Alternating current may be safer electricity, but direct current is more efficient electricity. The architectural lighting industry provides products that operate on alternating current (AC), 120 volts in North America and 220 volts in most of the rest of the world. But solid state LED lighting products, along with most electronic devices, use transformers to convert alternating current into direct current (DC), a process that wastes energy. Fluorescent lighting, which depends on electronic ballasts, can also operate more efficiently on direct current. Photovoltaic and wind power systems generate direct current. When you put those two facts together, you quickly realize that DC-powered lighting is a pretty good idea.
That's the basis on which EMerge Alliance was founded. For the last few years, I have watched the membership in EMerge Alliance grow from some leaders in architectural ceiling and lighting products to include a wide range of building products manufacturers as well as some major design firms, utilities, governmental agencies, and trade groups. The organization is:
An open industry association developing standards leading to the rapid adoption of DC power distribution in commercial buildings. These innovative standards integrate interior infrastructures, power, controls and devices in a common microgrid platform to facilitate the hybrid use of AC and DC power throughout buildings for unprecedented design and space flexibility, greater energy efficiency and improved sustainability.
According to EPRI (Electric Power Research Institute ), a pilot project for a Duke Energy Data Center is demonstrating a 15 percent energy savings for DC versus AC lighting. While it isn't a particularly sexy lighting project, this type of space represents an increasingly large proportion of the energy intensity of new and renovated commercial buildings. I expect within a few years that the energy and operating cost savings will make this approach a no-brainer for large open plan offices, as well as data centers.
From a lighting design point of view, this is exciting stuff. Imagine a ceiling grid with integrated DC-conductors that enable DC-powered LED and fluorescent lighting to be installed without additional wiring. The luminaires rest on the low-voltage power rails along with the acoustic ceiling tiles. As furniture arrangements shift, the lighting can be moved around with minimal effort. Control systems can provide individualized dimming and switching. While not yet commercially available, this sort of technology is on the near horizon and has been demonstrated at Lightfair since 2009. EMerge Alliance will make its Greenbuild debut this October in Toronto.
From a dMass point of view, this radically reduces the amount of material involved in the lighting of buildings. A substantial amount of copper and synthetic insulation is needed for UL-rated AC wiring. The wiring material plus the time and labor required to safely install it accounts for up to half of the total installed cost of architectural lighting systems.
The AC vs. DC issue has caught the attention of the green building community. The EMerge website already lists available products in four categories - Infrastructure, Power, Peripherals, and Controls - from big names like Armstrong Ceiling Systems, Osram Sylvania, and Cooper Lighting. More products are on the way. I will be watching for more pilot projects that actually integrate DC-driven building systems with DC-generating renewable energy technologies. We are moving closer to more being able to produce more widespread and economically viable net-zero energy buildings. Stay tuned.