Department of Defense Energy Manager’s Handbook phần 5 pps

• Fluorescent Lamps are the predominant type used in commercial

and industrial spaces in the U.S. They are relatively efficient,

have long lamp lives, and are available in a variety of styles. The

four foot T-12 lamp is the most common fluorescent lamp used in

offices today, but they are being rapidly replaced by T-10 and T-8

lamps. Energy efficient T-8 lamps are more expensive than the T￾12 lamps, however they provide 98% as much light and use about

40% less energy when installed with an electronic ballast.

• Electronic Ballasts - When replacing standard fluorescents with

the more energy efficient T-8s, it is necessary to replace the

existing electromagnetic ballasts with the electronic ballasts,

which operate at higher frequencies and convert power to light

more efficiently. Energy saving electromagnetic ballasts can cut

fluorescent lighting energy consumption by as much as 10%. The

life of these ballasts is approximately twice that of their

conventional counterparts.

• High Intensity Discharge (HID) refers to lighting provided by

mercury vapor, metal halide, and high-pressure sodium lamps.

Although originally designed for outdoor and industrial uses,

HIDs are also used in offices and other indoor application. The

principal advantage of mercury vapor HID lamps is their long life,

although they are only slightly more efficient than incandescent

lamps.

• Reflectors – Highly polished retrofit reflectors are being marketed

for use with existing luminaries (light fixtures) and can achieve a

50% reduction per fixture. Installing reflectors in most luminaries

can improve its efficiency because light leaving the lamp is more

likely to reflect off interior walls and exit the luminaire. Although

the luminaire efficiency is improved, the overall light output from

each is likely to be reduced, which will result in reduced light

levels. To ensure acceptable performance from reflectors,

measure “before” and “after” light levels at various locations in

the room to determine adequacy.

• Lighting Controls – Maximum energy efficiency cannot be

achieved without effective controls. Modern lighting controls

provide benefits ranging from energy savings and electrical

demand, to better support of the functions from which the lighting

is needed. Manual controls should be used in spaces that

accommodate different tasks or that have access to daylight.

Occupants should be encouraged to shut lights off when they are

not needed. Automatic controls such as occupancy sensors are

available for turning off lights in unoccupied areas, while auto￾dimming controls adjust light levels to existing daylight.

Scheduling controls activate, extinguish, or adjust according to a

predetermined schedule.

• LED Lighting - Light Emitting Diodes (LEDs) is one of today’s

fastest evolving lighting technologies. LED light sources are

more efficient than incandescent and most halogen light sources.

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White LEDS today can deliver more than 20 lumens per Watt,

and are predicted to achieve greater than 50 lumens per Watt by

2005. Other inherent features of LEDs include very low power

consumption and virtually no heating effect, making it ideal for a

wide range of new and existing applications. Due to the decrease

in energy used for the lighting of a building, air handling costs

drop, generating both additional initial and ongoing investment

savings. Another advantage of LEDs over conventional lighting

is that light emitted from an LED is directional. Incandescent,

halogen, or fluorescent lights are omni directional, emitting light

in all directions. Lighting must be redirected using secondary

optics or reflectors. Each time a light beam is reflected it looses

some of its intensity, resulting in fixture losses typically from 40

to 60%. The directed nature of LEDs can result in fixture

efficiencies of 80 to 90%, requiring less total lumens to provide

the same level of illuminance.

11.4.5. Office Equipment and Plug Load

Office equipment or plug load consists of the computers, monitors,

printers, photocopiers, facsimile machines, televisions, refrigerators,

vending machines -- virtually any equipment that gets "plugged in" to

electrical receptacles in the space. Energy efficient office equipment

provides equivalent or better performance than standard equipment to

users but using significantly less energy. Energy use in the office has

increased significantly in recent years due to rapid growth of

microcomputer use. This has led to a corresponding increase in

energy required to operate this equipment and associated loads on

heating, ventilation, and air conditioning systems. Federal guidelines

have been established to promote energy efficiency in the acquisition,

management, and use of microcomputers and associated equipment.

Plug load power density in watts per square foot may exceed the

lighting UPD in some areas of the facility. It is essential to make sure

that plug load energy is not ignored. The Energy Manager should

inventory major equipment, noting wattage where available. If

wattage is estimated from nameplate voltage and current, multiply by

0.3 for an estimate of actual average operating power. Primarily look

for ways to reduce operating hours of existing equipment and to

influence customer selection of properly sized energy-efficient

equipment in the future.

The ENERGY STAR® program, established by EPA in 1992 for

energy efficient computers, provides on its web page, a list of

products meeting its strict criteria for energy efficiency and other

environmental benefits. Also consider the following in attempting to

manage office equipment and plug load:

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