10 February 2006

Visualising energy consumption

suppose your kitchen faucet
were dripping gasoline

each 0.1 milliliter drip
containing enough energy
to heat a quart of water
one degree Fahrenheit
or (theoretically)
to power a one-watt device
for one hour

so a 100-watt lightbulb
consumes the equivalent
of 100 drips per hour
(one slow drip
every 36 seconds)

a solar panel
to produce 1 watt continuous
(one drip per hour)
can be as small as a 3*5 card
(3*5 feet for 144 watts, then)

a hand crank generator
can do 10-50 drips per hour
a bikepedal generator 100-200

the same gallon of gas
that propels your car some dozen miles
(with 20% mechanical efficiency)
or a 747 just 1000 ft
is 45,000 drips
(200 drips for a penny)
or 45 kilowatt-hour equivalents
19 days of 100W light

19 days of every-36-seconds drips
to fill a gallon can
5 cents per 1000 drips of gasoline
5 cents per kilowatt-hour of gasoline

in the USA a kilowatt-hour of electricity
costs about ten cents
or $4.50 for the energy equivalent
of that $2.25 gallon of gas

or $3 for 1.5 gallons of butane

or $2 for 125 cubic feet of natural gas

or $1 for 30 pounds of firewood

or 50 cents for 15 pounds of dirty black coal

or 25 cents for 5 milligrams of nuclear fuel

that gallon of gasoline
applied to heating water
would raise the temperature
of 250 gallons (ten showers worth)
by 50 degrees Fahrenheit

4 drips per degree per gallon
45 cents per electrically-heated shower

fuel cells aim to achieve
40% efficiency
converting methanol to electricity
but methanol has half the energy of gasoline
so a 500-drop fuelcell reservoir
may deliver 100-drops of gasoline-equivalent
powering a 10-watt device
for 10 hours

(butane lighters' reservoirs
by comparison
holding less than 50 drops)

an AA battery delivers
just 4 'drops' total
an AAA just 2
a 9v 5
9v lithium 10
a C 12
a D 24

a button-sized nickel-cadmium cell, 1 drip
a nickel-metal-hydride cell 2
laptop batteries 50-100
car-batteries 1000

in many 120V appliances
'drips' about once per hour

battery chargers
drip faster than this
wasting more drips than they recharge

a computer system drawing 300W
drips every 12 seconds
as would, on average
an electric hot water heater

a refrigerator maybe every 30 seconds