unit 8: energy production

• ones which cannot be produced again

• can be used up and become depleted.

energy found in nature such as raw fuels and other forms of energy received as input to a system

energy transformed from primary energy sources through energy conservation processes

thermal energy that is released into the surrounding environment after any process

• the amount of energy which can be extracted per unit mass of fuel

• measured in J Kg^-1

• equal to energy/mass

• the amount of energy which can be extracted per unit volume of a fuel

• measured in J m^-3

• equal to energy/volume

Es/ED = 1/density of the fuel

• primary and secondary energy

• not degraded energy

gases tend to have higher specific energy than energy density → makes gaseous fuels harder to transport as a greater volume is needed

• fossil fuels

• sunlight

• flowing water

• hydrogen (as it has to be extracted)

• electricity

• biofuel (has been processed)

a type of energy diagram where the width of each arrow is proportional to the amount of energy in that section.

to generate electricity, a secondary form of energy

• useful energy/power / input power/energy

• 0<e<1 or 0%<e<100%

• Solar power

• Wind power

• Hydroelectric power

• Tidal power

• Geothermal

• Biomass

• Coal

• Oil

• Natural gas

• Nuclear power

ones which cannot be depleted

• to slow down neutrons so that fission reactions can occur

• increases reactivity

• absorb neutrons which stops fission

• fission requires a nucleus to absorb a neutron

• decreases reactivity so increases safety

to hold the fuel

water to serve as a moderator, slowing down neutrons enabling fission

• renewable

• no harmful water product

• cost effective in the long run

• expensive to build

• requires a large, windy area

• low power output

the transfer of heat through matter by transferring kinetic energy from particle to particle with no net movement of the particles

• the transfer of thermal energy by the movement of a fluid

• hot fluids rise because it is less dense, the fluid then cools becomes more dense and sinks

• this creates a convection current

• the transfer of energy by electromagnetic waves / photons

• how the sun provides heat energy to Earth

• can happen in a vacuum

• photons are emitted from everything that has a temperature

• this is only visible in infrared light

• something that appears less hot can have heat energy inside, kept there by an insulator

• if heated to a high enough temperate objects will give of visible light

• knowing that T∝λ^-1 and T∝f so λ∝f^-1

• the “glow” coming from an object due to its temperature

• photons coming out of a black body

• all due to the temperature of the black body

an object which absorbs all of the radiation falling upon it and reflects none…

• when e=1 it is perfect emissivity

• for black bodies e is closer to 1

• varies with surface material

• Stephan-Boltzmann Law

• P=eσAT^4

• σ = Stephan-Boltzmann constant

• T must be in Kelvins

• the energy radiated by a body is electromagnetic radiation and distributed over an infinite range of wavelengths

• most energy is radiated at a specific wavelength λmax

• λmax = 2.9×10^-3/T (Kelvin)