The brightest domestic light bulbs use 250W, and bedside lamps use 40W.

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The brightest domestic light bulbs use 250W, and
bedside lamps use 40W. In an old-fashioned
incandescent bulb, most of this power gets turned
into heat, rather than light. A fluorescent
tube can produce an equal amount of light using
one quarter of the power of an incandescent bulb.
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How much power does a moderately affluent person
use for lighting? My rough estimate, based on
table 9.2, is that a typical two-person home with
a mix of low-energy and high-energy bulbs uses
about 5.5 kWh per day, or 2.7 kWh per day per
person. I assume that each person also has a
workplace where they share similar illumination
with their colleagues guessing that the
workplace uses 1.3 kWh/d per person Adding up we
get a round figure of 4 kWh/d per person.
Table 9.2. Electric consumption for domestic
lighting.
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Street-lights and traffic lights Public
lighting? Street-lights in fact use about 0.1
kWh per day per person, and traffic lights only
0.005 kWh/d per person both negligible What
about illuminated signs and bollards? There are
fewer of them than street-lights and
street-lights already came in well under our
radar, so we dont need to modify our overall
estimate of 4 kWh/d per person.
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• Vehicle lights on for traffic safety
• Do drivers have to use lights when driving all
  the time?
• compare with power used in moving the car
• assume 4 x 25 100 W bulbs
• electricity from a 25-efficient engine powering
  a 55-efficient generator, so the power required
  is 730W.
• A typical car going at 50 km/h consumes 1 liter
  per 12 km with an average power of 42 kW so
  additional lights are (730 x 100/42000) 2
• Electric cars?
• power consumption is 5 kW, so additional 100 W
  is again only (100 x 100/5000) 2.
• we can switch to LEDS for lower power.

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The economics of low-energy bulbs Generally I
avoid discussing economics, but Id like to make
an exception for lightbulbs. Osrams 20W
low-energy bulb claims the same light output as a
100W incandescent bulb. Moreover, its lifetime
is said to be 15 000 hours (or 12 years, at 3
hours per day). In contrast a typical
incandescent bulb might last 1000 hours. So
during a 12-year period, you have this choice
(figure 9.3) buy 15 incandescent bulbs and 1500
kWh of electricity (which costs roughly 150) or
buy one low-energy bulb and 300 kWh of
electricity (which costs roughly 30).
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Should I wait until the old bulb dies before
replacing it? It feels like a waste, doesnt it?
Someone put resources into making the old
incandescent light bulb shouldnt we cash in
that original investment by using the bulb until
its worn out? But the economic answer is
clear continuing to use an old light bulb is
throwing good money after bad. If you can find
a satisfactory low-energy replacement, ?
replace the old bulb now.
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What about the mercury in compact fluorescent
lights? Are LED bulbs better than
fluorescents? Will LED (light-emitting diode)
bulbs soon be more energy-efficient than
fluorescent lights?

• efficiency means lumens per watt (W)
• the Philips Genie 11W compact fluorescent bulb
  (figure 9.4) has a brightness of 600 lumens,
  which is an efficiency of 55 lumens per watt
• regular incandescent bulbs deliver 10 lumens per
  watt
• the Omicron 1.3W lamp, which has 20 white LEDs
  hiding inside it, has a brightnessof 46 lumens,
  which is an efficiency of 35 lumens per watt
• So this LED bulb is almost as efficient as the
  fluorescent bulb.
• But the LED bulb has a life of 50 000 hours, 8 x
  the life of the fluorescent bulb.

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Do CFLs contain mercury? CFLs contain a very
small amount of mercury sealed within the glass
tubing an average of 4 milligrams. By
comparison, older thermometers contain about 500
milligrams of mercury an amount equal to the
mercury in 125 CFLs. Mercury is an essential
part of CFLs it allows the bulb to be an
efficient light source. No mercury is released
when the bulbs are intact (not broken) or in use.
Most makers of light bulbs have reduced mercury
in their fluorescent lighting products. Thanks
to technology advances and a commitment from
members of the National Electrical Manufacturers
Association, the average mercury content in CFLs
has dropped at least 20 percent in the past year.
Some manufacturers have even made further
reductions, dropping mercury content to 1.4 2.5
milligrams per light bulb.
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How do CFLs result in less mercury in the
environment compared to traditional light bulbs?
Electricity use is the main source of mercury
emissions in the U.S. CFLs use less electricity
than incandescent lights, meaning CFLs reduce the
amount of mercury into the environment. As
shown in the table below, a 13-watt,
8,000-rated-hour-life CFL (60-watt equivalent a
common light bulb type) will save 376 kWh over
its lifetime, thus avoiding 4.5 mg of mercury.
If the bulb goes to a landfill, overall
emissions savings would drop a little, to 4.0 mg.
EPA recommends that CFLs are recycled where
possible, to maximize mercury savings.
Type Watts Hours of Use kWh Use Mercury
Mercury Landfill Total (mg/kWh) used (mg)
(mg) (mg) CFL 13 8,000
104 0.012 1.2 0.6 1.8 Incand. 60 8,000
480 0.012 5.8 0 5.8
http//www.energystar.gov/ia/partners/promotions/c
hange_light/downloads/Fact_Sheet_Mercury.pdf
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Outdoor lighting is very popular in the
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Example Staples Center in LA The solar
development guide co-authored by NRDC and BEF
leverages the examples set by the STAPLES Center
in Los Angeles and US Airways Center data in
Phoenix, two leading arenas already taking
advantage of solar panels.
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The article goes on to say If all all what
does this mean? arenas and stadiums had solar
installation equal to the STAPLES Center, they
would Reduce carbon emissions by
approximately 86.6 million lbs/yr, comparable to
taking 8,340 cars off the road Create enough
electricity to power roughly 4,812 American homes
for a year Save the equivalent of 33,970
barrels of crude oil per year.
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This is what MacKay refers to on p.
329 Annoying units Theres a whole bunch of
commonly used units that are annoying for various
reasons. Ive figured out what some of them mean.
I list them here, to help you translate the media
stories you read.
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Homes The home is commonly used when
describing the power of renewable facilities.
For example, The 300million Whitelee wind
farms 140 turbines will generate 322MW enough
to power 200 000 homes. 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 about 24 times
bigger. The home covers the average domestic
electricity consumption of a household, only.
Not the households home heating. Nor their
workplace. Nor their transport. Nor all the
energy-consuming things that society does for
them.
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Cars taken off the road Some advertisements
describe reductions in CO2 pollution in terms of
the equivalent number of cars taken off the
road. For example, Richard Branson says that
if Virgin Trains Voyager fleet switched to 20
biodiesel . then there would be a reduction of
34 500 tons of CO2 per year, which is
equivalent to 23 000 cars taken off the road.
This statement reveals the exchange rate one
car taken off the road ?? -1.5 tons per year of
CO2.
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Solar Thermal The benefits of solar are not
limited to hot and dry geographies such as
Southern California and the Southwestern U.S. 
The Boston Red Sox have installed 28 solar
panels at Fenway Park which currently generate
37 of the electricity used to heat water in the
park.  The stadium, built in 1912, is a great
example of how solar power can augment any
facility regardless of age or climate. Panels are
also being used in Pittsburgh, Seattle, and
Cleveland.
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Solar PV Nuremberg Soccer Stadium - It wouldnt
be a Top Solar list without Germany getting in on
the action. In 2006, the Nuremberg Soccer Stadium
was equipped with 140 kW of solar power by
Siemens. The company needed just three weeks to
install the system on over 1,000 square meters of
stadium roof space.