Power stations

PowerPower generationEnergy density

14May 2012

11 Physics 8.1, 8.2, 8.3 Power generation Tsokos 7.1

Define Power...

Power is the rate at which work is done or energy is transferred in Js-1 or W

where P is the power in Watts, E is the energy transferred in Joules, and t is the time taken in seconds

Define efficiency...

Efficiency is the proportion of useful energy transferred.

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

Animal power stations: How many would be needed for the equivalent of a 1GW nuclear power station?

Energy density

Fuel energy density MJkg-1

Coal 22-35

Oil 42

Natural gas 54

Uranium (nuclear) 9x107

Waste 10

Ethanol biofuel 30

Hydrogen 142

1. Calculate the mass of oil needed to power a 100Watt lightbulb for 1hour (efficiency is 35%).

2. Calculate the mass of uranium needed for a 1GW power station each year.

3. Calculate the mass of Coal burned in the world each year. By what proportion does this increase the concentration of CO2 in the atmosphere (currently 3000Gigatonnes)?

Image: http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg

Fossil fuels- coal, oil and natural gas

Advantages• high energy density• easy to transport• relatively cheap• stations can be sited

anywhere with water and transport links

• direct heating

Disadvantages• pollute, especially acid

rain• produce CO2

• extraction has environmental costs

• non-renewable