Energy is the capacity to do work, while power is the rate of doing work. Power plants convert energy into electricity using turbines powered by heat. Thermal efficiency determines how much energy can be converted, with larger plants generally more efficient but slower to adjust output. To meet varying demand, the electric grid relies on baseload, intermediate, and peaking power plants working together synchronized at 60Hz.

1. Energy 101:
Hanson Boyd
Basics of Traditional Power Generation

2. What is Energy?
 Energy - Capacity for doing work
 Common units: British Thermal Unit (Btu) or Kilowatt hour (kWh)
1 gallon of 1 ton of water 100ft in the air
gasoline 260 Btu
125,000 Btu
1 lb of molten lava Standard glazed
doughnut
4,000 Btu
900 Btu

3. Watt is Power?
 Power - Rate of doing work
 Common units: Watt (W, kW, MW)
Incandescent light bulb Air-conditioner Boeing 747
60 W 5 kW 90 MW
3.4 Btu/minute 280 Btu/minute 57,000 Btu/minute
(5,700 glazed dougnughts per
minute)

4. Turning Energy into Power
 There are many machines that do this
 Rockets, engines, dams, windmills
 How about electric motors?
 For this discussion we will only talk about heat
energy into electricity
 Can we turn all the heat energy in a pound of lava into
power?

5. Thermal Efficiency
1 lb of molten lava Sage Hall B08
@ 2,200 F @ -20 F
 Second Law of Thermodynamics

 At best we can only turn 83% of 4,000 Btu into useful
power

6. Thermal Efficiency
 Large steam turbine plant
 TH ~ 1,100 F
 TC ~ 100 F
 Efficiency: 55% – 60%
 Small gas turbine power plant
 TH ~ 2,300 F
 TC ~ 1,000 F
 Efficiency: 35% – 40%
 Automobile
 TH ~ 2,300 F
 TC ~ 1,400 F
 Efficiency: 25% – 35%

7. The Power Plant

8. What is a Turbine?

9. Power Demand
Energy cannot be effectively stored at grid levels

10. How do we deal with varying demand?
 Baseload plant
 Large and efficient
 Natural gas / Coal / Nuclear
 Slow startup and shutdown
 Intermediate load plant
 Medium size and efficient
 Coal / Natural Gas
 Follows load, spinning reserve, runs daily
 Peaking Plant
 Small and inefficient
 Runs only for a few hours when needed

11. Thermal Efficiency
 Large steam turbine plant
 TH ~ 1,100 F
 TC ~ 100 F
 Efficiency: 55% – 60%
 Small gas turbine power plant
 TH ~ 2,300 F
 TC ~ 1,000 F
 Efficiency: 35% – 40%
 Automobile
 TH ~ 2,300 F
 TC ~ 1,400 F
 Efficiency: 25% – 35%

12. Combined Cycle

13. Combined Cycle
GE FlexEfficiency* 50 Combined Cycle Power Plant

14. Connecting this power to the grid
 All power plants on a grid are “synchronized”
 Electric power is distributed as AC (60Hz for the US)
 Generators on a grid share the electrical demand
 Once synced they are electrically joined like a car clutch
 Generators share electrical demand

15. Summary
 Basic ideas:
 Energy - ability to do work
 Power - rate of doing work
 Power plants turn energy into useful power
 Only a fraction of energy can be turned into power (thermal efficiency)
 Bigger power plants tend to be more efficient but take longer to start and
stop than small ones
 Electric demand is irregular
 We need a combination of Baseload, Intermediate and peaking plants
 Generators and linked together and need careful management to avoid
blackouts