|Thing measured||unit name||symbol||value|
|mass||ton||t||1 t = 1000 kg|
|gigaton||Gt||1 Gt = 109 × 1000 kg = 1 Pg|
|volume||litre||l||1 l = 0.001 m3|
|area||square kilometre||sq km, km2||1 sq km = 106 m2|
|hectare||ha||1 ha = 104 m2|
|Wales||1 Wales = 21 000 km2|
|London (Greater London)||1 London = 1580 km2|
|energy||Dinorwig||1 Dinorwig = 9 GWh|
Throughout this book “a billion” (1 bn) means a standard American billion,
that is, 109, or a thousand million. A trillion is 1012. The standard prefix
meaning “billion” (109) is “giga.”
In continental Europe, the abbreviations Mio and Mrd denote a million
and billion respectively. Mrd is short for milliard, which means 109.
The abbreviation m is often used to mean million, but this abbreviation
is incompatible with the SI – think of mg (milligram) for example. So I
don’t use m to mean million. Where some people use m, I replace it by M.
For example, I use Mtoe for million tons of oil equivalent, and MtCO2 for
million tons of CO2.
There’s a whole bunch of commonly used units that are annoying for various
reasons. I’ve figured out what some of them mean. I list them here,
to help you translate the media stories you read.
The “home” is commonly used when describing the power of renewable
facilities. For example, “The £300 million Whitelee wind farm’s 140 turbines
will generate 322 MW – enough to power 200 000 homes.” The
“home” is defined by the BritishWind Energy Association to be a power of
4700 kWh per year [www.bwea.com/ukwed/operational.asp]. That’s 0.54 kW,
or 13 kWh per day. (A few other organizations use 4000 kWh/y per household.)
The “home” annoys me because I worry that people confuse it with the
total power consumption of the occupants of a home – but the latter is actually