Transcript Chapter 17
Chapter 17 Nonrenewable Energy Section 1: Energy Resources and Fossil Fuels • Fuels are used for 5 main purposes: 1. Transportation (# 1 use of crude oil) 2. Electricity (coal & nuclear power) 3. Heating and Cooling (oil, natural gas, electricity) 4. Cooking (natural gas or electricity) 5. Manufacturing (coal) The sustainability of a fuel for a particular use depends on: • • • • • The energy content of the fuel Cost Availability Safety By-products of using the fuel (waste) *Most of the energy we use comes from fossil fuels Fossil Fuels: • The remains of ancient organisms that have turned into coal, crude oil, and natural gas Two main problems with using fossil fuels: • Supply is very limited • Obtaining them and using them causes environmental problems (pollution) Electricity The energy from fossil fuels (coal) is often converted into electric energy Two disadvantages: 1. It is difficult to store 2. Other energy sources must be used to generate electricity How A Coal Burning Power Plant Works (fig. 3 page 468) How a coal-fired power plant works 1. Burning fossil fuels release energy in the form of heat, which is used to boil water and produce high-pressure steam 2. Steam is directed against blades of a turbine, which is set in motion 3. Turbine is connected to electric generator, which is set in motion, generating electricity 4. Steam from turbine is directed to condenser where it cools and becomes liquid water to be cycled again Energy Use • People in developed countries use more energy than people in developing countries Energy Use in the U.S. • Industrial Use 38% • Transportation 27% • Commercial 16% • Residential 19% Coal • Coal forms from the remains of plants that lived in swamps hundreds of millions of years ago – Layers of sediment compress the remains – Heat & pressure within the Earth’s crust cause the coal to form • Coal is the world’s most abundant fossil fuel, also the dirtiest • More than ½ of the electricity in the U.S. is generated by coal Coal Mining – Two Types 1. Surface Mining: a. Layers of rock & soil are removed to get coal that is near the surface b. This method is VERY destructive to the environment 2. Sub-Surface Mining: a.These are mines that are dug deep (50 meters or more) into Earth’s surface b.This type of mining is better for the environment, but more dangerous to the miners i. 3 Major Dangers 1. Mine collapsing 2. Black lung disease 3. Explosions of methane / natural gas • Advantages of Coal: 1.It’s cheap! 2.Very abundant 3.Needs little refining after being mined • Disadvantages of Coal: 1.Emits air pollutants (sulfur dioxide & mercury) 2.Causes acid precipitation Petroleum / Crude Oil: Formation of petroleum Comes from the decay of tiny marine organisms that became buried on the bottom of the ocean floor The heat from the Earth’s crust caused them to become oil after millions of years Locating and Drilling for Oil Most of the world’s oil is found in the Middle East (Saudi Arabia) Once an oil reserve is located an oil well is drilled The oil is brought to the surface by pumps and then refined at a refinery Refining Oil Heating the oil causes the petroleum to separate from the various compounds – this process is known as fractional distillation o Volatile compounds have different boiling points Low boiling point – gasoline & jet fuel o The compounds are collected at the various evaporation & condensation points o These compounds are used to make various petroleum based products Products from Crude Oil: 1.Gasoline – diesel 2.Motor Oil 3.Petroleum Jelly (Vaseline) 4.Gum 5.Plastics 6.Nylon Dacron 7.Kerosene Environmental Effects of Using Oil: Air pollution Sulfur dioxide, carbon dioxide, VOC’s Causes acid precipitation Causes water pollution Run off from streets Spills from oil tankers Spills from off-shore oil wells Natural Gas / Methane: Formation o Forms above oil reserves o Forms in the same manner as oil Transported through pipelines Provides about 20% of the world’s energy Cleanest burning fossil fuel World’s least abundant fossil fuel Section 2: Nuclear Energy Nuclear Power: Energy stored in the nucleus of an atom Nuclear power plants release this energy and use it to make steam The fuel in nuclear power plants is Uranium – 235 (U235) The nuclei of the uranium atom is bombarded with neutrons causing it to split into two parts – known as nuclear fission This splitting releases a large amount of energy and neutrons o The neutrons cause more nuclei to split causing a chain reaction In a nuclear bomb this reaction is uncontrolled In a nuclear power plant this reaction is closely controlled • (see Fig 15 on p. 477) How a typical nuclear power plant works 1. Energy released by the nuclear reaction heats water in the pressurized first circuit to a very high temperature 2. The superheated water is pumped to a heat exchanger, which transfers the heat of the first circuit to the second circuit. Water in the second circuit flashes into high-pressure steam 3. Steam is directed against a turbine, setting it in motion. The turbine sets the generator in motion, generating electricity 4. A third circuit cools the steam from the turbine and the waste heat is released from the cooling tower in the form of steam Advantages of Nuclear Energy: 1.Produces a large amount of energy and the fuel is compact 2.Does not produce air pollution or greenhouse gases 3.Nuclear power plants release less radioactivity into the environment than a coal burning plant Disadvantages of Nuclear Energy: 1.Building and maintaining a nuclear power plant is very expensive 2.Storage of radioactive waste (spent fuel) is very difficult and expensive a.Must be stored in an area that is geologically stable for tens of thousands of years. b.Yucca Mountain in So. Nevada (Mojave Desert outside Las Vegas) is being studied for such storage 3. There are a lot of safety concerns that any accident could be very dangerous a.Three-Mile Island (Harrisburg, PA) – the site of the most serious nuclear accident in the US in 1979. b.Caused by human error & faulty equipment c.Very little radiation escaped into the environment • The Future of Nuclear Power: • Nuclear Fusion: The combining of the nuclei of light weight atoms creating one heavy atom and generating a huge amount of energy Fusion Advantage: 1. It does NOT create radioactive waste Fusion Disadvantage: 1. In order for fusion to occur, the nuclei must be heated to extremely high temperatures (1 million degrees Celsius) 2. The nuclei must be maintained at very high concentrations 3. Nuclei must be properly contained **Achieving all three conditions simultaneously is extremely difficult