Environmental Engineering Reference
In-Depth Information
Calorie (c) The amount of heat it takes to raise the temperature of 1 gram of water by 1°C (1.8°F)
Kilocalorie
(C)
The amount of heat it takes to raise the temperature of 1 kilogram of water by 1°C (1.8°F)
Horsepower
(hp)
Primarily used in the combustion engine market, such as in autos, trucks, boats, and backup
generators; 1 horsepower = 746 watts
Joule (J)
The force of 1 Newton applied through 1 meter of displacement
Measures the rate of energy conversion and is defined as 1 joule per second; commonly used in
terms of kilowatt-hour (kWh) energy consumption; used by power plants to describe how much
energy they generate (megawatt-hours) and on home energy bills (kWh)
Watt (elec-
trical) (W)
Watt
(thermal)
Used in nuclear power plants to measure the amount of thermal energy generated
Common SI (International System of Units) Prefixes Used in Energy
Term
Definition
Kilo-
(k)
1,000 or 10
3
; common metric term that is used in the power industry
Mega-
(M)
1,000,000 or 10
6
; common metric term that is used in the power industry
1,000,000,000 or 10
9
; commonly used in the computer industry and in talking about energy needs
and energy produced in regions and smaller countries.
Giga-
(G)
1,000,000,000,000 or 10
12
; new term used in the computer industry and is becoming more common
in talking about the total energy needs and energy produced in a country
Tera-
(T)
Following is a table of conversion factors useful in environmental science. On the AP Environmental Science
exam, the conversion factors are provided, and conversions are rounded. For example, 1 kWh is equal to 3,413
BTU, but the AP Environmental Science exam rounds this number to 3,400 BTU, which makes multiplication
easier. Despite the fact that conversions are given on the exam, it is useful to familiarize yourself with the con-
versions below to build intuitive understanding of relationships between units.
Conversions
Symbol
Unit
Conversion
1 c
Calorie
3.968 BTU or 4,186 J
British Thermal
Unit
1 BTU
0.254 c or 1,055 J
1 W
Watt
1 W for 1 hour is 3.413 BTU
1 kW for 1 hour is 3,413 BTU
Note:
3,400 BTU is commonly used on the AP
exam to simplify calculations.
1 kWh
Kilowatt hour
1 MW
Megawatt
1,000,000 W or 1,000 kW
1 GW
Gigawatt
1,000,000,000 W, 1,000,000 kW, or 1,000 MW
1 hp
Horsepower
0.7457 kW or 2,545 BTU
