IEC_Elctrical Energy Storage.pdf

Today flywheels are commercially deployed for power

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Today flywheels are commercially deployed for power quality in industrial and UPS applications, mainly in a hybrid configuration. Efforts are being made to optimize flywheels for long-duration operation (up to several hours) as power storage devices for use in vehicles and power plants. Field Replaceable Bearing Cartridge Magnetic Bearing Integrated into Field Circuit Air-Gap Armature Smooth Back-Iron, No Slots & Low Loss Field Coil Flywheel Motor/Generator Rotor No Permanent Magnets Enables High Tip-Speed and High Output Power 7 The stator is the static part of the assembly at the top of the tower.
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24 S E C T I O N 2 Types and features of energy storage systems 2.3 Electrochemical storage systems In this section various types of batteries are described. Most of them are technologically mature for practical use. First, six secondary battery types are listed: lead acid, NiCd/NiMH, Li-ion, metal air, sodium sulphur and sodium nickel chloride; then follow two sorts of flow battery. 2.3.1 Secondary batteries Lead acid battery (LA) Lead acid batteries are the world’s most widely used battery type and have been commercially deployed since about 1890. Lead acid battery systems are used in both mobile and stationary applications. Their typical applications are emergency power supply systems, stand-alone systems with PV, battery systems for mitigation of output fluctuations from wind power and as starter batteries in vehicles. In the past, early in the “electrification age” (1910 to 1945), many lead acid batteries were used for storage in grids. Stationary lead acid batteries have to meet far higher product quality standards than starter batteries. Typical service life is 6 to 15 years with a cycle life of 1 500 cycles at 80 % depth of discharge, and they achieve cycle efficiency levels of around 80 % to 90 %. Lead acid batteries offer a mature and well-researched technology at low cost. There are many types of lead acid batteries available, e.g. vented and sealed housing versions (called valve-regulated lead acid batteries, VRLA). Costs for stationary batteries are currently far higher than for starter batteries. Mass production of lead acid batteries for stationary systems may lead to a price reduction. One disadvantage of lead acid batteries is usable capacity decrease when high power is discharged. For example, if a battery is discharged in one hour, only about 50 % to 70 % of the rated capacity is available. Other drawbacks are lower energy density and the use of lead, a hazardous material prohibited or restricted in various jurisdictions. Advantages are a favourable cost/performance ratio, easy recyclability and a simple charging technology. Current R&D on lead acid batteries is trying to improve their behaviour for micro-hybrid electric vehicles (cf. section 3.2.5) [etg08] [lai03].
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