After engineer David Kaneda’s firm moved into its own self-designed zero-energy building, an analysis of the zero-energy claim revealed that their photocopiers, printers, clock radios and coffee pots were threatening efforts to make the building self-sustaining.
“plug load” is The hot topic in the energy-efficient building design field these days. Unlike insulation, multipane windows and improved heating, ventilating and air-conditioning (HVAC) performance, this energy-efficiency strategy directly affects the work of electrical contractors. Contractors who work in the commercial sector, especially, will be hearing the term repeatedly.
The concept is pretty self-explanatory—plug load refers to the electrical loads in a building that are plugged into outlets, as opposed to hardwired into larger building systems. With energy codes driving down demand from cooling and lighting equipment, plug loads are beginning to attract the attention of standards developers. In the 2010 update to its energy standard, for example, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) calls for 50 percent of most outlets to be controlled by occupancy sensors, time-of-day systems or another form of automatic oversight.
ASHRAE 90.1, “Energy Standard for Buildings, Except Low-Rise Residential Buildings,” is the basis for the International Energy Conservation Code. It also establishes a baseline for the Leadership in Energy and Environmental Design (LEED) certification program and many state energy codes. State adoption of the biennial updates generally lags behind the publication date by two years, so the 2010 edition is just beginning to hit the books in local jurisdictions across the United States.
Environmentally minded architects and engineers are also beginning to understand the effect plug loads can have on their most-efficient building plans. These professionals are working toward the goal of net-zero-energy buildings—buildings that only use as much energy over the course of a year as they either produce on-site through solar or wind generation or that they offset through the purchase of utility-supplied renewable energy or renewable energy credits.
David Kaneda, P.E., A.I.A., LEED, is one of these thought leaders through the San Jose, Calif.-based electrical engineering firm he founded, Integrated Design Associates (IDeAs). The issue’s importance became clear to him when his firm moved into its own self-designed zero-energy building. During post-move analysis of that zero-energy claim, the firm discovered that its photocopiers, printers, clock radios and coffee pots were threatening efforts to make the building self-sustaining.
“The plug loads were a huge percentage to the point where they were becoming the biggest load in the building,” he said. “That’s when we realized they’re a critical piece.”
To help bring plug loads under control, Kaneda and others at IDeAs took a three-pronged approach. The first step was to investigate whether more efficient versions of their existing equipment were available. In the case of a conference room flat-screen television, they took a power meter down to the local big box electronics store to get actual readings on possible replacements.
“Energy Star generally gets you going in the right direction,” Kaneda said, suggesting baseline performance metrics for those in the market for new office electronics. However, he said, a lot of the nameplate data is inaccurate, and it might even be overstated.
The next step was to understand where phantom (or “vampire”) loads might be drawing power in equipment users thought they had turned off. The classic example of this kind of energy-waster is the cable or satellite set-top box attached to just about every U.S. television. Printers, fax machines and any other office machinery that has a continuously glowing indicator light also fall into this category. For phantom loads, Kaneda suggested using timers, occupancy sensors or other controls, along with the ability to shut off all power at the outlet. For example, his firm has connected a power-wasting drawing printer to a remote-control circuit breaker that is linked to the security system. When the last person to leave the office arms the security system, that breaker opens, and the load, which draws 30 watts even when not in use, is disconnected.
Kaneda’s third tactic involves making aggressive use of energy-saving software already included in some office equipment, such as the “sleep” and “hibernate” settings available in most laptop and desktop computers. Adopting virtual server designs in computer rooms is another method. Kaneda sees a lot of room for improvement here, though, because many equipment manufacturers haven’t optimized their products for such performance.
Among the winners in this move to reduce loads at the plug are the plug-makers themselves. Legrand’s WattStopper brand, for example, offers a range of sensors and controls, along with the Isole power strip, which is controlled by a connected occupancy sensor to turn off specified connected loads when an office space is not in use. Pete Horton, the company’s market development vice president, said the plug-load control field currently is wide open.
“The market is very new,” he said. “It’s going to be the Wild West for a little while.”
Taming this frontier will require electrical pros, from manufacturers and engineers, to figure out some best practices regarding how plug control should work.
“What we have to answer as an industry is what is the control going to be?” Horton said. “What are you going to use to sense? What is the control mechanism going to be? It may be motion or occupancy, but we have a lot of questions as to what we use to control and where we put it.”
A second big question for contractors and others involved in designing and installing individual control systems should be whether a job is intended for maximum return on investment (ROI) or to meet energy code-compliance concerns. Where ROI is the primary driver, clients might want to focus only on those outlets used most frequently. University dorms are one client category Horton sees as particularly interested in the bottom-line impact such control might have.
“Kids are coming in with so much [electronics], and they’re just leaving it all plugged in and running,” Horton said. “Lots of student dorms are looking for a solution.”
However, in a code-compliant build-out or retrofit project, the bottom line to meet ASHRAE 90.1 2010 is 50 percent of all outlets (with a few exceptions for life-safety applications), regardless of how frequently any single outlet may be used.
In cubicle and other office settings, an additional ASHRAE mandate regarding task lighting also could play a role in plug-load control. In these areas, lighting planners won’t have to include furniture-mounted task lighting (such as under-cabinet fixtures that plug into a receptacle) in overall lighting power-allowance calculations if that lighting is controlled by an automatic shutoff device. This provision could provide helpful flexibility when developing larger ambient-lighting plans by allowing higher lighting power densities in aisles and hallways, so long as task lighting is sensor-controlled.
Wireless devices are becoming an increasingly frequent method for enabling control schemes, thanks, in part, to new standards that enable devices from multiple manufacturers to communicate with each other. ZigBee is one such standard, developed and managed by the 420-plus companies now involved as members in the ZigBee Alliance. Though ZigBee-member companies primarily have focused on home automation applications (including locks, thermostats and home power strips that can be controlled using smartphone apps), they are beginning to expand into more commercial uses—especially with the alliance’s September 2011 completion of a BACnet-approved building automation standard.
Alliance chairman Bob Heile sees electrical receptacles becoming yet another controlled device in larger building automation systems that also address HVAC and other systems.
“In large commercial buildings, this doesn’t happen with each tenant. Everything is going to tie into the building automation system,” he said.
Even further out on the cutting-edge, some office equipment-makers are promoting the role direct current (DC) power could play in reducing plug-load demand, through another industry standards group, the EMerge Alliance. The idea, most practical in new construction and down-to-the-studs renovation projects, is to run a DC distribution system in parallel with standard alternating current (AC) wiring. The goal is a more efficient way of serving the growing number of laptop computers, cellphones and task lights that require transformers to turn wall-delivered AC power into the DC power they need to operate.
“You can’t help but notice the number of outlets that are being used as charging systems instead of power-delivery systems,” said Joel Zwier, chair of the EMerge Alliance’s furniture workgroup. He said the group wants to address the challenge of the energy lost in every one of those brick-shaped transformers and block-shaped plugs. “Isn’t there a better way of consolidating these transformers up the distribution stream?”
The alliance released a series of standards for ceiling-level DC distribution (for possible use supplying lighting and sensor equipment) and plans to release draft standards covering desktop applications this summer, Zwier said. The effort may seem quixotic, but it has drawn some heavy hitters to its side, including Steelcase (where Zwier works as the company’s lead for advanced applications and business development) and Herman Miller, along with Armstrong Ceilings. Those companies have been joined by lighting powerhouses Acuity Brands, Cooper, Hubbell, Osram Sylvania and Philips; several major electric utilities; and other team members.
The new standards will cover infrastructure components, such as wires and power supplies, along with connectors, peripherals and controls. However, Zwier said, while the standards will define performance criteria, the intent is to leave specific power distribution and delivery solutions up to individual manufacturers.
“We’re trying to be as open a platform as we can: power over Ethernet is definitely an active distribution system, and USB is growing in popularity. I would hate to presume the outcome before we go through our process,” he said. The effort could open “a window into the future where we are using these resources in a whole different way.”
ROSS is a freelance writer located in Brewster, Mass. He can be reached at email@example.com.