Creating efficient office lighting

An example of an office that used energy modeling for HVAC load analysis and a lighting optimization simulation analysis.

10/22/2013


Figure 2: This office lobby shows the LED spot downlights used in combination with the T-5 HO fluorescent cove lighting and daylighting influence. Courtesy: ccrd partnersA remodel of a 17,000-net-sq-ft commercial office space in a circa-1929 office in downtown Houston took advantage of both energy modeling for HVAC load analysis and a lighting optimization simulation analysis to determine the impact on yearly energy consumption. The baseline model, which used the existing space design, was modeled with its existing lighting (2x4-ft recessed lay-in return air T-12 light fixtures) that had previously been retrofitted from to 2-lamp T-8 fixtures. The existing lighting demand was 10 kW (input power). This retrofit design was compared to the same space, using dimmable energy-efficient solid-state high-output T-5 high output and LED luminaires with occupancy sensing control and natural daylight from the existing north-facing palladia windows, resulting in a reduced peak power demand of 8.2 kW.

In comparing the two analyses for the floor cooling and heating load requirements, the existing design had required approximately 7 cooling ton-hrs per year consumption, while the remodeled floor require 6 cooling ton-hrs per year consumption. Peak heating demand increased from 92 kBtuh to 125 kBtuh as a result of the redesign, with energy consumption increased from 500 therms to 592 therms. Replacing the 2-lamp T-8 parabolic fixtures with programmable, occupancy based T-5 high-output lamp pendant luminaires and LED downlights offset with natural daylighting allowed for a yearly reduction in energy consumption of 16%. As a result of decreasing the lighting W/sq ft, the heating consumption increased by 15%.

The majority of load reduction was due to lighting controls and use of daylighting for the space. The existing lighting design was based on manual occupant switching. As occupants left for the day, lights would be switched off; when the cleaning staff switched lights on after-hours, lights would be left on overnight. To reduce lighting consumption, the renovation took advantage of vacancy sensing. With a vacancy sensor strategy, lights are turned off automatically soon after an area is vacated, but occupants must turn lights on when they re-enter the space. In the renovation, lights tied to a vacancy sensor turn off 2 hours after they are energized after-hours. After the cleaning crew has left the space, lighting would reduce to 30% of the design level in the space, rather than remain at 100% design level with switching.

This illustrates the benefit of application of lighting modeling and energy/load modeling in developing a lighting retrofit design that is unique to the building by incorporating daylighting and task lighting, employing new energy-efficient LED technology, and controlling supplemental lighting in order to achieve energy savings, enhanced lighting, reduced equipment cost, and improved comfort and aesthetic benefit for the tenant. 

 


David B. Duthu is board principal at ccrd, where he has more than 37 years of experience in the fields of mechanical engineering design, technical engineering design, and project management. Nolan Rome is associate principal and lead mechanical engineer for ccrd and has been responsible for the design of all types of healthcare facilities including hospital expansions, cancer centers, and imaging centers in multiple states.



No comments
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
Water use efficiency: Diminishing water quality, escalating costs; Lowering building energy use; Power for fire pumps
Building envelope and integration; Manufacturing industrial Q&A; NFPA 99; Testing fire systems
Labs and research facilities: Q&A with the experts; Water heating systems; Smart building integration; 40 Under 40 winners
Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Protecting standby generators for mission critical facilities; Selecting energy-efficient transformers; Integrating power monitoring systems; Mitigating harmonics in electrical systems
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software
As brand protection manager for Eaton’s Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.