Lecture 13 & 14: Fossil Fuels and Nuclear Power

primary energy sources

sun, geothermal, coal, wood, nuclear

secondary energy sources

electricity; made from primary energy

in every energy transformation,

some usable energy is lost to the system

1st Law of Thermodynamics

• Conservation of Energy: the total amount of energy in the universe is constant

  • what you get is what you get

  • you cannot create energy from nothing

2nd Law of Thermodynamics

• Law of Entropy: heat cannot pass spontaneously from a colder to a hotter body

  • processes that involve energy transformation are unidirectional and irreversible leading to a dissipation of heat and increase entropy

  • any energy transformation will be less than 100% efficient - useful energy is lost as wasted heat

entropy

spontaneous dispersal of energy

EROI

the ratio between the energy delivered by a particular fuel to society and the energy invested in the capture and delivery of this energy (Energy Returned on Energy Invested)

In early times (and even today in less developed countries), the major energy source was

muscle power

Michael Faraday

invented generators in 1831

Electricity from fossil fuels is only

30-35% efficient

Thermal pollution

waste heat energy discharged into natural waterways

crude oil, coal, and natural gas

provide 86% of U.S. energy consumption and 87% of the word’s consumption.

3;1

it takes ___ units of power to create __ unit of electrical power

thermal pollution

waste heat energy discharged into natural waterways

crude, oil, and natural gas are also called

fossil fuels because they are derived from biomass that was produced many millions of years ago

Hubbert Peak Theory

the rate of petroleum production tends to follow a bell-shaped curve

1970

the time when the United Stated production of oil decline gradually as reserves were exploited

OPEC

a group of predominantly Arab countries that initiated an embargo of oil sales to US for military and economic support to Israel

natural gas

• methane, ethane, propane, butane

• much cleaner than either oil or coal

oil sand

sedimentary material containing bitumen (can be refined as oil)

oil shale

fine sedimentary rock containing kerogen (can be refined as oil)

fracking

a new technique for drilling that include injecting hydraulic fluid under high pressure to open up the shale and release the gas

coal

most abundant fossil fuel

strip mining

dynamite is used to break overlying layers, and then power shovels turn aside the rock and remove the coal

coal combustion

world’s largest source of CO2 (greenhouse gas most significantly forcing climate change)

CHP technologies

a factory or large building installs a small power plant that produce electricity and heats the building with the “waste” heat. Efficiency of 80%

Life-cycle assessment (LCA)

a technique to assess environmental impacts associated with all the stages of a product’s life from cradle to grave

scrubbers

used for cleaning the gases that pass through the smokestack of a coal-burning power plant

Fluidized bed combustion (FBC)

• a combustion technology used to burn solid fuel

• limestone neutralized the sulfur dioxide released by burning coal

nuclear energy involves

changes at the atomic level through fission or fusion (change the nuclei of atoms; form new elements)

fission

a large atom is split to produce two smaller atoms of different elements

fusion

two small atoms combine to form a larger atom of a different element; hydrogen into helium and occurs on the Sun

In both fission and fusion, the mass of the product is

less than the mass of the starting material, and the lost mass is converted to energy. (E=mc²) (Einsten)

radionuclide

a nuclide that exhibits radioactivity

radioactivity

spontaneous emission of radiation, either directly from unstable atomic nuclei or as a consequence of a nuclear reaction

radionuclides are also called

radioisotopes

Nuclear plants use

fission (splitting) of 235uranium

loss-of-coolant accident (LOCA)

occurs when a cracked reactor loses water

meltdown

enough energy is released to melt the core

nuclear power

• requires 75,000 tons of raw material per year

• emits no CO2 into the atmosphere

• emits no acid-forming pollutants

• possible meltdown

• produces 250 tons of radioactive wastes

coal power

• requires 2-3 million tons of raw fuel per year

• emits over 7 million tons of CO2 into the atmosphere

• emits over 300 thousand tons of SO2 into the atmosphere

• produces about 600 thousand tons of ash

radioactive emissions

subatomic particles (alpha and beta particles, neutrons) + high-energy radiation (gamma and X-rays); very high energy and can destroy biological tissues or cause mutations leading to cancer or birth defects

radioactive wastes

materials in the reactor that become radioactive by absorbing neutrons from the fission process

radioactive half life

the time for half the amount of a radioactive isotope to decay (always the same, regardless of the starting amount)

radioactive decay

a process in which unstable isotopes, as they eject particles and radiation, become stable and cease to be radioactive.