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chapter 15 and 16 APES Test
Terms in this set (41)
Net Energy;; the two laws of thermodynamics
The first law states: Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed, but energy can be changed from one form to another. You cannot get more energy out of something than you put in, so to get high quality energy you must use high quality energy. (There is no free lunch.)
The second law of thermodynamics states: Whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started out with, part of which is low-temperature heat energy dispersed to the environment.
Therefore the usable amount of high-quality energy available from a given quantity of an energy resource is its net energy. That is the total amount of useful energy available from an energy resource minus the energy needed to make it available to consumers.
How Net Energy is calculated
Net energy is calculated by estimating the total amount of energy available from the resource over its projected lifetime and then subtracting the estimated amount of energy used and automatically wasted because of the second law of thermodynamics, and unnecessarily wasted in finding, extracting, processing, and transporting the useful energy to consumers. When evaluating energy sources we need to look at net energy yield and understand that any energy source with a high level of subsidization from the government most likely has a low net energy yield and could not compete on the open market. Reducing energy waste improves net energy yields and is the fastest, cheapest, and most environmentally beneficial source of energy.
Petroleum, or crude oil, is a black, gooey liquid consisting of hundreds of different combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities. Crude oil is formed from the remains of ancient marine organisms that were buried beneath sediments and subjected to high temperatures and pressure. Conventional oil, or light, or sweet crude oil makes up about 30% of the world's estimated supply of oil while unconventional heavy oil is the rest. Heavy oil has the consistency of molasses and it takes a great deal of energy and money to extract it, which reduces its net energy yield.
Oil is a mixture of many different liquids and gases, whose components are used to provide energy for a variety of purposes. Its liquid components such as fuel oil and gasoline, are used for home heating and transportation in cars, airplanes, trucks and train engines. Gaseous components such as propane and butane are used for cooking and heating. Solid components include grease, wax, petroleum jelly, and asphalt.
Because of the United States' intense dependence on petroleum, and because most of the reserves of oil are in the Middle East and controlled by the Organization of Petroleum Exporting Countries (OPEC), there is concern over the reliance on politically unstable governments for such an important energy resource. These concerns have led to call for renewed oil exploration and drilling in environmentally sensitive areas such as offshore and in the Arctic National Wildlife Refuge (ANWR). However, most experts agree that it is not possible to solve the nation's energy problem in the long run through increased petroleum production. Rather, we must seek alternative fuels and focus on improved energy efficiency.
Making crude oil
Because it is a mixture of liquids, crude oil requires a separation and purification step between extraction and use that is not required of the other fossil fuels. This step takes place at an oil refinery and it makes use of a process called fractional distillation, which separates liquids based on differences in their boiling points. The refining of oil produces many different products in addition to those listed above, including petrochemicals that can be made, among other things, into synthetic fibers for clothing, plastics, pesticides, cleaning fluids, paints, and medicines.
crude oil consumption and reserves
The world is not about to run out of conventional oil in the near future. Geologists project that proven (deposits of crude oil that can be profitably extracted with today's technology) and unproven (probable reserves with a 50% chance of recovery and possible reserves with a 10 to 40% chance of recovery) will be 80% depleted sometime between 2050 and 2100, the remaining 20% will probably be too expensive to remove.
4 options... to crude oil consumption and reserves
use less oil
waste less oil
look for more oil
use other energy sources
coal coal coal
Coal is the most abundant fossil fuel, and is used to produce most of the world's electricity. In a coal-burning power plant, coal is pulverized into small pellets and burned to produce steam. The steam is directed across the blades of a turbine to rotate it and a generator then generates electricity. The environmental costs of mining and burning coal are severe. In addition to the environmental costs of mining, burning coal produces large quantities of air pollution including heavy metals, particulate matter, and sulfur dioxide. Burning coal also produces more carbon dioxide than other fossil fuels. Because of its abundance in China, India, and other developing countries, coal use and the associated environmental costs are likely to increase in the future.
Coal formation begins with peat, which forms from an accumulation of partially decomposed plant debris in waterlogged, anaerobic conditions. After being buried by millions of years of sediment accumulation, heat and pressure squeeze the water from the peat, and initiates a series of transformations into the ranks of coal. In order from youngest to oldest, after the formation of peat, the ranks of coal are lignite, sub-bituminous, bituminous coal, and anthracite coal. Anthracite coal has the highest energy content by weight, or energy density, followed in reverse order of formation by bituminous coal, sub-bituminous coal, and lignite. Although peat had the lowest energy content by weight and emits noxious smoke when burned, it is still used for fuel in some areas.
Mostly methane, (CH4) in composition, natural gas is formed and found alongside crude oil and coal. Like coal, it can be used in power plants to produce electricity, and it is also commonly used for cooking, and space heating. Burning natural gas produces less carbon dioxide per unit of energy than either of the other fossil fuels.
disadvantages with natural gas
Because it is a gas, natural gas is difficult to transport great distances. Pipelines are used to transport natural gas over hundreds or thousands of miles, but they are expensive, unaffordable in many developing nations. and subject to sabotage. Natural gas can be converted to liquefied natural gas (LNG) when placed under pressure at low temperatures. This makes it more convenient to transport large distances, but requires energy to compress, refrigerate, and transport the gas.
Like fossil fuels, nuclear energy is a nonrenewable resource. Huge environmental and social costs are associated with the extraction, processing, use, and disposal of radioactive nuclear fuel. In the 1950s, nuclear power was thought to be the solution to the world's energy needs, but safety concerns and unanticipated economic, environmental, and social costs undermined that dream. Nonetheless, nuclear energy still comprises 5 - 10% of world and U.S. energy supplies, all of which is electricity. A few countries generate far more of their electricity from nuclear energy than others; for example, France generates about 75% of its electricity from nuclear power.
making of nuclear energy
Nuclear power plants use the same method as those fired by fossil fuels to generate electricity, namely by heating water to produce steam, which rotates a turbine connected to a generator to produce electricity. Nuclear power plants use the process of nuclear fission rather than combustion of coal to heat the water that becomes steam. The most commonly used nuclear fuel is uranium, a radioactive element that is mined from the earth and enriched to increase the concentration of the fissionable U-235 isotope to about 3% from a naturally occurring abundance of less than 1%. Enriched uranium is pelletized and packed into fuel rods that are placed into the reactor core, along with a moderator that is used to slow down neutrons that are released during the fission reactions. Control rods, usually containing pure carbon as graphite, are interspersed with the fuel rods to absorb neutrons and regulate the rate of the fission reactions and the amount of energy produced.
After the used fuel rods are removed from the reactor core they are stored onsite in water-filled tanks. There is no long-term disposal site presently available for spent nuclear fuel rods and other waste, which is classified as high-level radioactive waste. A proposal t open the first high-level radioactive waste repository in the world at Yucca Mountain, Nevada has been delayed due to safety and security concerns and probably will not be opened any time soon.
Disadvantages to nuclear power
The environmental costs of nuclear power include the waste, runoff, air pollution, and land damage that result from the mining, processing, and transportation of uranium; the ecological damage due to the accidental release of radioactive materials; and thermal pollution in bodies of water being used as coolant for nuclear power plants. Other concerns include the lack of long-term storage for nuclear waste, the economic and environmental costs of decommissioning old nuclear power plants, the threat of terrorist attack and sabotage at nuclear power plants, and the safety of operating nuclear power plants near large populations. In Chernobyl, Ukraine, a meltdown in 1986 exposed millions of people across Europe to dangerous levels of radiation. At the Three Mile Island nuclear power plant in Pennsylvania, a meltdown was narrowly averted in 1979 that could have exposed the population of the East Coast of the United States to nuclear fallout.
New tech in nuclear power?
New reactor designs like advanced light-water reactors and pebble-based modular reactors are less susceptible to accidents and meltdowns and are touted by proponents as viable replacements for coal-burning power plants. While new reactor designs eliminate many of the safety concerns associated with the operation of the plant, they still require and do not eliminate the environmental and social costs associated with nuclear fuel. Finally, research into nuclear fusion, which is the type of reaction that generates the sun's energy, has yet to yield a viable solution to solve the world's energy needs and is not expected to do so before fossil fuel resources are exhausted.
Why is energy efficiency an important energy resource?
Reducing our energy use primarily through the reduction of the unnecessary waste of energy is probably the largest untapped source of energy available to us. It is abundant, clean, cheap and readily available and by using it we can save money, improve our national security, and drastically reduce our greenhouse gas emissions. Reducing our energy use can be accomplished in two ways; increasing energy efficiency, and through conservation measures.
is the measure of how much work we can can from each unit of energy we use. For example, if 500 Btu of electric energy is produced from 5,000 Btu of potential energy in a fuel, the efficiency is 500/5000 = 0.1 or 10%. (A Btu is a traditional unit of energy, it is equal to the amount of energy needed to heat or cool one pound of water one degree Fahrenheit.) Each unit of energy saved eliminates the need to produce the energy and it saves us money. The United States has improved its energy efficiency since 1980 but still lags behind Japan, Germany, and France.
How we waste energy
The second law of thermodynamics establishes that no energy transformation can be 100% efficient and that some waste heat must be produced when energy is converted from one form to another. In the United States roughly 84% of all commercial energy used is wasted, 43% unnecessarily. Most of this waste is a result of inefficiencies of:
-Incandescent light bulbs (95% of energy for light bulbs is lost to heat)
-industrial motors (non-variable speed motors often need braking)
-most motor vehicles (wastes about 80% of energy used)
-coal-fired power plants (wastes about 66% of energy used)
-nuclear power plants (wastes approximately 75%)
Another area of energy waste is that many (most) people live and work in leaky, poorly insulated, and badly designed buildings.
The future energy needs of the earth cannot be met with fossil fuels. Their limited supply, and the increased cost of exploiting less accessible resources, dictate that alternative energy sources be developed to replace them. As alternative energy sources are scaled up to meet the world's energy needs, the use of fossil fuels must also be conserved. Energy conservation simply refers to strategies that reduce the amount of energy that is being wasted. There are many ways for individuals to conserve energy.
Decrease energy for transportation
Reduce driving by using mass transit, walking, or riding a bike. Join a carpool (take the bus). Walk up and down stairs instead of using an elevator. Buy locally grown food and locally made products to reduce the energy required to transport goods to market. Replace a gas-guzzling car with a hybrid-electric or electric vehicle (particularly if you use photovoltaics to recharge the battery).
Decrease energy for heating
Decrease thermostat setting when it is cold and wear warmer clothing while indoors. Use less hot water and take cooler, shorter showers. Increase the amount of insulation in a home to reduce heat loss. Replace single-paned with multi-paned windows. Reduce heat loss by improving the seals around windows and doors. Replace a hot water heater that stores hot water in a tank with a tankless hot water heater.Install an active solar energy system to replace a furnace and hot water heater.
Decrease electricity use
Turn off lights when leaving a room. Increase the thermostat setting when it is hot to reduce the use of an air conditioner. Replace incandescent light bulbs with fluorescent bulbs, or better yet, led bulbs. Unplug electronics that have a standby mode when they are not in use, or plug them into a power strip and turn off the power strip when appliances are not in use. Install photovoltaic solar panels to provide electricity.
Drive hybrid cars
Hybrid-electric vehicles are becoming more common. These cars use a relatively small amount of gasoline by combining an electric motor with a small gasoline engine for vehicle propulsion. Some of the kinetic energy of the cat is used to drive an alternator that charges the batteries needed to power the electric motor. Hybrid-electric vehicles can have efficiencies several times that of a typical automobile getting up to 40-50 mpg.
Electric vehicles and plug-in hybrid vehicles both use electricity to charge batteries in the car. This likely uses electricity from an electric grid. Ideally, this electricity would be generated using an alternative source like solar or wind; however, if the electricity was produced by a coal or natural gas fired plants, fossil fuels would still be being consumed, albeit indirectly, to power the vehicle. By diverting the energy generation from the internal combustion engine of the car to a power plant, the consumer is trading off some of the environmental costs of operating a gasoline vehicle with those of operating the power plant. It will reduce the environmental costs of operating the vehicle either way, but using alternative energy sources to provide the electricity for an electric car is the best option for conserving fossil fuels as well.
Design buildings to conserve energy:
Green architecture, a design strategy based on energy-efficient and money-saving designs, makes use of natural lighting, passive solar heating, solar cells, solar hot water heaters, recycled waste water, and energy-efficient appliances and lighting. Some buildings also use living roofs covered with soil and vegetation to reduce winter heating and summer cooling costs. Superinsulation is also important in energy-efficient design. It involves insulating a house so heavily and making it as airtight as possible so that heat from direct sunlight, appliances, and human bodies can warm the building with little or no need of backup heating sources.
Retrofit existing buildings:
There are many ways to save energy and money in existing buildings including:
-insulate the building and plug leaks.
-replace windows with energy efficient windows (or use window quilts)
-stop other heating and cooling losses in heating ducts in -attics and basements
-heat homes more efficiently - use passive solar, heat pumps, or a high-efficiency natural gas furnace
-heat water more efficiently - solar heaters or pre-heaters, -tankless water heaters
-use energy efficient appliances - refrigerators with freezer on the bottom, front loading washing machines, -microwaves over conventional ovens, hang laundry out to dry, (or use moisture sensing dryers)
switch to cfl or leds for lighting
In addition to many of the same strategies for individuals, some industries can conserve energy by using a process called cogeneration. Large companies and power plants that burn fuel often waste excess heat by expelling it into the surroundings. In some cases, that excess heat can be used to produce steam that can generate electricity. If the excess heat is insufficient for generating electricity, it can be used to heat nearby building, thereby reducing the need to burn additional fuel.
governments need to help
Governments can help conserve energy by mandating energy standards. In the United States, for example, the Corporate Average Fuel Economy (CAFE) Standards were first enacted by Congress in 1975 to require automobile manufacturers to produce cars that meet a minimum fuel efficiency standard. CAFE standards were effective in raising the average mileage for U.S. cars from 13 miles per gallon in 1973 to 22 mpg in 1985. But a relaxation of standards in the mid-80s coupled with loopholes in the law and a changed mix of vehicles in the national fleet kept the average at 22 mpg until 2008. The 2012 version of the standards will raise the average mileage to over 54.5 mpg by 2025.
passive solar energy
Passive solar energy systems make direct use of sunlight to heat a building.
For thousands of years, people have built and oriented their homes to make use of the sun's energy. Passive solar energy systems make direct use of sunlight to heat a building. Since the path of the sun is predictable, a building can be positioned to maximize its utilization of the sun's energy. In the northern hemisphere, for example, windows placed along the south side of a building will allow sunlight to enter year-round and heat the interior. The heat can be stored in building materials like stone, concrete, or adobe, and in large tanks of water. Heat stored during the day can be released slowly during non-daylight hours. passive solar energy is more effective when it is used in combination with energy conservation measures such as thick or high r-value (r-value is the resistance of heat flow through a given thickness of material) insulation and well-sealed, multi-paned windows.
In order to reduce cooling costs and avoid overheating buildings that use passive solar energy systems during the summer, overhangs can be used that block out high-angle summer sunlight while allowing low-angle winter sunlight to enter. Deciduous trees can be planted where they shade the building in the summer while allowing winter sunlight to pass through their leafless branches.
Active Solar Energy
systems make use of pumps to move water or a fluid-like antifreeze through solar collectors, where it is heated by the sun and then pumped throughout a building to provide heat. An active solar system can also store the hot fluid and allow it to slowly release its heat throughout non-daylight hours. These systems can also be used to heat water and replace conventional hot water heaters.
(PV or solar cells) convert sunlight directly into electricity by making use of the electrical properties of the semiconducting element silicon. Solar cells can be used to generate electricity in remote locations far from an electrical grid. In these "off-the-grid" applications, excess electricity can be used to charge batteries that will provide electricity whenever sunlight is not available. Solar cells can be used on buildings that are connected to an electrical grid in such a way that the excess electricity they generate is fed into the grid, decreasing the need to generate electricity by other means. A big drawback to photovoltaic cells is their high cost (although the cost has been going down since this book was written).
solar energy plants
Solar power plants use sunlight to provide electricity for cities. A solar power tower makes use of an array of mirrors that focus sunlight to a single point where the concentrated solar energy is used to heat a fluid that heats water to produce the steam necessary to rotate a turbine attached to a generator that produces electricity.
Another type of solar power plant uses long parabolic mirrors that have a fluid-filled pipe running along the focus of each mirror that is heated by concentrated sunlight. The heated fluid is pumped to a boiler where it heats water to produce the steam necessary to generate electricity. In both of these examples the mirrors are mounted and use motors in such a way that they track the sun during daylight hours.
A solar power plant requires a large area of land in an arid location that receives intense sunlight throughout the year. This will result in habitat loss in the areas where the plant is built and limits the regions of the earth where such power generation is feasible primarily to desert biomes.
Hydroelectric power makes use of the potential energy of water stored in an elevated reservoir. Water released from the reservoir is made to flow through turbines that are connected to generators to produce electricity. Currently, hydroelectric power produces more energy than any other renewable energy source in the world - about 25% of the world's electricity (almost 20% of Maine's electricity).
Disadvantages of hydroelectric power?
The environmental costs of hydroelectric are associated with the large dams that are needed to store water for reliable energy production. Impacts include the flooding of habitat upstream from the dam and fragmentation of the river ecosystem. Fragmentation prevents large ranging or migratory species, such as salmon and river dolphins, from accessing part of their habitat. Societal costs include the displacement of human communities when homes are flooded to create the water storage reservoir, catastrophic flooding that could result from the collapse of the dam, and an increase in water-borne infectious diseases that are spread in slow-moving and stagnant water behind a dam. Another concern is that sediments normally carried downstream by a river accumulate behind dams, resulting in silting. Silt can be removed by dredging; if sediments are not removed, they will accumulate until the dam is no longer functional.
Wind power has been used for centuries to push the sails of ships around the world and to turn the windmills that pump water and make flour. The modern windmills of today are used to produce electricity, and when all of the environmental costs of resource extraction and pollution cleanup are factored in, wind energy is an inexpensive renewable source of energy. Winds are the result of the uneven heating of the earth by the sun. Differences in air temperature result in the movement of large air masses producing winds. Mountain ridges and passes are locations with concentrated reliable winds, and many wind farms have been built in these areas around the world. Offshore wind farms are currently being considered as a way of increasing the generation of electricity from wind. This also reduces the complaint of some who consider the wind farms that occupy ridges and passes to be a visual blight. Other concerns over wind energy include the noise produced by wind generators, interference with bird migration, and that even in the windiest places on earth, the strength and direction of wind are too unreliable to depend entirely on winds for energy without substantial backup systems.
Biofuels are a collection of different energy sources that all involve obtaining fuel from plant matter and animal waste. Burning wood, dung, crop wastes and other biomass has supplied humans with energy for thousands of years. Because wood can be harvested sustainably and since dung and crop wastes otherwise will be discarded, these are attractive and inexpensive sources of energy. However, the smoke from fires using biomass contains poisonous carbon monoxide, as well as ash, soot, and hydrocarbons, which are hazardous and may be carcinogenic.
Methane digesters can be used to convert animal waste from feedlots and factory farms into methane. Landfills and wastewater treatment facilities can collect the methane that is produced during decomposition. The methane from either source can be used, like natural gas, to produce electricity, for cooking, or to heat buildings.
How biofuel is produced
Sugar cane, corn, and other crops can be fermented into ethanol that can be used in automobiles. While there is concern that using food crops like corn and sugar cane to produce energy may increase food shortages in the world, the use of a nonfood alternative like switch grass may reduce such concerns. Ethanol produced from corn is also controversial because of the large inputs of fossil fuel energy currently required to produce it.
Biodiesel fuel is made from sources like used frying oil, waste products from meat processing, vegetable oil, and oil squeezed from algae. Biodiesel fuel replaces traditional diesel fuel, which is produced from crude oil, in automobiles whose diesel engines have been modified.
Geothermal energy makes use of the earth's internal temperature by tapping into high-temperature, high-pressure steam that exists below the earth's surface in some areas. Limited to use in areas where such conditions exist, usually neat tectonic plate boundaries, notably Iceland, have made extensive use of geothermal energy. The heat is also used to heat buildings and to generate electricity. Smaller systems, like those used in Maine, take advantage of the constant temperature found below the frost line in the ground. In the winter heat is drawn up from the ground and used to warm the house while in the summer the process is reversed.
Hydrogen fuel cells
Fuel cells use chemical reactions to produce electric current as it is needed. The most common fuel cells use hydrogen and oxygen as reactants and produce drinkable water as the only product. They are used in similar applications to batteries and the reactants in the chemical reaction can be replenished as needed. For hydrogen fuel cells, the oxygen in ambient air can be used, but hydrogen must be supplied as a gas or liquid. Obtaining and storing hydrogen is in itself energy intensive, so a fuel cell may not be a net producer of energy unless alternative methods such as solar energy are used to electrolyze water and generate fuel.
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