Generating Electricity Flashcards
What is the definition for Renewable Energy?
An energy source that can be replenished as fast, or faster, than it is being used, or will always be there. This is also called a sustainable source.
What is the definition for Green energy?
Not necessarily renewable, but it does not produce polluting gases or greenhouse gases such as carbon dioxide, so does not directly harm the environment.
What is the definition for Carbon Neutral?
The amount of carbon dioxide produced into the atmosphere by using the fuel is equal to the amount of carbon dioxide removed from the atmosphere in producing the fuel.
What are solar cells also known as?
Photovoltaic cells
How can we harness infrared radiation emitted by the Sun?
Using solar heaters
When a solar heater is mounted on a roof, we want the Sun to heat it, but also to reduce the heat transferred out of it to the surroundings when it is hotter. what are two ways this could be achieved?
- Insulation around it
- Paint the back silver
What are the advantages to solar cells?
- a source of green energy
- a source of renewable energy
- gets cheaper eventually
- they are flexible as you can always add more on
What are the disadvantages to solar cells?
- very expensive initially
- reliability of the sun (not always sunny and not sunny at nighttime)
What are three ways which we can use available resources directly to harness energy?
Light energy for electricity
The sun for heating
Geothermal heating and power
What are four ways which we can use available resources through direct spinning to harness energy?
Wind power
Hydroelectric power
Tidal power
Wave power
What are four ways which we can generate electricity by pressurised steam?
Geothermal power
Fossil fuels
Biofuels
Nuclear Fission plants
What is the temperature of the Earth two metres below ground?
15 degrees Celsius
What do solar cells cells do?
Solar cells directly transfer the visible light emitted by the Sun into an electrical current
In geothermal heating and power, what are the pipes filled with?
With heat-absorbing fluid
What heating process does geothermal heating and power rely on?
Conduction:
- water conducts heat from underground
- NOT convection because the water underground is forced through the pumps, not convected
What are the benefits of geothermal heating?
- Saves money by using less energy: cheaper heating bill (up to 80% lower than traditional heating systems)
- better for environment: doesn’t rely completely on fossil fuels, produces less greenhouse gases
How do generators work?
- When a current flows through a wire, a magnetic field is generated
- equally, when a wire is placed in a moving magnetic field, a current is started in the wire.
- Generators are just very, very large magnets rotated quickly between coils of coppe wire
- after this, all you need to do is find something to turn the axel which ten magnet is connected to (e.g wind, wave etc.)
How does wind power work?
- wind causes the blades of a turbine to rotate
- the turbine is connected to an axis, which is connected to a generator, which produces electricity
Why do we want to make the blades of a wind turbine as large as possible?
So that there is a larger surface area to capture more energy per second
What are the advantages to wind turbines?
- green energy source
- renewable energy source
- quite cheap to build
What are the disadvantages to wind turbines?
- lots of land is needed to put them in, which could be used for food farming, but you could place them at sea
- they are not very reliable as they need wind to operate and you need a lot of turbines together to create a large amount of energy
- noise pollution + can be seen as ugly
How do hydroelectricpower plants work?
- rainwater is stored in a reservoir behind a dam to create higher pressure
- Inside the dam are lots of hydraulic turbines which spin when water flows through them.
- this energy is then converted into electricity using the turbines to spin a generator
What are the advantages to hydroelectric power?
- green energy source
- renewable energy source
- ready supply of water
What are the disadvantages of hydroelectric power?
- They rely on rainfall
- They change the environment behind it, affecting plants and animals
What type of energy is stored in the water which is trapped behind a dam?
Gravitational Potential Energy
What type of energy is used to spin the turbines in a dam?
Kinetic energy
What are tides caused by?
The moon’s gravitational pull
What are the three main tidal power technologies?
Tidal barrages, tidal fences and tidal turbines
What is tidal power?
- tidal power is an energy source which comes from the movement of the tides
- these are reliable occurrences of two high tides and two low tides a day
- there are three ways to harness tidal power: tidal barrages, tidal fences and tidal turbines
Where can we install tidal power stations?
Along the coastline
What is the minimum water level height for tidal power to produce electricity?
5 meters
What are tidal barrages?
- A tidal barrage is a dam like structure with turbines placed at the bottom of the reservoir.
- dams collect rainwater to use, whereas tidal barrages use the potential energy generated by the change in height between high and low tides.
- this energy turns a turbine, generating energy
- it is the most efficient tidal technology
What are tidal fences?
- tidal fences directly exploit fast flowing underwater ocean currents for energy generation.
- Tidal fences are used in fast flowing areas such as the channels between two land masses.
- tidal fences force water to flow through them when there is a change in tide, making the turbines spin
What are tidal turbines?
- similar to wind turbines, however they work underwater
- Energy is produced when the mechanical energy of tidal currents turns turbines connected to a generator. The generator generates electricity.
What are the advantages to tidal power?
- controllable + reliable as tides will change
- renewable energy source
- green energy source
What are the disadvantages of tidal power?
- they change the natural habitat
- can affect shipping
- tidal barrages can flood an area when emptied
How does wave power work?
- to harness the energy from waves and transform it into electricity, concrete structures are built along the shoreline
- when a wave enters the structure from underneath, there is less space above, increasing the air pressure
- the air is ‘pushed’ or forced up, through the turbine. This spins the generator
- When the waves drop back down, there is a decrease in air pressure which sucks air back into the chamber, spinning the generator again.
- this is exactly how our lungs work during ventilation
What are the advantages of wave power?
- green energy source
- renewable energy source
- abundant (widely predictable)
- predictable as you can predict the tides
What are the disadvantages to wave power?
- noise + visual pollution
- highly dependant on wave length/speed/density
- affects shipping/ coastal companies
How does geothermal power work?
- Geothermal power uses the Earth’s natural heat from its’ core to boil water.
- Cold water is pumped down, into the ground, then heated by the earth and pumped back up as hot water and steam
- The steam is then used to turn turbine generators which transfer kinetic energy into electricity.
What are the advantages to geothermal power?
- green energy source
- renewable energy source
- use 1000-2000 times less carbon dioxide than fossil fuel power plants
- stable electricity prices
- take up very little land compared to traditional fossil fuel plants
What are the disadvantages to geothermal power?
- testing areas to see if they are suitable for geothermal power plants and building them is expensive, heavy upfront costs
- only some countries have the right land to use it (Iceland is good because it is volcanic)
- only stable with regular maintenance
What are fossil fuels and how do they work?
- burning something has been the oldest method of generating electricity
- fuels (coal, oil and gas) are formed over millions of years from the remains of dead plants (and some animals too). This makes them non renewable as it takes such a long time to produce new fuels.
- fossil fuel power stations burn the fuel in a furnace which heats water in a boiler. As the water boils, it is turned into water vapour (steam) which is forced through pipes and across turbines. These turbines are connected to large generators which transfer kinetic energy into electricity.
What are the three types of fossil fuel?
- Coal, oil and gas
- coal is the ‘easiest’ to make into energy as it requires the least amount of heat and pressure.
How is coal formed?
- coal is formed from old swamp plants that are compressed over millions of years by immense heat and pressure.
- In the UK, coal is mostly found in Northern Regions and Wales
How are oil and gas fuels formed?
-They are formed when plants and animals from hundreds of millions of years ago from oceans are compressed and decomposed.
What gas does burning coal also produce which contributes to acid rain?
Sulfur dioxide
What is meant by a greenhouse gas?
- Greenhouse gases trap thermal energy in the atmosphere which has escaped from the earth’s surface.
- this causes some energy to pass back to the earth’s surface.
- this is called the greenhouse effect and it keeps our planet warm.
- Too many greenhouse gases cause global warming.
What do all fossil fuels contain which leads to global warming?
- all fossil fuels contain carbon, which forms carbon dioxide when burnt
- carbon dioxide is a greenhouse gas, leading to global warming
Which fossil fuel: coal, oil or gas, takes the longest time to start burning?
- Coal, because coal is a solid, so it will burn slower
- solids burn slower because the only burn on the surface
- gases and liquids, like oil and gas, can burn almost instantly
- power stations sometimes grind the coal into a powder and blow the powder in as though it were a gas, to speed up burning.
What are the advantages to fossil fuels?
- readily available (at the moment)
- relatively easy to produce energy from them
What are the disadvantages to fossil fuels?
- non-renewable source
- increasing fuel costs
- release CO2 when burnt (greenhouse gas)
- Release sulphur dioxide when burnt (acid rain)
What are biofuels?
- biofuels include biodiesel and ethanol and are made from plants like maize, oil palms and oilseed rape.
- There are also some companies which make biofuels from animal waste and used cooking oil
- Biofuels are burned to heat water and create steam to turn turbines and generate electricity.
- Biofuels can be used in replacement of fossil fuels and biodiesel can be used in replacement of diesel in car engines
Which type of forest are palm oil plantations found in?
Rainforests
Why do some people think that biofuels are unethical?
Because using food crops could be seen as wasting food, it could cause food shortages or increase food prices.
Biofuels come from plants, which greenhouse gas do plants absorb?
They absorb carbon dioxide, this is called photosynthesis
Are biofuels expensive?
Yes
Is the economic benefit of biofuels certain?
No because, although biofuels are carbon neutral, this doesn’t take into account carbon dioxide emissions during growing, harvesting and transporting the crops. Therefore more carbon dioxide is emitted than absorbed.
What is the carbon cycle?
The carbon cycle shows how the element carbon is recycled across the world through the natural living process:
Photosynthesis – plants absorb carbon dioxide from the atmosphere and form it into sugar, starch and other organic compounds. This is the only process in the cycle that decreases the level of carbon dioxide in the atmosphere. If we replace all trees/plants which are removed from our forests for fuel, then the cycle remains balanced; the same amount of CO2 remains in the atmosphere.
Feeding – moves carbon in the form of biological molecules along the food chain.
Respiration – when living organisms (plants, animals and decomposers) respire they release carbon dioxide into the atmosphere (this is a form of excretion).
Fossilisation – if conditions are not favourable for the process of decomposition, dead organisms decay slowly or not at all. These organisms build up and, if compressed over millions of years, can form fossil fuels (coal, oil or gas).
Combustion – the burning of fossil fuels releases stored carbon dioxide into the atmosphere.
Excretion – when waste is removed from the body (urine). This excreted material can be broken down during the process of decomposition.
Egestion – the removal of faeces from an animal that will contain carbon. This egested material can be broken down during the process of decomposition.
Decomposition – when complex, carbon compounds in dead organisms, urine and faeces are broken down into simpler carbon compounds by bacteria or fungi.
What is the chemical reaction for burning ethanol?
Ethanol reacts with oxygen when it is burnt and produces water and carbon dioxide
What does fission refer to?
-fission refers to the splitting of a nucleus in an atom
How do nuclear power stations generate electricity?
- A nucleus is a very large source of energy as it needs to hold together repelling positive protons. When the nucleus of an atom is split, a lot of this energy is released in the form of heat.
- We use this heat to boil water so that we can transfer the kinetic energy of the steam into electricity using a generator.
- Nuclear power stations typically use Uranium-235 as it is unstable and easy to split its’ nucleus.
Is nuclear energy renewable?
No, it is non-renewable
Why are governments and the public reluctant to build new nuclear power plants?
- the impact of an accident would be disastrous
- the capital (initial) cost is high
- nuclear waste is extremely dangerous
Where do nuclear power stations have to be built?
-near water, because water is needed to be turned into steam
What are the advantages of nuclear power?
-nuclear fuels do not produce carbon dioxide or sulphur dioxide
What are the disadvantages to nuclear power?
- they are non-renewable as they will eventually run out
- if there is an accident, large amounts of radioactive material could be released into the environment. Nuclear waste remains dangerously radioactive and harmful to health for thousands of years. It must be stored safely.
Which energy sources are examples of water power?
Tidal power, hydroelectric power, wave power
