Earth’s Changing Environment
Lecture 16
Electric Power
Electric Power Generation
Electric Power Plant
Fuel
Boiler
Steam turbine
Generator
Air Pollution
Thermal Pollution
Transmission
End Use
Power Plant Capacity
Consider a 1000 MW
Capacity Plant
W = Watt = unit of
power
So, a 1000 MW plant
could provide a
maximum of 1000
million watts of power
or 1,000,000 kW of
power
Power Plant Energy Output
Energy = power x time
Express power in kilowatts
(kW) and time in hours; so,
energy will be in kWh or
“kilowatt hours”
During a 24 hour day, a
1000 MW plant could provide
1 million kW x 24 hours =
24 million kWh
Power Plant Annual Output
A typical coal-burning plant will operate at 70%
capacity.
Energy produced by a 1,000 MW plant =:
0.70 x 1x106 kW x 24 hours/day x 365 days =
6.13 billion kWh (annual)
A typical residential customer consumes 12,000 kWh
annually; so a 1000 MW plant can supply 0.5 million
customers.
Power Plant Energy Efficiency
A typical 1000 MW plant burns
enough fuel to release 3333 MW
of thermal power.
Efficiency
= output power / input power
= 1000 MW / 3333 MW
= 30 %
First Law of Thermodynamics
Energy must be conserved; so, the other 2,333 MW
is dumped as waste heat.
Second Law of Thermodynamics
Efficiency is always less than
100%.
Some energy is always dumped
as waste heat.
Typically coal plant efficiency
is 30%, but new plants may be
50% efficient.
High efficiency plants conserve
energy and reduce CO2
emissions.
Let’s do some calculations.
Electric Power Use
Current, Voltage, and Resistance
I = electric current (amps)
V = electric voltage difference (volts)
R = electric resistance (ohms)
I=V/R
Power
Power (watts) = I (amps) V (volts)
Power Losses
Power Loss = I2 R