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What are the different types of UPS and what are their benefits?

Marc Garner

Marc Garner

VP Secure Power Division, Schneider Electric, UK & Ireland
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Choosing between a UPS type can be a daunting task. Thankfully, Marc Garner, VP, Secure Power Division, Schneider Electric UK and Ireland, has the low down. 

In a world that’s become dependent on highly available and connected digital technologies, resiliency is of utmost importance. As such, the data centres and digital infrastructure providing today’s services must be built to withstand a multitude of unplanned events including fires, flooding, network failures and, more frequently, power outages.

In the latter case, the first line of defence in ensuring optimum digital service delivery is battery backup power protection, or more specifically, an uninterruptible power supply (UPS). The main purpose of the UPS is to buy time and prevent outages, using a battery-based backup system to restore mains power quickly, or to switch to an emergency standby power generation system.

There are, of course, many different types of UPS, catering for data centres of all size and scale. Each of these mission-critical systems, whether in the form of a hyperscale facility, a colocation data centre or a distributed edge computing environment, requires uninterruptible power protection against the threat of unplanned outages. As always, however, there is a trade off between cost and performance, and while some applications may only need enough backup to be shut down temporarily, other more mission-critical applications must remain operational, whatever the cost.

The impact of outages 

According to the Uptime Institute’s 2021 annual-data centre survey, “Power remains the leading cause of outages,” growing from 37% in 2020 to 43% in 2021. Further, 47% of respondents estimated the total cost of downtime to be somewhere in the region of $100,000 – $1 million.

Crucially, 76% of Uptime’s respondents also cited that downtime could have been prevented with better management, processes or configuration. This implies that utilising an IoT-enabled UPS, combined with real-time remote monitoring and management capabilities, and a proactive programme of maintenance, could greatly reduce the risk of outages or loss of service. In this article, we’ll explore the different types of UPS and their benefits.

Single-phase systems

In terms of UPS selection, single-phase systems like APC’s Smart-UPS and Easy UPS are used to back up desktop computers, IT and server rooms, and infrastructure in remote edge locations. They can also provide battery-based backup for electronic and gaming systems at home.

At the edge, single-phase systems can also be found within single rack micro data centre solutions, providing resilient battery backup for business-critical applications in commercial, retail, industrial and distributed IT environments. New research from IDC has also found that 44% of businesses are investing in edge computing to improve systems resiliency and reliability.

In the case of disruption to power, a switch is tripped to disconnect the load from its primary source of supply and switch it to the UPS battery, which becomes the main source of energy. Here single-phase systems can provide a simple to deploy solution to protect businesses from unexpected power failures.

Double conversion

Another common configuration is the double conversion online UPS, which is often found in enterprise data centres. In these power protection systems, the AC and mains source of power passes through a rectifier before charging the battery. The output from which is then converted back to AC (hence double conversion) before being connected to the load.

In such a configuration, the mains power path is delivered via the rectifier and inverter instead of through a transfer switch, so should the main source of power fail, the rectifier shuts down and the inverter draws power from the battery to supply the load. In this way, data centre managers can minimise power interruptions and ensure resilience and business continuity remain the key priorities at all times.

A final benefit of double conversion UPS configurations, or their derivatives such as hybrid conversion models, is the ability to provide input voltage conditioning to safeguard against fluctuations or variations in the mains power supply. As the primary energy source is first rectified from AC to DC and then inverted back to DC again, the supply to the load can be made consistent and resilience increased.

Green operating modes

As ever, with any technology-related decision, there are key trade-offs to consider between cost and utility. Although double-conversion UPS systems provide high levels of reliability, the continuous charging of the battery reduces electrical efficiency and can incur additional maintenance costs due to wear and tear on the components.

Many UPS systems, therefore, offer an Economy or Eco-Mode, in which a static bypass switch is deployed to connect mains power directly to the load. This can boost the energy efficiency of a UPS system from 97% in normal operating mode to 99%, yielding significant cost and energy savings over the life cycle. Further 3-phase UPS systems, such as Schneider Electric’s Galaxy VL, can deliver up to 99% efficiency using its patented ECOnversion operating mode.

From an energy efficiency perspective, ECOnversion helps data centre owners and operators working within cloud service provider and colocation facilities to gain the highest level of energy savings without sacrificing load protection. Operating modes such as this offer far greater levels of resilience compared to traditional ‘eco-modes’ due to the converter running continuously. This means that should an outage be experienced, the UPS will immediately provide backup power without any delays that could impact the load.

Efficiency and sustainability benefits

Another important development driving the efficiency of UPS systems is the growing popularity of Lithium-ion (li-ion) batteries as an alternative to traditional Valve Regulated Lead Acid (VRLA) cells. According to Uptime’s 2021 survey, “Nearly half of the owners and operators surveyed (47%) have adopted li-ion for at least some of their centralised UPS systems,” growing from 28% in 2019.

Although costing more in terms of capital expenditure (CapEx), li-ion batteries offer users greater power densities and a smaller footprint. They also have a longer operating life and can withstand many more charge and discharge cycles compared to VRLA. Further, they are far more energy efficient and offer a lower total cost of ownership over the life cycle, making them a key choice for data centre owners and operators looking to reduce their environmental impact.

Another key benefit is that they can be used in innovative technology applications, such as microgrids and peak shaving. Here the energy storage functions within Lithium-ion systems can make them a primary choice for operators looking to integrate the data centres of the future with the renewable energy capabilities of the grid, creating a sustainable and resilient digital infrastructure solution.

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