Lighting accounts for nearly 20% of the total electricity costs of commercial buildings in the United States. By consuming a significant amount of a building’s total electricity consumption and further influencing overall energy demand by the waste heat it emits, lighting is a primary focus for achieving significant energy reductions, and should therefore be prioritised as a focus area for sustainable energy initiatives, writes Mrigank Warrier, Assistant Editor, Clean India Journal.
All lighting systems experience a decrease in light output and efficiency over time, because:
- Lamp light output decreases (lamp lumen depreciation).
- Dirt accumulates on fixtures (luminaire dirt depreciation).
- Lamps burn out.
- Control systems drift out of spec or are overridden by occupants.
Pacific Northwest National Laboratory (PNNL) evaluated an LED replacement lamp that uses the same four-pin socket and electronic ballast as an incumbent CFL. Results showed energy savings between 40-50%, matching light levels and quality and payback under 3 years.
A survey of 245 buildings in the 2011 National Building Competition found that 30% of savings can be made in just one year.
Occupancy sensors can save 15% to 20% on lighting energy costs.
A lighting upgrade at a postal sorting facility in Reno, Nevada led to a 6% increase in worker output and a reduction in sorting errors.
Limit the use of accent lighting. Couple necessary accent lighting applications with lighting controls to ensure highlighted objects are illuminated or illuminated at full power only when occupants are nearby.
Reduce electrical lighting consumption and associated waste heat by pairing harvested daylight with automated dimmers and photosensors.
High efficiency LEDs use less energy, have significantly longer lamp life, and provide better light quality than fluorescent alternatives. Replace low-efficiency lighting technologies (incandescent, fluorescent, etc.) with higher efficiency, longer lasting LEDs.
When replacing fluorescent tubes with LEDs, consider replacing the entire fixture to maximise energy efficiency, product life, and to ensure safety. When retrofitting LED tubes in fluorescent fixtures, use an LED tube with an integrated driver to avoid incompatibilities with the fixture that could shorten the product life or deliver unsuitable light quality.
Role of occupancy sensors
Limit internal “night lighting” by utilizing occupancy sensors (currently allowed by safety codes) during off-peak hours.
Occupancy sensors should be considered for all spaces that are potentially often vacant, such as conference rooms, storage spaces, restrooms, lunch/break rooms and enclosed offices. Spaces used in common by tenants or visitors are primary candidates for occupancy sensors.
Manual overrides are an important feature for these sensors, as employees may wish to turn off the lights for presentations or to use daylight. Dimmers specifically designed for fluorescent or LED lighting are available and can add controllability for occupant comfort and energy savings.