Power stations

Power stationsThermal power stationsSankey diagramsWorld power generationTsokos p.430 qns3-7

11May 2012

11 Physics 8.1, 8.2, 8.3 Power generation Tsokos 7.1

Three Gorges Dam, Hydroelectric Power Station, China (22GW- largest power plant in the world)

Wind turbine, Denmark (40kW)

Nellis Solar plant, USA (200kW)

Wave generator, Denmark140kW (with 33kW wind turbines)

Thermal Power StationA In the boiler, the fuel burns in

air, making heat.

G The heat boils the water and

turns it to steam.

E The steam travels along pipes

and steam pressure turns the

turbine.

I The turbine drives the

alternator.

H The alternator generates

electricity.

C A step up transformer

increases the voltage of the

electricity.

B The electricity travels to

homes and factories along

power cables.

D In the condenser, cooling

water cools the steam.

F The recycled water is fed

back to the boiler to be used

again.

Power station efficiencyGenerating electricity in a typical thermal power station has an efficiency around 35%.Cyclical processes cannot convert all thermal energy to work. Excess heat can be used in combined heat and power plants.

Degraded energy

energy lost due to cyclical process of converting heat into work (2nd law of thermodynamics)

Fossil fuel typical efficiency

maximum efficiency

coal 35% 42%

oil 38% 45%

natural gas 45% 52%

heat engine

Tsokos p.416

Construct a Sankey diagram for a bouncing ball of mass 1kg dropping from 1m which bounces to 70% of

its height each bounce.

Generator (alternator)

Coil rotates in a magnetic field, kinetic energy is converted to electrical energy

Coal-fired thermal power station, Sofia, Bulgaria (0.5GW)

Susquehanna , Nuclear Power plant, Pennsylvania, USA (1.2GW)

Nesjavellir, Geothermal Power Station, Iceland (0.6GW)

Power generation

- Coal Oil NaturalGas Nuclear Hydro other Total

Electricity (TWｈ /year)

8,263 1,111 4,301 2,731 3,288 568 20,261

Proportion 41％ 5％ 21％ 13％ 16％ 3% 100%

Source of Electricity (World total year 2008)

Sources of electricity in France in 2006