8- Energy, Power and Climate Change Flashcards
Albedo (definition)
The ratio of the power that is scattered (reflected) from the surface over total incident power received. It is a ratio and has no units.
Black body radiation
The maximum theoretical amount of radiation that can be emitted from any surface
Carbon dioxide capture and storage
The general term for preventing the release of carbon dioxide into the environment
Coefficient of volume expansion
The fractional change in volume per degree change in temperature, units K^-1
Combined heating and power system
A system that improves the overall efficiency of electricity generation by using thermal energy created to for example supply hot water to people
Degraded energy
Energy that is transferred to the surroundings (thermal energy) is no longer available to perform useful work
Efficiency of coal
35%
Efficiency of gas
45%
Efficiency of oil
38%
Emissivity (definition)
Ratio of power radiated by a body over power radiated by a black body
Power radiated by a body
P = εσAT^4
When a body is a black body, the emissivity, ε, is…
1
Energy balance climate model (equation)
∆T = (Iin - Iout)∆t / Cs
Energy balance climate model (definition)
The variation of temperature of a planet if the incoming and outgoing radiation intensity differ
Energy density
The energy liberated per unit mass of fuel consumed, measured in J/kg
Oscillating water column ocean-wave energy converter
A converter that uses the kinetic energy of waves to generate electrical energy
Pros of fossil fuels
High energy density, extensive distribution network in place
Cons of fossil fuels
Leakage causes environmental problems, need extensive storage facilities
Electricity production process
Fuel, kinetic/thermal energy, rotating turbine, electrical energy
Process of colliding neutrons created in fission to collide with other nuclei to sustain reaction
Chain reaction
Critical mass
Minimum mass of uranium-235 for chain reaction to sustain itself
Moderator
Slows down neutrons in nuclear reactor by causing collisions between them and nuclei of the moderator (often water)
Heat exchanger
Transfers energy to heat water to produce steam to turn a turbine, allowing the nuclear reaction to occur in a sealed off place
Control rods
Movable rods that readily absorb neutrons. They can be introduced or removed from the reaction chamber in order to control the chain reaction
Fuel enrichment
Process by which the isotopic composition of a nuclear fuel is increased to make nuclear fissions more likely
Controlled nuclear fission
Excess neutrons are absorbed to ensure that the nuclear reactions take place at a constant rate
Pros of nuclear fission
High energy density, large reserves of nuclear fuel, no greenhouse gases
Cons of nuclear fission
Radioactive waste, nuclear weapons
Solar constant S
1400W/m^2
Insolation
Energy per square metre that arrives at Earth’s surface in a day
Insolation varies according to…
Distance from equator, season
Photovoltaic system
Incident sunlight produces a dc current and voltage, solar -> electric
Solar thermal system
Extracts thermal energy from sun to heat water, solar -> thermal
Pros of solar power
Free, renewable, clean
Cons of solar power
Daytime only, affected by weather, low energy density, requires large area
Average radiation intensity received by earth
250W/m^2
Pros of hydroelectric power
Free, renewable, clean
Cons of hydroelectric power
Very location dependent, high initial cost, changes environment
Pros of wave power
Free, reasonable energy density, renewable, clean
Cons of wave power
Needs large waves, maintenance and installation expensive, waves are irregular
Pros of wind power
Free, renewable, clean, ideal for remote locations
Cons of wind power
Requires wind, ulgy and noisy, expensive maintenance, best locations far from cities
Why doesn’t the melting of floating sea ice result in a rise in sea levels?
When ice melts it occupies a volume equal to the displaced water volume
Sea levels rise because _ melts
Land ice
