Unit 6 Review Book Flashcards
(25 cards)
Basic information about energy
energy is defined as the capacity to do work.
There are three types of energy:
potential energy is energy at rest—it’s stored energy
kinetic energy is energy in motion.
The third type of energy is radiant energy—for example, sunlight—and it is the only form of energy that can travel through empty space.
Two terms that describe the movement of energy around the Earth are convection, which is the transfer of heat by the movement of the heated matter, and conduction, which is the transfer of energy through matter from particle to particle.
Keep in mind that different energy sources are capable of storing types of energy that differ in quality.
For example, both wood and coal will burn to produce heat, but coal produces more heat because it contains higher energy quality.
Net energy yield refers to the comparison between the energy cost of extraction, processing, and transportation and the amount of useful energy derived from the fuel.
First Law of Thermodynamics
says that energy can neither be created nor destroyed; it can only be transferred and transformed. One example of such a transformation occurs in photosynthesis. In photosynthesis, radiant energy from the Sun is converted to chemical
energy in the form of the bonds that hold together atoms in carbohydrates.
Second Law of Thermodynamics
says that the entropy (disorder) of the universe is increasing. One corollary of this Second Law of Thermodynamics is that, in most energy transformations, a significant fraction of energy is lost to the universe as heat; for example, as we reviewed in Chapter 4, in food chains only about 10 percent of the energy from one trophic level is available for the next higher energy level upon consumption.
producing electricity, nonrenewable energy
Perhaps surprisingly, one of our biggest uses of energy is in the production of electricity. In other words, we use tons of energy each year to produce electricity—another form of energy!
In general, electricity is produced in the following way: an energy source provides the power that heats up water, transforming it into steam, which then turns a turbine.
Hence, the turbine converts kinetic energy (from the steam) into mechanical energy (the spinning of the turbine).
Now here’s where the generator comes in.
The generator consists of copper wire coils and magnets, one of which is stationary (stator) and the other of which rotates (rotor).
As the turbine spins, it causes the magnets in the generator to pass over the wire coils (or vice versa), generating a flow of electrons through the copper wire and thus producing an alternating current that passes into electrical transmission lines.
In lieu of steam, flowing water or wind can also provide the power needed to turn the turbine and produce electricity.
Well, the three main sources for electricity production are:
fossil fuels (provide 65 percent of the world’s electricity)
nuclear energy (provides 20 percent of the world’s electricity)
renewable energy sources (provide 15 percent of the world’s electricity)
Sources of energy, fossil fuels
During the Industrial Revolution (in the early 18th century), steam was produced almost exclusively through the burning of firewood and coal—and this, in turn, provided the energy for most mechanical processes.
In addition, fossil fuels can be made into specific fuel types for specialized uses (for example, gasoline for use in motor vehicles).
Today, oil is our primary power source.
About 33 percent of total global energy production comes from oil products; the runner-up to oil is coal, and the runner-up to coal is natural gas.
Together, the combustion of these three fossil fuels provides 81 percent of the world’s energy.
Combustion of fossil fuels
That combustion (burning) is a chemical reaction between the fuel (oil, coal, or natural gas) and oxygen that yields carbon dioxide and water and releases energy.
As developing countries become more developed, generally their reliance on fossil fuels for energy increases; and as a result, as the world as a whole becomes more industrialized, the demand for energy, and specifically for fossil fuels, increases.
Fossil fuels, as the name indicates, are formed from the fossilized remains of once-living organisms.
Over vast amounts of time, this organic matter was exposed to intense heat and pressure. Eventually, these forces broke down the organic molecules into oil, coal, and natural gas.
Finding oil, coal, and natural gas
Oil, or petroleum, is made of long chains of hydrocarbons; coal contains a mixture of carbon, hydrogen, oxygen, and other atoms.
Natural gas is made mostly of methane gas (CH4) with a mixture of other gases.
Generally, oil and natural gas are formed in the same areas.
These materials are found deep in the Earth under both land and ocean floor, where they are stored in the pores (spaces) between rocks.
Coal is found in long continuous deposits, called seams, at various depths underground. The seams represent areas where large amounts of plant remains were buried and eventually transformed into coal. We will cover the process of coal mining on the next page
Certain types of geologists locate fossil fuel reserves.
They plan and supervise the extraction of these fuels from the Earth.
Using knowledge of geology and rock formations, these scientists make predictions about which sites are most likely to have fossil fuel deposits.
They use exploratory wells to drill and sample a particular area.
If an exploratory well hits a fossil fuel reserve, it can provide an estimate of the amount of fuel that can be obtained from that area; this is called the proven reserve
It is important to know that although exploratory wells can provide a fairly precise estimate of the size of a reserve, these numbers are just educated guesses (not so proven after all!).
Amount of a resource that can be extracted from a reserve dependent on technologies available and cost of extraction, distribution of natural resources is not uniform
The amount of a resource that can be extracted from a reserve is dependent on the technologies available and the cost of extraction
If extraction costs are too high, it is not economically feasible to extract the resource.
If a coal seam is buried very deeply, for instance, it may cost more money and fuel to extract it than the value of the seam.
It is also important to keep in mind that the global distribution of natural energy resources (such as ores, coal, crude oil, and gas) is not uniform and depends on regions’ geologic history.
Thus, some political regions have vastly more access to these resources than do others.
Most renewable energy sources (to be discussed later in this chapter) are unevenly distributed in a similar way; however, different regions may be comparatively poor in one resource (such as sunlight) while rich in another (such as wind or geothermal energy).
Damage from getting and transporting oil
In 2010, the United States suffered one of its worst environmental disasters when an explosion on the Deep Water Horizon drilling rig caused oil to spill from the well into the Gulf of Mexico for three months. This was the largest marine oil spill in the history of the oil industry. Eleven men were killed during the explosion, and the spill caused a great deal of damage to both marine and wildlife habitats and local economies along the coast.
Drilling for oil is only moderately damaging to the environment because little land is needed to drill. However, since oil is transported thousands of miles by tankers, pipelines, and trucks, a lot of environmental damage can occur during transportation.
Different types of coal
The qualities of different types of coal are ranked by the number of BTUs that they produce upon burning.
The purest coal is called anthracite, which is almost pure carbon.
The second purest coal is bituminous, followed by subbituminous, and finally lignite— the least pure coal.
It’s heat, pressure, and depth of burial that determine which types of coal are formed by given deposits and the resulting qualities.
Underground mining
involves sinking shafts to reach underground deposits.
In this type of mining, networks of tunnels are dug or blasted, and humans enter these tunnels to manually retrieve the coal.
After production stops at these mines, cave-ins can occur, causing massive slumping or subsidence
Strip mining
involves the removal of the Earth’s surface, all the way down to the level of the coal seam.
The coal is then removed, the overburden (the earth that was removed) is replaced and topped with soil, and the area is contoured and re-vegetated.
Most states require strip-mine owners and operators to completely reclaim areas that are mined by taking all of the steps outlined above.
However, the process of mining and removing the coal from the Earth leaves hazardous slag heaps containing sulfur that can leach out and enter the water table.
Scrubbers
When coal is burned in the production of electricity, carbon dioxide, nitrogen oxides, mercury, and sulfur dioxide—all of which contribute to air pollution —are released as by-products.
However, some of these by-products can be removed through the actions of scrubbers, which contain alkaline substances that precipitate out much of the sulfur dioxide.
The neutral compound formed in the scrubber (calcium sulfate) is eliminated in waste sludge.
Two other waste products produced by the burning of coal are fly ash and boiler residue—you should be familiar with both of these terms for the exam.
Another problem with coal is that it often contains a significant amount of the element sulfur, both in the form of iron sulfide (pyrite) and as organic sulfur.
Sulfur is another contributor to air pollution.
While iron sulfide can be removed by grinding the coal into small lumps and washing it, organic sulfur is only released during the combustion (burning) of coal.
However, scrubbers can remove organic sulfur from the flue gases after the coal is burned.
Another solution to this problem is to burn the coal with limestone— the liberated sulfur then combines with the calcium in limestone to form calcium sulfate, which prevents it from being released through the flue.
Electrostatic precipitators
use an electric charge to attract dust particulates to metal surfaces where they can be gathered and disposed of as solid waste.
This is similar to your television screen being the dustiest surface in your living room due to electric properties of the device.
Natural gas basic info
Natural gas is made mostly of methane (CH4) as well as pentane, butane, and several other gases in small quantities.
As you learned earlier, natural gas is produced by the actions of heat and pressure over long periods of time.
It is also produced by living organisms (mostly by anaerobic bacteria).
Methane-producing bacteria can be found in landfills, swamps, and the intestines of various animals.
Here’s an interesting fact: while the largest source of methane is wetlands, the second largest source is our flatulent livestock.
Use of natural gas
Currently, natural gas is used for heating homes and cooking.
It can also be burned to generate electricity.
Some power plants are designed to switch between oil and natural gas fuels depending on the cost.
The engines of cars and trucks can be modified to burn natural gas instead of gasoline.
There is a landfill operator in the state of New Jersey who tested a process of trapping methane from a landfill, liquefying it, and then using the liquid methane to power the trucks that bring garbage to the landfill.
Fracking (hydraulic fracturing)
a process by which natural gas and oil are extracted from rock that lies deep underground.
A deep well is drilled and then millions of gallons of toxic fracking fluid—a mix of water, sand, and harsh chemicals— are injected at a high enough pressure to fracture the rock and release the oil or gas.
It’s a highly controversial practice that has been linked to earthquakes in the states of Arkansas, Ohio, and Pennsylvania.
It requires a large amount of water, which has to be safely stored after use due to chemical contamination.
Fracking can also cause groundwater contamination and the release of volatile organic compounds.
pros and cons of natural gas
Because of its simple molecular structure, natural gas produces only carbon dioxide and water when it burns.
It does not produce the oxides of nitrogen and sulfur associated with burning coal or oil.
Before you get really excited about natural gas, you should be aware of its dangers.
In an uncontrolled release (like a leak), it can cause violent explosions.
It is also more difficult to transport than coal or oil.
Because a tank can hold a small amount of gas, producers liquefy it by putting the gas under high pressure (Liquefied Natural Gas).
This process requires energy.
Natural gas can also be transported by pipes.
However, pipes carry the risk of leaks and explosions, and some habitats are damaged during the building of the pipe system.
Furthermore, methane is a potent greenhouse gas.
Furthermore, methane is a potent greenhouse gas.
Its chemical structure makes it 30 times more powerful than carbon dioxide at trapping heat in the atmosphere. And, as climate change continues to warm the Earth, the biochemical reactions by which certain bacteria produce methane will accelerate. This is a particular danger in habitats such as swamps and other wetlands as well as freshwater sediments. This situation, in which increasing concentrations of a greenhouse gases, in the atmosphere further accelerate the production of greenhouse gases, is just one of many feedback loops that makes the climate change unleashed by human activity so scary and difficult to quantify!
In order to understand how long our accessible fossil fuel supplies will last, you should know how quickly we are using up those fuels, ex. oil
Let’s take oil, the most widely used fuel, as an example.
The United States is by far the largest consumer of oil (followed by Saudi Arabia, Russia, Canada, and China) .
A quick bit of addition shows that these five countries alone consume almost 52 billion barrels of oil each day!
As you can imagine, that leads some scientists to ask questions about how long our supplies of oil (and the other fossil fuels) will last.
One well-known authority on the future of oil production, the late M. King Hubbert, stated that the end of oil as a cheap and easily available form of energy is in the near future and that we must begin to develop alternative fuel sources.
This theory is commonly known as Hubbert peak or “peak oil.”
Nuclear energy general
Nuclear energy is the world’s primary non-fossil fuel, nonrenewable energy source. In the United States, 20 percent of electrical energy is provided by nuclear power plants.
Worldwide, more than 400 nuclear power plants produce approximately 13 percent of the world’s electrical energy.
The United States and France lead the world in the creation of new nuclear facilities.
as it stands, nuclear power is considered a cleaner energy source than fossil fuels because it does not produce air pollutants, but it does release thermal pollution and hazardous solid waste.
