Applications uninterruptible power systems

Lead-acid batteries are also used for emergency power in uninterruptible power systems (UPS), telecommunications back-up systems, and safety equipment in critical applications such as hospitals and nuclear power plants. Stationary or standby battery designs and recharge profiles vary according to the specific system requirements. Large battery strings are connected in series to deliver up to several hundred volts. 

Uninterruptible power systems have become a virtual necessity for powering large or small computer systems where the application serves a critical need. Computers and data communications systems are no more reliable than the power from which they operate. The difference between UPS and emergency standby power is that the UPS is always in operation. It reverts to an alternative power source, such as the utility company, only if the UPS fails or needs to be deactivated for maintenance. Even then, the transfer of power occurs so quickly (within miUiseconds) that it does not interrupt proper operation of the load. 

Backup power is defined as any device that provides instantaneous, uninterruptible power. The term UPS (uninterruptible power supply) is an often used term, but can sometimes refer to systems that supply A/C power, or systems that supply power for no more than 30 to 60 minutes. A more general definition includes all types of power outputs and all backup times. Typical applications for backup power include telecommunications systems, information technology and computer systems, manufacturing processes, security systems, utility substations, and railway applications. Backup power systems are employed in cases where the loss of power results in a significant reduction in productivity or financial loss. 

Flaving had over 150 years of technical development behind them, lead-acid batteries can be custom-tailored to specific applications, such as those requiring deep discharge cycles (e.g., where the batteries are used as the sole power source for electrical equipment) and for battery backup uses such as in large uninterruptible power supply systems in data centers. Moreover, lead-acid cells not only have low internal resistance but also experience no memory effect as do some more exotic cell designs, such as NiCads. This enables these cells to produce enormous currents and have a moderately long, predictable life.1... 

In a different type of RUPS system, during loss of normal power the AC motor is supplied from a battery bank by means of an inverter (Figure 2.19). The batteries are kept charged by the normal power source. The motor is powered from the batteries until the batteries become depleted. In some applications, standby generators are used to supply the battery bank in case of loss of normal power. Other combinations are used to provide uninterrupted power to critical loads, but we will not attempt to review all the available technologies. It is sufficient to point out that low-frequency disturbances are effectively mitigated using one of the means mentioned in this section. 

Smaller fuel cells (1 kW and lower) may be used as portable power as well as back-up power (uninterruptible power supply) or as battery chargers. Small fuel cells are also being developed as battery replacement which would enable longer operation time for consumer electronics (such as laptop computers, cell phones, cameras, and music players). There is a wide array of possible fuel cell applications in military battery chargers, telecommunications, navigation systems, soldier power, computers, various power tools,... 

Stationary battery (cell) — Rechargeable -> batteries designed to be located at a fixed place. Stationary batteries are used mainly for uninterruptible power supplies (UPS) and standby applications. These cells are usually designed for high reliability and very long -> cycle life under shallow depth of discharge (DOD) conditions. The common chemical systems utilized for the production of stationary batteries are the -> lead-acid and -> nickel-cadmium batteries. Less common, and more futuristic is the - sodium-sulfur battery designed for KW and... 

MW for about 10 s, or about 4.5 kWh. They are often used in uninterruptible power supply (UPS) applications. Flywheels are much less costly than SMES and supercapacitors, and they compete with batteries in high-power, low-energy applications. The response time of a flywheel energy-storage system is of the order of a few milliseconds. 

Lead acid batteries have been used for more than 130 years in many different applications including automotive and various traction duties and also telecommunication systems and uninterruptible power supphes (UPS). The last two groups constitute the major part of the so-called stationary battery sector, and the lead-acid battery has proved to be a very reliable system for these appUcations. 

Large OCSM batteries are also suitable for other utility applications. Recently, the concept of a multifunctional energy storage system, which is useful to improve the utilisation of regenerative energies, has been evaluated [88]. This system includes three different functions (i) uninterruptible power supply (UPS), (ii) improvement of power quality, and (iii) peak load assists via the use of regenerating power sources, with surplus energy from periods of low demand stored in a battery for peak-load periods (see Chapter 10). 

We are living in a highly technologized environment. Thus the constant supply of energy is essential for many applications. Especially IT and communication technology is essential for processes, workflows and business transactions. Also the increasing demand for public safety results in continuously running equipment for control and information systems or security surveillance. In order to support this backbone of our daily life, critical infrastructures are quite often equipped with an uninterruptable power supply (UPS). Fuel cells can already be used for such applications. 

Pievatolo A., Tironi E. Valade I. 2004. Semi-Markov Processes for Power System ReliabilityAssessment with Application to Uninterruptible Power Supply, IEEE Uans-actions on Power Apparatus and Systems, Vol. 19, No. 5, pp. 1326-1333. 

Battery management systems are also commonly used in other battery applications such as material handling, uninterruptible power supplies, off-grid power systems, marine and battery banks for alternative energy sources. 

Uninterrupted power supply (UPS) systems — Supercapacitors can be used for temporary back-up power in UPS systems. They can provide instantaneous supplies of power without delays, helping to prevent malfunctions of mission-critical applications. Supercapacitors quickly bridge the power applications for stationary UPS systems that are augmented with fuel cells. In addition, supercapacitors are best suited to provide power for start-up and during peak load buffering. 

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