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Exam 6 – FINAL RENR 375 Ch.9 TB: 

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Concept 9-1: Energy resources vary greatly in their net energy yields – the amount of highquality energy available from an energy resource minus the amount of energy needed to make it available Without the inexhaustible supply of solar energy, the earth’s average temperature would be -240 C, and life as we know it would not exist Commercial energy, energy that is sold in the marketplace, is what we use to supplement the sun’s energy; currently most commercial energy comes from extracting and burning nonrenewable energy resources obtained from the earth’s crust, primarily carbon-containing fossil fuels – oil, natural gas, and coal About 92% of the commercial energy consumed in the world comes from nonrenewable energy resources – 87% from fossil fuels and 5% from nuclear power; the remaining 8% of the commercial energy used in the world comes from renewable energy resources – biomass, hydropower, geothermal, wind, and solar energy World energy consumption has increased every year since 1982 An important aspect of any energy resource is its net energy yield – the total amount of highquality energy available from an energy resource minus the energy needed to find, extract, process, and get that energy to consumers A resource’s net energy yield is calculated by estimating the total energy available from the resource over its lifetime and then subtracting the amount of energy used, automatically wasted because of the second law of thermodynamics, and unnecessarily wasted in finding, processing, concentrating, and transporting the useful energy to users We can also express net energy as the ratio of energy produced to the energy used to produce it; ; the ratio, called the energy return on investment (EROI); the higher the EROI, the greater the new energy yield; when the EROI is less than 1, there is a net energy loss The following general rule can help us to evaluate the long-term economic usefulness of an energy resource based on its net energy yield: an energy resource with a low or negative net energy yield can have a hard time competing in the marketplace with other energy alternatives that have medium to high net energy yields unless it receives financial support from the government (taxpayers) or other outside sources; such financial support is generally referred to as a subsidy, and providing it is called subsidizing Concept 9-2A: conventional crude oil is abundant and has a medium net energy yield, but using it causes air and water pollution and releases greenhouse gases to the atmosphere Concept 9-2B: unconventional heavy oil from oil shale rock and tar sands exists in potentially large supplies but has a low net energy yield and a higher environmental impact than conventional oil has Crude oil, or petroleum, is a black, gooey liquid consisting mostly of a mix of different combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities; it is also known as conventional oil and as light crude oil; it was formed from the decayed

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remains of ancient organisms that were crushed beneath layers of rock for millions of years; the resulting liquid and gaseous hydrocarbons migrated upward through porous rock layers to collect deposits of oil and natural gas, often trapped together beneath layers of impermeable rock After years of pumping, usually a decade or so, the pressure in a well drops and its rate of conventional crude oil production starts to decline; this point in time is referred to as peak production for the well; at a refinery it is heated to separate it into components with different boiling points in a complex process called refining Some of the products of crude oil distillation, called petrochemicals, are used as raw materials in cleaning fluids, pesticides, plastics, synthetic fibers, paints, medicines, and many other products According to the 2012 BP Statistical Review of World Energy in 2011 the world’s three largest producers of conventional light oil were Saudi Arabia (13.2%), Russia (13%), and the US (8%); the International Energy Agency projects that by 2017 the US is likely to be the world’s largest oil producer In 2011, the world’s largest consumers were the US (21%), China (11%), and Japan (5%); the Earth Policy Institute projects that by 2035 China will be using four times more oil than that of the US Geologists have provided us with estimates of the amounts of oil available to us; these estimates are called proven oil reserves – deposits from which the oil can be extracted profitably at current prices with current technology The world is not about to run out of conventional light oil in the near future, but the easily extracted cheap oil that supports our economies and lifestyles may be running low We can also rely more on unconventional heavy oil – a type of crude oil that does not flow as easily as light oil – from depleted oil wells and other sources The twelve countries that make up the Organization of Petroleum Exporting Countries (OPEC) have about 72% of the world’s proven crude oil reserves and thus are likely to control most of the world’s oil supplies for many years to come Today, OPEC’s members are Algeria, Angola, Ecuador, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates, and Venezuela; other countries including Canada and Russia also have large oil reserves According to BP in 2011, Venezuela had the largest portion of the world’s proven light oil reserves (18%), Saudi Arabia (16%), Canada (11%), Iran (9%), Iraq (9%), Kuwait (6%), the United Arab Emirates (6%), and Russia (5%); the US (2%), China (1%), and Japan (.003%) Based on the data from the US Department of Energy and the US Geological Survey (USGS), if global consumption of conventional light oil continues to grow at about 2% per year, then Saudi Arabia, with the world’s second largest crude oil reserves, could supply the world’s demand for oil for about 7 years; estimated unproven crude oil reserves under Alaska’s Arctic National Wildlife Refuge (ANWR) would meet the world’s demand for 1-5 months and the US demand for 7-24 months, and the Arctic Circle holds enough technically recoverable crude oil to meet the global demand for about 3 years at high production costs The US produces about 9% of the world’s crude oil but uses about 21% of the world’s oil production; the basic problem is that the US has only about 2% of the world’s proven crude oil reserves, much of it located in environmentally sensitive areas

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The decrease in dependence on oil imports between 200 and 2012 resulted from a combination of a weak economy, reduced oil consumption due to improvements in fuel efficiency, and increased production of oil from shale rock deposits; even so, the importation of oil results in a large annual transfer of wealth from the US to oil producing countries Currently, burning oil, mostly as gasoline and diesel fuel for transportation, account for 43% of global CO2 emissions Tar sand, or oil sand, is a mixture of clay, sand, water, and a combustible organic material called bitumen – a thick, sticky, tarlike heavy oil with a high sulfur content Northeastern Alberta in Canada has three-fourths of the world’s tar sand resources in sandy soil under a he area of remote boreal forest The amount of heavy oil potentially available in Canada’s tar sands is roughly equal to seven times the total conventional oil reserves of Saudi Arabia; if we include known unconventional heavy oil reserves that can be extracted from tar sands and converted into synthetic crude oil, Canada has the world’s third largest oil reserves According to a 2009 study by CERA, an energy consulting group, this process releases three to five times more greenhouse gases per barrel of oil than is released in the extraction and production of conventional crude oil Producing heavy oil from tar sands is one of the world’s least efficient, dirtiest, and most environmentally harmful ways to produce energy Oily rocks are another potential supply of heavy oil; such rocks called oil shales contain a solid combustible mixture of hydrocarbons called kerogen; kerogen is extracted from crushed oil shales after they are heated in a large container – a process that yields a distillate called shale oil Advantage of conventional oil: ample supply for several decades, net energy yield is medium but decreasing, low land disruption, efficient distribution system Disadvantages of conventional oil: water pollution from oil spills and leaks, environmental costs not included in market price, releases CO2 and other air pollutants when burned, vulnerable to international supply interruptions Advantages of heavy oils from oil shale and tar sand: large potential supplies, easily transported within and between countries, efficient distribution system in place Disadvantages of heavy oils from oil shale and tar sand: low net energy yield, releases CO2 and other air pollutants when produced and burned, severe land disruption and high water use Concept 9-3: conventional natural gas is more plentiful than oil, has a medium net energy yield and a fairly low production cost, and is a clean-burning fuel, but producing it has created environmental problems Natural gas is a mixture of gases of which 50% to 90% is methane (CH4); it also contains smaller amounts of heavier gaseous hydrocarbons, such as propane and butane, and small amounts of highly toxic hydrogen sulfide; it is a versatile fuel that can be burned to heat space and water and to propel vehicles Conventional natural gas lies above most reservoirs of crude oil When a natural gas field is tapped, propane and butane gases are liquefied under high pressure and removed as liquefied petroleum gas (LPG); it is stored in pressurized tanks for use mostly in rural areas not served by natural gas pipelines

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So that it can be transported across oceans, natural gas is converted to liquefied natural gas (LNG) at a high pressure and at a very low temperature of about -162 C In 2011, the International Energy Agency estimated that recoverable conventional supplies of natural gas – held primarily by Russia, Iran, Qatar, and Turkmenistan – could meet the current global demand for about 120 years; that year the world’s three largest producers of natural gas were the US (20%), Russia (19%), and Canada (5%) When burned, natural gas releases much less CO2 per unit of energy produced than do coal or oil According to a 2012 study by the National Academy of Sciences, people living within 900 meters of a natural gas well are likely to have up to 17 times more CH4 in their groundwater than those who live farther away Unconventional natural gas is also found in underground sources; one is coal bed methane gas found in coal beds near the earth’s surface across parts of the US and Canada; another is methane hydrate: methane trapped in icy, cage-like structures of water molecules Advantages of conventional natural gas: ample supplies, versatile fuel, medium net energy yield, emits less CO2 and other air pollutants than other fossil fuels when burned Disadvantages of conventional natural gas: low net energy yield for LNG, production and delivery may emit more CO2 and CH4 per unit of energy produced than coal, fracking uses and pollutes large volumes of water, potential groundwater pollution from fracking Concept 9-4A: conventional coal is plentiful and has a high net energy yield at low costs, but using it results in a very high environmental impact Concept 9-4B: we can produce gaseous and liquid fuels from coal, but they have lower net energy yields and using them would result in higher environmental impacts than those of conventional coal Coal is a solid fossil fuel that was formed in several stages from the remains of land plants that were buried 300 million to 400 million years ago and then subjected to intense heat and pressure over those millions of years In 2012, coal-burning power plants generated about 45% of the world’s electricity, 37% of the electricity generated for the US, and 79% of that in China; the three largest coal-burning countries are China, the US, and India Coal is the world’s most abundant fossil fuel; the USGS estimates that identified US coal reserves could last about 250 years at the current consumption rate and that identified and potential global supplies of coal could last for 200-1,100 years, depending on how rapidly they are used The US holds 28% of the world’s proven coal reserves, followed by Russia 18%, China 13%, Australia 9%, and India 7% The major problem with coal is that it is by far the dirtiest of all fossil fuels to burn Soot = black carbon particulates The burning of coal accounts for at least one-fourth of the world’s annual CO2 emissions Advantage of coal: ample supplies in many countries, medium to high net energy yield, low cost when environmental costs are not included

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Disadvantages of coal: severe land disturbance and water pollution, fine particle and toxic mercury emissions threaten human health, emits large amounts of CO2 and other air pollutants when produced and burned We can convert solid coal into synthetic natural gas (SNG) by a process called coal gasification, which removes sulfur and most other impurities from coal; we can also convert it into liquid fuels such as methanol and synthetic gasoline, through a process called coal liquefaction; these fuels, called synfuels, are often referred to as cleaner versions of coal Advantages of synthetic fuels: large potential supply in many countries, vehicle fuel, lower air pollution than coal Disadvantages of synthetic fuels: low to medium net energy yield, requires mining 50% more coal with increased land disturbance, water pollution, and water use, higher CO2 emissions than coal Concept 9-5: when safely operated, nuclear power plants have a low environmental impact and a low accident risk, but the use of nuclear power has been limited by a low net energy yield, high costs, a public fear of accidents, long-lived radioactive wastes, and its role in spreading nuclear weapons technology The source of energy for nuclear power is nuclear fission, a nuclear change in which nuclei of certain isotopes with large mass numbers are split apart into lighter nuclei when struck by neutrons The fission reaction takes place in a reactor; each fission release two or three more neutrons plus energy; these multiple fissions within a critical mass of nuclear fuel form a chain reaction, which releases an enormous amount of energy that can be used to produce electricity Nuclear fission produces radioactive fission fragments containing isotopes that spontaneously shoot out fast-moving particles (alpha and beta particles), gamma rays ( a form of high-energy electromagnetic radiation), or both; these unstable isotopes are called radioactive isotopes, or radioisotopes A nuclear power plant is a highly complex and costly system designed to perform a relatively simple task: to boil water and produce steam that spins a turbine and generates electricity Light-water reactors produce 85% of the world’s nuclear generated electricity (100% of the US) A nuclear power plant is only one part of the nuclear fuel cycle, which also includes mining uranium, processing and enriching the uranium to make fuel, using it in a reactor, and safely storing the resulting highly radioactive wastes in the form of depleted or spent fuel rods for thousands of years until their radioactivity falls to safe levels One of the biggest components of nuclear waste is spent fuel rods When a nuclear power plant comes to the end of its useful life, mostly because of corrosion and radiation damage to its metal parts, it must be decommissioned, or retired – the last step in the nuclear power fuel cycle Nuclear fusion is a nuclear change in which the nuclei of two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus, releasing energy in the process; scientists hope that controlled nuclear fusion will provide an almost limitless source of intense heat and electricity

Ch. 10 TB:   

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Concept 10-1: energy efficiency improvements could save at least 33% of the energy used in the world and up to 43% of the energy used in the US Concept 10-2: we can use passive and active solar heating systems to heat water and buildings, and we can use direct sunlight to produce high-temperature heat and electricity Concept 10-3: we can use water flowing over dams, tidal flows, and ocean waves to generate electricity, but environmental concerns and limited availability of suitable sites may limit our use of these energy resources Concept 10-4: when we include the environmental costs of using energy resources in their market prices, wind power is the least expensive and least polluting way to produce electricity Concept 10-5A: solid biomass is a renewable resource, but burning it faster than it is replenished produces a net gain in atmospheric greenhouse gases, and creating biomass plantations can degrade soil and biodiversity Concept 10-5B: we can use liquid biofuels derived from biomass in place of gasoline and diesel fuels, but creating biofuel plantations can degrade soil and biodiversity and increase food prices and greenhouse gas emissions Concept 10-6: geothermal energy has great potential for supplying many areas with heat and electricity, and it has a generally low environmental impact, but the sites where it can be made use of economically are limited Concept 10-7: hydrogen is a clean energy source as long as it is not produced with the use of fossil fuels, but it has a negative net energy yield Concept 10-8: we can make the transition to a more sustainable energy future by greatly improving energy efficiency, using a mix of renewable energy resources, and including the environmental costs of energy resources in their market prices Improving energy efficiency solutions: prolongs fossil fuel supplies, reduces oil imports and improves energy security, very high net energy yield, low cost, reduces pollution and environmental degradation, buys time to phase in renewable energy, creates local jobs Advantages of passive or active solar heating: medium net energy yield, very low emissions of CO2 and other air pollutants, very low land disturbance, moderate cost (passive) Disadvantages of passive or active solar heating: need access to sun 60% of time during daylight, sun can be blocked by trees and other structures, high installation and maintenance costs for active systems, need backup system for cloudy days Advantages of solar thermal systems: high potential for growth, no direct emissions of CO2 or other air pollutants, lower costs with natural gas turbine backup, source of new jobs Disadvantages of solar thermal systems: low net energy yield and high costs, needs backup or storage system on cloudy days, requires high water use, can disrupt desert ecosystems Advantages of solar cells: medium net energy yield, little or no direct emissions of CO2 and other air pollutants, easy to install, move around, and expand as needed, competitive cost for newer cells

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Disadvantages of solar cells: need access to sun, some designs have low net energy yield, need electricity storage system or backup, costs high for older systems but dropping rapidly, solar-cell power plants could disrupt desert ecosystems Advantages of large-...