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Climate & Calculating BTU’s in Environmental Science

By Dr. Rick Woodward

Saving Math to the Last1. There are four free response questions.

2. All four questions are weighted equally.

3. The suggested time is about 22 minutes for answering each question.

4. There will only be one out of the four questions that focuses specifically to math calculations involving conversions.

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Saving Math to the Last

5. Calculators are not allowed and you must show all of your work in order to receive credit.

6. Math is only a small percentage of the AP Environmental Exam. I have been focusing on conceptual knowledge of the environment and intuitive test taking skills.

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This Thursday’s Examwill have 50 multiple Choice Questions & 1 Math Free Response

It Will cover:

1. The parts of a nuclear reactor and their specific functions.

2. How energy is converted into electricity.

3. Global Warming Gases.

4. Heavy Metals

5. Thirty questions pulled from Barron’s prep questions.

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Reviewing Climate Change

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What are the Greenhouse Gases?

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Atmosphere

1. The gas that is responsible for trapping most of the heat in the lower atmosphere is

a. Water vapor

b. ozone

c. carbon dioxide

d. oxygen

e. nitrogen

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Correct Answera. Water Vapor

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Cloud Formation Review

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Monsoons2. Characteristics or requirements of a monsoon

include all of the following EXCEPTa. A seasonal reversal of wind patterns.b. Large land areas cut off from continental air

masses by mountain ranges and surrounded by large bodies of water.

c. Different heating and cooling rates between the ocean and the continent.

d. Extremely heavy rainfall.e. Heating and cooling rates between the oceans

and the continents are equivalent.

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Correct Answer

e. Monsoons are caused by winds from the southwest or south that bring heavy rainfall to southern Asia in the summer.

-They are created by temperature gradients that exist between ocean and land surfaces.

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Albedo

3. The surface with the lowest albedo would be

a. Snow

b. Ocean

c. Forest

d. Desert

e. Black topsoil

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Correct Answere. Albedo is a measure of

reflection of sunlight from a surface. Dark objects absorb energy, light surfaces reflect sunlight.

-Dark topsoil would absorb the most energy and, therefore, would reflect the least resulting in the lowest albedo.

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Jet Streams

4. Jet streams travel primarily

a. North to South

b. South to North

c. East to West

d. West to East

e. In many directions depending on a multitude of factors

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Correct Answerd. Jet streams are large-scale

upper air flows that travel from west to east.

-They are located between 3 ½ an 7 ½ miles above the Earth’s surface.

Jet StreamA. The jet stream is a current of

fast moving air found in the upper levels of the atmosphere.

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Low Pressure vs. High Pressure Air Masses5. A low-pressure air mass is

generally associated with

a. Hot, humid weather

b. Fair weather

c. Tornadoes

d. Cloudy or stormy weather

e. Hurricanes

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Correct Answer

d. Cloudy or stormy weather

What’s a Watt?

A. The basic unit of energy is the watt (named after Scottish engineer James Watt).

B. An incandescent light bulb uses 25-100 watts.

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What’s a Kilowatt?C. One kilowatt (kW) is equal to a thousand

watts.

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What is a Kilowatt Hour (KWh)?D. When electricity use is measured over

time, it is measured in kilowatt hours (kWh) .

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What is a kilowatt hour?

E. How many kilowatts (kW) of electricity are used (or produced) over how many hours?

F. Leaving a 100 watt light bulb on for 10 hours will use 1,000 watt hours – or one kilowatt hour.

G. Your electricity bill probably measures your electricity consumption in kilowatt hours.

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What is a Megawatt?H. The capacity of large-scale power plants

is usually on the scale of megawatts (MW).

I. One MW is equal to one million watts, so we’re talking about a very large amount of energy

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What is a megawatt?J. As a general rule of thumb, each MW of a

coal plant’s power plant capacity can supply around 650 average American homes (Assuming 10,000kWh/year demand of average US home and 75% capacity for a coal plant).

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What’s a gigawatt?

K. For very large-scale power plants, capacity is often discussed in gigawatts (GW).

L. A GW is one billion watts, or one thousand MW.

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What’s a gigawatt?M. The ill-fated Chernobyl nuclear power

plant, for example, had a capacity of 4,000 MW – that’s 4 GW - which accounted for about 10% of Ukraine’s electricity production at the time.

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Nuclear Reactor Diagram

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Nuclear Reactor

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What’s a gigawatt?

N. China’s Three Gorges Dam, the world’s largest power plant of any kind, which will eventually be 22.5 GW.

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Wednesday (January 25, 2012)Today’s agenda:

1. Brief review of BTU’s

2. Free Response Question

3. Test tomorrow with one redemption assignment worth 10.5 pts. (30 Questions come from Barron’s multiple choice question and twenty come from me (global warming and nuclear power))

4. Collecting your extra credit Ms. Benki signature from Saturday and show me your paper work

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General Information on Energy Units

1 Gallon of water = 8 pounds

1 BTU = The amount of energy required to raise the temperature of 1 pound of water by degree F.

1 Kilowatt-hour – 3,400 BTU’s

Energy questions are all about conversions and simple math.

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**Distinguishing Between Power & Energy

A. Power has a unit of Watts (W). Energy has the unit Joule (J) and is equal to power over the time dimension. 1J = 1Ws.

B. When converted into Watt hours, it is simply done by multiplying by 3600.Hence, 1Wh = 3600 Joule.

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BTU’s = British Thermal UnitsA fundamental unit of energy in the English system. B. The amount of heat required to raise the

temperature of 1 pound of water 1 degree Fahrenheit.

1 gallon of water = 8 pounds

-Problems involving calculations:1. They give you assumptions2. They give you extra information that may not be used.3. Always show your work4. No Calculators

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BTUSome Fun BTU Facts:1. Gas-fired electrical power plant.2. 15,000,000 kW-h of electricity every

24 hours (1 day)3. Plant requires 13,000 BTUs of heat

to produce 1 kW-h of electricity4. 1 ft3 of natural gas supplies 1000

BTUs of heat energy

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Go to Water Heater Question Then pass out sample BTU

Question.

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Calculation of BTUs

1. Calculate BTUs of heat needed to generate electricity produced in 24 hours.

(1) Start with an equal sign =(2) Next write down the units you want to

be in = BTUs

(3) Next, what did you have to start with? The answer to this question is 24 hours24 hours = BTUs 1

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Calculation of BTUs

(4) Next, what do you know about hours so that you can cancel the term? The answer is that 15,000,000 kW-h are produced every 24 hours.

24 hours x 1.5 X 107 kW-h = BTUs

1 24 hours

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Calculation of BTUs

Note: We are now in kW-h and we have to end up in BTUs. Was there any information regarding kW-h and BTUs? The answer is yes. 13,000 BTUs are required for every 1 kW-h.

24 hours x 1.5 x 107 kW-h x 13,000 BTUs =

1 24 hours 1 kW-h

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Calculation of BTUs

Correct Answer

= 2.0 x 1011 BTUs per day

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Next Question

Calculate the number of cubic feet of natural gas consumed by the power plant each hour.

Calculation Set Up

2.0 x 1011 BTUs x 1 ft3 x 1 day =

1 day 1,000 BTUs 24 hours

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Correct Answer

= 8.3 x 106ft3 natural gas per hour

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Water Heater Question worth 6 points1. They give you assumptions2. Other information.3. There may be information that you do not need to use.4. Always label your parts/components of question in essay.5. You don’t have to answer the questions in order.

Water heater 50 degrees Fahrenheit. Assume water heater is 100% efficient.Use 40 gallons of water per day.Heat water up to 140 degreeOne gallon of water = 8 pounds No calculators can be used on test. What is a BTU: British Thermal UnitDefined: The energy needed to raise one gallon of water by one

degree Fahrenheit.One Kilowatt hour = 3400 BTU

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Question A

Calculate the yearly energy (in BTU’s) used to heat the water. (you get three points just for setup)

-change gallons to pounds first.

40 gal 8 pounds 90 degrees F BTU__ 365 days___ = BTU’s

Day gallon 1 pound F year Year

(40 gallons)(8 pounds) = 320 pounds of water

(320 pounds) (90 degrees F) = 28,800

365 days x 28,800 = 10,512,000 BTU/Year

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Question B

Add an insulation pad to the water heater and save 5% of the energy.

10,512,000 BTUs/ gal

1,051,200 = 10%

2/1,051,200 = 525,600 BTUs/year

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Question C Discuss the economic and environmental cost of replacing your water

heater. (0rganizational tool: Make this grid/chart for these types of questions)

Economic Cost Environmental Cost 1. Purchase cost 1. Throwing old one away 2. Labor to install 2. Landfill space

3. Packaging, etc.Benefit Benefit1. Save money on energy cost 1. more efficient/less energy used2. Less maintenance cost 2. Recycle old metal

(works for dishwasher and washing machine, a-c, etc.)

Now take this information and write about it. (Use Complete sentences)

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Question D

List 2 ways to save energy.

(write your responses in the form of a paragraph.)

1. Lower the thermostat.

2. Taking shorter showers

(Don’t list more than 2 ways): Graders only look at your first two responses.

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E. Convert to Kilowatt hours

Convert to kilowatt hours

10,512,000 BTU’s

10,512,000 BTUs 1 Kwh = Kwh

3400 BTUs

34/105,120 =

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Question 1 (Growth Rate)

Rule of 70. 70/growth rate = the number of years it will take for the population to double

In 1999

U.S. Population 278 million

World Population 6 billion

Growth Rate

U.S. 1%

World 1.4%

70/r = # years for population to double

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Growth Rate Question Continued

a. In what year will the United States population double based on the growth rate?1.4/70 = 50 (1999 + 70 = 2069)

(1.4)(50) = 70 yearsb. In what year will the World’s

population double based on the growth rate?

(1999 + 50 = 2049)