Category Archives: geek

What’s a Watt

A Watt (W) is the unit of power of equal to one joule of energy per second.

In terms of electromagnetism, one watt is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt (V), ie. W = V * A. If your computer monitor is plugged to the mains at 240 V and it requires 1.5 A, the power it spends is 240 V * 1.5 A = 360 W

A laborer over the course of an 8-hour day can sustain an average output of about 75 watts. In terms of sports biomechanics, mass times acceleration due to gravity times height divided by the time it takes to lift the object to the given height gives the rate of doing work or power. A human climbing stairs needs 200 watts of power.

The best non-doping cyclists in history could deliver almost three times as much power:

Miguel Indurain Bernard Hinault Eddy Merckx Jaques Anquetil
Tour de France Winning Years 1991-95 1978-79,81-82,85 1969-72,74 1957,61-64
RacingWeight (kg) 79 68 75 68
Height (cm) 187 173 183 174
Resting Heart Rate 28 bpm 38 bpm 44 bpm 45 bpm
Maximum Heart Rate 195 bpm 170 bpm 162 bpm 180 bpm
Lung Capacity 7.8 litres 7.2 litres 6.9 litres 6.9 litres
Power Output 550 Watts 450 Watts 500 Watts 400 Watts

A car engine produces 25,000 watts (approximately 33.5 horsepower) while cruising.

The net capacities of average nuclear power plants range between about 500 and 1300 MW (106 W).

Real-time monitoring of the demand of electricity in Spain
Source: REE Spain

The largest offshore wind farm in Germany, Innogy Nordsee 1, will have a combined capacity of 960 MW (106 W) to be delivered by 150-180 wind turbines. Spain had an installed capacity of wind power of 16 GW (109 W) in 2008 (source: REE). In 2012 wind power was, for the first time ever, the source that contributed most to the annual electricity demand coverage with a share of 21.1%. This compares with nuclear which contributed 21%.