Uninterruptible power supply (UPS) systems have incorporated in their structure an electrochemical battery which allows for smooth power supply when a power failure occurs. In general, UPS systems are based on lead acid batteries; mainly a valve regulated lead acid (VRLA) battery. Recently, lithium ion batteries are getting more and more attention for their use in the back-up power systems and UPSs, because of their superior characteristics, which include increased safety and higher gravimetric and volumetric energy densities. This fact allows them to be smaller in size and weight less than VRLA batteries, which are currently used in UPS applications.The main purpose of this paper is to analyze how Li-ion batteries can become a useful alternative to present VRLA. In this study, three different electrochemical battery technologies were investigated; two of the most appealing Li-ion chemistries, lithium iron phosphate (LFP) and lithium titanate oxide (LTO) were compared with lead acid batteries, in terms of their basics characteristics (e.g. capacity, internal resistance) and their dependence on the operating conditions.

Fuel cell technology is now a viable alternative to generators and extended-run batteries, allowing IT and facility managers more flexibility in the specification, installation, and operation of critical facilities and avoids environmental issues of other sources. This paper briefly explains the use of fuel cell technology in extended runtime applications. A specific fuel cell based extended runtime system has been developed and the paper describes the major system constituents. Substantial size reductions (in terms of footprint) have been achieved compared to battery solutions.

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