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34 5.1 Current and Alternative Operation Practices Luminaires with low power consumption can reduce operating costs. Also, the control meth- odologies available with the new light sources, LEDs in particular, create opportunities to imple- ment lighting systems that are able to be dimmed and adapted to the needs of the users of the space. The Energy Technology Assistance Program (ETAP) investigates bi-level lighting retrofits in parking lots and garages for energy-use optimization based on the occupancy of the parking lot or garage. The program also provides technical assistance and cash rebates. Using energy- efficient luminaires and implementing adaptive lighting, energy usage can be reduced by 20% to 70% (ETAP, 2011). 5.2 Luminaire Selection One way to save energy and minimize costs is to replace existing light fixtures with energy- efficient, high-performance fixtures, including LED, IFL, and FL. 5.3 Light-Triggered Adaptation One approach to save energy is to control some of the luminaires with a dusk-to-dawn plug- in sensor. This is an established technology that works with all luminaires. These sensors, which are usually standardized, simply turn on the luminaire when the illuminance drops below a preset value, and turns off the luminaire when the illuminance exceeds a certain preset value. They require no connection to time-of-day or other control circuits. Based on current building design practices, there is usually significant lighting provided by sunlight in the first one or two bays from the outside of the garage, but this is highly dependent upon siting and design of the overhangs, knee walls, openings, and ceiling height, so a sunlight survey is required. 5.4 Usage-Driven Adaptation 5.4.1 Volume Peaks When adopting usage-driven adaptive lighting, energy consumption is associated with the level of activity in the parking garage. Airport garages do not have the same pattern of user vol- ume as other parking garages, because flights arrive and depart during a longer time span than typical business and retail hours. Although airports differ from each other in operating hours, most flights operate between 5 a.m. and 12 a.m., so in many airports, there is a low-volume window of four to five hours where lighting could be reduced. Also, while airport garages see C H A P T E R 5 Lighting Operation Options
Lighting Operation Options 35 significant vehicular occupation and traffic most hours of the day, in large, long-term parking garages, the usage of individual bays and drive lanes can be quite low. Establishing a particular airportâs hours of operation, flight schedule, and traffic patterns, and performing a cost-benefit analysis, would help determine if usage-driven adaptive lighting is the best approach for a particular airport garageâs lighting design. 5.4.2 On/Off Adaptive Lighting Luminaires can be turned on when vehicles and pedestrians are present, and off when they are not. Since there is a move to provide patrons with better information about the location of available spaces, there may be some synergy where the occupancy sensors can also trigger the lighting. Another low-complexity approach uses local motion-detection sensors and timers. When vehicles pass, and for a certain time after they pass, the luminaires would be turned on. At other times, they would be turned off. On/off adaptive systems require luminaires that can be rapidly power cycled without signifi- cantly reducing the lamp life. Those include fluorescent and inductive fluorescent lamps, LEDs, and OLEDs. 5.4.3 Bi- and Multi-Level Adaptive Lighting On/off is not the only adaptive lighting approachâfor those luminaires that can be dimmed, bi- and multi-level adaptive lighting approaches are also possible. MH lamps can be dimmed, and LEDs and OLEDs can be both rapidly turned on and off and dimmed. OLEDs can be pro- hibitively expensive, LEDs less so, and both can be dimmed nearly infinitely. Most LED lumi- naires are designed for dimming, and are available with a dimmable drive circuit operated via a 1- to 10-volt controller. In addition, wireless technology can be harnessed to communicate with a controller at the luminaire. That way, the sensors controlling the luminaire need not be located at the luminaire itself, and the luminaire can be driven using a number of inputs, including occu- pancy sensing, volume adaptation, and light-level adaptation, all using a single control system. Moreover, bi-level retrofits provide other advantages, such as reducing the maintenance cost and increasing the safety and security; controlling the lighting level, which can be used to alert drivers and pedestrians of approaching vehicles; increasing visual acuity with higher color tem- peratures; and better illuminating darker spots within the parking structure with uniform light distribution. Table 11 shows bi-level parking lot and garage project financials (ETAP, 2011), in an example in which the following assumptions have been made: ⢠ETAP rebate levels: LED $200/fixture, T8/T5/Induction $100/fixture, lamp and ballast retrofit (garage only) $40/fixture ⢠number of fixtures: 175 for garages, 45 for lotsâ1-for-1 retrofits ⢠annual operating hours: 8,760 for garages, 4,380 for lots ⢠bi-level fixtures operate at 50% power 25% of the time ⢠energy rate: $0.15/kWh ⢠standard utility rebate: $0.05/kWh and $100/peak kW reduction ⢠estimated maintenance savings: $25 per fixture for garages, $100 per fixture for lots. Recommendation: When considering adopting an energy-saving lighting design, consider luminaire selection, the potential for ETAP rebates, and light- and user-adaptive lighting.
36 Airport Parking Garage Lighting Solutions Source: VTTI compiled from ETAP data Existing Retrofit Project Summary Location Type Existing Fixture Existing kWh Fixture Proposed kWh kWh Saving x 1000 Annual Energy Cost Savings Total ETAP Rebate Utility Incentive Net Project Cost Payback in Years Parking Garage 150W HPS 287,438 90W LED, bi-level 120,724 167 $25.0k $35.0k $10.0k $93k 3.54 Parking Garage 100W HPS 211,554 New vapor lite 72,434 139 $21.9k $17.5k $8.5k $47k 2.02 Parking Lot 100W MH 90,272 220W LED 37,942 52.3 $7.85k $9.0k $2.6k $26k 2.76 Parking Lot 250W HPS 58,145 150W Induct 27,766 30.4 $4.55k $4.5k $1.5k $19k 3.27 Table 11. Bi-level parking lot and garage project financials.
