11May 2012
Power stations
Power stations
Thermal power stations
Sankey diagrams
World power generation
Tsokos p.430 qns3-7
11 Physics
8.1, 8.2, 8.3 Power generationTsokos 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, Denmark
140kW (with 33kW wind turbines)
Thermal Power Station
A 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 efficiency
Generating 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
Source of Electricity (World total year 2008)
Natural
Gas
Nuclear
Hydro
other
Total
8,263 1,111
4,301
2,731
3,288
568
20,261
41％
21％
13％
16％
3%
100%
-
Coal
Electricity
(TWｈ
/year)
Proportion
Oil
5％
Sources of electricity in France in 2006