By Scott Jordan
Lighting can account for 30 percent or more of the total electrical load in commercial buildings, which is why energy-efficiency initiatives typically focus on making sure lights are off when they aren't needed. One strategy that is receiving increased attention is load shedding, where selected electrical loads in a commercial building, including lighting, are reduced at various times during the day.
In its simplest form, load shedding involves reducing the electrical load by a certain percentage in response to a request from the electric utility. This situation typically occurs during summer months, when electrical loads are strained due to excessive air-conditioning usage. Users who opt to conform with the utility often enjoy the benefits of lower electrical rates.
While HVAC is often a prime candidate for load shedding, lighting should also be considered. Lighting can account for as much of a commercial building's electrical load as air-conditioning - a 2006 study found that commercial lighting accounts for 30 percent of the total electrical load in California during the summer peak period of 2 p.m. to 5 p.m., while air-conditioning accounts for 32 percent. Often, lighting loads can be reduced by up to 30 percent without undue discomfort to building occupants. Further, by reducing lighting loads, the HVAC load is also reduced because heat gain by lighting is reduced.
Typical load-shed requests come from the utility via a phone call or e-mail, or by monitoring a website. Typically, building management must be in a position to respond quickly to the load-shed request. Whole-building, schedule-based lighting-control systems that are Web-enabled are perhaps best positioned for this effort because a facility manager can access the system via a common Web browser at any time. For owners of multiple buildings, Web-enabled lighting control can seamlessly perform load shedding at each building from one central location. Building management can quickly respond to a utility request and ascertain if the planned reduction in load has been accomplished.
Automated Demand Response
Load shedding could soon become more sophisticated through automated demand response. In most load-shed applications today, the utility will call or e-mail building management with an energy-reduction request, typically in the morning or the previous day. But, with automated demand response, the utility would send a signal to a building's power meter or building-automation system, which would then turn off pre-selected lighting loads automatically.
Though such systems have yet to be deployed, automated demand response could be the next technological step toward greater energy savings. A study by San Francisco-based Pacific Gas and Electric Co. indicates that the energy and cost savings could be significant - for example, a high-end specialty retail store could shed as much as 40 percent of its lighting load. An additional benefit could be an improved rate structure for building owners who choose to participate in a voluntary load-shedding program compared to owners who do not.
Building owners and facility managers can learn more by investigating suppliers with extensive background in lighting control and experience in implementing demand-side management systems. Focusing on suppliers that will be sensitive to a building's unique needs is also important.
Scott Jordan is product marketing manager at Palatine, IL-based Square D/Schneider Electric (www.us.squared.com).