[Technology Report]
Multiple Standards Confound Power-Supply Designers
The melange of energy-efficiency standards used to be good for a “green” label. But how much difference really exists between them?
SURVEYING THE STANDARDS So what are the standards worldwide? Let's start with CEC-400. While there are specs for almost everything that uses electricity, much of the attention seems focused on external supplies—the ubiquitous wall-wart and the laptop ac-dc converter. It's not that any one of them burns so much power while sitting idle. It's that there are so many of them, always plugged in, always burning that power.
With respect to external power supplies that operate from nominal 115-V, 60-Hz power, CEC-400 specifies both efficiency and no-load power consumption. Supplies rated up to 1 W (according to their nameplate) must exhibit at least 49% efficiency. Supplies rated for more than 49 W must be at least 84% efficient.
In between, you take the natural log of the nameplate output, multiply it by 9, and add that number to 49%. (The specification expresses this in terms of , rather than as a percent.) Starting on July 1, 2008, the base efficiency numbers go up to 50 and 85%. In terms of standby power, if the supply is rated for less than 10 W, no-load consumption cannot exceed 0.5 W. For supplies rated from 10 to 250 W, maximum no-load consumption cannot be more than 0.75 W.
That covers many consumer products. But home-entertainment products such as TVs, DVD players and recorders, digital TV (DTV) adapters, and compact audio products have standby power requirements, but no efficiency targets. Also, their effective dates vary.
Maximum standby power requirements for TVs and DVD devices kicked in last January. They're both 3 W. DTV adapter and compact audio products have until next January, at which point DTV adapters may consume no more than 1 W in STB standby-passive mode and 8 W in STB-on mode. The spec for compact audio products says "2 W in Audio standby-passive mode for those without a permanently illuminated clock display. 4 W in Audio standby-passive mode for those with a permanently illuminated clock display."
U.S./INTERNATIONAL: ENERGY STAR Like all of the voluntary standards, Energy Star is a labeling program that relies on companies testing their own products according to established methodologies and reporting the results.
A product that meets or exceeds basic energy requirements can be marked with a special label indicating its energy-efficiency characteristics. The product is also listed on the Energy Star Web site, which lets consumers compare products with otherwise roughly equivalent performance characteristics for energy efficiency.
The U.S. Department of Energy and the Environmental Protection Agency (EPA) sponsor the Energy Star certification program. Australia, Canada, Japan, Taiwan, and the European Union have Energy Star programs that are closely related to the U.S. model, but more limited.
Australia's Energy Star is primarily concerned with office equipment and consumer electronics. In Japan, Taiwan, and the European Union (EU), programs focus on office equipment. There's also interest in Mexico, China, and Brazil in implementing Energy Star, but these are developing relationships.
Interestingly, there's a link between voluntary Energy Star and the prescriptive California Commission. In baseline standards for electronic products such as external power supplies and home entertainment equipment, Energy Star tends to mirror CEC-400, so it's not as if one type of program is more technically rigorous than another.
80 PLUS: 80 Plus is an incentive program funded by electric utility companies to integrate more energy-efficient power supplies into desktop computers and servers. To meet the program standard, supplies must achieve 80% or greater efficiency from full rated power down to 20% of rated power ( explicitly, at 20%, 50%, and 80%).
In addition, the full-load power factor must be at least 0.9. Participating utilities fund a rebate system that rewards OEMs and system integrators with cash for each server or PC they sell powered with an 80 Plus power supply. Details can be found at www.efficientpowersupplies.org/methods.asp.
EU PROGRAMS: CODES OF CONDUCT In Europe, the European Commission and the European Association of Consumer Electronics Manufacturers (EACEM) developed codes of conduct for consumer products. An initial agreement in 1997 addressed standby power levels in TVs and VCRs. In 2000, a second agreement for reducing the standby losses of audio equipment was concluded. Then in 2003, a new agreement for TVs and DVDs was reached.
A 1999 initiative on Policy Instruments to Reduce Stand-by Losses of Consumer Electronic Equipment led to two codes of conduct—one for external power supplies and another for DTV services. A further code for broadband communication equipment is under development.
For external power supplies, the target-for products released after January 1, 2005 varied by capacity, with standby power ranging from 0.3 W for supplies rated at less than 15 W to 1 W for supplies rated between 60 and 150 W. By January 1, 2007, all supplies are supposed to have the same maximum no-load power consumption: 0.3 W.
For TVs, the code of conduct includes a feature reminiscent of U.S. fleet specifications for automobile fuel economy. The present maximum permitted standby power level is10 W, but the average standby of all units from any one manufacturer must be less than 6 W. By 2009, the "fleet" average must be reduced to 3 W, still with no models consuming more than 10 W.
One interesting thing about the European code of conduct for external supplies is that the population of manufacturers and their supplies is small enough to be comprehended in a single graph. The results from 2005 were presented in March of this year. With nine companies reporting on 130 models, 92% of the power supplies tested met the criteria (see the figure).
Of course, the code of conduct isn't the only standard in Europe (see "Energy-Efficiency Standards Around The Globe" at www.electronicdesign.com, ED Online 13111). The EU Eco Label, Energy Plus, the Group for Energy Efficient Appliances (GEEA), Germany's Blue Angel, and Nordic Swan are out there, too (see the table).
And don't forget about the Asian market. The China Energy Conservation Project hasn't had much to say about electronics, but that will change. Korea's voluntary Energy Saving Office Equipment & Home Electronics Program and Japan's Top Runner program shouldn't be ignored either.
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