| Lighting is an element of our home and work
environment that affects our life in many different ways.
Lighting lets us see to carry out the daily tasks of life; it
affects our comfort and mood, and it can provide safety and
security. Lighting and lighting fixtures also play a major role
in the interior decoration of our homes.
Our consumption of electricity related to lighting also
affects our budgets, both at home and in our workplaces. The
Department of Energy reports that we spend, on average, 5-10% of
our electric bills on lighting in our homes. In some regions of
the U.S. this amount can be as high as 25% where
air-conditioning is a modest portion of the bill.
As a point of beginning, let's look at some basic concepts
that will help us to better understand how these savings can be
achieved.
Energy Efficiency with Lighting
Saving lighting energy requires either reducing electricity
consumed by the light bulbs and light fixtures or reducing the
length of time that the lights are on. This can be accomplished
by:
- Reducing the amount of time that lights are on. This can
be accomplished by using dimmers and other lighting
controls, and educating family members to turn off unneeded
lights.
- Lowering wattage, which involves replacing bulbs or
entire fixtures with bulbs and fixtures that provide the
same amount or greater amounts of light with but with
reduced electricity usage. Today, this can be accomplished
most easily by replacing inefficient incandescent bulbs with
incandescent/halogen bulbs or compact fluorescent bulbs.
Making the appropriate lamp selection
A "lamp" is the term used in the lighting industry to
describe what is most commonly called a light bulb. The key to
lighting energy savings lies in the choice of lamp that we use.
There are three primary families of lamps, or bulbs:
- Incandescent
- Fluorescent
- High Intensity Discharge
Incandescent lamps have historically been the most frequently
used in residential applications due to their low initial cost.
Incandescent sources, however, are relatively inefficient in
their conversion of electrical energy to visible light and can
therefore add unnecessary electrical costs to our electric
bills.
Fluorescent and High Intensity Discharge lamps have been used
most often in commercial and industrial applications. Their
initial cost is more than incandescent lamps, but they are much
more energy-efficient and last significantly longer.
Due to major improvements over the last few years in the
color rendering abilities of fluorescent lamps, and the
availability of small fluorescent bulbs called "compact
fluorescent lamps" or "CFL's", fluorescent lamps are now a very
viable alternative to incandescent lamps for home lighting use.
As an example, for the same amount of electrical energy, compact
fluorescent bulbs produce 3-4 times more light than an
incandescent bulb.
Incandescent Options
Incandescent lamps are the least expensive to buy but the
most expensive to operate. Incandescent lamps also have the
shortest lives of the common lighting types. They are also
relatively inefficient compared with other lighting types.
The three most common types of incandescent lamps are
- standard incandescent
- tungsten halogen
- reflector lamps.
Standard incandescent
Known as the "A-type light bulb," these lamps are the most
common yet the most inefficient light source available. Note
that a larger wattage lamp or bulb may not be the most energy-
or cost-effective option, depending on how much light is needed.
"Long- life" bulbs, with thicker filaments, are a variation of
these A-type bulbs. Although long-life bulbs last longer than
their regular counterparts, they are less energy efficient. The
best option to achieve energy-efficiency is to replace "A" lamps
with compact fluorescent lamps, which will be discussed below.
Tungsten halogen
This newer type of incandescent lighting achieves better energy
efficiency than the standard A-type bulb. These lamps are more
expensive than standard incandescents but can have significant
impact on achieving greater light output than standard
incandescent lamps.
Reflector lamps and Parabolic Aluminized Reflector lamps
Reflector lamps (Type BR) are designed to spread light over
specific areas and are used mostly in recessed downlight
fixtures.
Parabolic aluminized reflectors (Type PAR) are an excellent
replacement for the BR lamps. They have a specially designed
reflector that is highly efficient in pushing light into the
space.
Fluorescent
Fluorescent lighting is used mainly indoors both for
general/ambient lighting and task lighting and is about 3 to 4
times as efficient as incandescent lighting. Fluorescent lamps
last about 10 times longer than incandescents. To gain the most
efficiency, you should install fluorescents in places where they
will be on for several hours at a time.
You can also increase the energy savings for existing
fluorescent lighting by replacing them with a more efficient
model (providing a lower wattage but approximately the same
light output), or by replacing the existing fixture with a more
efficient model.
Compact fluorescent
Compact fluorescent lamps (CFLs) are the most significant
lighting advance developed for homes in recent years. They
combine the efficiency of fluorescent lighting with the
convenience and popularity of incandescent fixtures.
CFLs can replace incandescents that are roughly three to four
times their wattage, saving up to 75% of the initial lighting
energy. Although CFLs cost from 10 to 15 times more than
comparable incandescent bulbs, they also last 10 to 15 times as
long. This energy savings and superior longevity make compact
fluorescent lamps an excellent choice for residential use.
As previously discussed, CFLs are one of the best energy
efficiency investments available. When introduced in the early-
to mid-1980s, CFLs were bulky, heavy, and too big for many
incandescent fixtures. However, newer models with lighter
electronic ballasts are only slightly larger than the
incandescent lamps they replace. The new CFLs also produce a
better color for the home.
CFLs come in integral and modular designs. Integral CFLs have
a ballast and a lamp in a single disposable unit. Modular
designs feature a separate ballast that serves about five lamp
replacements before it wears out.
High-Intensity Discharge
High-intensity discharge (HID) lamps provide the highest
effectiveness and longest service life of any lighting type.
They are commonly used for outdoor and street lighting, but have
very limited applications in homes. Their residential use is
limited to outdoor lighting for driveways, backyards, etc.
Replacing Lamps and Fixtures
"Relamping" means substituting one light bulb for another to
save energy. You can decide to make illumination higher or lower
when relamping. But be sure that the new bulbŐs light output
fits the tasks performed in the space and conforms to the
fixture's specifications.
Matching replacement bulbs to existing fixtures and ballasts
can be challenging, especially with older fixtures. Buying new
fixtures made for new lamps produces superior energy savings,
reliability, and longevity compared with relamping.
Energy-Efficiency with Lighting Controls
Lighting controls are devices for turning lights on and off
or for dimming them. The most useful controls for increasing
lighting energy-efficiency in a home are dimmers, photocells,
and occupancy sensors.
- Dimmers reduce the wattage and output of incandescent
and fluorescent lamps and significantly increase the service
life of incandescent lamps. Dimming fluorescents requires
special dimming ballasts and fixtures, but does not reduce
their efficiency.
- Photocells turn lights on and off in response to natural
light levels. Photocells switch outdoor lights on at dusk
and off at dawn, for example.
- Occupancy sensors activate lights when a person is in
the area and then turn off the lights after the person has
left. They are popular for areas such as closets and
recreation rooms.
Energy-Efficiency with Ceiling Fans
Although ceiling fans cannot contribute directly to savings
on lighting energy costs, but they can contribute significantly
to savings on electrical costs associated with space heating and
cooling. Household electrical costs associated with space
heating and cooling are in the range of 35-45%. Using a ceiling
fan can help to cool our homes in summer, and helps to more
efficiently distribute heated air in winter.
Although it's difficult to place an exact savings amount
related to the use of ceiling fans, it's an established fact
that ceiling fans can help to reduce electrical costs by
creating greater efficiency in how we heat and cool our home
environments. Especially in summer, it's often more comfortable
to turn off the air-conditioner at night, and use a ceiling fan
at low speed in the bedroom.
Appoint a Household Energy Monitor
To educate your family members on the importance of energy
conservation, appoint a Household Energy Monitor to turn off
lights, set the thermostat, and to keep the windows/doors closed
if the air conditioning or heater is on. Rotate the position so
that all family members share in the responsibility. For the
energy and money your family saves, have a family outing while
knowing that your family is contributing to energy conservation.
Lighting and Electricity Concepts
Wattage, Lumens and Efficacy
Wattage is a measurement of the electrical energy used by an
electrical device, such as a light bulb, but it is not a
measurement of the amount of light being produced. The
measurement of light output from a lamp is the lumen. All light
bulbs have a lumen rating, and it is the relationship between
the lumens being produced and the wattage being consumed that
can provide us valuable information about the energy-efficiency
of a light bulb.
Efficacy
The relationship between lumens and wattage is called
efficacy. This is the ratio of light output from a lamp to
the electric power it consumes and is measured in lumens per
watt (LPW).
Incandescent lamps have an efficacy range from 15 lpw to
slightly over 20 lpw. Fluorescent lamps have an efficacy range
from 60 lpw to almost 100 lpw. As you can see from these
numbers, the choice of light bulb can have a significant impact
on electrical energy consumption. |
