Ch 5: Macrogeneration Flashcards
(34 cards)
Which fossil fuel as of 2019, does the UK currently rely on very heavily?
Natural gas
Which fossil fuel does the UK intend to phase out by 2025?
Coal, due to the highly polluting nature of the coal.
What are the percentages of fossil fuels used for energy?
42% natural gas
18% nuclear
18% wind
6% biomass
5% coal
What are the 4 stages of the fossil fuel power plant?
- Combustion of the fuel
- Evaporation of water
- Steam used to turn a turbine
- Condensing in the cooling towers
Recall stage 1 (combustion of the fossil fuel).
The fuel is combusted to release the chemical energy, specifically releases the thermal energy.
Recall stage 2 (evaporation of water).
The thermal energy extracted is used to heat the water in the furnace. The temperature of the water increases considerably, and it evaporates at 100 C into steam. The steam is ejected from the furnace to the steam turbine.
Recall stage 3 (steam used to turn the turbine).
The steam, which is high velocity water molecules, collides with the fins of the steam turbine causing it to turn. There is energy lost from these molecules and thermal so the steam will exit with a lower temperature. This hit steam is now sent to the cooling towers.
Recall stage 4 (condensing in the cooling towers).
The hot steam from the turbine enters the cooling towers where there is energy loss so the steam turns back to water. This cold liquid is then re circled back to the furnace and the process is repeated.
What is the disadvantage of cooling towers?
There is energy lost and ejected into the atmosphere as they pass through the cooling towers so this reduces the efficiency. The efficiency is around 40%. A new method, Combined Heat and Power (CHP) aims to capture the lost energy and use it to heat buildings.
What is the definition of direct renewable energy sources?
These renewable energies take energy from a renewable source such as wind or waves in the ocean and can convert this into electrical energy directly.
What are some examples of direct renewable energy sources?
- Wind
- Hydroelectric
- Wave
- Tidal
What is the definition of indirect renewable energy sources?
These take energy from a renewable energy such as the sun using a physical characteristic of the material being used and convert this energy into electrical energy.
What are some examples of indirect renewable energy sources?
- Solar PV
- Biomass
What are the energy changes involved in generating electricity from wind? (Going down for each stage in order)
Wind = Ke
Hub = Ke of blades
Gearbox = Ke of high speed shaft
Generator = electrical energy
Thermal and sound energy is lost from each progressing stage.
What are the energy changes involved in generating electricity from solar? (Going down for each stage in order)
Sun = radiant
PV panel = electrical energy
Thermal and sound energy losses at the progressing stage
What are the energy changes involved in generating electricity from hydroelectric? (Going down for each stage in order)
Dam = GPE
Moving water = Ke
Turbine = Ke
Generator = electrical energy
Thermal and sound energy lost at each progressing stage
What are the energy changes involved in generating electricity from tidal? (Going down for each stage in order)
Behind tidal barrier = GPE
Moving water = Ke
Turbine = Ke
Generator = electrical energy
Thermal and sound energy lost at each progressing stage
What are the energy changes involved in generating electricity from wave? (Going down for each stage in order)
Sun = radiant energy from sun produces wind with Ke
Waves = Ke of wind causes Ke of waves
Wave generator = Ke
Generator = electrical energy
Thermal and sound energy lost at the last 2 progressing stages
What are the energy changes involved in generating electricity from biomass? (Going down for each stage in order)
Biomass fuel = chemical energy
Burning fuel = thermal energy
Steam = thermal energy (thermal loses)
Turbine = Ke (thermal and sound loses)
Generator = electrical energy (thermal and sound loses)
How is electricity distributed through the National Grid?
The electricity produced in the power station is at 22kV.
A step-up transformer steps-up the voltage to between 275kV and 400kV.
The electricity can now be sent across the National Grid through the transmission lines.
A step-down transformer then reduces the voltage to 33kV for industry, and 11kV for distribution.
It is reduced to 240V for use in homes.
Why is a step-up transformer used in the National Grid?
A step-up transformer increases the voltage, but this is done to reduce the current to a minimum. Minimising the current to reduce energy loses before transferring electricity across the grid is the risk of the step-up transformer.
What is the definition of a SMART Grid?
A computer-controlled electricity network that switches input from one energy source to another as demand for energy varies on the grid.
What are the key requirements in a SMART grid?
- Predict demand - the grid will have a network of intelligent meters in the National Grid to accurately predict demand.
- Measuring output from renewables - need intelligent meters to detect the output from renewables across the National Grid.
- Adapting non-renewable power outputs - the electricity provider must establish the demand for electricity all day. The outputs must be monitored constantly, so that the additional contributions from fossil fuel power plants can be calculated. This info can then be sent to power stations to increase or decrease output.
- Exporting or Importing to other nations - there is a possibility that there will be extra electricity produced, so this can be exported to other nations and also can be reversed so they can receive electricity is needed.
What are the benefits of a SMART Grid?
- Maximise renewables
- Minimise fossil fuels
- Control electricity demand
