An all-electric, battery-powered prototype demonstration bus under joint
development by Mitsubishi Heavy Industries, Ltd. (MHI), the government
of Manitoba, Manitoba Hydro, Red River College and New Flyer Industries
Canada ULC has been completed and was recently unveiled in Manitoba, Canada. The bus will be demonstrated on the streets of Winnipeg over the next two years.
The 40-foot “E-Bus” is based on New Flyer’s 40-foot Xcelsior heavy-duty
transit bus and is powered by a 120 kWh lithium-ion rechargeable battery
pack developed by MHI. The $3-million electric bus project costs are
split equally between the Government of Manitoba, Manitoba Hydro and
Mitsubishi Heavy Industries.
The cells are MHI’s MLiX prismatic 50Ah, 3.7V cells (185 Wh-class). The
MLiX batteries use lithium compound oxide (nickel, manganese, and
cobalt) for the cathode material, along with a graphite anode,
high-strength separator, electrolyte, and electrolyte additives to
attain high voltage and high capacity, a high energy density to volume
and weight, a high charge/discharge rate, and long life (3,500 cycles or
more, 80% DOD @ 1C.)
Gravimetric energy density of the cells is 132 Wh/kg; volumetric energy density is 266 Wh/L.
The flat-plate stacked structure of the electrode achieves high
charge/discharge rates, long life, and a high-level of safety by
eliminating the stress difference generated at the inner/outer spiral
electrode, and at small radius positions caused by electrode
expansion/shrinkage, and the directional heat transfer (rolling
direction only; seen in a spiral electrode), according to MHI.
MHI also makes a 20Ah cell using the same chemistry. The 50 Ah battery
was designed to have a high energy density through the use of a
conductive network with a proper dispersion of conductive materials,
while the 20 Ah battery was designed to have a high power density for
hybrid vehicles by reducing the internal resistance with an optimized
electrode thickness.
Other steps taken to augment the capacity of the battery were adjusting
the separator porosity, diffusing the lithium-ion in the electrolyte,
and easing the insertion to the negative electrode through optimization
of the conductive materials, electrolyte composition, and electrolyte
additives.
The E-Bus project is being implemented under the Memorandum of
Understanding (MOU) on Renewable Energy Development signed in December
2010 between the Government of Manitoba and MHI, under which the two
parties agreed to collaborate towards realizing an advanced low-carbon
society.
The agreement created the structure for a series of potential
collaborative projects between Manitoba and MHI in eight areas:
electrification of transportation and recharging infrastructure
projects; battery-storage technologies; heat-pump technologies; advanced
biofuels technologies; wind-energy technologies; energy-efficiency
technologies and systems; solar technologies and silicon processing; and
integrated energy production, storage and utilization demonstrations.
As the first step of the initiative, the partners have been working
since April 2011 to develop and demonstrate a lithium-ion rechargeable
battery-powered bus and recharging technology.
Going forward, the project will test the E-Bus’s compatibility in cold
weather through actual operation. Also, it will contribute to the study
of promoting electrification of transportation using electric
powertrains such as lithium-ion rechargeable batteries, and
establishment of recharging infrastructure, aiming to respond to the
need for environmental burden reduction in the transportation field.
MHI views this project as a very important step for popularizing
lithium-ion rechargeable batteries in the North American electric bus
market, a market which the company expects to grow.
Source: Green Car Congress
Friday, June 8, 2012
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