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System or Luminaires

A luminaire is a complete lighting unit, comprised of a light source (lamp or lamps), together with the parts that distribute the light, position and protect the lamps, and connect the lamps to the power supply. Good luminaire can distribute light well, separate task lighting with ambient lighting, provide controllability, etc.  Choosing luminaires that efficiently provide appropriate luminance patterns for the application is an important part of energy efficient lighting design.  One of the main current and future research trend is innovation in luminaire to enhance the lighting experience and ensure design flexibilities in different functional requirements. The reflectivity of the material and the maintenance factor of luminaire is dependant on the material selection and robust design.

Luminaires Performance

A performance of a luminaire is significant for estimating the energy efficiency of the overall lighting system and design. It is defined in terms of light output ratio (LOR), i.e. the ratio of lumens emitted by the luminaire to lumens emitted by that luminaire’s lamps. The efficiency of a luminaire is subject to the lamp type, control gears, optical components, and material of reflective surface. High reflective surfaces have improved the LOR enabling the luminaire to transfer more than 70% of lamp output.

For an efficient design, LOR is considered along with the room index to estimate the co-efficient of utilization. The CU accounts not only for light losses within the luminaire, but also for the effects of room configuration and surface reflectance. Each lamp type and luminaire manufacturer have different co-efficient of utilization for their product. Better the ratio, lesser the number of luminaires required in a space to lit the area as per the desired lux level. Most general lighting luminaire manufacturers provide co-efficient of utilization data for different room index value for their respective luminaire product. In case where, the co-efficient of utilization ratio of less than 0.5, it is recommended to either upgrade the light source to more efficient lamps or use controls for indirect reduction of lighting capacity.

Luminaires come in variety of size, shapes and wattage, etc.

  1. Recessed Cove lighting fixture: It is mounted in a cove light & direct the light towards the wall.
  2. Indirect pendant lighting fixture: They hang from the ceiling and are usually suspended from cables. The lamp is completely hidden from below and a reflector directs all of the light up toward the ceiling.
  3. Direct/ indirect pendant lighting fixture: A direct / indirect pendant also hangs from the ceiling, but it directs light up and down. Mostly used in offices where general lighting is required, but there is also a need for task lighting immediately below the fixture.
  4. Recessed lighting fixture: used in commercial and institutional construction. Fixtures are sized to work with common ceiling tile sizes. LED’s should be used in these recessed light fixtures.
  5. Wall wash light fixture: They are recessed lights with reflectors that direct the light toward the wall. They are most often used to highlight art, signage, or other items on a wall.

Type of Luminaires

  1. Wall Sconce: Decorative fixture that is mounted to a wall. They provide general room lighting, but are mostly decorative.
  2. Task Lighting: Lights that are used to illuminate specific tasks or work that is being done. Task lights can be lamps, lights mounted to desks, under cabinet lights, or any lighting that helps people see their work better.
  3. Under Cabinet Lighting Fixture: Lights are often mounted below cabinets so that tasks on the counter below can be seen easily. These can be found in homes and offices and are generally controlled from a nearby switch or a switch on the light fixture.

The luminaire system consists of the luminaire itself along with its reflectors, lenses and housings, as well as the lamps and ballasts. System performance depends on how well all these components work together, as well as many other factors including room finishes, daylight contribution, room geometry, and task components.

  1. Lamps and lamp holders or sockets: Efficient luminaires use the most efficient sources appropriate for that luminaire type. Luminaires should be selected specifically to take advantage of the source’s unique features, particularly with respect to size and thermal performance.
  2. Ballasts to start and operate the lamp
  3. Reflectors to direct the light: Appropriate use of reflector materials (specular or diffuse) will maximize luminaire efficiency while maintaining the desired light distribution.
  4. Shielding/diffusion components (lens, diffuser, louver, or the like) to shield the lamps from the eyes at normal viewing angles, reduce discomfort and disability glare, and to distribute light evenly
  5. Housings to contain the above elements as well as electrical components, such as wiring connections

An efficient luminaire optimizes the system performance of each of its components.

Ballast
Regulated current to a lamp is a key component of any lighting system. Ballast is used in lighting technologies to ensure regulated current. Many types of ballasts are available in the market. The selection of ballast type should be done considering the functional requirement of light source and the efficiency of the ballast itself. Two of the commonly used ballast types are electro-magnetic ballast and magnetic ballast.

Key advantages of electronic ballast:

  • Operates at high frequency of AC voltage and eliminates the flicker and noticeable hum
  • Light weight and reduced heat load
  • Energy efficient products saving 20 – 30 % of energy compared to other ballasts
  • Could be easily connected to controls

Key disadvantages of electronic ballast:

  • Difficult to recycle compared to electro-magnetic ballast
  • Shorter life compared to electro-magnetic ballast

Key advantages of electro – magnetic ballast:

  • Very robust
  • Longer life time
  • Easy to recycle

Key disadvantages of electro – magnetic ballast:

  • Operated at lower frequency of AC voltage resulting in flicker and noticeable hum
  • Higher heat load
  • Energy intensive products
  • They can give off excessive electro – magnetic fields

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