Transcript Making current cars more efficient

Making current cars more efficient
• Minimize the force required:
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Make m small
Make Cr small
Make CD small
Make Af small
Make v small
Or any combination of reducing these values
Flex-Fuel Vehicles
• Internal combustion engines designed to run
on more than one fuel
• Second fuel is usually ethanol or sometimes
methanol
• Fuel blend is detected by sensors that adjust
ignition and timing to match the mixture
• Most North American vehicles are optimized
to run on mixtures up to E85.
The first Flex Fuel Vehicle
• Any guesses?
The first flex fuel vehicle was
• The Ford Model T!!!!
• Designed to run on
petroleum, ethanol or
kerosene
• Prohibition made
ethanol unviable and
decreasing costs of
petroleum made it
more attractive
• 1909-1927
Alternatives to the internal combustion
engine
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Flywheels
Electric batteries
Hybrids
Alcohol
Hydrogen
Flywheels
• Energy storage device
• Flywheel is spun up and the energy is stored as rotational energy to
be used at a later time
• Designed to resist losses of rotational energy due to friction, etc
• Energy stored is given by
• Ek = Iω2
where I = moment of inertial of the flywheel, and ω is the angular
velocity.
• The moment of inertial is a function of the mass and the distance
from the center of rotation
• So the structure of the flywheel and the rotational rate determine
the amount of energy stored.
• Ultimate limit on the energy storage is the strength of the flywheel.
Spin it too fast, and it will tear itself apart.
Flywheel vehicles
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Could extract energy from braking-rather than waste the energy into frictional
heating of brakepads, reverse the engine and spin up the flywheel.
Need to be recharged on the power gird, saves gas, but drains electricity
The big implementation problem is materials which can withstand the stress
needed to spin the flywheel fast enough to make this a worthwhile alternative.
Prototype mass transportation vehicles have been built (In Sweden and by
Lockheed)
Used in Formula 1 racing to recover energy lost in braking and along with a
continuously variable transmission to improve Formula one car acceleration.
Also used in the incredible hulk roller coaster at Universal Islands of Adventure in
Orlando, Fl.
– Ride starts with an uphill acceleration, rather than a gravity drop.
– Flywheels are used to provide the initial energy impulse, otherwise the park would brown out
the local energy grid everytime the ride began.
Hybrids
• Still use gasoline powered engines, but combine them with (usually)
batteries to achieve better fuel economy.
• Different from a flex-fuel vehicle:Flexible fuel vehicles (FFVs) are designed
to run on gasoline or a blend of up to 85% ethanol (E85).
• no loss in performance when operating on E85.
• FFVs typically get about 25-30% fewer miles per gallon when fueled with E85.
• Idea is to use as small as possible a gasoline engine, and only when it can
be run at peak efficiency.
• Use excess power to recharge the battery (no need to tap the power grid)
• Use energy from braking (regenerative braking) to also charge the battery
• Work best in stop and go driving.
• Major initiative in the auto industry right now.
• Result in using less gas-stretching our fossil fuels
Hybrid cars
Hybrid Models
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Hyunai Sonata Hybrid
Honda CRZ and Fit
Mercedes Benz ML 450
BMW
Dodge Ram
Chevy Silverado
Toyota Prius
Chevy Volt –WKU president drives one
– has a total driving range of up to 379 miles. For the first 35 miles, it
can drive gas free using a full charge of electricity stored in its 16-kWh
lithium-ion battery. When the Volt’s battery runs low, a gasolinepowered engine seamlessly operates to extend the driving range
another 244 miles on a full tank.
Pure electric vehicles
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Powered by an electric motor, rather than a gasoline engine
Needs batteries – current generation of batteries have 520 times less energy
density than gasoline.
Need to be charged from the power grid
If all the vehicles in the US were converted to electric cars, it would triple the
current electric energy generation
Recharging electric vehicles takes time- several hours, whereas it takes minutes to
refill your gas tank
Batteries have a finite lifetime, need to be replaced every 2-3 years at a current
cost of 1000
Limited range (less than 100 miles before recharging is needed)
Ultimate limit is current battery technology-current lead acid batteries have not
changed much in 100 years.
Environmental effects from the disposal of lead acid batteries
No new promising battery technologies on the horizon to substantially help
electric cars
Electric Car Engine
Types of electric vehicles
• Ford Focus EV due in late 2011
• Nissan Leaf - out now
Fuel cells
• An electrochemical conversion device
• Chemical reactions cause electrons (current)
to flow
• Requires a fuel, an oxidant and an electrolyte (
a substance that contains free ions and acts as
a conductor)
• Typical type of fuel cell is called a proton
exchange membrane fuel cell (PEMFC)
Hydrogen Fuel Cells
• Clean-only emission is water
• Expensive to produce
• Highly efficient-in an automobile, efficiencies
of converting fuel energy to mechanical
energy of 60% could be achieved, almost
double the current efficiencies
• Hydrogen itself has issues as a fuel source
Issues with Hydrogen
• Abundant in nature, but not a freely available
fuel
• Must be unbound from compounds
• Currently obtained via steam reforming
– Steam and a nickel catalyst react, producing H
– Need steam at very high temperatures, 1600F
• In the future, H is anticipated to be produced
by the electrolysis of water, requiring large
amount of water and electricity
Electrolysis
• Pass an electrical current through water and
obtain H
• Pass a direct current from a battery or other DC
power supply through a cup of water (salt water
solution increases the reaction intensity making it
easier to observe).
• Using platinum electrodes, hydrogen gas will be
seen to bubble up at the cathode, and oxygen will
bubble at the anode.
• Choice of the electrode is critical, you do not
want a metal that will react with oxygen
Issues with Hydrogen
• Storage-occurs in gas form at room temperature,
hard to contain
• As a liquid, it can be stored, but needs
temperatures of -253 C.
– As a liquid, its energy density increases 1000 times
– In principle, could replace gasoline as a liquid fuel, but
not practical at this time
• One solution is to store it as a metallic hydride
(the negative ion of Hydrogen in a compound
with another element) at room T.
Issues with H
• Highly explosive
– Forms a volatile mixture with air
• A mixture of 4-75% of H in air is explosive,
compared with natural gas which is only
explosive in a range of 5-15% concentration in air
• Ignition energy is small, needing only 2 x 10-5 J
(basically a spark of static electricity can ignite H)
• Only good news is its low density means if there
is a H leak, it disperses quickly
Hydrogen
• Hindenburg disaster
• Hindenburg was a
German passenger airship
(zeppelins) built for
transatlantic air flight.
• Filled with Hydrogen
• Something caused
ignition of the Hydrogencause is debatable
• 36 fatalities out of 79
people onboard
Alchohol
• Use methanol or ethanol as a fuel
– Already gone over ethanol
• Methanol is already in use at Indy 500 race
– Proven that no significant loss of performance is
experienced (though they are in the process of switching
to ethanol)
• About ½ the energy content of gasoline
• Produces only CO2 and water
– Some nitrogen oxides produced in the engine
• Can be manufactured from re-newable sources
(biomass for example)
• Technologies exist now.
Disadvantages
• Very dangerous
– Burns with no visible flame-needs a colorant
added
– Fumes are toxic
• CO2 is a greenhouse gas
• Currently made mostly from natural gas-a
non-renewable fossil fuel
• Possibly more corrosive than ethanol to
engine parts
Use in liquid fuel cells
• Another use is as a input to a
liquid feed fuel cell
• In these cells, Methanol
replaces hydrogen
• Methanol has a much higher
energy density and is easier to
store than H
• Current methanol fuel cells
produce power too low for
vehicles, but can be used in
cell phones, laptops etc
• Advantage is that they store
lots of power in a small space,
which they over a long period
of time
Environmental effects of energy production
• All of our energy producing mechanisms have
some effect on the environment
– Production of waste products pollutes air, water
and ground
– Disruptions to local ecosystems
• Our job is to understand and mitigate these
effects to the best of our ability
• Philosophy : If it hurts (the environment)
when you do that, don’t do that!
Air pollution
• If its in the air, its in your body
• Components of the Earth’s Atmosphere:
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Nitrogen
78.08%
Oxygen
20.95%
Argon
0.93%
Also small amounts of Neon, Helium, Krypton,& Hydrogen
• In addition, there are compounds whose
concentrations vary with height: water vapor, carbon
dioxide, methane, carbon monoxide, ozone, ammonia
• These are naturally occurring concentrations, any
additional influx or destruction of these compounds
via human beings alters the system.