General Overview
A lighting plant consists of the electrical distribution system and one or more light fixture systems. The electrical distribution system provides power to the light fixture system, which provides the actual illumination to indoor spaces, emergency evacuation routes, and outdoor areas. The electrical distribution system receives electricity from the power grid, which then is distributed through switchgear and panelboards. A lighting plant and associated systems are shown in Figure 1. Measurements may be taken at the electrical distribution or light fixture system levels.
Lighting Plant Systems and Components
Electrical Distribution System
The electrical distribution system is comprised of main and secondary switchgear and panelboards. The switchgear distributes electricity to the panelboards, and the panelboards provide electricity to the light fixture systems. Panelboards typically serve light fixture systems in multiple spaces across a facility and are generally broken down by floor or smaller spaces on a floor. Sometimes multiple electric panelboards are required to provide power to a single space such as a warehouse, gymnasium, or garage. Components of an electrical distribution system are shown in Figure 2.
Panelboards can have mixed loads or be dedicated just to lighting. Mixed panelboards serve the light fixture systems and other electrical loads such as receptacles, office equipment or miscellaneous plug loads. Dedicated panelboards exclusively serve light fixture systems including interior, exterior, and emergency lighting.
Light Fixture System
The light fixture system is comprised of the luminaires, lamps, and controls. Controls can be manual or automatic. All lighting systems have some form of manual controls such as wall switches within a space or electrical disconnects (circuit breakers) at the panelboard. Some lighting systems have automatic controls which may include a control panel and sensors. Components of a light fixture system are shown in Figure 3.
Evaluation of Energy Consumption
To quantify the energy consumption of the lighting plant, the components of all lighting systems should be measured. Some facilities may have a combination of the above-mentioned systems and a level of engineering judgement will be necessary to determine how much of what to measure.
|
Plant Quantification |
Values to be Quantified |
Energy Consuming Component |
|
Lighting plant electricity usage (kWh) |
Average hourly kWh served by the electrical distribution system |
Further Reading
- Richman, EE. (2016). “Measurement and Verification of Energy Savings and Performance from Advanced Lighting Control.” Richland, WA: Pacific Northwest National Laboratory.