Get IT managers or CIOs together, and the topic will quickly turn to the biggest potential bottlenecks to data center expansion: power and heat. Even though IT managers can now pack more processing power into less real estate than ever, these high-density computing environments can be a huge drain on operating budgets, for several key reasons:

• Expanding power demands. Those blade servers that are required to satisfy business users' demands are consuming three to five times as much power as previous generation equipment in the same footprint. Electricity consumption by U.S. data centers rose 39% between 1999 and 2005, according to an Uptime Institute survey of members.
  
• Increasing power costs. Utility rates have risen three times in the last year alone, accounting for 20-30% of data center operating costs. For many IT organizations, energy costs represent the largest component of total cost of ownership -- and the most stifling influence on IT expansion.
  
• Excessive heat. As you well know, blade servers generate a lot of heat. At 30 kW of power consumption per rack, you would need the equivalent of two 5 ton household ac units for cooling.

Cooling requirements add huge costs to the business case for data center expansion.

If you manage a data center -- or engineer the architecture for clients who do -- you know how critical these issues have become. It is a challenge to provide efficient power protection and distribution for growing loads, while ensuring adequate cooling of IT equipment.

The good news is that even a small data center can save tens of thousands of dollars simply by making wise choices in server and power-delivery infrastructure. For example, the 3-year utility savings from an energy-efficient server can nearly equal the cost of the server itself. Couple this strategy with energy-efficient power and cooling systems, and a midsized data center with 1,500 servers could save millions of dollars in three years.

Sound good? It ought to. If the idea of dramatically reducing energy costs intrigues you, read on to discover how to gain this edge for your organization. To begin, look at the top three factors contributing to high-energy costs -- which also represent the top three opportunities for reducing those costs:

• Servers and other IT equipment
  
• Power distribution and protection systems
  
• Data center cooling systems

How Energy-Efficient Is Your IT Equipment?

With most IT equipment -- servers especially -- the central processing unit (CPU) consumes the most power. Major processor vendors, such as Intel and AMD, have been focusing on developing chipsets that provide higher processing capacity for less power, so overall efficiency of servers should be improving.

The second biggest culprit in power consumption is power conversion within the server. Most IT equipment operates from single-phase, ac power sources (208 V and 120 V in North America and 220 V to 240 V internationally). Within IT equipment, a power supply unit (PSU) converts the ac power to dc voltages, typically at 12 V. This 12 V current is then converted to the various dc voltages required by processors and chipsets -- such as 1.8 V, 3.3 V and 5 V -- using point of load (POL) voltage regulators (VRs).

Server efficiency depends on the efficiency of the internal power supply and voltage regulation.

The typical PSU operates at around 80% efficiency -- often as low as 60-70%. In a standard server, with the PSU operating at 80% efficiency and VRs operating at 75% efficiency, the server's overall energy efficiency would be around 60%.

Several industry initiatives are improving this figure. For example, EPA Energy Star programs related to enterprise servers and data centers and 80PLUS-certified power supplies are both increasing the efficiency of IT equipment. The industry really took notice when Google presented a white paper at the Intel Developer's Forum in September 2006, saying it had increased the energy efficiency of typical server power supplies to at least 90%, up from 60-70% previously.

The initial cost of such an efficient PSU is higher, but the energy savings quickly repay it. If the PSU operates at 90% efficiency and VRs operate at 85% efficiency, the overall energy efficiency of the server would be greater than 75%.

Server utilization represents another potential avenue of cost savings. Most servers in business applications are running at only 15-20% of maximum capacity, yet they use far more than 15-20% of maximum power consumption. Virtualization, whereby servers are partitioned to serve multiple applications, could improve overall server utilization, but only to a point. Enterprises might be better off to deploy servers that can scale down power requirements when processing low loads. When selecting servers, be sure to evaluate their energy efficiency at various processing levels.

How Energy-Efficient Is Your Power Infrastructure?

Most IT equipment is not directly powered from the facility power source. Power typically passes through an uninterruptible power supply (UPS) for power assurance, power distribution units (PDUs) that distribute the power at the required voltage throughout racks and enclosures, and has circuit breakers to avert problems related to short circuits in the power delivery system.

PDUs typically operate at a high efficiency of 97-99%, so the efficiency of the power infrastructure is primarily dictated by power conversion efficiency in the UPS. How much power does the UPS consume to do its job, keeping voltage within acceptable limits and supplying battery backup during utility outages?

Advances in UPS technologies have greatly improved the efficiency of these systems. In the 1980s, most UPSs used silicon-controlled rectifier (SCR) technology to convert battery dc power to sinusoidal ac power. Products using this technology operated at a low switching frequency and were 75-80% efficient at best. With the advent of new isolated gate bipolar transistor (IGBT) switching devices in the 1990s, switching frequency increased, power conversion losses decreased accordingly, and UPSs could run at 85-90% efficiency.

When even higher-speed switches became available, there was now no need to have transformers in UPS systems, which helped boost efficiency to 90-94%. Eaton's new Powerware BladeUPS -- optimized for today's IT equipment power supplies -- operates at 97-98% efficiency.

What Happens to UPS Efficiency at Typical Utilization Levels?

When evaluating a UPS, it's not enough to know the peak efficiency rating it can deliver at full load, especially since you would be unlikely to be operating the UPS under those conditions. Since so many IT systems use dual power sources for redundancy, the typical data center loads its UPSs at less than 50% capacity, as little as 20-40% in some cases.

You would expect efficiency to be lower when the UPS is operated at partial loads, but to what degree? Previous generation UPSs (those bought before 1990) are markedly less efficient at low loads. Even most of today's UPSs are noticeably less efficient under the loads typically expected of them. For the very energy-conscious IT manager, the new Powerware BladeUPS system offers a very flat efficiency profile of 95+% down to 20% loading.

Even small increases in UPS efficiency can quickly translate into thousands of dollars. Comparings annual and 5-year energy costs for the BladeUPS and a less efficient solution, in a small computer room with 20 racks, the more efficient UPS can pay for itself over its practical lifespan through energy and cooling savings alone.

If the former UPS operated at 88% efficiency, it would take only three years for the more efficient UPS to deliver more than $30,000 in savings.

In addition to dramatic cost savings, high UPS efficiency extends battery run times and produces cooler operating conditions within the UPS. Lower temperatures extend the life of components and increases overall reliability and performance.

How Energy-Efficient Are Your Data Center Cooling Strategies?

As much as 30-60% of the data center utility bill goes to support cooling systems, including air handlers and chiller systems. If that figure seems too high, it is. Many computer room cooling systems are inefficiently deployed. That means your organization might have some ready opportunities to reduce this cost through best practices:

• Use hot aisle/cold aisle enclosure configurations. By alternating equipment with high and low heat output, you can create a more uniform air temperature throughout the data center.
  
• Use blanking panels inside equipment enclosures so air from hot aisles doesn't mix with air from cold aisles.
  
• Seal cable outputs to minimize "bypass airflow," whereby cool air is short cycling back to cooling units instead of circulating evenly throughout the data center. This phenomenon affects as much as 60% of the cool air supply in computer rooms.
  
• Orient computer room air conditioning units close to the enclosures and perpendicular to hot aisles, to maximize cooling where it is needed most.

Further optimization of the cooling systems can be achieved by using:

• Air handlers and chillers that use efficient technologies such as variable frequency drives (VFD)
  
• Air- or water-side economizers
  
• Humidity and temperature settings according to ASHRAE guidelines

A Powerful Business Case For Energy-Efficient Strategies

When you combine energy-efficient IT equipment, power infrastructure, and cooling strategies, the cumulative effect presents a powerful business case.

Consider the example of a 1U server using 300 W of power to do its work. In a typical data center, this 1U server would require about 1,341 W to operate. In three years, you would spend $3,500 to power this server, which is probably about what you paid for it in the first place.

Now imagine you had best-in-class equipment and process -- energy-efficient servers, power delivery, and cooling systems. Now the 1U server requires only 696 W to operate. In three years, your best-in-class equipment and best practices would save more than $1,700 in energy costs.

The savings quickly compound. A small data center with 350 such servers would save more than a half million dollars in three years. A mid-sized data center with 1,500 servers would reduce its utility bill by $2.5 million.

Where Do You Go From Here?

To improve the energy efficiency of an existing data center. . .

Conduct an audit of the data center and its support infrastructure, and compare it to industry benchmarks. The Uptime Institute recommends an approach called the Power Usage Effectiveness (PUE) ratio:

In this equation, total facility power is the total power required to support all IT equipment, backup power systems, and cooling systems. IT equipment power is the actual line cord power drawn by all IT equipment in the data center. A practical approximation for the IT equipment power would be the output power from UPSs.

After applying this calculation to several data centers, the Uptime Institute recommends an ideal PUE of 1.6 and a realistic goal PUE of 2 for a well-designed and operated data center. The Institute estimates that most U.S. data centers have a PUE of 3.0, with an average of 2.4.

If your data center PUE falls into this average range, you have definite opportunities to improve energy efficiency by taking any of these actions:

The Rright UPS Can Minimize Cooling Costs

A more efficient UPS dissipates less power as heat and reduces the cost of cooling. In the example shown earlier, the UPS operating at 97% efficiency reduces air conditioning costs by $246 a month, compared to a model that rates only 5.5 points lower in efficiency.

The savings compound with data center size. For example, in a mid-sized data center with 200 racks at 15 kW per rack, the more efficient UPS would reduce cooling requirements by 47 tons, compared to another UPS that operated at 91.5%. A large data center with 2,000 racks at that same density could expect a 469-ton reduction in ac requirements with selection of the more efficient model.

• Upgrading UPSs to higher efficiency technology
  
• Installing energy-efficient features to the existing cooling system
  
• Following best practices in computer room layout to avoid wasting cool air.

In a greenfield data center or major expansion/upgrade of an existing data center. . .

• Include energy efficiency as a key requirement in design criteria, alongside expectations for reliability and uptime.
  
• Consider energy efficiency in calculations of total cost of ownership when selecting servers and other IT equipment.
  
• Understand all your options in purchase decisions for UPS and cooling systems, to identify the technologies that will provide the lowest operating costs.

With best practices and the right choice of equipment, data center managers can reduce energy consumption by nearly 50%. That means that almost half of the power utility bill will fuel actual IT processing, compared to less than 25% of the power supplied to a nominal data center today. With a more efficient allocation of power, you will not only reduce utility bills and total operating cost, but also achieve more with available backup power and cooling systems -- delaying the point where those systems would have to be upgraded to match data center expansion.