Sustainable Energy - Without the Hot Air

http://www.ck12.org Chapter 5. Useful Data

5.1 Quick reference

SI Units

The watt.This SI unit is named after James Watt. As for all SI units whose names are derived from the proper name
of a person, the first letter of its symbol is uppercase (W). But when an SI unit is spelled out, it should always be
written in lowercase (watt), with the exception of the “degree Celsius.”

from wikipedia

SI stands for Système Internationale. SI units are the ones that all engineers should use, to avoid losing spacecraft.

TABLE5.1:

SI units

energy one joule 1J

power one watt 1W

force one newton 1N

length one metre 1m

time one second 1s

temperature one kelvin 1K

TABLE5.2:

prefix kilo mega giga tera peta exa

symbol k M G T P E

factor 103 106 109 1012 1015 1018

TABLE5.3:

prefix centi milli micro nano pico femto

symbol c m μ n p f

factor 10 −^210 −^310 −^610 −^910 −^1210 −^15

SI units and prefixes

My preferred units for energy, power, and transport efficiencies

TABLE5.4:

My preferred units, ex-

pressed in SI

energy one kilowatt-hour 1 kWh 3600000 J

power one kilowatt-hour per day 1 kWh/d

( 1000

24

)

W' 40 W

force one kilowatt-hour per 100

km

1 kWh/100 km 36N

time one hour 1h 3600s

one day 1d 24 × 3600 s' 105 s

one year 1y 365. 25 × 24 × 3600 s '

π× 107 s