Energy Flows

The SI unit for power – the rate of flow of energy – is the watt. Around 174 petawatts (174,000 terawatts) comes in from the sun, and – plus or minus the rate of energy release from or addition to reserves of one kind or another – goes back into space, three-quarters of it as low-grade heat. The world economy, mostly by drawing down fossil reserves, draws 15 TW (0.015 PW).* Around half this is converted to 2 TW of electrical power and distributed by the grid.

Table from Wikipedia entry for International System of Units

Standard prefixes for the SI units of measure
Multiples Name deca- hecto- kilo- mega- giga- tera- peta- exa- zetta- yotta-
Symbol da h k M G T P E Z Y
Factor 100 101 102 103 106 109 1012 1015 1018 1021 1024
Fractions Name deci- centi- milli- micro- nano- pico- femto- atto- zepto- yocto-
Symbol d c m μ n p f a z y
Factor 100 10−1 10−2 10−3 10−6 10−9 10−12 10−15 10−18 10−21 10−24

*Demand is expected to double to 30 TW by 2050. Satisfying this increase in demand with some combination of nuclear and renewable energy sources will be a challenge. Check the numbers here.


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