Transportation
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From our first week of
class, we derived air friction, where SA is surface area into
wind, and Sh
is the shape factor (½ to 2), ρ = 1.23 kg/m3, F
in Newtons, v in m/s F = m a ρ = m / Vol F = ρ A dx dv/dt ρ = m / A Δx F = ρ A dx dv/dt ρ = m / A dx F = ρ A ∫ v dv m = ρ A dx F = ρ A ½ v2;
but we need to also include a shape factor F
= ½ ρ SA Sh v2
( Sh = ½ to 2 )
Fad =
(1/370) Af CD v2 à Our book uses this Where CD is drag, 0.03 to 1.17 (or the shape factor) Af à ft2 is the
surface area; and v à mph
These are the same equation except one is SI units, the other is English units. |
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For objects on ramps à Fll to ramp = sinθ mg Where sin θ = oppo / hypotenuse Our book defines s, s = 5 / 100 e/g. for a 5% grade
means the hill drops 5 feet for every 100 ft of distance, which is oppo/hyp or sin θ
So force down a hill, Fhill, à à à
Fhill = s mg (mg à lbs) Our book also includes
rolling friction (tires, bearing, etc), à à à Fr = Cr m v
Please convert velocity to mph when using this equation to avoid confusion à Cr =
0.01 (mph); g = 32 ft/s2 à Cr = 0.007
(ft/s); g = 32 ft/s2 E.g. if m = 2000 kg =
137 slugs Given:
14.6 kg = 1 slug Or use Rule of Thumb…1
kg ∝ 2.2 lbs 2000 kg ∝ 4400 lbs; 4400 lbs/32.2
ft/s2 = 137 slugs So a 2000 kg car traveling at 70 mph has a rolling friction
of Fr
= Cr m
v Fr
= 0.01
(4400/32) 70 = 96 lbs |
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Example 1 If your old Volkswagen Bug weighs 1600 lbs and you are traveling at 50 mph, what is your rolling resistance force? Fr = Cr m v Fr = 0.01(1600/32) 50 Fr = 25 lbs |
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Example 2 This Volkswagen now travels down a 3% incline ramp, does it have to use its brakes or accelerator traveling at 50 mph. Fup = Fdown Fad + Fr = Fhill CD Af v2 /370 + Cr m v = s mg .3 (24ft2)502/370 + 25 lbs = .03(1600lbs) 49 lbs + 25 lbs = 48 lbs 74 > 48, so must accelerate |
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Example 3: Old school car eff
When I was in high school, “I knew someone” who drove an auctioned police interceptor. One of these was the EH1 modified version of the E360 police engine. When you pushed this car, average gas mileage was 4.5 mpg. What is the efficiency of the stop and go traffic in the city? 1 gal of gas = 1.2e8 Joules
Ans: Ff = CD Af v2 /370 + Cr m v Ff =.3 (30ft2)502/370 + 0.01(3600/32) 50 Ff = 117 lbs
ΔE = 117 lbs (4.5mile)(5280ft/mile) = 2.8e6 ft-lb
2.8e6 ft-lb (1m/3.3ft)(4.5N/lb) = 3.8e6 Joules Let’s round up: 4 x 106 Joules Energy in 1 gallon of gas = 120 x 106 Joules
So what was the average efficiency? Eff = 4/120 = 3.3% efficient |
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Example 4: What about a Prius?
A Prius has the dimensions of 1.77 m x 1.49 m and weighs 3030 lbs. Calculate the Resistance Force.
Fresistance = Fad + Fr Fad + Fr CD Af v2 /370 + Cr m v Ff =.2 (28ft2)502/370 + 0.01(3000/32) 50 Ff = 84 lbs
ΔE = 84 lbs (50mile)(5280ft/mile) per gallon ΔE = 22e6 ft-lb = 30e6 Joules / gal
Energy in 1 gallon of gas = 120 x 106 Joules
Eff = 30/120 = 25% efficient This is VERY good…most cars less than 20%
due to water heating, exhaust heat and motor friction.
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Common Batteries
Large Scale (Grid storage)
Moderate scale (home/cars) Lithium iron phosphate or LFP à LiFePO4
(my favorite and Tesla is China) Hybrid cars, some power tools,
aviation (Chinese patent is expiring in 2022, will be in MUCH greater use
after mid 2022) Moderate energy density, great
lifespan; Safe lithium ion battery Lithium manganese oxide battery or LMO à LiMn2O4
or Li2MnO3 Hybrid cars, some cell phones and
laptops, medical equipment…this was the 1st lithium battery and
safest of all. Lithium nickel cobalt manganese oxide or NMC à LiNiMnCoO2 Electric vehicles Lithium nickel cobalt aluminum oxide or NCA à LiNiCoAlO2 (Tesla in USA) Tesla electric vehicles, high specific
energy, good lifespan Lithium nickel Manganese aluminum oxide or NMA à LiNiMnAlO2 Lithium Titanate or LTO à Li2TO3 Battery backups/smart grids, vehicles and
bikes Lithium Vanadium Phosphate or LVP à LiVPO4 Subaru G4e, and doubled the energy
density…still prototype Lithium cobalt oxide or LCONMA à LiCoO2 Small devices like laptops…very popular
for this segment, poor lifespan, high specific energy Small scale Cell phone batteries, are lithium polymer with LiCoO2 as cathode (safety risks)
OLD NiMH (nickel metal hydrides were good in early 2000s) |
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Electric Vehicle technology is
currently winning
With
Elon Musk’s new patent (2021), which eliminates the tab design, the reduced
path length for recharging the batteries have been cut by a factor of 100. This will lead to much faster charging since
a short path length, less heat buildup.
The
first Tesla’s with this new tabless-battery design are planned for sale in end of
2022.
The recharge rate will be
approximately 200 miles in 5 to 10 minutes without reduced life.
·
Dec
2022, update…Tesla is having difficulty ramping up some of the new design
batteries
· https://electrek.co/2022/10/20/tesla-progress-4680-battery-cells-reduces-dependence/
The
LPO patent is ALMOST (later in 2022), more electric cars will be using LPO
soon, including Tesla outside of China.
Up until now, only Tesla’s (mainly within China and also shipped to
Europe) have been able to use LPO, lower energy density, but much longer life.
What can derail the
electric cars?
· Possibly the battery
waste!!!
·
Electrical
infrastructure
·
Any
other suggestions?
Late 2022
-
Lithium
Iron Phosphate are starting to be replaced with Lithium Iron Manganese
Phosphate
-
Sodium
ion batteries
o
https://www.nextbigfuture.com/2022/10/catl-will-mass-produce-sodium-ion-batteries-in-2023.html
o
energy
densities of 160 W-hr/kg (similar to lithium ion, best lithium ion close to 300
W-hr/kg)
o
faster
charging….no more than 15 min for standard 300 mile battery packs (assuming
infrastructure)
o
almost
eliminates any fire risk (similar to lithium iron phosphate)
-
solid
state batteries (actually semi-solid state)
o
faster
charge times
o
https://www.torquenews.com/video/bad-news-tesla-nio-getting-150-kwh-semi-solid-state-batteries
o
These
are still in prototype stage, but are current deployed as two small fleets
Fly wheels
Competitor to batteries?
Can flywheel technology drive out the battery from car
hybrids? | Physics | The Guardian
“Compared
with batteries, flywheels offer the prospect of improved fuel efficiency:
energy remains in a mechanical form, rather than morphing through mechanical to
electrical to chemical, so conversion losses are reduced. Flywheels are light(ish), typically coming in at 6-8kg. (To deliver up to 60
kilowatts of power despite their low mass, they spin at centrifuge-like speeds
of up to 60,000rpm.) And they don't present so many tricky issues when it comes
to disposal.
In 2010,
Porsche put a flywheel into its 911 GT3 RS Hybrid. A year later, Jaguar
showcased its prototype flywheel hybrid XF holding the promise of a 20%
improvement in fuel efficiency. Then in 2012, Audi Sport's flywheel hybrid,
the R18 e-tron quattro became the first hybrid car to win the legendary Le Mans 24-hour
endurance race. In 2013, Volvo announced that its flywheel hybrid
prototype could offer a 25% improvement in fuel economy.”
What about home “battery”
storage
We all know about the state
of net metering, so why not add electrical storage?
concrete-flywheel-storage-system-for-residential-pv
What about hydrogen and fuel cell
vehicles
Requires
about 3x natural gas to make equivalent energy hydrogen.
So
if $8 / MBTU for natural gas, then $24 / MBTU for hydrogen, then the hydrogen
must be delivered.
Electrolysis
on site
Electricity
at $0.15 / kW-hr is equivalent to $80 / MBTU for hydrogen
Fuel
cell vehicles are very efficient, where ICE engines lose 80% (20% efficient),
fuel cell efficiencies are 60%.
We
know that ICE vehicles immediately lose about 80% of the energy.
Another source for cost of Hydrogen
https://www.energy.gov/eere/fuelcells/hydrogen-production-electrolysis
Electrolysis is a leading hydrogen production pathway to
achieve the Hydrogen
Energy Earthshot goal
of reducing the cost of clean hydrogen by 80% to $1 per 1 kilogram in 1 decade
("1 1 1"). Hydrogen produced via electrolysis can result in zero
greenhouse gas emissions
Compression costs
Typical
35 MPa and 70 MPa H2 compressors cost $50,000- $140,000 each and consume
2-4 kWh/kg of electricity (compressing 20-350 bar) [5]. Hydrogen gas heats up
when expanded requiring high pressure hydrogen chillers to precool before
filling FCEV fuel tanks which cannot exceed 85 °C. The hydrogen combustibility
range of 4-75% in air requires additional safety equipment increasing the
station cost. Modern tube trailers for gaseous H2 delivery are rated
for 35 MPa which equates to 809 kg of H2 and cost $633,750 [6].
Cryogenic tanker trucks for liquid hydrogen (LH2) delivery have a 4000
kg H2 capacity, cost $600,000, and have been established for decades
[7].
https://digitalcommons.unomaha.edu/cgi/viewcontent.cgi?article=1011&context=econrealestatefacpub#
Note:
this does NOT include repair costs.
Hydrogen is measured by the kilogram. 1
kilogram is 1 gallon of gasoline equivalent (gge)
e.g. The
Toyota Murai has a 5 kg tank and EPA estimate miles
of 312 miles.
At
this station (about 2 miles from CalPoly), the hydrogen truck deliveries
replace the tube trailers approximately 3-4 times per day, during this 25
minute replacement time, the hydrogen vehicles wait.
Notification
App: when the tube trailer is depleted,
all drivers are notified immediately that the station is waiting for a fuel
delivery, and are notified of approximate “ready” time.
February
2022 update: Good NEWS for Hydrogen. I spoke to one of the hydrogen truck delivery
drivers, 40 new stations are being developed and should be opening soon SoCal
(initial completion date was all should be opened and available by end of
2023). This will more than double the
stations in SoCal…so these lines should be going away.
Hydrogen
may become viable in SoCal SOON!!!
March 2022 update: Sad news with Ukraine, but if Europe adds
more renewables and with the advances with the
elimination of precious metals from the catalyst for electrolysis this is a
GREAT way to address their energy crisis.
Add in more pumped storage combined with renewables…and add in renewable
hydrogen from the excess from renewables (similar with pumped storage) can be
the solution to the energy shortages in Europe…will take 2 to 5 years, but they
now have solutions.
Hydrogen
for natural gas power plants…and hydrogen for their vehicles.
Major positives for Hydrogen - 15 February 2022
https://cosmosmagazine.com/science/chemistry/hydrogen-electrolysis-precious-metals-catalyst/
Cobalt Manganese
Oxides may even be better than platinum and iridium. Co2MnO4
We
now can ditch these precious metals
We did not have enough of these precious metals for electrolysis
to EVER be viable, but this is NOW changing!!!
Interesting
Links
https://interestingengineering.com/tidal-turbine-generates-power-12-solar-panels
https://hackaday.com/2022/02/02/underwater-tanks-turn-energy-storage-upside-down/