Common terms and units
1 joule and 1 watt are very small quantities compared to the
amounts of energy and power typically considered, especially when we look at
national energy use. So it more more common
to use multiples of ten for both
quantities (for example 1 megajoule (MJ) = 106 joules, ie 1 million
joules, and 1 kilowatt (kW) = 103 watts).
- energy is the capacity to do work. There are several different forms of energy,
and energy can be transformed from one form into another more useful form. For example,
chemical energy is the energy stored in the molecules of a fuel such as
coal or wood, and is converted into thermal energy or heat by combustion.
The kinetic energy of the wind is converted into mechanical energy
of a wind turbine, and then into electrical energy. The basic unit of energy
is the joule (abbreviated as J).
- power is the rate at which energy is converted or transmitted. Thus,
energy = power x time, or power = energy / time.
Power is measured in watts (abbreviated as W).
1 watt is defined as the power
produced when converting 1 joule of energy per
second, which can be written as 1 J/s (or 1 J s-1)
The standard prefixes used are:
Electrical power consumption is often expressed in units of kilowatt-hours (kWh).
A 1 kilowatt device running for one
hour uses 1 kilowatt-hour (kWh) of energy; this is equal to 3.6 megajoules.
1 Gg per GWh is equivalent to 1 kg per kWh
1 Gg per PJ is equivalent to 1 g per MJ
Energy and Power in Perspective
|75 to 250 W
||Output from human pedal-powered generator
|1 - 3 kW
||Power generated by typical roof-top photovoltaic system
|600 kW - 2 MW
||Power generated by a wind turbine
||energy used by a 100 W bulb in just under 17 minutes
|900 MJ = 250 kWh
||Daily amount of solar energy falling on a roof (50 sq.m) in Armidale
|648 PJ = 180 TWh
||Total electricity generation in Australia 1998 - 1999
||Energy used for electricity generation in Australia 1998 - 1999
- 1 ton = 1016.0469 kilograms = 2240 pounds. (long ton or British ton)
- 1 short ton = 907.184 kg = 2000 pounds (U.S. ton)
- 1 metric ton = 1000 kg (tonne)
- 1 pound = 0.453592 kilograms (avoirdupois)
- carbon dioxide (CO2 )
- methane (CH4 )
- nitrous oxide (N2O)
- oxides of nitrogen (NOx)
- carbon monoxide (CO)
- non methane volatile organic compounds (NMVOCs)
The term CO2 equivalent (CO2–e) emissions from combustion
of a fuel source refers
to the sum of the carbon dioxide emitted plus the
equivalent global warming
potential of associated
emissions of other greenhouse gases, usually only methane and
CO2–e is computed by scaling greenhouse gas emissions according
to their global warming potential (GWP), and adding. CO2 is defined to have
a GWP of 1,
methane (CH4) has a GWP of 21, and nitrous oxide (N2O)
has a GWP of 310.
Thermal efficiency of power stations.
Thermal efficiency is
the energy supplied in electricity
expressed as a percentage of the
energy contained in the fuel used to
produce the electricity - typical value around 35% (Delta Electricity 2001).
'Polycyclic Aromatic Hydrocarbons' is an aggregate substance group made up of
the 16 US EPA Priority Pollutant PAHs (or the subset of those for which data is available)
and reported as 'total' PAHs. This list of PAHs and CASR number is provided below.
- Acenaphthene (83-32-9)
- Anthracene (120-12-7)
- Acenaphthylene (83-32-9)
- Benz(a)anthracene (56-55-3)
- Benzo(a)pyrene (50-32-8)
- Benzo(b)fluoranthene (205-99-2)
- Benzo(ghi)perylene (191-24-2)
- Benzo(k)fluoranthene (207-08-9)
- Chrysene (218-01-9)
- Dibenz(ah)anthracene (53-70-3)
- Fluoranthene (206-44-0)
- Fluorene (86-73-7)
- Indeno(123-cd)pyrene (193-39-5)
- Naphthalene (91-20-3)
- Phenanthrene ((85-01-8)
- Pyrene (129-00-0)