1 Electrochemical Energy Storage

The problems related to the differed time between production and use of electrical energy produced by renewable sources makes storage systems an integral part of Renewable Energy Sources (RES), especially for stand-alone systems. Furthermore, for grid-connected systems, the stability of the electric system and the quality and stability of the delivered voltage will result in a high quality system in the presence of intermediate storage. Storage systems are particularly onerous for RES and, as a consequence, their cost and life-time significantly affect the total cost of the whole system. The relation between technical and economical characteristics in terms of dimension and technology to be employed has to be singled-out and optimized depending on the circumstances and, for different applications, in terms of release time of the stored energy and outbound power. The alternatives to obtain a continuous, reliable and cost-effective availability of electricity include: diffusion of RES, production from clean carbon technologies and others sources technical evolution of the transmission grid for the connection of these sources to the loads programs to meet power/energy demands and management of the loads. The diffusion of storage technologies in the public grid include several benefits: the optimization of the grid for the fulfilment of base-load the way to facilitate the power trade-off in RES systems fluctuating over time or available only during day-time easy integration in grid of the energy requirements for hybrid vehicles the chance of investments differentiation in the distribution grid to be adapted to temporary peak-loads. resources for the provision of auxiliary services directly to the electricity provider. The different storage technologies can be classified on the basis of the different methodologies utilized: mechanical (compressed air energy storage, flywheels) electrochemical (lead-, nickel-, high temperature salts-, redox-batteries, hydrogen. electrical (capacitors, supercapacitors). Although some storage technologies could work for several applications, the most part of the different options is not economically applicable to different functional categories. Their