Kosky, Balmer, Keat and Wise: Exploring Engineering, Fourth Edition
Solution Manual Chapter 17:
Electrochemical Engineering
Useful conversion factors:
1.00 kJ = 0.278 Wh; 1.00 Wh = 3.600 kJ, 1.00 US Gallon = 3.79 liters; 1.000 metric ton
(tonne) = 1,000. kg, one electron charge = 1.60 x 10–19 coulombs, Avogadro’s number =
6.022 x 1026 /kmol., standard molar volume = 22.4 m3/kmol or equivalently, Ru is the
universal (i.e., per kmol) gas constant, 8.31 x 103 J/K•kmol.
17-1. A vehicle has a 15. US gallon gas tank and can be filled from empty in 60. seconds.
a) What is the rate of power transferred to the vehicle? b) If the vehicle is converted to
an all battery system using a battery pack to replace the gas tank, what is the rate of
power transferred to the batteries if it takes 4.0 hours to charge?
(Assume the density of gasoline of 740 kg/m3, its heat of combustion is 46,500 kJ/kg, and the
battery’s energy density is 525 kJ/liter). A: a) 33. MW, b) 2.1 kW
Need: Power transferred to a) a gasoline powered vehicle, b) an electric
one during their respective fill up times.
Copyright ©2015, Elsevier, Inc
Kosky, Balmer, Keat and Wise: Exploring Engineering, Fourth Edition
17-2 A windmill produces mechanical power according to this formula:
AVP 3
2
1
where is its efficiency (assume = 60.%), = density of air (1.00 kg/m3), V = wind
speed in m/s (assume 5.0 m/s), and A is the cross-section of the mill that faces the wind
(assume it is circular with a radius of 35.0 m).
a) How many kW does the windmill produce?
b) To load level, you have a battery storage device that can store 2.00 MWh. How
long will you be charging it?
c) If the energy storage density you can achieve is 125 Wh/kg, how big is this storage
battery in tonnes?
Need: a) Windmill power in kW, b) battery charging time for 2.00 MWh
discharge rate, and c) weight of battery storage pack.
Know: Formula to size power from windmill; dimensions and other
factors: ( is its efficiency (assume = 60.%), = density of air (1.00
kg/m3), V = wind speed in m/s (assume 5.0 m/s), and A is the cross-section
of the mill that faces the wind (assume its radius is 35.0 m))
Kosky, Balmer, Keat and Wise: Exploring Engineering, Fourth Edition
.
17-9 Design a battery pack composed of D cells (6.35 cm long × 3.18 cm diameter, each
weighing 0.100 kg). The final package (see figure) must supply 42.0 V (a coming
standard for all cars) at 30.0 A for 2.00 hours. Each cell produces 3.0 V and has a power
producing density of 125 W/kg and an energy storage density of 125 Wh /kg. Estimate W
and L for the package.
Need: Size of battery pack composed of D cells given the pack
must deliver 42.0 V at 30.0 A for 2.00 hours.
Kosky, Balmer, Keat and Wise: Exploring Engineering, Fourth Edition
17-10 Compare a battery made from the following pairs of aqueous ½ cells: Mg++
+2e– ↔ Mg(s) and Cu++ + 2 e– Cu(s) with Fe++ + 2 e– Fe(s) and Ag+ + e–
Ag(s). What will be the voltages and can you speculate on the relative weights of
the batteries if the densities of Mg(s), Cu(s), Fe(s) and Ag(s) are 1740, 7190,
7,780 and 10,500 kg/m3 respectively? (Hint: A significant part of the weight of
an electrochemical cell is the weight of its electrodes.)
Need: Cell voltage and a measure of their respective weights for
these cells:
