“The World We Create” NATS 101 Section 6 Please, turn in your homework 02/10/08

PROJECT 1 Due Next Tuesday, Feb 17 Available in D2L (Content Section) 100 points total 5 questions  to hand in 1 question  D2L QUIZ (10 points)SURVEY (3 e-points)

FRONT CLASSROOM AF C 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 Problems There 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 Controlled Uncontrolled

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, people were displaced, and were exposed to ionizing radiation.

Chernobyl Effects Environmental 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 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 Gas Hydro Nuclear 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 Source The Sun puts 3.8 X J of energy into the Earth each year The world consumes 4.1 X 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 Facts The 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 Fusion Stars 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 Needs 1. 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 / ft 2 ) = 54 Wh / ft 2 (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 ft 2 / 54 Wh) = 533 ft 2 in Tucson