Chapter 2 An Introduction to Energy

Objectives Differentiate among renewable, nonrenewable, and inexhaustible energy sources. Summarize the present energy consumption trends in the united States and worldwide. Recognize various factors that influence the exploration and development of different energy resources.

Introduction Energy is the ability to do work. It is one of the driving forces behind a modern, technologically advanced economy. In addition to technical factors, factors such as politics, economics, and environmental concerns must be considered when making decisions about the development and use of particular energy technologies.

Energy: the ability to do work Wind that causes a windmill to operate a pump and pump water is an example of the effect of work. Energy produced by the wind causes the work. Renewable energy sources are those that can be replaced when needed. Wood is a fuel source that can be regenerated in a relatively short period of time. Nonrenewable energy sources cannot be replaced once used. Fossil fuels such as coal, natural gas, and oil are good examples. Inexhaustible energy sources are those that will never run out. The sun, wind, and waves are the most obvious examples.

Types of Energy Potential Energy is energy waiting to happen. Water behind a hydroelectric dam is potential energy until it is used to spin a turbine for producing electricity. Kinetic Energy is defined as energy in motion. The water that spins a turbine in a hydroelectric plant is an example of kinetic energy.

Forms of Energy 1. Light energy: is energy visible to the eye. 2. Heat energy: can be measured in terms of temperature. 3. Mechanical energy: energy produced by mechanical devices such as gears, pulleys, levers, or by more complex devices such as the internal combustion engine. 4. Chemical energy: is potential energy locked within a substance like coal or oil. 5. Electrical energy: is energy associated with the flow of electrons. Electricity powers most of our appliances. 6. Nuclear energy: is energy associated with the power of the atom. Used for nuclear power generation.

Measuring Energy The most basic unit of heat energy is known as the British thermal unit (Btu). One heating unit is equivalent to 100,000 Btu. Quantity of fuel necessary to produce 1 heating unit is 15 lbs. of coal, 1.1 gal. liquid propane, or 30 kWh of electricity.

A Brief History of Energy Consumption in the United States Energy sources in early America primarily consisted of wind, water, and wood. By the 1800s coal replace wood as the main energy source, with the advent of the steam engine. The internal combustion engine was perfected in the 1900s and petroleum became the primary energy source for automobiles. As society advances, so does its producing capability, and energy consumption.

Energy Conversion Energy conversion is the changing of one form of energy into another. Efficiency is the term used to measure the extent to which an energy form is usefully converted into another form of energy. The law of entropy states that whenever an energy form is converted from one form to another, some loss will occur. The internal combustion engine (automobile engine) is only around 25% efficient (fig 2-9, page 47).

Energy and the environment The consumption of fossil fuels leads to environmental problems such as acid rain and greenhouse effects. Acid rain occurs when the byproducts of combustion such as carbon dioxide and nitrous oxides and sulfur oxides condense in the atmosphere, only to come back down to earth with rain. The layer of greenhouse gases surrounding our planet is not allowing the heat produced by the sun to escape the earth’s atmosphere as easily as it once did. This leads to a phenomenon known as global warming. Global warming is an increase in the average temperature of the earth’s atmosphere, which could cause the melting of the icecaps, which could alter shorelines, and the changing weather patterns, which could alter agricultural productivity.

Fighting Back: Conservation and Recycling Aluminum can recycling helps save 95% of the energy required to produce new aluminum products. Recycling one plastic bottle can save enough energy to light a 60 watt bulb for 6 hours. Recycling is the best way to conserve energy, as the energy to create new paper, plastic, or glass bottles out of recycled materials is far less than what it takes using new raw material.

Summary Energy is the ability to do work. Potential Energy is energy waiting to happen. Water behind a hydroelectric dam is potential energy until it is used to spin a turbine for producing electricity. Kinetic Energy is defined as energy in motion. The water that spins a turbine in a hydroelectric plant is an example of kinetic energy. The most basic unit of heat energy is known as the British thermal unit (Btu). The law of entropy states that whenever an energy form is converted from one form to another, some loss will occur. The internal combustion engine (automobile engine) is only around 25% efficient. Acid rain occurs when the byproducts of combustion such as carbon dioxide and nitrous oxides and sulfur oxides condense in the atmosphere, only to come back down to earth with rain. Recycling is the best way to conserve energy, as the energy to create new paper, plastic, or glass bottles out of recycled materials is far less than what it takes using new raw material.

Home Work 1. Define kinetic energy and give an example. 2. What is a Btu? 3. What is the efficiency of an automobile engine? 4. What is acid rain? 5. Why is recycling important?