Lighting accounts for a quarter of the energy used by a building and 10 percent of building costs, yet commercial building operators have not reaped the benefits of lighting control systems largely because of the cost involved in retrofitting, says a Lawrence Berkeley Lab and the government’s General Services Administration study.
The Commercial Building Partnership (CBP) study focused on ways to overcome the cost barrier and the lack of knowledge about lighting control systems. The study’s goal was to develop affordable advanced controls to eliminate wasted lighting energy in existing commercial buildings.
The lighting team had ambitious plans to achieve 80 percent lighting energy savings in existing commercial buildings with controls that cost $2 per square foot installed by 2015, and to work with industry to create the next-generation controls. The CBP study then set out to measure energy savings at 10 demonstration sites in seven federal buildings in California and Nevada.
They began by replacing existing lighting with lighting specific to each workstation, that consisted of a new energy-efficient luminaire with a built-in occupancy sensor and individual-controlled digital dimming ballast centered over each workstation. This system enables users to control both occupancy sensing and light level tuning for each workstation, so users could set lights as they pleased. Similar relighting arrangements have achieved 40 percent lighting energy savings and greater occupant satisfaction with workspace lighting, CBP’s authors say.
With data logs placed in circuits, the study obtained pre- and post-retrofit usage data for a range of scenarios, with demonstration pilots that took place for one or two years at each location. What they found was that usage varied greatly from location to location in each stage. Cutting out standby power at night could lead to even more savings, the study says.
It varied from a 0.75 kilowatt-hour per square feet, per year improvement at the Chet Holifield Federal Building in Laguna Niguel, California, to a 4.29 kilowatt-hour per square feet, per year difference at the Roybal Federal Building in Los Angeles, California. The before-and-after energy savings in the buildings studied ranged from 26 percent to 66 percent, with an average savings of 46 percent.
Areas such as conference rooms and grand jury rooms, occupancy controls led to huge savings — often because such rooms are used by many but belong to none, so lighting used to be left on before controls were installed.
But new lighting equipment did not always reap rewards – the study found it paid off in only two out of 10 installations, because of the installation costs. In conclusion, the study says building managers need to be trained on the advantages of lighting control and how to leverage it.
The market is recognizing that energy savings can be had from monitoring lighting and other energy use. Last October, Aginova launched a Sentinel product line of battery powered WiFi-based sensors for monitoring temperature, relative humidity and energy for myriad applications. The product packages include WiFi sensing hardware, a portable alarm unit, and software for monitoring, reporting and storing condition data over time.
Chart credit: Lawrence Berkeley Lab