Environmental Engineering Reference
In-Depth Information
Chapter 10
Energy storage technologies
Energy storage systems (ESS) are tailored to the type of fuel being used or to the
mechanical, chemical, thermal or electrical form of energy directly stored. Liquid
fossil fuels used as feedstock for the engine include gasoline, liquefied petroleum
gas (LPG), natural gas (NG) or hydrogen (H
2
). Mechanical storage systems include
flywheels (FW) plus pneumatic (hydraulic) and elastic mediums to store energy in
its kinetic and potential energy forms, respectively. Hydraulic storage systems
generally use pneumatic means such as a nitrogen bladder as the actual storage
medium with the hydraulics as part of the actuation system.
A taxomomy of ESS previously done illustrates the relative energy density of
the various mediums [1]. Table 10.1 is a summary of these fundamental ESS.
Fundamental ESS in the ideal case can be differentiated by the medium of
storing energy, whether it is a nuclear bond, covalent bond or molecular (ionic)
bond. Storage in nuclear bonds (fusion and fission) has energy storage density some
six to seven orders of magnitude higher than storage in covalent bonds (gasoline,
LPG, NG), which in turn has an energy storage density some three orders of
magnitude greater than electrochemical, mechanical or electromagnetic systems
(molecular bonds). The remainder of this chapter is devoted to understanding ESS
of a practical nature that are suited to hybrid propulsion.
Example 1:
The company EESTOR advertises a composition modified barium
titanate ceramic powder with polyethylene terephthalate binder capacitor targeted
for application to electric vehicles, which is referred to as their electric energy
storage unit (EESU) [2]. An EESU of 52 kWh storage at 3.5 kV is claimed to have
a specific energy of
>
400 Wh/kg and energy density of
>
700 Wh/L.
Solution:
Given that each capacitor cell has
L
¼
5.08 mm,
W
¼
11.43 mm,
t
¼
9.732
m
m and dielectric
k
-factor of 18,543:
(a)
How many individual parallel plate capacitance cells are necessary to
form a
C
0
¼
30.693 F capacitor when all the cells are connected in
parallel?
(b)
What is the electric field across each capacitive element when charged to
maximum potential,
U
mx
¼
3,500 V?
