Energy and the EnvironmentNon-Renewable Resources

http://www.nap.edu/video/aef_video.html

America's Energy Future from the National Academies

Energy Introduction

• Heat Engine: a device that can convert heat energy to mechanical energy (or work).– Fancy name for a car engine, a power plant, your

refrigerator, air conditioner, etc.

• Efficiency of a heat engine is expressed in terms of the temperature difference between the hot side and the cold side. Efficiency = (Thot – Tcold)/Thot

• Energy Efficiency – the percentage of energy put into system

that does useful work.• Cars are only about 20 to 30% efficient. • Coal fired power plants are around 35% efficient.

In gasoline-powered vehicles, over 62 percent of the fuel's energy is lost in the internal combustion engine

Energy makes everything happen and can be divided into two types: Stored energy is called potential energy.Moving energy is called kinetic energy.

Energy can be found in a number of different forms: •chemical energy•electrical energy •heat (thermal energy) •light (radiant energy) •mechanical energy •nuclear energy

Energy in fuels is converted to electrical energy to power machines which is more convenient and can be transferred quickly over small or great distances.

2 disadvantages:1) Difficult to store2) Other energy sources were used to generate it

We can use both renewable and nonrenewable energy sources (fossil fuels) to do this

Generating Electricity -- electricity is the result of electrons flowing through a conductor

• Spinning wires inside a magnetic field, or vice verse, causes electrons to move in the wire, and moving electrons produce electricity

• Converts motion into electrical energy

US vs. Global Energy Source

US Energy Sources Global Energy Sources

Natural Resources – any natural material that is used by humans such as water, petroleum, minerals, forests and animals.

Classified as:1) Renewable resources -- is a resource that can be replaced relatively quickly by natural processes. ex. Fresh water, air, soil, trees, and crops

2) Non-Renewable resources -- is a resource that forms at a much slower rate than the rate that it is consumed.Ex. Minerals and fossil fuels

Once the supply of a nonrenewable resourceis used up, it may take millions of years to replenish it.

Resources are said to be depleted when a large fraction of theresource has been used up. Some renewable resources can also be depleted. For example, iftrees are harvested faster than they can grow naturally in an area, deforestation will result.

copper mine

Renewable and Nonrenewable Resources

Renewable Nonrenewable

energy from the sun metals such as iron, aluminum,and copper

water nonmetallic materials such as salt,sand, and clay

wood fossil fuels

soil

air

Is there something on the renewable side that seems questionable as a renewable resource?

Non-Renewable Energy Sources = Fossil Fuels• Oil • Coal• Natural gas• Nuclear (uranium)• Fuel wood

Fossil fuel use

Dates back to ancient civilizations

In the 18th century, James Watt’s developed the coal burning steam engine which drastically changed our way of production – Industrial Revolution

Petroleum and natural gas use began a little over 100 years ago

Today, many products rely on fossil fuels in manufacturing and transportationEx. Synthetic fibers (nylon, rayon, polyester), plastics, paints, packaging

Four main purposes of fossil fuel use: transportation, manufacturing,heating and cooling buildings, and generating electricity to run machines and appliances.

Fossil fuels

•contain stored energy in the form of hydrocarbons – compounds made of carbon and hydrogen

•are the accumulated and compressed remains of ancient plants and animals that changed into coal, oil, or natural gas •are central to life in modern societies

Two major problems:1) the supply of fossil fuels is limited 2) obtaining and using them has environmental consequences

This map shows coal, oil, and natural gas deposits in the United States.

Uneven distribution of fossil fuels is due to geologic history of the areas.

Coal Formation

Coal is composed of decomposed and fossilized plant remains. These plants lived in swamps hundreds of millions of years ago. Much of the coal in the United States formed about 300 million to 250 million years ago, when vast areas of swampland covered the eastern United States. As ocean levels rose and fell, these swamps were repeatedly covered with sediment. Layers of sediment compressed the plant remains, and heat and pressure within the Earth’s crust caused coal to form.

Coal DepositsMost of the world’s fossil-fuel reserves are made up of coal. Asia and North America are particularly rich in coal deposits.

Two major advantages of coal: 1) Relatively inexpensive 2) needs little refining after it has been mined

A majority of the electricity generated in the United States comes from coal-fired power plants using steam turbines.

Underground mines can have a minimal effect on the environment at the surface. However, surface coal-mining operations sometimes remove the top of an entire mountain to reach the coal deposit. In addition, if waste rock from coal mines is not properly contained, toxic chemicals can leach into nearby streams.

The environmental effects of coal mining

Surface mining - also known as opencast or opencut mining - is only economic when the coal seam is near the surface.

Underground MiningThere are two main methods of underground mining: room-and-pillar longwall mining

Air Pollution and Coal Burning

The quality of coal varies. Higher-grade coals, such as bituminous coal, produce more heat and less pollution than a lower-grade coal, such as lignite. Sulfur is found in all coal and is a major source of pollution when burned.

Air pollution and acid precipitation is a result of burning high-sulfur coal without adequate pollution controls are serious problems in countries such as China.However, clean-burning coal technology has dramatically reduced airpollution in countries such as the United States.

Beijing, China

When coal burns, it releases carbon dioxide and other emissions in flue gas, the billowing clouds you see pouring out of smoke stacks.

Clean Coal Technologies

1) Coal washing - removes unwanted minerals by mixing crushed coal with a liquid and allowing the impurities to separate and settle.

2) Wet scrubbers - or flue gas desulfurization system - removes sulfur dioxide by spraying flue gas with limestone and water. The mixture reacts with the sulfur dioxide to form synthetic gypsum, a component of drywall.

3) Low-NOx (nitrogen oxide) burners - reduces the creation of nitrogen oxides by restricting oxygen and manipulating the combustion process.

4) Electrostatic precipitators - removes particulates by charging the particles with an electrical field and then capturing them on collection plates.

5) Gasification (coal is changed into a gas) avoids burning coal altogether. Steam and hot pressurized air or oxygen combine with coal in a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity.

Oil and Natural Gas Formation

Oil and natural gas result from the decay of tiny marine organisms that accumulated on the bottom of the ocean millions of years ago.

After these remains were buried by sediments, they were heated until they became complex energy-rich carbon molecules. Over time, these molecules migrated into the porous rock formations that now contain them.

Much of the oil and natural gas in the United States is located in Alaska, Texas, California, and the Gulf of Mexico.

Petroleum is oil pumped from the ground and is also known as crude oil

Anything that is made from crude oil, such as fuels,chemicals, and plastics, is called a petroleum product.

Locating Oil Deposits Oil is found in and around major geologic features that tend to trap oil as it moves in the Earth’s crust.

These geologic features are bound by impermeable layers of rock prevent the oil from escaping.

Most of the world’s oil reserves are in the Middle East.

Large oil deposits also exist in the United States, Venezuela, the North Sea, Siberia, and Nigeria.

Geologists use different methods to locate oil in rock formations.

Once data has been gathered, exploration wells are drilled to determine thevolume and availability of the oil deposit. If oil can be extracted at a profitable rate, wells are drilled and the oil is pumped or flows to the surface.

After petroleum is removed from a well, it is transported to an oil refinery to be converted into fuels and other petroleum products.

The Environmental Effects of Using Oil

1) Burning releases pollutants into the atmosphere and contributes to the formation of smog which can cause health problems.

Emissions regulations and technology such as catalytic converters have reduced air pollution in many areas, but is an issue in developing countries

Many scientists also think that the carbon dioxide released from burning petroleum fuels contributes to global warming.

2) Oil spills are another potential environmental problem of oil use.

Recent measures to prevent oil spills from tankers include:a) requiring new tankers to be double-hulled so that puncturing the outer hull does not allow the oil to leak out

b) quicker response time to clean up oil spills (more oil pollution comes from everyday sources, such as leaking cars measures to reduce everyday contamination of waterways from oil lag far behind the efforts made to prevent large spills)

Natural Gas - • gaseous mixture of hydrocarbons—predominantly methane

(CH4)• a good example of how advances in technology can make a

fuel more common. In the past, when natural gas was encountered in an oil well, it was burned off because it was considered a nuisance.

As technology improved, transporting natural gas inpipelines and storing it in compressed tanks became

more practical.Now, many more oil wells recover natural gas. Burning natural gas produces fewer pollutants than

other fossil fuels

Environmental Impacts of Natural Gas

The extraction of natural gas and the construction of natural gas power plants can destroy natural habitat for animals and plants.

Possible land resource impacts include erosion, loss of soil productivity, and landslides.

Hydraulic fracturing or fracking is the process of creating fissures, or fractures, in underground formations to allow natural gas and oil to flow.

Water, sand and other additives are pumped under high pressure into the formation to create fractures in the rock.

Methane Hydrate - The Gas Resource of the Future?

Methane hydrate is a cage-like lattice of ice inside of which are trapped molecules of methane, the chief constituent of natural gas.

If methane hydrate is either warmed or depressurized, it will revert back to water and natural gas.

Hydrate deposits generally occur in 2 settings: 1) under Arctic permafrost 2) beneath the ocean floor

Nuclear Energy - originates from the splitting of uranium atoms in a process called fission.

Fission releases energy that can be used to make steam, which is used in a turbine to generate electricity. The nuclei of uranium atoms are bombarded with atomic particlescalled neutrons. These collisions cause the nuclei to split releasing energy. If a fission reaction is allowed to continue, this chain reaction will escalate quickly. One example of an uncontrolled fission reaction is the explosion of an atomic bomb. In contrast, nuclear power stations are designed so that the chain reaction produces a controllable level of energy.

Hiroshima (left) and Nagasaki (right)

Fission Neutrons are released from the fission, or the splitting, of auranium atom’s nucleus. Some of these neutrons then cause other atoms to undergo nuclear fission in a process called a chain reaction.

How Nuclear Energy Works

A Reactor is surrounded by a thick pressure vessel filled with a cooling fluid. Concrete walls also surround reactors.Inside a reactor metal fuel rods contain solid uranium pellets which are bombarded with neutrons. The chain reaction that results releases energy and produces more neutrons.

The reactor core contains control rods, which are made of a material such as boron or cadmium that absorbs the neutrons to prevent an uncontrolled chain reaction.

When the control rods are lowered between the fuel rods, they slow the fission reactions. If the control rods are lowered completely, they prevent fission and shut down the reactor.The heat released during nuclear reactions is used to generate electricity in the same way that power plants burn fossil fuels to generate electricity.

How a Nuclear Power Plant Works

Nuclear Power Generation in Virginia

Dominion Power operates four nuclear units at its two Virginia nuclear power plants. Two units are located at the South Anna Power Station in Louisa County and two are located at the Surry Power Station in Surry County.

The Advantages of Nuclear Energy

•Does not produce air-polluting gases

•When operated properly, nuclear plants release less radioactivity than coal-fired power plants •Many countries with limited fossil fuelreserves rely heavily on nuclear plants to supply electricity.

•France, for example, generates about three-fourths of its electricity from nuclear power. France produces less than one-fifth of the air pollutants per person than does the United States, which relies on fossil fuels for almost 70 percent of its electricity needs.

Disadvantages of Nuclear Power/ Environmental Impacts

•Building and maintaining safe reactors is very expensive.

•Uses large quantities of water for steam production and for cooling •Water discharged from the power plant is higher in temperature and can contain heavy metals, salts and traces of radioactive uranium

•Storing nuclear waste fission byproducts can remain dangerously radioactive for thousands of years

•Uranium mining and fuel development produce radioactive waste

•Used fuel, liquids, and equipment from a reactor core are also considered hazardous wastes

•Every 18 to 24 months, nuclear power plants must shut down to remove and replace the "spent" uranium fuel

•Storage sites for nuclear wastes must be located in areas that are geologically stable for tens of thousands of years.

Safety Concerns of nuclear power plants Fission process can get out of control –

The world’s worst nuclear reactor accident occurred at Chernobyl in the Ukraine in 1986.

In the United States, the most serious nuclear accident occurred in 1979 at the Three Mile Island nuclear power plant in Pennsylvania.

A May 1986 aerial photo of the damaged reactor at the Chernobyl nuclear power plant

Three Mile Island Nuclear Power Plant

ChernobylFukushima Daiichi-- Level 7

Three Mile Island – Level 5

The Future of Nuclear Power?

One possible future energy source is nuclear fusion.

It occurs when lightweight atomic nuclei combine to form a heavier nucleus and release tremendous amounts of energy.

Potentially it is a safer energy source than nuclear fission because it creates less dangerous radioactive byproducts.

There are 3 technical (requirements) difficulties surrounding fusion1) extremely high temperatures (about 100,000,000ºC, or 180,000,000ºF). 2) high concentrations of nuclei 3) proper confinement

During nuclear fusion, the nuclei of two forms of hydrogen(deuterium and tritium in this case) join to form helium, which releases large amounts of energy.