Energy in Green Building: The Carbon Imperative and

the Ruby Slippers

Dr. Alexandra “Sascha” von Meier

Professor, Dept. of Environmental Studies & Planning

Sonoma State University

www.sonoma.edu/ensp

CO2 emissions ≈ 7 GtC/y

Natural carbon cycle ≈ 50 GtC/y

1 GtC/y = 1 billion tons of carbon per year, which may be bound in CO2 or other compounds

CO2 emissions ≈ 7 GtC/y

CO2 removal from atmosphere ≈ 3 GtC/y

7 800

3

Burning fossil fuel means combustion of hydrocarbons:

CXHY + O2 → CO2 + H2O

hydrocarbon + oxygen → carbon dioxide + water

where the proportions of CO2 and H2O depend on X and Y

GISS analysis of global surface temperature; 2008 point is 11-month mean.

Source: Jim Hansen, 2008

Five Stages of Receiving Catastrophic News Denial Anger Bargaining Depression Acceptance

Source: Arctic Council and International Arctic Science Committee, www.acia.uaf.edu

Slide: John Holdren

Source: Intergovernmental Panel on Climate Change, Climate Change 2007: Synthesis Report

Climate stabilization (at 450 ppm CO2) requires global emissions to peak by 2015 and to fall to ~80% below 2000 levels by 2050

Slide: Jim Williams

California’s Big Step Forward:

Assembly Bill 32

2050 Target (EO 03-05)

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2008 Estimate

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2050 Goal

Executive order

Historical

Emissions

Inventory

Electricity

Transportation

Industry

Slide: Snuller Price

American Heritage Dictionary, 10th ed.

Physical Meaning of Energy:

Energy = the ability to do work

Force

distance

Work = Force · distance

Energy = the ability to do work

Potential energy = mgh

(mass, gravitational acceleration, height)

Kinetic energy = ½ mv2

(mass, velocity)

velocity

Examples of Energy

Natural gas in the pipeline (chemical)

Gas flame on my kitchen stove (chemical to thermal)

Hot water in the kettle (thermal)

Electricity in the wall outlet (electrical)

Spinning blade of the coffee grinder (mechanical kinetic)

Pancakes & maple syrup (chemical)

Vase sitting on top shelf (mechanical potential)

Vase falling down to floor (mechanical kinetic)

Radioactivity (nuclear to radiant)

Sunshine (radiant to thermal)

Wind (mechanical kinetic)

Because a measurable quantity of energy is conserved during any conversion of one form to another, it makes sense to give a single name to that quantity.

Matter and Energy Resources

“High Quality” means

concentrated

pure

easy to use

in an orderly state

“Low Quality” means

dispersed

impure

more difficult to use

disordered

High quality energy:

mechanical, electrical, radiant

Medium quality energy:

nuclear, chemical

Low quality energy:

thermal (heat)

2nd Law requires: Some of the chemical fuel energy will be degraded into heat. The amount of mechanical work or electricity produced will be less than the fuel input.

Basic lesson:

Use energy sources matched in quality with end use needs.

Units of energy:

calories

kilocalories

joules

kilowatt-hours (kWh)

British Thermal Units (BTU)

therms (105 BTU)

quads (1015 BTU)

Units of power:

calories per hour

joules per second = watts

kilowatts (kW)

BTU per hour

Power = energy per unit time

Electric usage 232 kWh $0.11/kWh

Gas usage 52 therms $0.71/therm

Conversion factors: 1 therm = 100,000 Btu = 105 Btu

1 kWh = 3,413 Btu

Questions:

• Which is my greater energy consumption – electricity or gas?

• Which is more expensive per unit energy – electricity or gas?

Electric usage 232 kWh $0.11/kWh

Gas usage 52 therms $0.71/therm

Conversion factors: 1 therm = 100,000 Btu = 105 Btu

1 kWh = 3,413 Btu

Convert 232 kWh into therms by multiplying

by the conversion factors (3,413 Btu / kWh) and (1 therm / 105 Btu):

232 kWh x (3,413 Btu / kWh) x (1 therm / 105 Btu) = 7.9 therms

→ I use 7.9 therms worth of electricity

$ 0.115 / kWh

PG&E electric rates have stayed about the same over the past five years

$ 1.04 / therm

$ 0.92 / therm

PG&E gas rates have gone up from $0.70 / therm

Electric rate $ 0.115 / kWh

Gas rate $ 0.92 – 1.04 / therm

Which is more expensive, gas or electricity?

Conversion factors: 1 therm = 100,000 Btu = 105 Btu

1 kWh = 3,412 Btu

$0.115/kWh x (1 kWh/3,412 Btu) x (105 Btu/therm)

= $3.37/therm

→ electricity is over three times as expensive as natural gas

Time for a break, maybe?

Portfolio of renewable energy resources Problematic issues: • spatial and temporal constraints on energy availability • requires sophisticated, integrated planning

In my opinion, these are the most readily solvable problems.

Pacific Gas & Electric, 1989

Exclusion zone radius 18 km, area 109 m2

Incident solar radiation 1000 W/m2

at conversion efficiency 0.1

could generate 108 kW or 100 GW of solar power

at capacity factor 0.2 would produce 5% of U.S. electric energy