Topic 8: Energy Production Flashcards
Define The Law of Conservation of Energy
“Energy cannot be created or destroyed, only changed from one form to another.” (To transfer energy work is done, with the exception of thermal energy transfer)
Define fuels
Sources of energy.
Define energy density
The energy liberated per unit volume of fuel consumed. (Jm-3 or MJm-3)
Define specific energy
The energy liberated per unit mass of fuel consumed. (Jkg-1 or MJkg-1)
Define The Second Law of Thermodynamics
It is not possible to convert heat completely into work as some heat is always lost to the surroundings (known as degraded energy).
Define primary sources of energy
Sources that have not been transformed or converted before use eg. directly burning coal to heat something.
Define secondary sources of energy
Sources that result from the transformation of a primary source eg. electrical energy generated by coal-fired power stations
Define renewable energy
Energy that cannot be used up.
Define non-renewable energy
Energy that can be used up because they are used at a greater rate than they are produced.
Give the advantages and disadvantages of fossil fuel usage
Advantages:- Very high energy density- Easy to transport - Cheap- Power stations can be built anywhereDisadvantages:- Combustion products are harmful to the environment (eg. acid rain and greenhouse gases)- Fuel extraction can damage the environment- Non-renewable energy source- Power stations need large amounts of fuel
Give the efficiency of fossil fuels —> electrical energy(coal, oil and natural gas)
Coal (35%)Oil (38%)Natural gas (45%)
Define degraded energy
The heat energy that is lost to the surroundings.
How is electrical energy generated? (General process)
The flow of a fluid (eg. moving water, pressurised steam, wind) is used to spin a turbine which then spins a generator. The magnets spinning past copper coils in the generator produces electrical energy.
Define a kilowatt-hour
The amount of energy used by a 1kW device in one hour.
How are fossil fuels used to generate electricity?
Fossil fuels are burnt in power stations and the thermal energy released is used to boil water and create steam. This steam is used to spin turbines which are attached to generators that produce electricity.
How do nuclear power stations generate electricity?
Naturally occurring uranium-238 is enriched to uranium-235.A neutron source is used to initiate nuclear fission. The power stations use the energy released from nuclear fission to heat water, create steam and spin a turbine/generator to produce electricity.
What are the three key components of a nuclear reactor?
1) The moderator (eg. heavy water)This makes fission happen by slowing down the high-energy neutrons so that they are more likely to collide with the uranium-235. 2) Control rodsThe control rods control the rate of fission by absorbing neutrons. By lowering them into or out of the reactor core the fission reaction can be controlled. 3) Heat exchangerThe water heated from the fission reaction enters the heat exchanger and its thermal energy is transferred to a separate circuit containing cold water to convert it into steam to drive turbines.