Physics: Unit Three

?
P3.1 - Energy demands
Burning 1kg of fossil fuel releases about 30 million joules of energy.
1 of 23
In coal, oil and most gas-fired power stations, the burning fuel heats water in a boiler. This produces steam, which drives a turbine that turns an electricity generator. Coal, oil and gas are fossil fuels, which come from long-dead animals/plants.
Methane gas can be collected from cows or animal manure, from sewage works, decaying rubbish, etc. It can then be used in small gas-fired power stations.
2 of 23
A biofuel is any fuel taken from a living or recently living organisms. They can be used in place of fossil fuels.
Some examples of biofuels are ethanol (from fermented sugar cane), waste vegetable oil, plants such as rapeseed, straw, nutshells, and woodchip.
3 of 23
A biofuel is: renewable as its biological source either regrows or is continually produced, so it can be used at the same rate as replaced; it is carbon-neutral as carbon that living organism takes in can balance amount released when burnt.
Nuclear fuel takes energy from atoms.
4 of 23
Fuel in a nuclear power station is uranium/plutonium. Uranium fuel is in sealed cans and core of reactor. Nucleus of uranium atom is unstable and can split, and when it does, energy is transferred and becomes very hot.
Energy of core transferred by fluid (coolant) pumped through core. 1) Coolant is hot when leaves core. Flows through pipe to heat exchanger, then back to reactor core. 2) Energy transferred used to turn water to steam, to turn electricity generators
5 of 23
Nuclear power stations - uses uranium/plutonium; releases 300,000 MJ/kg; makes radioactive waste that needs to be stored for years; no greenhouses gases.
Fossil fuel power station - uses coal/oil/gas; releases 30 MJ/kg; makes non-radioactive waste; greenhouse gases as fossil fuels are burnt.
6 of 23
P3.2 - Energy from wind and water
A wind turbine is an electricity generator at the top of a narrow tower. Power generated increases as wind speed increases. They are unreliable as when there is little to no wind, no electricity is generated.
7 of 23
A wave generator uses waves to make a floating generator move up and down, which turns the generator. A cable between it and the shoreline delivers electricity to grid system. May be ineffective due to extreme weather conditions, cables, sealife.
Hydroelectricity can be generated when rainwater that's collected in a reservoir flows downhill, which turns a generator at the bottom.
8 of 23
A tidal power station traps water from each high tide behind a barrage. The high tide can then be released into the sea through turbines. The turbines drive generators in the barrage.
One of the most promising sites for a tidal power station in Britain is the Severn estuary. This is because the estuary rapidly becomes narrower as you move up-river away from the open sea. So it funnels the incoming tide and makes it higher.
9 of 23
In some coastal areas, electricity is generated by the tidal flow passing through undersea turbines on the sea bed. Underwater cables are used to connect these turbines to the national grid.
P3.3 - Power from the Sun and the Earth
10 of 23
Today's solar cells convert less than 10% of the solar energy they absorb into the energy transferred by electricity.
Solar cell panels - are useful where only small amounts of electricity are needed or in remote places; they are very expensive to buy but they cost nothing to run; lots of them are needed (and plenty of sunshine) to generate enough power to be useful
11 of 23
A solar power tower uses thousands of flat mirrors to reflect sunshine on to a big water tank at the top of a tower. The mirrors on the ground surround the base of the tower.
1) Water in the tank is turned to steam by the heating effect of the solar radiation directed at the water tank. 2) Steam is piped down to a ground level, where it turns electricity generators. 3) Mirrors are controlled by a computer to track the Sun
12 of 23
A solar panel tower in a hot dry climate can generate more than 20 MW of electrical power, which is enough to power a few thousand homes.
Geothermal energy comes from energy released by radioactive substances deep within the Earth.
13 of 23
The energy transferred from these radioactive substances heats the surrounding rock. So energy is transferred by heating towards the Earth's surface.
Geothermal power stations can be built in volcanic areas or where there are hot rocks deep below the surface. Water gets pumped down to these rocks to produce steam. Then the steam that is produced drives electricity turbines at ground level.
14 of 23
In some areas, buildings can be heated using geothermal energy directly. Heat flow from underground is sometimes called ground source heat. It can be used to heat water in long underground pipes. It's then pumped around the buildings.
P3.4 - Energy and the environment
15 of 23
Burning fossil fuels can also produce sulphur dioxide. This gas causes acid rain.
Carbon capture and storage (CCS) technology could be used to stop carbon dioxide emissions into the atmosphere from fossil fuel power stations. Old oil and gas fields could be used for carbon dioxide storage.
16 of 23
Nuclear Power: advantages & disadvantages
Advantages - no greenhouse gases, much more energy transferred from each kg of uranium fuel than fossil.
17 of 23
Disadvantages - used fuel rods contain radioactive waste, nuclear reactors are safe in normal operation but an explosion could release radioactive material over a wide area.
Renewable energy sources and the environment: advantages & disadvantages
18 of 23
Advantages - never run out as always replenished by natural processes, don't produce greenhouse gases or acid rain, don't create radioactive waste products, can be used where connection to the National Grid is uneconomical.
Disadvantages - renewable energy resources cannot meet demand, wind turbines create noise and disturb locals, tidal barrages affect river estuaries and animals, hydroelectric schemes need water and cause dams, solar cells need a large amount of land
19 of 23
P3.5 - Big energy issues
Reliability problem with hydroelectric - upland reservoir could run dry.
20 of 23
Reliability problem with wind, waves - wind and waves too weak on very calm days.
Reliability problem with tidal - height of tide varies both on a monthly and yearly cycle.
21 of 23
Reliability problem with solar - no solar energy at night, and variable during the day.
Variable demand for electricity met by nuclear and coal-fired power stations for constant electricity, gas-fired power stations and pumped-storage schemes for changes in demand, renewable energy resources when demand is high or low
22 of 23
Capital costs are lowest for gas-fired power stations and greatest for wind and nuclear power, including decommissioning costs. Overall costs including fuel costs are the lowest for hydroelectricity, and greatest for offshore wind farms.
Nuclear power stations, fossil-fuel power stations that use carbon capture technology, and renewable energy resources are all likely to be needed for future energy supplies.
23 of 23

Other cards in this set

Card 2

Front

In coal, oil and most gas-fired power stations, the burning fuel heats water in a boiler. This produces steam, which drives a turbine that turns an electricity generator. Coal, oil and gas are fossil fuels, which come from long-dead animals/plants.

Back

Methane gas can be collected from cows or animal manure, from sewage works, decaying rubbish, etc. It can then be used in small gas-fired power stations.

Card 3

Front

A biofuel is any fuel taken from a living or recently living organisms. They can be used in place of fossil fuels.

Back

Preview of the front of card 3

Card 4

Front

A biofuel is: renewable as its biological source either regrows or is continually produced, so it can be used at the same rate as replaced; it is carbon-neutral as carbon that living organism takes in can balance amount released when burnt.

Back

Preview of the front of card 4

Card 5

Front

Fuel in a nuclear power station is uranium/plutonium. Uranium fuel is in sealed cans and core of reactor. Nucleus of uranium atom is unstable and can split, and when it does, energy is transferred and becomes very hot.

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Energy resources »