1. Workings of a generator Energy sources Renewable and non-renewable Energy density

3. If a magnet is moved inside a coil an electric current is induced (produced)

4. A electric current is induced because the magnetic field around the coil is changing.

5. A generator works in this way by rotating a coil in a magnetic field (or rotating a magnet in a coil)generator

6. “This is our most successful energy project. When we dug the foundation for the wind turbine, we struck oil.”

7.  Finite (being depleted – will run out)  In general from a form of potential energy released by human action  Coal, oil, gas (fossil fuels), Uranium.

8.  Mostly directly or indirectly linked with the sun  The exception is tidal energy

18. Fuel% total energy production CO 2 emission g.MJ -1 Oil4070 Natural gas2350 Coal2390 Nuclear7- Hydroelectric7- Others< 1-

19.  The energy that can be obtained from a unit mass of the fuel  J.kg -1  If the fuel is burnt the energy density is simply the heat of combustion

20.  Coal - 30 MJ.kg -1  Wood - 16 MJ.kg -1  Gasoline – 47 MJ.kg -1  Uranium – 7 x 10 4 GJ.kg -1 (70000000 MJ.kg -1 )

21.  Imagine 1 kg falling 100m.  Energy loss = mgh = 1x10x100 = 10 3 J  If all of this is turned into electrical energy it gives an “energy density” of the “fuel” of 10 3 J.kg -1

22. Generally (except for solar cells) a turbine is turned, which turns a generator, which makes electricity.

23. In electricity production they are burned, the heat is used to heat water to make steam, the moving steam turns a turbine etc.

24.  Relatively cheap  High energy density  Variety of engines and devices use them directly and easily  Extensive distribution network in place

25.  Will run out  Pollute the environment (during mining sulphur and heavy metal content can be washed by rain into the environment)  Oil spillages etc.  Contribute to the greenhouse effect by releasing greenhouse gases

26.  Freeing Energy from the Grid Freeing Energy from the Grid

27.  A coal powered power plant has a power output of 400 MW and operates with an overall efficiency of 35%

28. 1. Calculate the rate at which thermal energy is provided by the coal 2. Calculate the rate at which coal is burned (Coal energy density = 30 MJ.kg-1) 3. The thermal energy produced by the power plant is removed by water. The temperature of the water must not increase by more than 5 °C. Calculate the rate of flow of water.

29.  Calculate the rate at which thermal energy is provided by the coal

30. Efficiency = useful power output/power input Power input = output/efficiency Power input = 400/0.35 = 1.1 x 10 3 MW

31.  Calculate the rate at which coal is burned (Coal energy density = 30 MJ.kg-1)

32. 1 kg of coal burned per second would produce 30 MJ. The power station needs 1.1 x 10 3 MJ per second. Mass burned per second = 1.1 x 10 3 /30 = 37 kg.s -1 Mass per year = 37x60x60x24x365 = 1.2 x 10 9 kg.yr -1

33.  The thermal energy produced by the power plant is removed by water. The temperature of the water must not increase by more than 5 °C. Calculate the rate of flow of water.

34. Rate of heat loss = 1.1 x 10 3 – 0.400 x 10 3 = 740 MW In one second, Q = mcΔT 740 x 10 6 = m x 4200 x 5 m = 35 x 10 3 kg So flow needs to be 35 x 10 3 kg.s -1