Nonrenewable Energy Resources Chapter 12 Nonrenewable Energy Resources

The first Earthday April 22, 1970 Several events in the 60’s prompted the creation. Well explosion off the coast of Santa Barbara CA in January, 1969. 3 million gallons of crudes oil dumped. Our reliance on oil and other fossil fuels has only increased. Spills can happen during any part of the process: leaks, explosions, extraction, transport. March, 1989: Exxon Valdez super tanker crash into Prince William Sound, Alaska. 53 million gallons. April, 2010: BP Deepwater Horizon oil well in the Gulf of Mexico. Killed 11 workers, injured 17, 206 million gallons of oil dumped. 2005: BP oil refinery in Texas. 15 workers killed. April, 2010: Coal mine explosion in West Virginia. 29 miners killed.

Most of our Energy Most of our energy comes fro nonrenewable sources (sources that once they are used up, they cannot be replenished). Two main categories: Fossil fuels and Nuclear fuels. What affects the rate at which energy is used? Availability Affordability More recently, environmental impacts. In 2005, U.S. used 355GJ per person per year (5x greater than the world average) Overall, 20% of the world uses 70% of the energy!

Nonrenewable Energy Nonrenewable energy resources- fossil fuels (coal, oil, natural gas) and nuclear fuels. Annual consumption worldwide by resource.

Energy Use Commercial energy sources- those that are bought and sold, such as coal, oil and natural gas. Subsistence energy sources- those gathered by individuals for their own use such as wood, charcoal and animal waste.

The history Up to 1875: wood predominant energy source. 1875: Coal came into wider use. Early 1900’s: oil and natural gas join coal as primary sources of energy. 1950: Nuclear enters the mix and hydroelectricity becomes more prominent.. 1970’s: decline in oil and resurgence of coal. Today (U.S. and worldwide): in order of increasing importance…oil, coal, natural gas. Major outputs of energy use are work and waste (heat, CO2, and other pollutants).

The U.S. Produces 70% of the energy it needs. 30% from other countries. Energy use varies both seasonally and regionally. Air conditioning/heating needs. The type of energy used is a function of many factors: ease of transport, amount of energy per mass of fuel, etc.

Energy uses Certain types of energy are better suited for particular jobs: Transportation: gasoline or diesel is preferred because it is a liquid source which is relatively compact meaning it has a high energy-to-mass ratio, they also provide or cut off the energy with great speed. Down side, they are bigger pollutants, require a great deal of refining, etc. One of the best ways to determine the best source for the job is to consider the energy efficiency. Second law of thermodynamics: as a source of energy is transformed its ability to do work diminishes.

Overall Fuel Efficiency of U.S. Automobiles

EROEI (Energy return on energy investment) Energy obtained from the fuel Energy invested to obtain the fuel **The bigger the EROEI, the better. EROEI=

Process of Energy Use

Transportation efficiency Public transportation is much more efficient than traveling by car (because most people travel alone). Car efficiency goes up as more people are added. In the United States vehicle choice plays an important role. Most do not choose by fuel efficiency alone but also by comfort, convenience and style. Recent legislation says that by 2016, the overall fleet average MPG must be at 35.

Primary vs. Secondary Sources of energy: Primary: coal, oil, and gas (burning at the source). Secondary: Electricity (obtained from the conversion of a primary source). Electricity is clean at the point of use but there are many pollution tradeoffs before that point. Greatest efficiency comes with the fuel that entails the fewest conversions from the original source.

Electricity Generation

Electricity Generation The burning fuel from coal transfers energy to water, which becomes steam. The kinetic energy contained within the steam is transferred to the blades of a turbine, a large device that resembles a fan. As the energy in the steam turns the turbine, the shaft in the center of the turbine turns the generator. This mechanical motion generates energy.

Energy Efficiency Most coal burning power plants are about 35% efficient.

Cogeneration Cogeneration- using a fuel to generate electricity and to produce heat. Example- If steam is used for industrial purposes or to heat buildings it is diverted to turn a turbine first. This improves the efficiency to as high as 90%.

Fossil fuel comparisons

Coal Coal- a solid fuel formed primarily from the remains of trees, ferns, and other plant materials that were preserved 280-360 million years ago. Four types of coal ranked from lesser to greater age, exposure to pressure, and energy content. These four types are: lignite, sub-bituminous, bituminous, and anthracite. The largest coal reserves are in the United States, Russia, China, and India.

Coal

Advantages and Disadvantages of Coal Energy-dense Contains impurities Plentiful Release impurities into air when burned Easy to exploit by surface mining Trace metals like mercury, lead, and arsenic are found in coal Technological demands are small Combustion leads to increased levels of sulfur dioxide and other air pollutants into the atmosphere. Economic costs are low Ash is left behind Easy to handle and transport Carbon is released into the atmosphere which contributes to climate change Needs little refining

Petroleum Petroleum- a mixture of hydrocarbons, water, and sulfur that occurs in underground deposits. Oil and gasoline make this ideal for mobile combustion, such as vehicles. Formed from the remains of ocean-dwelling phytoplankton that died 50-150 million years ago. Countries with the most petroleum are Saudi Arabia, Russia, the United States, Iran, China, Canada, and Mexico.

Petroleum

Advantages and Disadvantages of Petroleum Convenient to transport and use Releases carbon dioxide into atmosphere Relatively energy-dense Possibility of leaks when extracted and transported Cleaner-burning than coal Deliberate and accidental releases of waste oil Possible that it might melt permafrost and interfere with the calving of caribou along pipelines Releases sulfur, mercury, lead, and arsenic into the atmosphere when burned

Natural Gas Natural gas- exists as a component of petroleum in the ground as well as in gaseous deposits separate from petroleum. Contains 80 to 95 percent methane and 5 to 20 percent ethane, propane, and butane. Largest uses are for electricity generation and industrial processes in the U.S. Also used for residential heating, clothes dryers, stoves, water heaters.

Advantages and Disadvantages Natural Gas Contains fewer impurities and therefore emits almost no sulfur dioxide or particulates When unburned, methane escapes into the atmosphere (potent greenhouse gas) Emits only 60% as much carbon dioxide as coal Exploration of natural gas has the potential of contaminating groundwater Large quantities of water used during extraction

Other Fossil Fuels Oil sands- slow-flowing, viscous deposits of bitumen mixed with sand, water, and clay. Bitumen (tar or pitch)- a degraded type of petroleum that forms when a petroleum migrates close to the surface, where bacteria metabolize some of the light hydrocarbons and others evaporate.

The Hubbert Curve Hubbert curve- a graph that shows the point at which world oil production would reach a maximum and the point at which we would run out of oil. He predicted in 1969 that 80% of world reserves would be used up within 60 years.

The Future of Fossil Fuel Use If current global use continues, we will run out of conventional oil in less than 40 years. Coal supplies will last for at least 200 years, and probably much longer. Technological advances in renewable energy will someday make oil less desirable. Uranium also offers a desirable alternative to fossil fuels and their negative affects on the environment and their release of greenhouse gases.

Nuclear Energy

Nuclear Energy Often rejected because of concerns over the dangers of nuclear accidents, radioactivity, and weapons. Fission- a nuclear reaction in which a neutron strikes a relatively large atomic nucleus, which then splits into two or more parts.

Nuclear Reactors Uses the same basic principles to create electricity as the coal plant except that a fission reaction (of U-235) provides the heat.

1 neutron + 235U  142Ba + 91Kr + 3 neutrons

Nuclear Reactors Fuel rods- the cylindrical tubes that house the nuclear fuel used in a nuclear power plant. Nuclear power plants work by using heat from nuclear fission to heat water. This water produces the steam to turn the turbine, which turns a generator. Control rods- cylindrical devices that can be inserted between the fuel rods to absorb excess neutrons, thus slowing or stopping the fission reaction.

Nuclear ore Large commercial uranium mining operations exist in Australia, Western U.S., and parts of Canada. 70% of the electricity generated in France comes from nuclear and it has wide use in Lithuania, Germany, Spain, the UK, Japan, China and South Korea. The U.S. gets 20% of their electricity from nuclear. Currently 104 plants in the U.S.

Advantages and Disadvantages of Nuclear Energy No air pollution is produced Possibility of accidents Countries can limit their need for imported oil Disposal of the radioactive waste Chernobyl and 3 Mile Island

Radioactive Waste High-level radioactive waste- the form used in fuel rods. Low-level radioactive waste- the protective clothing, tools, rags, and other items used in routine plant maintenance. Uranium mine tailings- residue left after uranium is mined and enriched.

Radioactive Waste Radioactive waste- once the nuclear fuel can not produce enough heat to be used in a power plant but it continues to emit radioactivity. This waste must be stored in special, highly secure locations because of the danger to living organisms. Cannot be incinerated, disposed of using chemicals, shot into space, dumped on the ocean floor. Remains a threat for 10 half-lives (the accepted number by scientists).

Yucca Mountain Current disposal of spent fuel rods is on location. In 1978 the U.S. department of Energy began examining the Yucca Mountain site in Nevada as a permanent storage area. In 2006 the DOE released a report confirming the soundness of the site. A few years later after a presidential changeover, the project was cancelled. (Obama administration)

Fusion Nuclear fusion- the reaction that powers the Sun and other stars. This occurs when lighter nuclei are forced together to produce heavier nuclei and heat is released. Fusion is a promising, unlimited source of energy in the future, but so far scientists have had difficulty cotaining the heat that is produced.