Lecture 4: January 28, 2010

Announcements:

Overview

ways to save energy resources

• reduce use by using current sources more efficiently
• account for all energy use: operating and embedded
• switch to renewable energy sources

1. Energy efficiency

define energy and power

• energy is the ability to do work (force over a distance)
  • kWatt*hr is energy
• power is the energy used per unit time
  • kWatt
• conversions

energy transformation results in work + heat

• each step looses some energy
• example:
  • use 110 wall socket to charge a battery
  • use a battery + an inverter to run an appliance

negawatt

• Amory Lovins
• investing in saving a watt is cheaper than creating facilities to create an additional watt

Energy equivalents:

1 gal of gas = 6.3 pounds --> 19 lbs of CO2

1 gal of gas = 31 kwhr of energy

20 to 40 kwhr per day at $0.10 per kwhr --> $2 to $4 day of electricity

2. Energy accounting

The questions are:

1) Is it better to build expensive stuff that requires less energy to run or use cheaper stuff?

• higher embedded and lower operation energy
• lower embedded and higher operation energy

2) How do we account for these different types of energy and make decisions based on that information?

 

4 examples:

• home energy
• aluminum recycling
• foot-print of a car
• life-cycle analysis of cars

a. Home energy

How much energy is saved when we build an energy efficient house?

How much energy is in all the materials in a house?

link

energy efficient vs. standard home

cold climate

What can we do in warm climates? Roofing designed to radiate heat.

 

b. aluminum recycling

Energy savings of:

for each can recycled

0.07 + 3.9 +7.3 + 0.07 + 16.6 = 27.94

70.4 + 7.3 + 0.07 + 16.6 = 94.37 kwhr/kg of aluminum

28/94 = only 30% as much energy per can

some estimates say that it's only 5% of the energy for a recycled can

even assuming 5 kwhr/kg of cans:

75 cans per kg

67 watt*hr per can

unrecycled can would be 1300 watt*hr/can

20 of those cans would be equivalent to a gallon of gas in energy

Discuss -

 

c. carbon footprint of a car

Carbon footprint is the amount of average arable land it would take to consume the carbon emitted by the particular activity.

example - ecological footprint of using a car

d. lifecycle analysis

full accounting of costs from construction, through use, and to recycling or disposal

simple example:

• energy used to construct an automobile (about 10 to 15%)
• energy used during the life of the vehicle (about 75 to 85%)
  • gas
  • repairs
• energy used to deconstruct and dispose of the vehicle (about 5 to 10 %)

controversy "Prius vs. Hummer - dust to dust"

claims by the CNW Marketing:

• Prius is more expensive to operate ($2.87/mile) (mostly from gas costs) over its lifetime than a Hummer ($2.07).
• Nickle used in the Prius is causing destruction of the forests in Canada.
• Recycling and disposal costs for the battery in the Prius would be very high.

these ideas were picked up by the media and may have "disorted the public debate" (according to the Pacific Institute).

response for other institutions that study such issues

• the claims are very sensitive to the assumptions
• CNW didn't publish assumptions or have any peer review that might have helped catch these
• for example used 109k miles for Prius and 379k miles for the Hummer H1, and 12 year lifetime for the Prius and 35 years for the Hummer.
• CNW assumed that the majority of the energy is associated with the production of the vehicle whereas all other studies show it's around 10%

links:

• KATU
• The Car Connection
• The Pacific Institute

 

3. Switching to renewable

need to take the same steps in analysis
(maybe not in this order)

What are the short-term/immediate energy efficiency gains?

• using the energy near where it was created
• generating the energy as it's needed
• avoiding transmission losses

Is this really a product of service that is worthwhile?

• improving quality of life
• Genuine Progress Indicator vs. GDP

What is the global impact

• carbon emissions in excess of consumption is a global impact
• carbon footprint gets at this
• other forms of pollution (Hg, N into oceans, etc)

What's a better way to assess the overall impact?

• LCA
• consumption of energy, water, and land

 

Assignments

Read the chapter from Multiple Perspective on "Accounting"

Read the Wiki and Encyclopedia of the Earth pages.

Study the vocabulary list.

The mini-quiz is being delayed to probably Tuesday night.