The first-annual DC Building Power Japan (DCBPJ) conference held last month in Tokyo included numerous important “firsts,” such as the first comprehensive review of dc power architectures from homes to data centers to micro-grids; the first joint meeting of the EPRI DC Power Partners and the Japan DC-Power Industrial Partners; the approval of a provi-sional standard for 380-V dc data center powering; and the first public tours of high-voltage dc-powered data centers.
The key presentations included a joint paper on “Specifications for the 400Vdc Power Supplies and Facility Equipment” by Keiichi Hirose, senior research engineer with NTT Facilities, and Dennis Symanski, senior project manager with the Electric Power Research Institute. They reviewed the development status of 400-V dc power-supply specifications for data center applications.
At the end of the event, during the joint meeting of the EPRI DC Power Partners and the Japan DC Power Industrial Partners, a provisional standard for 380-V dc data center powering was approved. That proposed standard was patterned after a parallel development effort taking place at the European Telecommunications Standards Institute (ETSI) and is expected to be in harmony with any standard developed by ETSI.
The selection of 380 V dc was based on a survey of several factors. For example, in a telecom facility, using seven strings of 24 cells each with a float voltage of 2.275 V dc results in a nominal voltage of 382.2 V. A survey of 60 ac-dc power supplies designed for data center applications found the output voltage of the power factor correction (PFC) circuits ranged from about 340 to 390 V dc.
GOING GREEN
Hiroaki Koshin, group manager for new product technologies development with Panasonic Electric Works Corp., pre-sented a review of “AC-DC Hybrid Wiring Systems for Residential Installations.” Panasonic is taking a leading position in the development of new residential power architectures to enable the efficient integration of solar cells, storage batteries, electric vehicles, and other advanced devices while also reducing greenhouse gas emissions.
The week before the DCBPJ conference, Panasonic Corp. revealed that it plans on investing $1 billion by 2012 in a shift to make its primary business equipping buildings with solar power and other “green” technologies. The shift in emphasis comes in the wake of Panasonic’s purchase of Sanyo Electric Co., which has already invested heavily in energy storage and solar technologies, and will be combined with systems that Panasonic has already invented.
Sanyo is already offering electric homes that feature solar panels and lithium-ion batteries for the provision of backup power on the Japanese market. Panasonic envisions new technology that will let consumers monitor their electricity use in the home via a data display on their television sets. The system would be able to connect and monitor all of the appliances in a home. The company feels that these technologies should be able to reduce energy consumption in the home by 30% to 50%.
ON THE GRID
Looking at larger-scale micro-grid installations, Tsai-Fu Wu, vice president with the National Chung Cheng University, presented his group’s experience with “Hybrid AC and DC Power Distribution Systems.” Wu’s experiments produced a number of interesting results. The use of a hybrid ac and dc power distribution system produced efficiency improvements of about 10%, reduced system component counts about 25%, improved overall power quality, and reduced the impact of the facility on the utility grid. And, its modular design makes it easy to expand capacity as demand grows.
Takashi Yuba, manager with the Research and Development Department with Fujitsu Components, and Brian Davies, director of engineering with Anderson Power Products, presented alternative solutions for 400-V dc connectors. Until now, the lack of connectors with international safety approvals was a major factor limiting the adoption of high-voltage dc power distribution. Now, there are multiple options.
And on the second day of the conference, Professor Takashi Tomita of the University of Tokyo reviewed “The Move-ment of International Standardization of Low-Voltage Direct Current Distribution.” According to Tomita, the dissemination of renewable energy, such as photovoltaics and associated energy storage systems, together with the appearance of the plug-hybrid vehicle, will accelerate the development and adoption of low-voltage dc power distribution in residences and other buildings.