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There
are numerous reasons the Internal Combustion Engine (ICE) remains the dominant
energy source in automotive production. When looking at alternatives to the
high energy and power density of petroleum, there is no Energy Storage System
(ESS) in existence that meets the high standards set by the ICE. Numerous
options are being studied and include alternative batteries, fuel cells,
alternative power sources and ultracapacitors (UC). Energy derived from natural
resources including solar and wind power have potential but are impractical
until greater ESS technologies are developed. Hybrid Electric Vehicle
technology holds the promise of reducing petroleum demand in transportation but
is a fairly new industry. It’s potential impact necessitates new system design
and better energy storage.
Energy-storage
devices used in hybrid electrics charge during periods of low power demands and
discharge during periods of high power demands, acting as catalysts to provide
energy boost. Chemical batteries, currently the primary energy-storage devices
in ground vehicles have their own issues. The current size and weight of
battery applications make them impractical, gas hybrid electrics that use large
batteries to store energy from braking events require power approximately >1kWh. Plug in hybrid electric vehicles
which can be recharged using the existing power grid require power
approximately >5kWh.
Ultracapacitors
(UCs) have higher power densities than batteries, but very low energy. There
have been proposals to combine batteries and ultra-capacitors to develop
a hybrid ESS with high energy and high power
specifications. In this kind of ESS, the power fluctuation of the battery
is reduced and the life of the battery is increased.
Increasing
the all electric range (AER) of vehicles by 15% almost doubles the incremental
cost of the ESS. This is due to the fact that the ESS of HEVs requires higher
peak power while preserving high energy density. Similarly, increasing the
energy capacity from 20-40 miles of electric range capability provides an extra
15% reduction in fuel consumption but also nearly doubles the incremental cost.
Many current Hybrid Electric Vehicles use nickel-metal hydride (NiMH) although
there is growing interest in replacing them with lithium-ion batteries due to
their higher overall energy density.
Lithium-ion batteries
store more than twice as much energy as the next-best technology, the
nickel-metal-hydride (NiMH) batteries currently used in today’s gas-electric hybrids.
The reason: lithium is the lightest solid element. To make lithium-ion
batteries practical for mass-produced electric-drive vehicles, new technologies
must increase the energy the batteries store and the speed with which they can
discharge it. Once lithium batteries have met energy-storage, power-delivery,
durability, and cost goals, a massive investment in manufacturing capacity will
be needed to produce them in bulk for use in the automotive industry. | 
