IEC_Elctrical Energy Storage.pdf

27 standards for ees for mature ees systems such as

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2.7 Standards for EES For mature EES systems such as PHS, LA, NiCd, NiMH and Li-ion various IEC standards exist. The standards cover technical features, testing and system integration. For the other technologies there are only a few standards, covering special topics. Up to now no general, technology-independent standard for EES integration into a utility or a stand-alone grid has been developed. A standard is planned for rechargeable batteries of any chemistry. Standardization topics for EES include: terminology basic characteristics of EES components and systems, especially definitions and measuring methods for comparison and technical evaluation - capacity, power, discharge time, lifetime, standard EES unit sizes communication between components - protocols, security interconnection requirements - power quality, voltage tolerances, frequency, synchronization, metering safety: electrical, mechanical, etc. testing guides for implementation.
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36 S E C T I O N 2 Types and features of energy storage systems 2.8 Technical comparison of EES technologies The previous sections have shown that a wide range of different technologies exists to store electrical energy. Different applications with different requirements demand different features from EES. Hence a comprehensive comparison and assessment of all storage technologies is rather ambitious, but in Figure 2-9 a general overview of EES is given. In this double- logarithmic chart the rated power (W) is plotted against the energy content (Wh) of EES systems. The nominal discharge time at rated power can also be seen, covering a range from seconds to months. Figure 2-9 comprises not only the application areas of today’s EES systems but also the predicted range in future applications. Not all EES systems are commercially available in the ranges shown at present, but all are expected to become important. Most of the technologies could be implemented with even larger power output and energy capacity, as all systems have a modular design, or could at least be doubled (apart from PHS and some restrictions for underground storage of H 2 , SNG and CAES). If a larger power range or higher energy capacity is not realized, it will be mainly for economic reasons (cost per kW and cost per kWh, respectively). Figure 2-9 – Comparison of rated power, energy content and discharge time of different EES technologies (Fraunhofer ISE)
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37 On the basis of Figure 2-9 EES technologies can be categorized as being suitable for applications with: Short discharge time (seconds to minutes): double-layer capacitors (DLC), superconducting magnetic energy storage (SMES) and flywheels (FES). The energy-to- power ratio is less than 1 (e.g. a capacity of less than 1 kWh for a system with a power of 1 kW).
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