Eps219 – Energy and the Environment Homework#1 – Due at the start of class, Thursday, Jan. 22, 2015

In the $45-48/barrel range.

2) (10 pts) Ch1, #17: What changes would you have to make personally if the amount of energy that you use per year was mandated for a 25% reduction?

(Take any reasonable answers)

3) (10 pts) Ch1, #24: From current data on the Web, find the present (or most recent) numbers for world and U.S. consumption of energy. Cite your URLs.

Accept various answers:

World: ~550 Quads (quadrillion BTUs), or ~150,000 TW-hours, or ~18 TW, or ~13 billion toe (tons of oil equivalent), or ~550 exajoules/year

The US is about 1/5 of these numbers.

4) (15 pts) Ch2, Q#2: Discuss the types of energy transformations that are involved in the following devices or events: a) striking a match; b) windmill; c) ball rolling off a tabletop and bouncing on the floor until it stops; d) microphone; e) flashlight.

(3 pts each)

a) match: chemical to thermal + light

b) kinetic (wind) to kinetic (shaft rotation)

c) PE to (KE + TE) to PE to (KE + TE) etc.

d) sound to electrical

e) chemical to electrical to light

5) (10 pts) Ch2, Q#6: Refer to the discussion of energy losses in a car. What are some ways to increase the fuel efficiency of a car?

Full credit if they have 3 or more of these:

Decrease mass, increase aerodynamics, increase engine performance, drive slower

6) (10 pts) Ch2, P#26: The per capita rural consumption of household energy in some Bangladesh villages is 7 x 10⁹ J/yr. What fraction of the U.S. average per capita energy use is this?

U.S. annual per capita residential use = 3.6 Å~ 1011 Å~ 0.20 (Fig. 1-8) = 72 Å~ 109 J/yr. therefore Bangladesh per capita use is 10% of U.S.

0.1 kW Å~ 2 d Å~ 24 h/d Å~ $0.12/kwh = 58 cents

8) (10 pts) Ch2, P#32: If the average electrical power usage of an American home is 2 kW, then for how many homes could electricity needs be met by one 2 MW wind turbine?

The book answer is 1000, but this is wrong. There will be some energy lost along the electric wires.

Full credit: a bit less than 1000

6 pts: 1000