Lecture XII

Physics 367

Moving Down the Road

Controlling energy use and pollution has become a worldwide concern. Why?

Approximately 20% of the total energy use in the US goes into operating cars.

Approximately 25% of retail sales are car related.

Approximately 8% of the GNP is connected with automobile expenditures.

And 20-25% of all deaths in the US are car related accidents.

These figures are staggering.

We have a system where our lives depend on automobiles.

Much of the pollution we cause is from cars.

The cost of owning a car

Cars are not cheap to own or operate (see the problem of the day). Changes in our thinking have resulted from understanding the issues:

fuel consumed(gal/kmi) = 0.01116(wt in lbs)+2.871

a 2000 lb car can get 39.7 mi/gal

car design - drag force (~v²)

don't drive too fast

car emissions - cars are the leading cause of photochemical pollution

CO replaces oxygen in blood and is difficult to remove - symptoms: - burning in eyes
- impaired judgment

Lead causes brain damage

Nitrogen and Sulfur Oxides cause acid rain, damage forests

Pollution control devices are needed!

Catalytic Converter - platinum catalyst
CO, HC and NO_x become CO₂, N₂ and O₂
however back pressure increases - increasing gas consumption

PCV valves - reuse gas

Stratified charge engine (Civic)

Methanol and Ethanol
up to 15% ok in most engines results in improved economy and less emissions (50%) but it is more expensive than gas.

Pollutants, measured in grams/km
	Gasoline	Methanol Blend
CO	20.3	2.4
NO_x	2.0	0.22
Unburned hydrocarbons	1.38	0.20

Efficiency of various forms of transportation

55% of all travel involves trips less than 10 miles

56% of all commuting trips involve only 1 occupant

26% of commuting trips were on public transportation

Options to change this situation include

education

Comparison of Energy costs for various transportation modes
	Energy Cost (kJ/passenger km)
Mode	AAAS 1972	DOT 1987	ORNL 1993
Bicycle	130
Walking	200
Motorcycles		2,276	1,174
Automobile		1,957	2,462
School bus		10,837	552
Transit bus		25,416	2,460
Intercity bus	1,050	771	622
Airplane		3,175	3,168

larger gas tax as in Europe which cut individual travel by 40%

raising fuel economy

70-80mi/gal
- but each mi/gal costs $1 billion in retooling costs
- existing devices - 30% to 44 mi/g
- advanced technology - 50%

Improving car efficiency
Measure	Improvement
Decrease drag	10% reduction implies 2.3% efficiency gain
Reduce weight	10% reduction implies 6.6% efficiency gain
Rear wheel to front wheel drive	5% to 10%
Use overhead cams	3% to 6%
Add two valves per cylinder	5%
Variable valve timing	15% to 25%
Torque converter lockup	3%
Advanced transmissions	4.5% to 8.0%
Fuel injection systems	3% (throttle body) 6% (multipoint)
Engine friction reduction	~6.0%

balance fuel economy against pollution

- fuel economy(EPA) = 2423 mi/gal/

[0.866(HC)+0.429(CO)+0.273(CO₂)]

- minimization of NO_x

30% lower mileage and 29% more HC
- minimization of HC

400% more NO_x and 10% less mileage

hybrid electric technology

- featuring: decreased drag, front wheel drive, fuel injection, 1.5l gas and 110hp electric motors, CVT transmission, flywheels, etc.

Problem of the day

How much does it cost to operate a car?

To address this problem we need to consider the types of costs which go into operating a car.
Cost to buy a car depreciated over its life.
Cost to operate a car per mile of use
Cost to repair a car per mile of use
Cost to insure the car per mile of use

So need some input:

A typical car lasts 7 years
A typical cars costs $22,000
A typical car travels 10,000 mi/yr
A typical car gets 27 mi/gal
Gasoline costs $2.30 /gal
A car costs $700/yr to maintain
Insurance costs $1000/yr

I- Purchase price/mi = $22,000/70,000mi 0.31/mi
II-Operation/mi = $2.30/gal x 1gal/27mi 0.09/mi
III-Maintenance/mi = $700/10,000mi 0.07/mi
IV-Insurance/mi = $1000/10,000mi 0.10/mi
It costs around $0.57/mi to operate a car!

How has this number changed over the years?

In 1970 a car cost $2,000 new (Chevy Nova). It got 17 mi/gal and cost $150/yr to maintain. The cost of gas was around $.30/gal. The cost of insurance was around $150/yr.

To compare we must correct for inflation at around 5% per year for 35 years:

New cost = old cost x (1.05)³⁵
= old cost x 7.6

I- Purchase price/mi = $15,200/70,000mi 0.22/mi
II-Operation/mi = $2.28/gal x 1gal/17mi 0.13/mi
III-Maintenance/mi = $1,140/10,000mi 0.11/mi
IV-Insurance/mi = $1,140/10,000mi 0.11/mi
It cost around $0.57/mi (in 2005$) to operate a car in 1970!

Lessons learned?