7.1 Nonrenewable energy-fossil fuels and 7.2 Nonrenewable energy-nuclear soucres
Energy usage
Natural Gas
Coal
Nuclear power
nonrenewable energy sources: fossil fuels (oil, coal, and natural gas) and in the nuclei of certain atoms (nuclear energy) ()% of the commercial energy used in the world comes from the nonrenewable energy resources
Renewable energy resources: wind, flowing water (hydropower), energy from the sun (solar energy), biomass (trees and other plants), and heat in the earth's interior (geothermal)
Electricity is mostly produced by coal, also coal is used to create heat for industrial processes like creating steel
Coal has actually overtaken oil as the world's largest energy resource.
Measuring energy: net energy is the amount of high-quality energy available from a given quantity of energy resource, minus the high-quality energy needed to make the energy available. Net energy=energy output-energy input, can be measured in different ways: Kilowatt- hours, BTUs, joules
energy density: the amount of energy available per kilogram of the resource. (remember: uranium-235)
Oil
The second most widely used energy resource
We use oil to transport people and goods, heat homes,used to power vehicles, grown food and make other energy resources available for use, and manufacture most of the things we use every day from plastics to cosmetics to asphalt and roads
crude oil or petroleum or conventional oils, contains a mixture of combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities
Geologists survey landscapes on the ground and from the air to identify rock formations that might have oil deposits beneath them, they make a seismic survey of its rock formations
Refining oil: -crude oil from a well cannot be used as it is. It has to be transported to a refinery by pipeline, truck, rail, or ship (oil tanker)
In refinery: oil is heated in pressurized vessels to separate it into various fuels and other components with different boiling points in a process called refining.
Future of oil is low net energy, right now oil has a medium net energy (and is decreasing)and is more destructive (higher environmental impact)
shale oil- oil which is integrated within bodies of shale rock (requires large energy input, reducing its net energy)
oil sands/tar sands: a mixture of clay, and sand water, an organic material called bitumen (obtained by drilling vertical wells) minimal land disruption
hydrofracking: integrated within bodies of shale rock, as opposed to trapped between layers of shale rock Problems: huge energy input, uses large amounts of water, wastewater (slurry): can contaminate local environment and groundwater, fracking causes small earthquakes
Horizontal drilling, hydraulic fracturing (aka hydrofracking)
Hydraulic fracturing: high pressure pumps force a mixture of water, sand, and a cocktail of chemicals through holes in the well pipe to fracture the shale rock and create cracks, when the pressure is released a mixture of the oil or natural gas and about half of the slurry flows to the surface through the well pipe
Natural gas is a mixture of gases: 50-90% methane
heavier gaseous hydrocarbons such as propane and butane, small amounts of highly toxic hydrogen sulfide
versatile fuel: widely used for cooking, heating, and industrial purposes
advantages: cheaper to extract, less expensive and take much less time to build, burns cleaner than oil and much cleaner than coal Disadvantages:could shift to reliance on renewable clean energy resources, drilling, pri=oduction and distribution process for natural gas leaks large quantities of methane into the atmosphere, huge inputs of energy, risk of groundwater pollution
Coal is a solid fossil fuel formed from the remains of land plants that were buried and exposed to intense heat and pressure for 300-400 million years
Coal is the most abundant fossil fuel, coal is burned to power plants to produce electricity and is burned in industrial plants to produce intense heat required to make steel and cement
Coal is by far the dirtiest of all fossil fuels (largest emitters of CO2), mining of coal severely degrades land, releases large amounts of black carbon particles, causes various severe illnesses such as emphysema.
Coal ash-forever toxic: can contain dangerous, indestructible chemical elements such as arsenic, lead, mercury, cadmium, and radioactive radium
People are turning away from coal to have cleaner energy like natural gas
Solid coal can be converted into synthetic gas (SNG) by a process called coal gasification, which removes sulfur and most other impurities from coal
Synfuels are often referred to as cleaner versions of coal
A nuclear power plant is a highly complex and costly system designed to perform a relatively simple task boil water to produce steam that spins a turbine and generates electricity, it created heat by a controlled nuclear fission reaction, the reaction takes place in the core of a reactor.
Nuclear fission: nuclei of certain isotopes with large mass numbers (such as uranium-235) are stuck by a neutron, this splits the heavy nuclei apart into lighter nuclei and releases energy
Chain reaction: this fission also releases neutrons, which fly out and cause more nuclei to fissio, those nuclei split too, releasing more energy and more neutrons which go on to split more nuclei
the cascade of fissions can result in a chain reaction that releases enormous amount of heat energy in a short time
the fuel for a nuclear reactor is made from uranium ore which is mined from the earth's crust, uranium is common among rocks and seawater
Nuclear meltdown- a coolant, usually water, circulates through the reactor's core to remove heat and keep the fuel rods and other reactor components from melting and releasing massive amounts of radioactivity into the environment
A containment shell made of thick, steel-reinforced concrete surrounds the reactor core to help keep radioactive materials from escaping into the environment, protect the core from outside threats like hurricanes and attacks.
The nuclear fuel cycle:
building a nuclear plant, mining uranium, processing and enriching the uranium to make fuel, using it in a reactor, safely storing the resulting highly radioactive wastes for thousands of years until their radioactivity parts safely for thousands of years
Advantages of nuclear power low CO2 emissions, no toxic emissions, as long as the reactor is operating safely, the power plants itself has a low environmental impact and low risk of an accident
Disadvantages: high cost, low net energy, threat of nuclear weapons, nuclear waste
Nuclear waste: enriched uranium, spent-fuel rods are so thermally hot and highly radioactive that they cannot be simply thrown away. (10 years after being removed from a reactor it can still emit enough radiation to kill a person standing 1 meter away in less than 3 minutes