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ii AP Environmental Science: 2006–2007 Workshop Materials Table of Contents Special Focus: Energy and Climate Change Introduction David Hong. 3 Electric Power from Sun and Wind Fred Loxsom. 4 Understanding Climate Change and Our Rivers and Lakes: Systems Thinking Alan W. 13 Energy Balance as a Basis for the Greenhouse Effect and Global Warming Thomas B.
20 Personal Energy Audit Pamela J. 35 An Energy Primer for the AP Environmental Science Student Thomas B. 56 Important Note: The following set of materials is organized around a particular theme, or “special focus,” that reflects important topics in the AP Environmental Science course. The materials are intended to provide teachers with resources and classroom ideas relating to these topics.
The special focus, as well as the specific content of the materials, cannot and should not be taken as an indication that a particular topic will appear on the AP Exam. AP Environmental Science: 2006–2007 Workshop Materials Special Focus: Energy and Climate Change Introduction David Hong Diamond Bar High School Diamond Bar, California An AP Environmental Science course includes the scientific study of topics that have daily relevance in the lives of students. Newspapers and magazines frequently report on the same environmental issues that AP Environmental Science students are discussing in class. An AP Environmental Science course should provide students with the scientific and intellectual tools required to critically evaluate the reports about the environment they encounter in the media.
It is important that an AP Environmental Science course be dynamic—changing to reflect the most recent findings of the science that composes its curriculum. One environmental issue which has been the subject of much recent attention in the media is global climate change. The considerations above, along with the magnitude of the problem, contributed to the choice of energy and climate change as the theme of these materials. The objective is to provide AP Environmental Science teachers with resources they can use to supplement the units they teach on energy and climate change.
The articles include activities that students can use to evaluate their personal energy consumption, to compare alternative energy sources, to analyze and make connections using a systems-thinking approach to understanding climate change, to increase their understanding of the greenhouse effect, and to practice successfully converting between various energy and power units. Moreover, the materials contain thought-provoking passages that may be used to initiate class discussions on all these topics. The importance of educating an informed citizenry alone would validate the selection of energy and climate change for special focus. The weight of these topics in the Topic Outline of the AP Environmental Science Course Description provides a more practical rationale.
Preparing students to answer questions about energy resources and global climate change is a critical task for AP Environmental Science teachers. Over the years, the AP Environmental Science Exam has included free-response questions that tested student knowledge of nuclear and coal-fired power plants, home heating, electric vehicles, and alternate sources of energy. Furthermore, explanations of the mechanism of global warming and its consequences are often point-worthy responses to questions on the AP Exam that require students to describe or discuss the environmental consequences of a human activity. Future sets of themed materials will continue to assist teachers as they prepare their students for a lifetime of learning about the environment.
AP Environmental Science: 2006–2007 Workshop Materials Special Focus: Energy and Climate Change Electric Power from Sun and Wind Fred Loxsom Eastern Connecticut State University Willimantic, Connecticut Many environmental problems are related to energy consumption. A college-level environmental science survey course should include the following energy-related topics: acid mine drainage, oil spills, acid rain, global warming, nuclear waste disposal, and catastrophic flooding due to failure of water retention dams. These are just examples and one could generate a much longer list. Approximately 85 percent of the energy used by our society is generated by burning fossil fuels, and energy experts think that energy-related environmental impacts could be reduced by switching to renewable energy resources such as wind power and solar energy.
In this module, we will explore the feasibility of using the sun and wind to generate a significant amount of global electric energy. This quantitative module describes the electric energy generated by wind turbines and photovoltaic arrays. The efficiency and cost of these technologies are compared and their abilities to reduce carbon dioxide emissions are estimated. Electric Power About a third of the energy consumed globally is used to generate electricity.
Annual consumption of electric energy equals approximately 16 trillion kWh (16 × 1012 kWh) globally, and approximately one-quarter of that energy (4.0 trillion kWh) is consumed in the United States. On average each of the 6.5 billion people on earth consumes approximately 2,500 kWh of electric energy each year. Divide this amount by the number of hours in a year (8,760) to calculate the average per capita global electric power consumption: 285 watts (roughly three 100-watt light bulbs). Exercise 1 develops rough estimates of these figures using data from typical U.
electric utility bills. This exercise produces good estimates if the electric bill of a four-person family is assumed to equal “$150/month” and electricity costs 10 cents per kilowatt-hour. This exercise will help students understand the difference between energy (expressed in kilowatt-hours) and power, the rate of consuming energy (expressed in watts): power = energy / time. AP Environmental Science: 2006–2007 Workshop Materials Special Focus: Energy and Climate Change Over the next 20 years, global annual electric energy consumption is projected to increase by 10 trillion kWh, and U.
annual consumption is projected to increase by 1. Although it is expected that most of this increased demand for electric energy will be supplied by consuming fossil fuel resources, some of this electric energy will likely be supplied by renewable energy resources. Renewable Energy Most electric energy is produced by fossil fuel power plants (mostly coal-burning plants) and by nuclear power plants. Approximately 17 percent of global electric power is produced by renewable energy, mostly by hydroelectric power plants.
A tiny fraction (about 0.023 percent) of global electric energy is produced by other forms of renewable energy such as wind power and solar power. In the following sections, we will consider the feasibility and cost of using the sun and wind to produce electricity. Electricity from the Wind Wind turbines convert the kinetic energy in the wind into electric power. The overall efficiency of this conversion process is around 35 percent.
Wind farms are located in areas with strong persistent winds such as the American Midwest, coastal zones, and mountain passes. A typical utility-scale wind turbine is rated at 1.5 MW, although turbines rated at 3.5 MW have become common. The rating of a turbine means that with sufficiently high wind speed, the power generated by the turbine will equal the rated power.5 MW turbine running at its rated power for 24 hours a day for a full year would produce 13 million kWh of electric energy. Because winds are variable, wind turbines run at their rated power only a fraction of the time.
This fraction is called the turbine’s capacity factor; this factor depends upon the location of the wind turbine. Exercise 2 estimates the cost of using wind turbines to supply 10 percent of the projected 1.5 trillion kWh increase in U. electric energy demand over the next 20 years. Although many environmentalists would argue that the most cost-effective and environmentally responsible approach to this project would be to reduce demand through more efficient use of electricity, the $45 billion cost of the turbines spread over 20 years seems quite modest.
This exercise introduces the concept of payback time, the time it takes for the benefits of a project to equal its cost. This concept is important to students’ understanding of the economic viability of an investment. The payback time estimated in this exercise indicates that wind power is economically practical. AP Environmental Science: 2006–2007 Workshop Materials Special Focus: Energy and Climate Change Students should be introduced to the controversies involving the large-scale application of wind power technology.
For example, Cape Wind, the offshore wind park proposed for the shallow water between Cape Cod and Nantucket, has supporters and opponents among environmental groups. Some groups are concerned that the project will interfere with migrating birds and harm marine ecosystems; other groups think the environmental advantages of using clean renewable energy will greatly outweigh its negative impacts. Electricity from the Sun Solar cells are semiconductor materials that convert sunlight directly into electricity. Practical electricity-generating devices made from solar cells are usually called photovoltaic (PV) panels.
Arrays of PV panels are currently providing electricity for signal lights, remote power needs, residences, and electric utilities. Exercise 3 estimates the cost and payback of using residential rooftop PV systems to supply 10 percent of the projected 1.5 trillion kWh increase in U. electric energy demand over the next 20 years. The results of exercise 3 are interesting because they indicate that the solar energy resource is adequate to produce a substantial amount of electricity using a fraction of existing residential rooftops.
On the other hand, these results also illustrate the high cost of photovoltaic power systems. Many analysts believe that substantial decreases in the cost of PV systems are needed before these systems will be used to generate significant amounts of electric energy. AP Environmental Science: 2006–2007 Workshop Materials Special Focus: Energy and Climate Change Exercise 1: Electric Energy Consumption 1. What is your average monthly household electric bill? _________________________ ($/month) 2.