Background Information
In order to teach this unit, there are basic resources knowledge students need to know. The first concept is fossil fuels. Fossil fuels are coal, petroleum, and natural gas and these fuels are found in various parts of the world and are extracted and transported to provide energy to the consumer. The second concept is renewable energy. Renewable is energy that can be continually replenished like the sunlight, wind, geothermal and biofuels. Renewable energy is capable of supplying human energy for about another billion years. The third concept is the Dine' Philosophy of Education about how Nihodzaan (Mother Earth) and Yadilhil (Father Sky) represent balances of all moving elements. Mother Earth is the form of Changing Woman, because she nurtures life and Father Sky provides life-giving rain.
Fossil Fuels
Fossil fuels contain high amounts of carbon and were formed naturally in the Earth by the decomposition of dead organisms from millions of years ago. They take millions of years to form by heat and pressure in the Earth's layers, and are depleting faster than it takes the Earth to replenish them. An estimation of over 80% of the energy that is consumed in the world comes from fossil fuels, and carbon dioxide gas is emitted into the atmosphere causing the Earth's temperature to rise contributing to global warming which is an environmental concern.
Coal
Coal formation began during the Carboniferous Period which was about 360 million years ago (4). It is the remains of ancient plant life that originally accumulated in swamps and peat bogs that was then transformed by the pressure and heat within the plate movements. The sediments build-up with tectonic movements pressed down deep into the Earth's crust twisting and shearing creating physical and chemical changes in ancient plant into peat (organic soup), then with more time and pressure it converted the residue into coal. Coal is a combustible, composed of carbon, hydrogen and oxygen. The quality of coal deposit is determined by temperature, pressure, and the length of time in formation, known as 'organic maturity'.
Peat is converted into lignite or 'brown coal' it is a coal type with low organic maturity. Lignite is soft and its color ranges from pitch black to various shades of brown. An additional million more years with the continuing effects of pressure and temperature, the lignite changes into materials known as 'sub-bituminous' coals. As more chemical and physical change occurs, the coals become blacker and harder forming 'bituminous' or 'hard coals'. As additional changes increase and progress with the right conditions, the organic maturity of the coal continues and finally forms anthracite.
Coal is found in almost in every country in the world and the largest reserves are in the China, India, Russia, and the United States. During the centuries of explorations, the features, locations, and sizes of the coal reserves were discovered in various countries. The accessibility and size of the coal reserves in the ground were debatable because variables were involved like is the reserve abundant and is it economically and technically extractable. A geological map of the area was created and analyzed, then geochemical and geophysical surveys are conducted, and finally an exploration drilling is done. This process gives an accurate picture of the land to be developed. The area will establish a mine if the coal has a large amount and sufficient quality; then mining operations can begin.
The two methods to obtain coal are by surface mining and underground mining. The type of mining depends upon the geology of the coal deposit. Based on the coal production timeline, underground mining currently outputs a larger share of the world coal production than surface mining. But, coal production countries have a common mining preference; they preferred surface mining because it extracts more coal.
Surface mining is also known as opencast or open-cut mining and is economical when the coal layer (seam) is near the surface. 90% or more of the coal can be extracted compared to underground mining. Large opencast mines use very large equipment, machines, and vehicles to remove the overburden (top layers of the soil and rocks) and to transport the overburden and coal.
Underground mining operations have two methods of mining, the room-and-pillar and long-wall mining. The room-and-pillar mine is the oldest mining method. The coal deposits are mined at the coal seam into grids like a tic-tac-toe line. The lines are the tunnels and the spaces in between are the pillars. This mining method leaves 40% of the coal in the seam. Longwall mining encompasses the total extraction of coal from a long seam by sections. A self-guiding hydraulic power jack would hold the ceiling while another machine called the shearer extracts the coal. After the section of coal is extracted, the ceiling is allowed to collapse. The Longwall mining method extracts more coal than room-and-pillar. These machines are state-of-the-art equipment and miner personals need to be highly skilled and well-trained when using technological machineries underground.
Coal is traded and transported globally by barges, pipelines, ships, and trains. Depending on the distance, trucks and conveyors are used for short distances.
Petroleum
Petroleum is 'rock oil,' associated with crude oil and natural gas. Petroleum is found in most oil fields or reservoirs with natural gas which is a lighter gas above the petroleum, then crude oil and saline water at the bottom. It is discovered in pockets, seams, and in underground pools below the Earth's crust. Petroleum is a compound mixture of hydrocarbons and paraffin formed from decomposition of ancient animal and vegetation life usually found in deep rock bands at various levels. When fissured and refined, it produces petrochemicals that convert into thousands of products. These petroleum products are commonly put into barrels and one barrel of petroleum equals 5604 cubic-feet of natural gas, 1.45 of liquefied natural gas (LNG) (5).
Crude oil has varied appearance and composition, from black to dark brown and some may be yellow, red or green. It is found in semi-solid form mixed with sand and water, like bitumen which is a sticky, black tar-like form which is very thick and heavy. The Athabasca oil sands in Canada have crude bitumen sand oil. The Orinoco oil sand in Venezuela has a large amount of extra heavy fluid sand oil. This oil sand is called unconventional oil because they have different processes when extracting it, unlike the traditional oil well methods.
The formation processes of petroleum were from organisms that came from single cell organism known as plankton, diatoms, and blue - green algae. These simple organisms were abundant during ancient times, about 550 million years ago. Rapid burial of the single-celled organisms within fine-grained sediments preserved them. This provided the organic materials called protopetroleum, which progressed into petroleum by a series of biological, chemical, and physical changes. The protopetroleum begins to chemically rearrange converting organic matter into kerogen. This dark colored, insoluble bacteria-altered kerogen is the source of hydrocarbons. Biogenic methane is one hydrocarbon generated and it is initiated by the process of decomposition of organic matter by anaerobic microorganisms (able to live in absence of oxygen).
Depending on the depth, temperature, geological age, maturation stage, amount and type of organic matter, kerogen begins oil generation and it occurs by thermal degradation and cracking (heavy hydrocarbon molecules are broken up into light molecules). Specific temperature and depth create variations of gas, like wet gas. This type of gas contains liquid hydrocarbons known as LNG.
Petroleum is collected in traps within the Earth's layers known as structural and stratigraphic traps. The basic characteristic of a trap is any shape like a closed, inverted container. A structural trap is formed by tectonic movements, fold or fault rocks. The most common structural traps are anticlines, an up-fold of rock bands that are like oval shapes on geologic maps. About 80% of the world's petroleum was found in anticline traps. Another kind of structural trap is the fault trap, this is when a fault line slips and moves the rock bands and forms a barrier to enclose the petroleum. Other structural traps are formed with salt domes and are formed by the upward movement of the salt masses which usually occur along the fold or fault line.
A second major type of oil trap is the stratigraphic trap; it is similar to sediment deposition or erosion. When tectonic movements control deposition and erosion in sedimentary basins, stratigraphic traps are formed. When fossil carbonate reefs, marine sandstone bars, and deltaic distributaries are buried they create a potential reservoir which is usually surrounded by fine grain sediments that act as a cap rock. When sediments deposit into the sea, it changes the course land to fine grain sand and in time changes the permeable sediments to an impermeable barrier that eventually traps migrating petroleum.
Liquid petroleum is easily transported and everyday 80 million barrels of oil are moved from producers to consumers. Offshore oil production accounts for about 30% of the total world oil production and about half of the world production of natural gas. Most countries that have coastline will have offshore oil or natural gas production rigs. Offshore drilling for oil and natural gas on the continental shelf is conducted deep in the water over 2,200 meters deep. Many of these rigs are movable and can float while being moved and while drilling. The functioning span of a rig is usually about 20 years and portions of the rig can be reused or the whole rig can be redeveloped and if not, it must be decommissioned.
The search for natural gas and oil is extremely costly, difficult, and often unsuccessful. Locating gas or oil reservoirs and extracting them is difficult because the waters may be stormy and very deep. The potential reservoirs are identified by using and analyzing a survey; it determines if the seam contains gas or oil and is unknown until the drill bit penetrates the cap rock. Direct drilling to a specific location a few kilometers away requires sophisticated computer technology. Just above the drill bit a navigation device is installed to send feedback information to find the exact position of the well to be measured and monitored. Four types of offshore rigs use the drill to locate wells: the submersibles, jack-ups, drill ships, and semi-submersibles.
Submersibles are rarely used and can be used on shallow water. Jack-ups are usually towed to a location. Then the legs are lowered to the seafloor and the hull is jacked up to the sea surface. A drill ship looks like ordinary ships but has a derrick on top which drills through a hole in the hull. It is anchored or positioned with computer controlled propellers along the hull which constantly corrects the ship's drift. Semi-submersible is a mobile structure with its own locomotion. Superstructure rigs are supported by columns sitting on hulls or pontoons which are ballasted below the water to provide stability in rough, deep seas.
When gas or oil is discovered, the drilling rig is replaced by a production platform. The production platform is constructed at the site using a barge equipped with heavy cranes. Depending on size of the discovered field, water depth, and distance from the shore, the size, shape, and type of platform will constructed. The platform is constructed of steel and secured to the seafloor with steel piles and will house all equipment and accommodate about 80 workers. There are concrete structures which are big enough to store oil and gravity holds them onto the sea floor. The world's biggest platform is bigger than a football field and rises above the water as high as a 25 story building, housing 500 workers. When an oil field is discovered in shallow water and near land or another platform, a smaller remote controlled monopod platform is used. Another type of floating structure is a Floating Production Storage Offloading (FPSO) vessel. The Tension Leg platform is another type of platform used for deep water production which is assembled from steel or concrete and then anchored to the sea floor with vertical tendons (reinforced strand in prestressed concrete).
Drilling for oil is called "spudding." It is the initial stage of drilling, when the drill is lowered onto the sea floor. Two types of bits are used, a roller cone shape rock bit with three cone steel or tungsten carbide (an inorganic chemical 3 times stronger than steel or titanium) teeth, or a diamond bit which is embedded with small industrial diamonds. The drill bit (about 21 to 91 cm) is attached to a drill pipe and is rotated by a turntable on the platform floor. As the drilling deepens into the sea floor, extra lengths of pipe are attached. Drilling takes many weeks or months before the targeted area is reached. The weight of the drilling fluid acts as the first line of well control by keeping underground pressure in constant check. If an influx of pressurized gas or oil occurs during drilling, a well control is maintained through the rig's blowout prevention system (BOP). The BOP is a set of hydraulically operated values and other devices that seals off the well and routes the wellbore fluids to a specialized pressure controlling area. Well trained personal operate highly reliable equipment to minimize the possibility of a blowout or uncontrolled fluids flowing from the well. Directional drilling is when drill bits are steered laterally several kilometers towards the petroleum reservoir. One production platform will drill a number of wells in variety of directions and inclinations until a target is found. When the well has been drilled and target found, a production casing is set and cemented. Tubing is lowered into the hole with "packers" that seals the space between the tubing and the casing. At the end of the well, the casing is perforated at predetermined depths by small explosive charges. The small holes in the casing allow the gas or oil to flow to the surface using its natural pressure. If a drilled hole is dry and not worth developing, it is plugged using cement and then abandoned.
Pipelines, marine vessels, tank trucks, and rail tank cars are used to transport oils, compressed and liquefied hydrocarbon gases, liquid petroleum products and other chemicals from the site to pipeline terminals, refineries, distributors and consumers. Crude oils and liquid petroleum are transported, handled, and stored in their natural liquid state. Hydrocarbon gases are transported, handled, and stored in both the gaseous and liquid state. It must be completely confined in pipelines, tanks, or cylinders prior to use. Liquefied hydrocarbon gases at -162 °C are stored, handled, and shipped as liquids, taking up a small amount of space. When it is released into difference storage, the atmospheric temperatures cause the liquid to expand and become gas.
Natural Gas
Natural gas is a combustible mixture of hydrocarbon gases, containing methane with other hydrocarbons like ethane, propane, butane, carbon dioxide, oxygen, nitrogen, hydrogen sulfide, and rare gases. It exists in the form of gas fields in formations of porous rocks as gas caps above the crude oil or in crystalline forms. Scientists who study the interior parts of the Earth and petroleum have theories of how thermogenic methane is formed. Organic particles, time, pressure and high temperatures deep beneath the earth break down the carbon bonds. The deeper the natural gas is discovered, the purer the gas (methane) because the increase of pressure and the hotter temperatures form more natural gas than oil. However, natural gas can also be cooled to about -162 °C (-260 °F) and converted into liquefied natural gas (LNG). While in liquid form, natural gas takes up only 1/600 of the volume of its gaseous state and it is stored and transported to places that do not have pipelines (6).
Natural gas is commonly extracted by drilling vertically into the Earth's surface. A single vertical drill well is limited to the gas reserves it encounters. Today, hydraulic fracturing or fracking is preferred when extracting natural gas because wells drill horizontally and acidizing processes are used to access large amounts of gas. Horizontal drilling is drilling straight down from the surface, and then the drill can be directed to go sideways. Acidizing is a process of dissolving acidic components then inserting them into the gas well to dissolve rocks that block the flow of gas. Hydraulic fracturing is a process that separates open rock formations with high-pressure streams of water, chemicals, and sand. The sand props open the rocks allowing gas to escape. It is then stored and transported. Using the fracking process requires huge volumes of water. A community that utilizes the water table would be unwise to use this process.
After natural gas is extracted, it is commonly transported through pipelines that can be from 2 to 60 inches in diameter (7). The United States has more than 200 pipeline systems that are made up of about 500,000 kilometers (300,000 miles) of conducting pipelines that transfer gas to all 48 states. This system requires more than 1,400 compressor stations to ensure that the gas continues on its path, 400 underground storage facilities, 11,000 locations to deliver the gas, and 5,000 locations to receive the gas (8).
Natural gas is measured in normal cubic meters or standard cubic feet. In 2009, the United States Energy Information Administration (EIA) estimated that the world's proven natural gas reserves are around 6,289 trillion cubic feet (tcf) (9). Most of the reserves are in the Middle East, with 2,686 tcf in 2011, or 40 percent of total world reserves (10). The US has just over 4% of the world's natural gas reserves.
Renewable Energy
Renewable energy is any energy source that comes directly or indirectly from natural processes. Renewable electricity can be produced from solar (sunlight) energy and photovoltaic cells, wind energy, geothermal, and biofuels.
Sunlight energy
Solar energy is the radiant energy produced by the sun. The sun with other solar powered resources such a wind and water are a majority of the renewable energy on the Earth. The Earth receives 174 pet-watts (PW) of solar radiation at the upper atmosphere, 30% is reflected back into space and the rest is absorbed by clouds, oceans, and land (11). The land surfaces, oceans, and the atmosphere absorb solar radiation which increases their temperature. Humans utilize solar energy in different ways: heating and cooling, lighting, cooking, and cleaning. Solar technology captures, converts, and distributes energy using passive or active methods. Active solar techniques use photovoltaic panels and solar thermal collectors to accumulate the energy. Passive techniques involve positioning a building to the sun, selecting materials with thermal mass properties, and using materials with light dispersing properties (12).
A photovoltaic cell (PV) is a device that converts light into electrical currents using photoelectric reactions at the atomic level. Photoelectric effects absorb light and release electrons; then, released electrons are captured creating an electric current that is used as electricity. The photoelectric effect was first discovered by a French physicist, Edmund Bequeral, in 1839. He discovered certain materials would produce a small amount of electric currents when exposed to light. Then, in 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel Prize in physics (13). Eventually, the advances of photovoltaic technology gained recognition; space programs and the energy crisis crunch in the 70's opened the doorway by exposing solar technology to the people.
The basic structures of photovoltaic cells are made of a semiconductor material known as silicon. A thin semiconductor is coated with a film of silicon to form an electric field with positives on one side and negatives on the other. When the photons (particles of solar energy) hit the cell, some are reflected, some pass right through and others are absorbed. Only the absorbed photons will generate electricity, and this is when electrons are knocked loose from the atoms in the semiconductor. Electrical conductors attach to the positive and negative sides will form an electrical circuit. When the electrons leave their position, gaps are formed and when many electrons carry a negative charge they travel to the surface of the cell causing an imbalance of charge between the negative and positive lines. When the two surfaces are connected to a load, such as an appliance, then electricity will flow through the connection. The demand for more electric flow created a bigger frame called a photovoltaic module; this is when multiple cells are added to a larger frame to supply more electricity at a certain voltage. Bigger modules can be combined to form multiple arrays to make a larger structure producing direct-current electricity. Today, photovoltaic cells have multiple junctions stacked upon each other to capture high-energy photons and to concentrate electricity.
Solar thermal energy uses the sun's rays to heat liquid at very high temperatures. The liquid is circulated through tubes so it can transfer heat into the water, thereby producing steam. In turn, the steam is converted into mechanical energy by using a turbine to generate electricity. It is similar to a coal generating plant; instead the thermal energy plant uses heat collected from the sun. The three types of solar thermal power systems are: parabolic trough, solar dish, and solar power tower. A parabolic trough is a long parabolic shaped reflector that focuses the sun's rays as it moves east to west during the day. It's unusual shape can focus the sun to 30 to 100 times its normal intensity on the receiver pipe located along the focal line of the trough achieving operating temperatures over 750 °F (14). Heated fluid is circulated through pipes transferring heat to water, producing high-pressure superheated steam. The steam passes through the heat exchangers and cools down then it recirculates through the pipes and is heated up again. Parabolic troughs are aligned in numerous rows called a "solar field" and are aligned on a north to south horizontal axis operating at full power using solar energy.
Solar dish systems use solar rays to collect intense heat onto collectors while tracking the sun. The dishes are constantly facing the sun to concentrate energy at the focal point of the dish. A solar dish's central temperature ratio is higher than the parabolic trough. In the dish, a mechanism converts heat by compressing a cold fluid then the fluid heats up and expands through a turbine or a piston to produce work. The engine is attached to an electric generator to change the mechanical power to electric power. The solar dish is ideal and suitable for remote and rural areas where electricity is difficult to obtain.
A solar power tower is a central receiver surrounded by hundreds to thousands of flat sun-tracking mirrors called heliostats. The power tower must be a large structure to collect and produce solar energy from the many heliostats. The heliostats reflect and concentrate the sun's energy into the tower by about 1,500 times to heat fluids within the tower. The heated fluids will transfer into a steam drum and then into a turbine that will produce electricity. After the steam cools, it becomes fluid and is transported in a steam condenser. Then, it is transferred into the tower continuing the cycle. This system is unique because it has the ability to store solar energy and is able to transmit electricity when needed, even at night or during cloudy days. The southwest states are ideal places to establish a solar power tower because of the abundance of land acreage and a tower can produce enough electricity for about 50,000 homes.
Wind energy
Wind is the movement of air caused by the gases of the Earth's atmosphere moving with the sun's heat on the surface of the Earth. As long as the sun shines, the wind will blow causing hot air to rise and cooler air moving beneath. Today more and more people are using wind turbines as their energy producer for electricity. The energy hungry countries favor these giant white pinwheels because wind is free and can produce thousands of megawatts of electricity. These turbines can be as tall as a 20 story building and usually have three 60 meter long blades that are connected to a generator that produces electricity. The turbines look like giant propellers on a long pole. A huge turbine can generate enough electricity to support 600 homes. Certain areas with high wind frequency have wind farms encompassing ten to hundreds of wind turbines lined together. Not only are wind turbines on land, but they are on offshore waters. Currently these offshore turbines are mainly in Europe. Globally there are about two hundred thousand wind turbines operating. In addition to these huge pinwheel giants, smaller wind power systems are produced to generate power to individual homes and in isolated rural communities. Small wind turbines are able to power equipment like parking meters, street lights, wireless internet, and traffic lights.
There are various types of wind turbines, some rotate horizontally or vertically. The horizontal axis turbines have a rotor and electrical generator at the top of the tower. Majority of them have a gear box which connects the large blades rotating quickly to the electrical generator. The turbine is usually positioned upwind because the rotating blades produce turbulence behind it. The blades are stiff because extreme winds cannot push them into the tower. They are also positioned at a designated distance in the front of the tower. The wind turbines have three components on a horizontal axis turbine; first is the rotor and the blades, second is the generator component, the control electronics, and the gear box, third is the tower and rotor mechanism. These monolith blades and towers are white because aircraft are able to view these high pinwheels during daylight.
The vertical axis turbines have the rotor shaft structured vertically and these turbines do not need to face the wind to be effective. These turbines can be mounted on rooftop buildings and will redirect the wind and will double the wind speed. A majority of these vertical turbines are small and are used on homes, low towers, rural schools and medical facilities. Many of these small wind turbines are used off-grid, or where there is no electricity or where the grid is unstable.
Geothermal energy
Geothermal energy is stored in the form of heat deep beneath the Earth's surface. It emits almost no greenhouse gases and provides a continuous uninterrupted supply of energy that will heat homes, buildings, and generate electricity. The word geothermal originated from the Greek language, geo meaning "Earth" and theme meaning "heat." The interior of our Earth contains a huge source of geothermal energy and people have been using it for centuries, like the natural heated spring groundwater and the steam for geysers that was trapped within hot rocks below the Earth. This happens when groundwater seeps below the earth near a dormant volcano, and the water is heated by pools of molten rock at depths of 3,000 meters. When groundwater remains under the Earth's surface it is known as a geothermal reservoir. Certain locations on the Earth's crust near volcanic activity have deep fractures that cause molten rocks to seep close to the surface heating groundwater. It is a reliable resource because it is limitless and can be found anywhere on the Earth. The country of Iceland is known to have an abundance of geothermal energy resources.
As man probes deeper in the Earth's core and upper mantle (lithosphere) more thermal energy will be used. When extracting the heat within the lithosphere a process needs to be established. First, a borehole is drilled into the fractured rock down to the level of temperatures of 150-200 °C. Next, water is pressured into the existing fractures to the reservoir and hot rocks. When water pressure is removed a slight opening remains due to the water permeating into porous rocks. The fractured reservoir is monitored by micro-seismicity equipment. Then a second borehole is drilled into the existing fractured reservoir and cold water is pumped into the first borehole. The cold water is heated and exchanged heat happens in the reservoir; then it is abstracted to the surface where it is used for electricity.
Biofuels
Biofuels are fuels made from living organisms, and are clustered into three categories: first generation biofuels are mainly made from sugar, starch and vegetable oil, the second generation biofuels are made from nonedible plants, and the third are made from algae and other microbes. The primary component of the first generation of biofuels is ethanol, and most gasoline sold in the United States contains ethanol. The second and third generation biofuels are known as "advanced biofuels."
Biofuels are fuels from biomass like living organisms or any organic matter from decomposing matter to plants, animals, woods, agricultural crops, and even manure. Biofuels have been steadily increasing during the last decade. Today, biofuels provide about 3% of road transport fuel globally.
Ethanol fuel is the most commonly used biofuel globally. It is an alcohol fuel produced by fermentation of sugars stemmed from any sugar or starch product like wheat, corn, sugar cane, sugar beets potatoes and any fruit waste. The method of producing ethanol is to break down sugars from starches known as enzyme digestion, fermenting sugars, distillation (requiring heat), and drying. In addition to ethanol, propanol and butanol are other alcohols.
Biodiesel, green diesel, and vegetable oil are other types of oils and fats used to run automobiles, commercial trucks and city buses. Oils and fats are hydrogenated oils that can blend with diesel fuel. Gases like bioethers, biogas, and syngas are other biofuel products. Bioether is an oxygenated fuel that acts as an octane enhancer. Biogas is methane produced by anaerobic digestion from biodegradable waste like landfill gas and manure from cattle farms. Syngas is a mixture of gases (carbon monoxide, hydrogen, and other hydrocarbons) produced for internal combustion engines, turbines, or wood gas generators. Another first generation fuel is solid biofuels which is raw fuels like wood chips, sawdust, grass trimmings, manure, and other agricultural waste. These raw fuels are ground into concentrated fuel products like wood pellets that then are used to fuel boilers and wood stoves in residential homes.
Second generations biofuels are currently in study and still developing like cellulose, algae, hydrogen, and mixed alcohols. Working with cellulose is difficult because it is a slow process and researchers are analyzing cattle's digestive system and using it as a comparison to laboratory production. Various countries are currently researching this process, too.
There are pros and cons connecting to biofuels like the "food vs. fuel" discussion, the sustainability, the production of biofuel, the water resources, and energy balance. Looking more into the second generation biofuel may be part of the solution, like algae. Looking for the perfect fuel will not solve energy global issues but man can and needs to balance the trade-offs. As the population expands and the demand for energy increases, we will need every available form of energy from the gifts of the Earth and the sun. These gifts need to be environmentally and economically sustainable.
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