil rotates at a frequency of
60 revolutions per second and a current
I
is 10 amperes, calculate the peripheral velocity
V
, the
force
F
on each length
L
of the coil and the corresponding electric field
E
, the electric potential
difference
is placed in a magnetic field of strength
B
=
across the coil slip rings, and the external torque
T
applied to the armature.
Problem 4.3
A capacitor for storing 100 MJ of energy in an electric drive vehicle utilizes a dielectric of thickness
h
farad/meter. The maximum electric field
E
is
3E(9) volts/meter. For this capacitor, calculate the electric potential
=
0.1 mm and electric permittivity
=
2E
(
−
11
)
, the required capacitance
C
, the capacitor area
A
, and the volume of dielectric material.
Problem 4.4
A typical automotive lead-acid battery stores 100 ampere-hours of charge. Calculate the charge in
coulombs. Assuming that the battery can discharge its full charge at an electrode potential of 12
volts, calculate the energy stored in the fully charged battery.
Problem 4.5
A pumped storage plant is being designed to produce 100 MW of electrical power over a 10-hour
period during drawdown of the stored water. The mean head difference during this period is 30 m.
Calculate the amount of electrical energy to be delivered and the required volume of water to be
stored if the hydropower electric generator system is 85% efficient.
Problem 4.6
The characteristics of a battery powered electric vehicle, listed in column 1 of Table 8.3, give an
electric energy storage of 18.7 kWh and a battery mass of 595 kg. If the batteries were replaced
by an electric, magnetic, or flywheel energy storage system of characteristics given in Table 4.2,
calculate the mass and volume of these alternative systems. Would any of these alternatives be
practical?
