Daylight in buildings can save energy if the electric lighting is switched or dimmed in response to changes in daylight levels.
The company in this example operates three warehouses with offices and a green house in California. An energy survey was performed on-site to collect nameplate and operational data for the lighting systems, and to identify potential energy efficiency measures.
On the audited campus only two buildings have equally laid out skylights installed. Warehouse A has some skylights in the center of the building. They all would be able to utilize daylight, especially adding the harvested daylight in the door areas of the buildings. During the audit we also heard the comment that sometimes some of the light circuits in warehouse B are not switched off over night although nobody had worked.
Figure 1: Skylights
Automatic lighting controls (ALC) increase the probability that day lighting will save energy. ALC enable the client to cut lighting energy costs from 40% to as much as 70% or more. These savings are achieved through integration of multiple lighting control strategies, including scheduling, day-lighting, occupancy sensing and personal control. Smart strategies ensure optimal operation while maximizing savings and occupant comfort.
Occupancy sensors can be integrated into the ALC to turn lights on when an area is occupied and off when it is empty. In addition, glare and contrast must be controlled so occupants are comfortable and will not override electric lighting controls.
We recommend installing an ALC at warehouse B as this building has different departments with different schedules and therefore we think that a smart light control strategy (figure 2) will reduce the energy consumption and lower the peak load level.
Figure 2: Automatic lighting controls
Costs and Assumptions
We assumed that all existing fixtures are staying in place with the same wattage and that the lights are on during the night for about 30% of the year. We have not calculated any benefits from daylight harvesting nor from reducing the peak demand by either switching off or dimming lights. We anticipate that savings will be higher than projected as peak-day pricing from PG&E will be introduced for all customers in 2011.
Demand response (DR) can be a strategy to reduce costs, but can also be a complex operational issue when considering integrating your lighting with the utility grid structure. New technologies tap into demand response for dramatic benefits to control lighting loads during periods of peak demand. Participation in demand response programs sponsored by local utilities reduces peak energy use and the electrical burden on the
Costs were estimated and have to be verified. The potential incentive was based on the PG&E program “Incentives for business energy efficiency retrofit projects” for Lighting.