““The World We Create”The World We Create”NATS 101NATS 101Section 6Section 6

Please, turn in your homework

02/10/08

PROJECT 1PROJECT 1Due Next Tuesday, Feb 17Due Next Tuesday, Feb 17

Available in D2LAvailable in D2L(Content Section)(Content Section)

100 points total100 points total5 questions 5 questions to hand into hand in

1 question 1 question D2L D2L

QUIZ (10 points) SURVEY (3 e-points)

FRONT CLASSROOM

A FC

D

E

B IG

H

Ethanol Reading

Thursday’s Debate

Economy Con

Economy Pro

Dependence Pro

Dependence Con

Pro Con Environment

Energy Supply Pro

Energy Supply Con

UNIT 1: Energy Sources,

Conventional or Alternative?

Nuclear and

Solar Energy

Expected Learning Outcomes:

Estimate the number, area, and cost of the solar panels needed to produce certain amount of energy.

Evaluate the costs and benefits of using solar cells to generate electrical energy.

Describe how the energy of stars like our Sun is generated and how we take advantage of it;

Evaluate the costs and benefits of the development and use of nuclear reactors;

Major ProblemsThere are two major problems associated with the

operation of nuclear reactors:

Nuclear Waste

Nuclear Accidents

Beyond Control

An uncontrolled chain reaction can lead to an explosive energy release. This is what

happens in nuclear weapons and in the melt down at a nuclear power plant.

vs

ControlledUncontrolled

Nuclear Disasters:Three Mile Island

If you had been working IN the plant at the time of the Three Mile Island “meltdown”,

you would have absorbed less radiation than you would from an X-Ray.

On March 28, 1979, there was a “major”

accident at Three Mile Island in Pennsylvania.

Nuclear Disasters: Chernobyl

On April 26, 1986, a reactor at the Chernobyl Nuclear Power Plant exploded, sending a plume of

radioactive material into the air.

The plant at the time was under loose regulation from the Communist Soviet Union. The workers were found to

be inexperienced and poorly trained.

As a result of the explosion, 56 people died, 150 000 people were

displaced, and 260 000 were exposed to ionizing radiation.

Chernobyl Effects

Environmental EffectsEnvironmental Effects

• 200,000 sq kilometers were affected.• Many birds were reported with stunted tail feathers. • High levels of cesium were found in mushrooms, berries and game.

Albino

Branched

Biological EffectsBiological Effects

• 4,000 cases of thyroid cancer in children.• Psychosocial effects among survivors.• Besides deaths, mental health impact was “the largest public health problem.”

Estimating Costs

Total Deaths

Deaths/Energy

US Cents/kW-h

Coal 3837 342 2.47

Gas 1651 85 6.78

Hydro 3776 883

Nuclear 56 8 1.76

Loss of life expectancy (Risk factor):

Nuclear events < 0.1 Car accident ~150 Smoking ~2300

What do you think…The Governor of your State wants to build more

nuclear power plants to better address increasing energy needs. It had been such a hot topic, it has

come down to a vote.

Discuss in your groups, 5 minutes.

Given the information we have discussed in the class:

How will you vote? Why? Consider costs/benefits for your community.

Nuclear Processes

generate

Lots of Energy

Lower cost; more efficient;

low air pollution;low risk.

Benefits

Some Waste

Radioactive; Biological and Environmental

effects; long lasting.

Costs

Current Usage

Solar Energy Two different types of solar energy:

Energy is harnessed directly from the sun;

Energy is captured by solar devices.

Other energy sources that are created by energy from the sun:

Primary

Direct

Secondary

Indirect

Wind, Biomass, Hydro

The Ultimate Power SourceThe Sun puts 3.8 X 1024 J of energy into

the Earth each year

The world consumes 4.1 X 1020 J each year.

There is enough energy from the sun to accommodate

the World’s energy needs!

What is the SOURCE of all this Energy?

Some FactsThe current chemical composition of our Sun is 94% of Hydrogen (H) and 6% of Helium (He). The Helium atom is heavier than the Hydrogen atom.

What is happening inside the Sun?

Where does the solar energy come from?

What would you expect to happen when all the hydrogen is gone?

You have 3 minutes

H

He

The amount of hydrogen in the Sun is decreasing over time, and the amount of helium is increasing.

The total mass of the Sun is decreasing.

Nuclear FusionStars are powered by a nuclear reaction known as

NUCLEAR FUSION. This process involves:

Forcing two relatively small nuclei into a new, heavier atom;

The transformation of a small amount of mass into energy.

Life Cycle of Stars

H

He

Our Sun

Sun’s Evolution

The Sun as a Primary Source

Natural light: skylights, windows

Solar hot water heaters

Solar cooking

Solar power plants

Solar panels/cells

Photovoltaic Cells

Solar cells (PV) made with special types of materials (Semiconductors, such a silicon);

An electron flow is initiated by light of a certain energy.

Efficiency Most commercially available solar cells are 15-20% efficient;

The overall efficiency of producing electricity using coal is ~26%.

$$ Solar Panels $$

You’re building a new house, and are particularly concerned with “Going Green”, you’re thinking of installing Solar Panels.

What might be some of your concerns with doing so?

Take 2-3 minutes to discuss with your group, some of the factors you will consider in making your decision.

Select a spokesperson to share your ideas with the class.

Concerns? . . .• Energy requirements for the average home

per day;• Power (Energy per hour) generated by solar

panels;• Amount of sunlight in a particular area;• Cost: per solar panel, installation;• Others . . .

Let’s Calculate: Energy Needs Using the information provided,

as well as help from group mates, calculate:

1. How much energy (in Wh) is needed to operate the average home for one full day?

2. How much energy can be generated a day by 1 square foot of solar panel during the daylight hours in (a) Tucson? (b) Chicago?

3. Based on these energy requirements, how many square feet of solar panels are needed to operate the average home in (a) Tucson? (b) Chicago?

You have 5-7 minutes

Energy Needs1. Energy used per day: (24 h) x (1.2 kWh / h) = 28.8 kWh 28.8 kWh x (1000 Wh / kWh) = 28,800 Wh

2. Energy generated per day In Tucson: (5.4 h ) x (10 Wh / h / ft2) = 54 Wh / ft2 (total during Tucson’s daylight hours)

3. Square feet of solar panels needed:

(Total Energy Available / day) x (Area/Total Energy Provided) = Total square footage needed

(28,800 Wh) x (1 ft2 / 54 Wh) = 533 ft2 in Tucson