Selecting Lithium-ion UPS for Healthcare Applications

Over the last two years, organisations have been deploying their business continuity plans. Whilst in the UK, they may now be reverting to a new normal, their business, operational and technology strategies are far more intertwined than before the pandemic. No more so than in the healthcare industry, where we are seeing greater interest in lithium-ion battery UPS systems.

What is a Lithium-ion UPS?

In an uninterruptible power supply, the battery provides a store of DC power used to power the inverter when the mains power supply fails or fluctuates (voltage or frequency or both) outside of a pre-set input window. The battery powers the inverter until either the mains power supply is restored, a standby power generator starts-up or the battery energy reserve is exhausted.

The most used battery in a UPS system and other standby power applications (from security to alarm panels) is a valve-regulated lead acid (VRLA) type. A lead acid battery is suitable for standby applications and the technology evolved from the automotive industry. Think traditional car or generator batteries, where the battery set is required to power the starter-motor and keep power to certain electrical circuits i.e., tracking or security systems.

Types of Lithium Battery

Lithium-ion UPS based systems have been one of the most hotly anticipated developments in uninterruptible power supplies. Lithium-ion or Li-ion is a generic term for a lithium-based battery but there are several types including:

LiFePO4 is the most used lithium battery in a Lithium-ion based UPS system in which offers a longer working life, more cycles and faster recharge times than a traditional VRLA battery UPS. Service life can be almost double (10years plus) than a lead acid battery which will either be a 5year or 10year design life system.

For more information on lithium-battery types see:
https://inverted.in/blog/types-of-lithium-ion-batteries-available-in-the-market

Lithium-ion UPS Advantages

As in the electric vehicle industry, lithium-ion has been a transformative factor and the same is forecast for the UPS industry. The reasons for this include:

• Compact Energy Density: Lithium-ion UPS systems will be more compact than UPS with VRLA batteries. This is because li-ion batteries have greater power densities allowing them to store more energy in the same volume than a lead acid battery. For UPS systems this means a more compact footprint and form factor, especially for longer duration runtimes. The more compact footprint means it may be easier to find suitable floor or rack space for a lithium-ion UPS close to the point of usage i.e., to protect a particular medical system within a hospital environment. In terms of weight, a Li-ion UPS will also be up to 40% lighter.
• Recharge Times: a lead acid battery will recharge to 80% within 24hours. This can be a problem in healthcare and IT applications where there could be frequent power outages and/or generator failure. A lithium-ion battery will recharge to 100% within 6-8hours, recovering 3 times faster than a lead acid battery.
• Battery Cycling and Replacement Costs: in a UPS system the most expensive consumable item is the battery whether it is a lead acid or lithium-type. The most used lead acid battery in uninterruptible power supplies below 20kVA will be a 5year design life requiring replacement within years 3-4 of operational service. For larger UPS systems a 10year design life battery is typically used, and this will require replacement in years 7-8 of operation. In terms of cycles, a lead acid has a typical design cycle (charge/discharge) capacity of three hundred, where as a lithium-ion battery is around 5,000. A lithium-ion battery will be more expensive than a lead-acid, but the operational life can be from typically 8-10 years or more. For smaller UPS systems therefore, the operational and service costs can be 50% or more lower than a VRLA lead acid battery UPS, based on the fact that lithium-ion UPS prices will fall as volume usage continues to increase.
• Temperature Tolerance: lead acid batteries require an ambient temperature of around 20-25⁰C to ensure their design life. Whilst this is within the ASHRAE recommended range for server rooms and data centres it does limit where a UPS can be operated within and can add to the cooling load. Lithium-ion batteries are more temperature tolerant (up to 30⁰C and higher) and do not degrade to as rapidly as lead acid in high ambient temperatures.
• Warranty Periods: a more traditional lead-acid battery set has a warranty of 2-3 years, dependent upon the manufacturer with 5year warranty extensions possible. A lithium-ion UPS should have a 3-5year warranty and longer extensions may be possible. The longer warranty periods can also lead to lower UPS maintenance contract pricing and service costs as a lithium-ion battery can be more dependable over say a 5year operational period than a lead acid battery.

Whilst a lithium-ion UPS may have a higher cost to purchase than a lead-acid based system, overall, its operational and service costs, and compact size mean than it can be a more cost-effective option. Other applications include energy storage.

Renewable Energy Storage

Uninterruptible power supplies started out as backup power devices, providing their critical loads with stored energy when the mains power supply fails or fluctuates. The rapid recharge times of lithium-ion is already proving why it is the battery type of choice for electric vehicles and renewably energy storage. A UPS system can be used in an equivalent way where renewable energy generation is available, and the lithium-ion battery is large enough.

A lithium-ion UPS system can be charged overnight when peak electricity costs are lowest and/or charged using renewable energy generated from nearby solar PV or wind turbines. The stored energy can be released to power the critical loads when energy costs are highest. Alternatively, the energy storage during traditional usage can be used to support national grids when peak shaving is required to maintain the grid frequency.

Larger lithium-ion UPS can also be used to support spikes in power demands by for example, medical imaging systems. In a situation where the available supply is limited to say 150kW, a suitable 3phase UPS installed with a lithium-ion battery, could use its stored energy to meet additional power spikes in demand from its battery set. In this instance, the Li-ion UPS is being used as both an energy storage system and a tertiary power supply.

HTM 06-01 provides information on the design, installation and testing of all fixed wiring and integral electrical equipment used for electrical services. HTM 06-01 recommends that batteries used for tertiary power supplies, for example, those used in an uninterruptible power supply, should have a design life of 10 years. For UPS systems this means having a UPS with a 10year design life lead acid battery or a lithium-ion battery set.

HTM 06-01 also defines a tertiary power supply as a third power supply that supplements the PES (primary energy supply) and the SPS (secondary power supply), usually in the form of an uninterruptible power supply or battery system. Whilst the SPS is more typically a standby power generator or CHP plant, lithium-ion UPS can provide an alternative eco-friendlier technology, compared to a diesel generating set. Battery-based systems are certainly preferred where noise pollution and fuel storage can be issues. Lithium-ion batteries are already being used in the UK as grid-scale energy storage devices and there is no reason why they could not be used locally to replace local standby power generators.

For more information on HTM 06-01 see:
https://www.england.nhs.uk/publication/electrical-services-supply-and-distribution-htm-06-01/

Summary

Whether we are talking about public or private hospitals, healthcare service providers, doctors’ surgeries or even pharmaceutical manufacturing and scientific research centres, the need to harness the latest technologies to meet service demands or innovate at pace was always there. Whilst, new medical procedures and treatments may rely on new diagnosis, delivery, and monitoring systems, very often there has been slight change to the more traditional critical infrastructure systems including critical power and cooling. Lithium-ion UPS provide a way to innovate at the infrastructure level and help organisations such as the NHS move closer to meeting their 2019 commitment to reduce carbon emissions by 51% by 2025.