1. Uses of Energy

2. Energy, Work, Power, Climate
We like to convert E to do work.
Conservation of E says we cannot create E, but we can transfer E between objects.
E can be transferred by inputting thermal E to object.

3. Fuels release Thermal Energy
We use released heat from fuels to transform to other types of E we use to do work.
Turn a piston or a turbine.

4. A Cyclic Process needed to do continuous work.
Engines convert fuel to KE.
In order to have continuous work, system must be returned to original state.
E is “lost” when system returns to original state.

5. Hamper ex: hot air balloon rises to force rope to rotate a spool thus doing work. Once rope is used up, balloon must cool to return to ground & be re-heated a cycle. Some heat is “lost” in the process when balloon cools to return to ground.

6. Steam turns a turbine. Convert Heat > KE > Electric + Heat

7. Most processes involve significant E lost to (unwanted) heat.
Degraded E define
Flashlight battery puts out 100 units, only 10 units transferred to light the rest is degraded “lost” to heat.

8. Branch width = proportion.
Sankey Diagrams show E transfer. Straight arrow shows % useful work. Curved shows % degraded work.
Coal Fired Plant
Branch width = proportion.
input
Straight branch useful.

9. Sankey Diagrams – some more specific about heat losses.

10. a. Calculate the overall efficiency of the engine.
Ex 1: In a car engine chemical E is converted to KE of the wheels as shown.
a. Calculate the overall efficiency of the engine.
b. Calculate the engine efficiency ignoring frictional losses.

11. Eff = useful work x 100 % tot work
a J/ 1000 J x 100% = 30%
~ 550 J “lost” to friction.
b. ( ) J /1000 J x 100% = 85 %

12. We like to convert E to electricity.
Need some fuel to get a turbine spinning.

13. Power Plant Heat/ Steam Fuel source: Coal, Gas, Oil Nukes.
Coils Magnets
Electric
Fuel source:
Coal, Gas, Oil
Nukes.
Recycle water

14. List some energy that depend on the sun.
Coal
Oil
Wood
Solar
Wind

15. List some energy not from the sun.
Tidal
Nuclear
geothermal

16. Energy Density Fuels rated by density
The amount of energy per kg fuel.
Oil much denser than wood.

17. Wood = 4765 kg Coal = 2492 kg Oil= 1727 kg
Ex 2. Use the Energy density table Hamper to calculate the following: A steam engine has 4500 kW of power. If we wish to run the engine for 5 hours, how many kg of each type of fuel will be needed?
Wood = 4765 kg Coal = 2492 kg Oil= 1727 kg

18. Energy Density 235U = 9 x 107 MJ/kg

19. Power Plants 5:30 min

21. Nuclear problem Hamper 187.