Traditionally, commercial electrical systems are based on alternating current (AC). The utility grid delivers AC power, which the building distributes. Low-voltage devices include a rectifier that converts AC to direct current (DC), with associated electrical losses.
Adoption of low-voltage devices such as LED lights, controls and sensors is surging in commercial buildings. This inspired the reimagining of building power delivery systems as DC-based microgrids. The EMerge Alliance defines a DC microgrid as an “electrical system that can efficiently distribute, consume and potentially create and store direct current electricity to power a wide variety of electrical devices in and around buildings when connected to a utility grid or when disconnected as an island.”
Generically, a DC microgrid deploys a DC-power distribution network feeding power to devices and loads such as lighting, controls, sensors, motors, fans, computers/IT equipment and other electronics. Renewable energy (DC) from on-site generators (solar, wind, etc.) may feed the microgrid.
The results include higher efficiency and lower typical conversion losses and reduced operating costs, and fewer components (i.e., junction boxes, etc.). Other advantages include the basic benefits of low voltage, such as lower-cost equipment, greater safety, faster installation and more flexibility. For lighting, LED drivers would no longer require a rectifier and potentially related components, reducing materials, size and cost of LED lamps and luminaires. In fact, the driver may even be eliminated.
Since 2008, the EMerge Alliance has developed standards promoting adoption of DC power distribution in commercial buildings within a hybrid AC/DC system. More recently, it has begun working on residential standards. Utility AC power is combined with on-site DC power and delivered as high-voltage DC to modules, which converts it to low-voltage DC to power devices. Installation may occur with or without a ceiling grid; integration with lighting control and data systems may be accomplished with wireless connections.
Standards-compliant member products carry an approved logo. Armstrong’s DC FlexZone, a ceiling suspension system that distributes DC power to connected devices such as lighting, is an example of an EMerge-compliant DC microgrid platform. A variety of lighting FlexZone-compatible products is available from manufacturers such as Acuity, Eaton, JLC Tech, Sylvania and Philips Lighting.
While a founding member of EMerge, Eaton developed its own platform, the distributed low-voltage power (DLVP) system, which the company says it will make available to other manufacturers. DLVP is based on a hybrid AC/DC platform similar to EMerge. Each power module features multiple low-voltage outputs for powering multiple addressable LED luminaires and connecting controls and sensors in a plug-and-play configuration. By providing power and bidirectional communication in a single plenum-rated cable, Eaton claims DLVP can reduce a lighting project’s total installed cost by up to 20 percent.
Recently, power over ethernet (PoE) emerged as a low-power microgrid option. Based on IEEE standards (802.3) or ad-hoc, which are evolving toward delivering more power, PoE systems pass DC power and data over network cabling, specifically twisted-pair ethernet cabling. A single cable can provide both power and data connection to devices, resulting in both low-voltage and a digital ceiling. Because power and data pass through the network in a standardized manner, software-based building control and data retrieval become harmonized similar to the approach’s wireless alternative.
Cisco, which developed PoE in 2000 to support IP-based telephone systems, has developed Digital Ceiling Partners, providing a PoE infrastructure around which multiple systems can be converged and controlled using a web-based interface. The combination may form a vector for industrial internet of things (IIoT) deployment. Partners include Cree, Eaton, Philips and more.
PoE is suited to applications where the owner wants data network integration, the building infrastructure is capable of controlling everything with a single wired system, and operating personnel can run the system and process the analytics. As the IIoT develops, demand for standardized lighting and controls that can deliver data and services is expected to grow. But IIoT implementation faces hurdles, such as security.
For the EC, the development of a DC power market presents opportunities and challenges. Generally, low-voltage installation does not require a licensed electrician and thus involves lower labor rates and potentially broader competition. PoE installation involves networking hardware, software, advanced controls and digital sensors, which may be unfamiliar.
Both wired and wireless systems offer similar capabilities, so the choice focuses on installer and user preferences. Should this market significantly expand, ECs may position themselves as valuable experts through education if they want to maintain a prominent position. Alternatively, the EC may become focused on delivering power while other specialists, possibly from the IT world, emerge to deliver connected lighting and IIoT solutions.