Before the ink was even dry on ENERGY STAR’s Tier 1 computer server spec (published in May of this year), the EPA has began working on Tier 2. The Tier 1 spec immediately met with criticism because it only covered smaller servers (up to four processor sockets), only addressed power supply requirements in idle mode, and did not include the popular blade-type servers. The new spec tries to address such shortcomings.
For Tier 2, ENERGY STAR was exploring using a net power loss approach (NPL) for evaluating power supply efficiency in operation, specifying a maximum allowed power loss through the power supply in actual operating conditions, both idle and full load power. This would have replaced the multi-load efficiency tests in the current spec, which focuses on load points of 10%, 20%, 50%, and 100%. However, after reviewing actual test data, ENERGY STAR proposes to keep the specification requirements the same, with NPL reporting included only as part of the Power and Performance datasheet requirement.
Table 1: Efficiency Requirements for Computer Server Power Supplies
| Power Supply Type | Rated Output Power | 10% Load | 20% Load | 50% Load | 100% Load |
|---|---|---|---|---|---|
| Multi-Output (AC-DC & DC-DC) | All Output Levels | N/A | 85% | 88% | 85% |
| Single-Output (AC-DC & DC-DC) | All Output Levels | 80% | 88% | 92% | 88% |
Source: ENERGY STAR
In addition, power supplies must meet the minimum power factor requirements for all loading conditions presented in Table 2 (below) where the output power is greater than or equal to 75 watts. Manufacturers are still required to measure and report power factor values for applicable loading conditions less than 75 watts to qualify for ENERGY STAR.
Table 2: Power Factor Requirements for Computer Server Power Supplies
| Power Supply Type | Rated Output Power | 10% Load | 20% Load | 50% Load | 100% Load |
|---|---|---|---|---|---|
| DC-DC (All) | All Output Levels | N/A | N/A | N/A | N/A |
| AC-DC Multi-Output | All Output Levels | N/A | 0.80 | 0.90 | 0.95 |
| AC-DC Single-Output | ≤ 500 watts | N/A | 0.80 | 0.90 | 0.95 |
| > 500 – 1,000 watts | 0.65 | 0.80 | 0.90 | 0.95 | |
| > 1,000 watts | 0.80 | 0.90 | 0.90 | 0.95 |
Source: ENERGY STAR
The new spec also covers servers with more than four processor sockets, server appliances (servers dedicated to services such as firewalls, encryption services, etc.), fully fault tolerant servers and multi-node servers. However, it is still under consideration whether the spec will include blade servers.
Considering the impact that the ENERGY STAR label may have upon sales (for example, see the article: PG&E Offers Incentives for Energy Star Servers), it is well worth watching how the final spec comes down.
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