## Energy Units and Conversions

##### by Dennis Silverman

##### U. C. Irvine, Physics and Astronomy

####
Energy Units and Conversions

1 Joule (J) is the MKS unit of energy, equal to the force of one Newton
acting through one meter.

1 Watt is the power of a Joule of energy per second

Power = Current x Voltage (P = I V)

1 Watt is the power from a current of 1 Ampere flowing through 1 Volt.

1 kilowatt is a thousand Watts.

1 kilowatt-hour is the energy of one kilowatt power flowing for one
hour. (E = P t).

1 kilowatt-hour (kWh) = 3.6 x 10^{6} J = 3.6 million
Joules

1 calorie of heat is the amount needed to raise 1 gram of water 1
degree
Centigrade.

1 calorie (cal) = 4.184 J

(The Calories in food ratings are actually kilocalories.)

A BTU (British Thermal Unit) is the amount of heat necessary to raise
one
pound of water by 1 degree Farenheit (F).

1 British Thermal Unit (BTU) = 1055 J (The Mechanical Equivalent of
Heat Relation)

1 BTU = 252 cal
= 1.055 kJ

1 Quad = 10^{15} BTU (World energy usage is about 300
Quads/year, US is about 100 Quads/year in 1996.)

1 therm = 100,000 BTU

1,000 kWh = 3.41 million BTU

#### Power Conversion

1 horsepower (hp) = 745.7 watts
#### Gas Volume to Energy Conversion

One thousand cubic feet of gas (Mcf) -> 1.027 million BTU = 1.083
billion
J = 301 kWh

One therm = 100,000 BTU = 105.5 MJ = 29.3 kWh

1 Mcf -> 10.27 therms
#### Energy Content of Fuels

Coal
25 million BTU/ton

Crude
Oil
5.6 million BTU/barrel

Oil
5.78 million BTU/barrel = 1700 kWh
/ barrel

Gasoline
5.6 million BTU/barrel (a barrel is 42 gallons) = 1.33 therms / gallon

Natural gas liquids 4.2 million BTU/barrel

Natural
gas
1030 BTU/cubic
foot

Wood
20 million BTU/cord

#### CO2 Pollution of Fossil Fuels

Pounds of CO2 per billion BTU of energy::

Coal
208,000 pounds

Oil
164,000 pounds

Natural Gas 117,000 pounds

Ratios of CO2 pollution:

Oil / Natural Gas = 1.40

Coal / Natural Gas = 1.78

Pounds of CO2 per 1,000 kWh, at 100% efficiency:

Coal
709 pounds

Oil
559 pounds

Natural Gas 399 pounds