Boost Your Data Center Efficiency with Multi-mode UPS Systems

When consulting-specifying engineers look at the hundreds of technology factors that go into a data center’s design, they know that even small variables, when multiplied by big numbers, add up quickly. That’s the case with seemingly small incremental increases in energy efficiency for uninterruptible power supply (UPS) systems used in data centers around the world.

According to the Uptime Institute, traditional transformer-based UPS devices represent only 12% of a typical data center’s energy consumption, given power use and energy conversion inefficiencies and heat loss. Although they account for only a fraction of the total energy consumption in a data center, even small improvements in UPS energy conversion efficiency can add up to significant lifecycle operational cost savings.

Figure 1: Typical Data Center AC-Power Configuration

Traditional double conversion UPS units (Figure 1), which protect the load during outages — use a rectifier to convert the alternating current (ac) power to direct current (dc) power, and an inverter to provide safe and clean ac power to the load using either the main or battery power.

Unfortunately, in this scenario power efficiency is the price paid for protection. Transformer-based double conversion UPS systems have a typical power efficiency rating in the range of 88% to 92%. As a result, double conversion UPS systems place a steep toll on annual data center energy operating budgets.

Newer three-level insulated gate bipolar transistor (IGBT) UPS technologies, which reduce switching and filtering power conversion losses, offer efficiency levels approaching 97% in double conversion mode, and up to 99% efficiency when operating in energy-saving multi-mode. These new, three-level UPS topologies create new OpEx rationales when designing data center power systems and specifying UPS technologies.


Multi-mode Transfer Speed


So what’s that optimum switching or transfer time? According to a Green Grid white paper on multi-mode (or eco-mode), “if, for example, a UPS has a transfer time of greater than 10 ms and is paired with information technology (IT) equipment that has ride-through capabilities of only 10 ms, the UPS may not be able to support the IT equipment.”

That’s one of the reasons a few companies design their multi-mode UPS products with transfer speeds of less than 2 ms. The technologies that help achieve these speeds are seamless and represent a robust set of power disturbance detection, analysis, and control systems.

When a multi-mode UPS unit’s responsive monitoring technologies detect any sort of deviation on the main or bypass power path, the inverter is immediately turned on to allow quality power to flow from the double conversion premium protection mode. In the same instant, the static switch on the bypass path from the utility is turned off to block the disturbance from reaching the load.

A variety of disturbance analyzers and fast-switching technologies are employed in combination, including

• An instantaneous adaptive voltage error detector that monitors subtle changes in amplitude and duration
• A root mean square (RMS) voltage error detector that computes the RMS of all three UPS output voltages for variances
• An output short circuit detector that, after a breaker is tripped, will automatically increase line current to rapidly clear and reset the breaker
• A sophisticated transient inverter controller that quickly manages the transfer of the load to inverter power and back again to the bypass path.

All of these advanced monitoring and control systems work in concert to anticipate and respond to a comprehensive set of possible power conditions, creating a transfer switch speed of less than 2 ms. This speed helps to maximize the intermittent transfer to double conversion protection, while maintaining higher multi-mode efficiency for the majority of the time when quality utility power is flowing.


Lifecycle Costs


In evaluating efficiency and lifecycle costs for multi-mode UPS systems, some might ask: If our UPS running in double conversion already gets us to 93% efficiency, why take a “risk” for a few percentage points in efficiency? Can that extra energy efficiency provide a significant return?

Figure 2: Small percentage improvements in power efficiency can yield significant savings over a 10-year period.


If we look at a UPS deployment at a typical 10 MW data center realizing just a 1% gain in efficiency, we can see a significant impact over 10 years. As Figure 2 shows, while CapEx (Capital Expenditure) are fixed, a Total Cost of Ownership (TCO) evaluation of the OpEx (Operating Expense) for running an UPS over 10 years creates an operational savings of $1.4 million when energy efficiency improves a single percent — from 93% to 94% efficiency. With newer multi-mode UPS technologies that provide up to 96.5% efficiency, that savings could jump to almost an additional $3.4 million.

As both corporate and data center providers challenge their consulting-specifying partners to deliver projects that balance capital and lifecycle costs, as well as ensure the reliability and energy efficiency of their facilities, new multi-mode UPS efficiency models provide a compelling set of tools for data center designers and engineers.


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Strategic Media Asia (SMA) is one of the approved CPD course providers of the Chartered Institution of Building Services Engineers (CIBSE) UK. The team exists to provide an interactive environment and opportunities for members of ICT industry and facilities' engineers to exchange professional views and experience.

SMA connects IT, Facilities and Design. For the Data Center Design Consideration, please visit 

(1) Site Selection,
(2) Space Planning,
(3) Cooling,
(4) Redundancy,
(5) Fire Suppression,
(6) Meet Me Rooms,
(7) UPS Selection,
(8) Raised Floor,
(9) Code & Standards,
(10) Transformers and Harmonic Distortion, and

(11) Multi-mode UPS Systems

All topics focus on key components and provide technical advice and recommendations for designing a data center and critical facilities.

Four Monitoring Capabilities for Data Center Power Systems

The primary method that people use to measure the energy effectiveness of their data centers is power usage effectiveness (PUE). PUE compares the power used for computing capacity and the overall power used by the data center (PUE = Total Facility Power / IT Equipment Power). The inverse of PUE is data center efficiency, according to The Green Grid association.


Currently, the industry average PUE is reported to be around 2.0, but a number of new and proven data center infrastructure technologies are available to advance efficiency and reduce PUE to 1.5 or lower without compromising availability. There are 4 key actions data center managers can take with integrating monitoring capabilities into power systems that can help improve efficiency and advance PUE.

Monitoring Power Usage


With power densities and energy costs rising, the ability to monitor energy consumption is essential for advancing PUE. Where power is measured can have an effect on how efficiency is measured.

For a comprehensive picture of data center power consumption, power should be monitored at the UPS, the room power distribution unit (PDU), and within the rack. These data points should be consolidated and reported within an enterprise data center infrastructure management (DCIM) tool that can be shared by both facilities and IT management. DCIM tools (if specified early and fully integrated) can provide an overarching view of the data center, which will provide insights into how effectively or ineffectively the computing power of the data center is being used.


Specifically, measurements taken at the UPS provide a base measurement of data center energy consumption that can be used to calculate PUE and identify energy consumption trends. Monitoring the room PDU prevents overload conditions at the PDU and helps ensure power is distributed evenly across the facility.







The best view of IT power consumption comes from intelligent PDUs inside racks, which feature integrated monitoring and control capabilities to enable continuous power monitoring and feedback to the DCIM tool. Because rack power consumption varies based on equipment within the rack and its load, each rack should be equipped with a PDU—two for dual bus environments—capable of monitoring power consumption to the rack PDU, as well as overload-protected receptacle groups and, where required, at the receptacle level.


These systems can provide PDU, branch-level, and receptacle-level monitoring of voltage, kW, current, and kWh, giving the most direct measurement of power consumption and supporting higher data center efficiency and availability.



Monitoring Rack Conditions


With increasing densities, a single rack can now support the same computing capacity that used to require an entire room. Visibility into conditions in racks can help prevent many of the most common threats to rack-based equipment, such as accidental or malicious tampering.

If specified and installed correctly, rack monitoring units can be configured to trigger alarms when rack doors are opened, water or smoke is detected, or temperature or humidity thresholds are exceeded. Many units are equipped with cameras to capture video of the event. These “eyes inside the rack” can be connected to central monitoring systems where environmental data can be integrated with power data from rack PDUs, while providing local notification by activating a beacon or other alarm if problems are detected.



Monitoring Energy Efficiency


Automating collection and analysis of data from power systems can help reduce energy consumption while increasing IT productivity. Energy efficiency monitoring can track total data center consumption, automatically calculate and analyze PUE, and optimize the use of alternative energy sources.

Using real-time data from the many support systems, the monitoring system can track and trend total infrastructure power use and compare this to capacities. For example, for UPS power output, determine when UPS units are running at peak efficiency, and report Level 1 (basic) PUE. Monitoring at the room or row PDU provides the ability to more efficiently load power supplies, dynamically manage cooling, and automatically calculate Level 2 (intermediate) PUE. Panel board monitoring provides visibility into power consumption by non-IT systems, including lighting and generators, to ensure efficient use of those systems.






Finally, rack-level monitoring provides the most accurate picture of IT equipment power consumption and can support Level 3 (advanced) PUE reporting. The ability to automate data collection, and consolidate and analyze data related to efficiency—which is one of the primary jobs of the DCIM tool—is essential to data center optimization. These functions free up data center staff to focus on strategic IT issues.



Monitoring Batteries


Batteries have long been known as a weak link in the power chain. To prevent data loss and increase uptime, most data centers specify and require a dedicated battery monitoring system, which should be installed when the data center goes online. Using a predictive battery monitoring method can provide early notification of potential battery failure. The best practice is to implement a monitoring system that connects to and tracks the health of each battery within a string.

The most effective systems continuously track all battery parameters, including internal resistance, using a dc test current to ensure measurement accuracy and repeatability. Supported by a well-defined process for preventive maintenance and replacement, monitoring batteries can significantly reduce the risk of dropped loads due to battery failure, optimize battery life, and improve safety. The use of a battery monitoring system has an excellent payback period but, more importantly, provides peace of mind to the data center operator that the power system will react and support a load during a power outage.




INTELLIGENT CONTROLS


Previous generations of infrastructure systems were unable to adjust to dynamic load variations. UPS systems, meanwhile, operated most efficiently at full load, but full-load operation is the exception rather than the norm. The lack of flexibility in power systems led to inherent energy inefficiency.

Integrating intelligent control capabilities into data center power systems can help minimize the amount of energy being lost by enabling data center managers to tailor the performance of the UPS system to the specific efficiency and availability requirements of the site. When proper application of these capabilities is followed, it can enable double-conversion on-line UPS systems to operate at efficiency levels up to 97% while the inverter remains in operation.

Advanced UPS systems can employ an energy optimization mode that powers the load in reverse-transfer mode while keeping the UPS inverter at the ready to pick up the load in the event of a utility disturbance. An even higher degree of energy optimization provides power conditioning as well. The result is increased efficiency without compromising availability.

It is important that data center managers do not compromise on distribution and server power supply performance. Attention to distribution transformer and server power supply efficiencies can also reap huge benefits in improving PUE. Deploying TP1-rated distribution transformers can improve partial load efficiency by as much as 0.5%. High-efficiency server power supplies, while initially more expensive, can pay for themselves over their useful life.

About the Blogger


Strategic Media Asia Ltd (SMA) is one of the Approved CPD Course Providers of the Chartered Institution of Building Services Engineers (CIBSE). SMA exists to provide an interactive environment and opportunities for members of IDC industry and engineers to exchange professional views and experience on data center design, critical infrastructure system, electrical and mechanical facilities, etc.

SMA connects IT, Facilities and Design. For details, please visit our website at http://www.stmedia-asia.com/trainings.html.

Singapore continues to drive the demand for data centers

A majority or 78 percent of Singapore’s IT decision makers who participated in a recent survey plan to definitely or probably expand their data centers in 2013, with 82 percent planning for 2014. More than two thirds of the respondents who plan to expand this year prefer to locate their new data centers in Singapore as compared to other countries in the region. The research, conducted by Campos Analysis & Research on behalf of Digital Realty Trust, Inc., indicates that 83 percent will use a partner for design and build or to lease wholesale space, or both.

Of the Singapore-based respondents in the survey, 11 percent cited owning six or more data centers. Approximately 67 percent said they had built a new data centre in the past 24 months. Of those with plans to expand in 2013, 61 percent say they plan to expand in more than one location.

Commenting on the survey results, Kris Kumar, Senior Vice President and Regional Head of Asia Pacific for Digital Realty, said, “It is clear that Singapore’s data centre users are driving their expansion initiatives forward to manage the exponential growth in IT applications and data storage. With the high costs of individual new construction and the limited number of appropriate new sites, IT decision makers see the value of working with a data centre provider such as Digital Realty to fulfill these requirements.”

The average desired space and power requirements for data centre expansion initiatives are 14,000 square feet and 5.4kW per rack respectively. The research also indicates that the respondents’ need to track and manage data center power usage effectiveness (PUE) has increased over the last year. Most companies (80 percent) likely to expand in 2013 are extremely or very confident that they can comply with future energy (86 percent) or carbon emission regulations (82 percent).

“The continued focus on energy efficiency will drive change in the type of requirements customers have for their data centers,” explained Kumar. “This will highlight the capabilities of solution providers, such as Digital Realty, that can deliver data centre designs that are not only resilient, but also extremely efficient.”


Adopted from Networks Asia (www.networksasia.net)