IUTs and SSLs Headline at the Green Building Power Forum

June 03, 2009 by Jeff Shepard

Several new and emerging technologies were showcased at Darnell’s first-annual Green Building Power Forum (GBPF) this week in Anaheim, California. In addition to advances in dc-power for data center and other critical facilities, a new class of intelligent universal power transformers (IUTs) and new advances in solid-state lighting (SSL), were among the widely-discussed topics.

Don Mulvey, Executive Vice President with Roal Electronics USA started off the GBPF by discussing the "Reliability of AC Versus DC Powered Lighting Systems." He detailed how a distributed dc power architecture for SSL can provide numerous benefits compared with a traditional ac architecture. As presented, a distributed dc power architecture reduces the number of ac-dc power converters, simplifies the system design, reduces cost, enables redundancy and battery back-up, and leads to increased reliability. Additional benefits include lower installation costs, easier maintenance, and even reduced product development costs.

Expanding on the SSL analysis in the opening presentation, Brian Fortenbery, Program Manager with the Electric Power Research Institute presented a vision of "DC Distribution and the Home of the Future." According to Fortenbery, in addition to enabling the integration of distributed generation resources and improving overall efficiency, "a dc-powered home could become a component of a network that increases the security, quality, reliability and affordability of the electric power system."

Development of IUT technology may be a key enabler of dc distribution in residences and other buildings. As presented by Fortenbery, an IUT for a residence would take input power at 13.8kVac from the grid and provide 48Vdc for the home wiring. This is a specific example of the general IUT concept for a power electronic replacement for today’s conventional distribution transformers. The IUT will provide the cornerstone for advanced distributed automation of the electric grid.

The IUT is expected to bring multiple benefits including: a lower-cost alternative for voltage transformation in distribution systems at a time when conventional transformer costs and lead times are increasing rapidly, elimination of the liquid dielectrics of conventional transformers and the associated costly spill cleanups, enabling a communication link and monitoring capability in the IUT to diagnose problems in the IUT , supporting parts-wise repair, enables distribution system monitoring, and supports advanced automation and more efficient operations, improvements in efficiency of distribution operations, because the IUT is more efficient than conventional transformers at partial loads and because the added functionality improves efficiency in distribution system operations, reductions in spare inventory costs associated with warehousing many types of conventional distribution transformers, due to the IUT’s modularity, reduced unit weight and size compared to conventional transformers, and added functionality, such as voltage regulation and distribution system monitoring capabilities, relative to conventional transformers.

Turning to data center power, Tomm Aldridge, Director of Intel’s Energy Systems Research Laboratory, described an in-depth case study conducted by Intel® Corp. in conjunction with EYP Mission Critical Facilities (an HP Company) and Emerson Network Power. The study compared the costs and benefits in selecting a 400 Vdc design over the typical North American 480-208 Vac design for a 5.5 megawatt (MW) data center. Aldredge concluded that using already-available 400Vdc components, energy savings of approximately seven to eight-percent could be achieved over high efficiency, best practices 480-208 Vac, with a 15-percent electrical facility capital cost savings, as well as a 33-percent space savings, and 200-percent reliability improvement.

Continuing the analysis of the benefits of dc-powered data centers, Stefan Lidstrom, Chief Technology Officer with Netpower Labs AB focused on "Maximizing Overall Energy Efficiency in Data Centers." Dr. Lindstrom added two more elements into the discussion including the possibility of integrating photovoltaic panels directly into the 400-Vdc power distribution system and the introduction of the "NetLight," a 400Vdc LED tube designed to replace conventional fluorescent tubes in high-voltage dc distribution architectures. All the drive and control electronics are included in the tube which can operate over an input range of 280-400Vdc, provides 3X the energy efficiency of a conventional fluorescent tube and has an operating life of 6-10 years. Since the lighting is connected to the same back-up power grid as the rest of the data center, the NetLight eliminates the need for separate emergency lighting.