## The Automobile

### U.S. Energy consumption by sector

U.S. Energy consumption, by economic sector

### U.S. Transportation energy

U.S. direct transportation energy consumed by each transportation mode.

### Internal combustion engines

150 kW internal combustion engine.

Best theoretical engine efficiency ~ 30%.

But typically, 15-20%.

### Energy flow for gas-fueled car

What is the efficiency of this car?

eff=10/70 = 1/7 ~14%

### Electric cars

Comuta-Car... in Goshen

Is an electric car a zero-emission vehicle? If not, where are the emissions happening?

**'electric' mileage**:
$(5 mi) / (kwh)$ works out to 103 miles for the 2009 cost of 1 gallon of gas.

**$CO_2$** **emissions**: equivalent to a 48 mpg gasoline car.

**Top-speed**: ~35 mph (30 mph in the winter).

**Range:** 40 miles fully charged. (Average 2nd car in the U.S. driven
27 miles per week).

Conversion of ElectricE -> MechanicalE in a DC motor: >90% efficient.

**Cost** in 1993: used 1980s model ~$2500.

Cost of replacing batteries ~ $800.

**2010: Chevy Volt** estimated to cost $33,000 after rebates has a small
gas engine (to charge batteries) as well as batteries.

Cost of replacement batteries... unknown. For Honda Civic hybrids, costs range from $2,000-4,300.

### Efficiency - revisited

Is there a better way than "miles per gallon" to measure transportation efficiency?

Particularly if you want to take into account how **many** people are being transported?

Choose between **mpg / # of people** or **# of people
$\cdot$ mpg** ...?

**people $\cdot$ miles per gallon** is the measure
of efficiency we want! It's a number that gets larger the more people we put
in the vehicle.

### Comparing transportation

* The energy content of gasoline is converted to food Calories to figure the energy efficiency of humans.

### Sample test question

"Which is more efficient: 3 people driving in a van that gets 21 mpg, or 1 person driving a Prius that gets 48 mpg?"

The van is getting 3 passengers $\cdot 21 mpg$

$
= 63 $(passenger
miles) $ / (gal)$.

The Prius is getting 1 passenger $\cdot 48 mpg$

$
= 48 $(passenger
miles) $ / (gal)$.

### Sample life question

"Which investment is more likely to save more energy: buying a 48 mpg Prius or buying a house within less than a mile from where you work?"

### Moving freight

The equivalent efficiency criteria for moving freight is to multiply the "gas mileage" times the weight (or, ahem, mass) moved.

Why might the barge come out the best?

* TDM encyclopedia from vtpi.org

### Animal kingdom

Comparing many different animals by the number of kg $\cdot$ km they can move on 1 MJ of energy

Maybe that's why he's smiling?

Small group discussion:

* Other than technical improvements to vehicles, how could you reduce the amount of energy you personally expend on transportation?
* Which of these suggestions involve *no* negative "quality of life" impact?

### Steam-electric plant

80% of electricity is produced in steam-electric power plants. This includes both coal- and nuclear- plants.

### Steam turbine

### CO2 emissions from coal

Howstuffworks addresses the cost
of powering one lightbulb. They find that when burning **714
lbs of coal**,
a total of **1852 lbs of $CO_2$** is produced. How is it possible to have
a greater weight of $CO_2$ emitted tham the weight of what we started burning??

$CH_n + $ several$ O_2 \rightarrow CO_2 + $ several$ H_2O$

Carbon comes from coal, Oxygen comes from atmosphere.

### Energy flow: electric generator

**Efficiency :** 900 MW / 2500 MW = 0.36 = **36%**

### Cogeneration

**Efficiency**: (900 + 1200)/2500 = 84%

Also called "Combined Heat and Power" (CHP).

Mirant Kendall Cogeneration Station (1949), in Cambridge, Massachusetts.

### Suggested Exercises

Conceptual exercises, Chapter 7: 25, 27, 28, 30, 33, 35