Advances in energy storage : latest developments from R&D to the market Wherever energy is available but not immediately used energy storage can be utilized. Energy storage technologies help to absorb energy and release it at a later time (or in a different place) when it is needed. Hence energy storage makes surplus energy usable and is therefore equivalent to energy sources like fossil fuels and their market competion. Conventional energy resources crude oil natural gas and coal for example share many energy storage qualities while not being renewable. They allow for a wide variety of storage methods at high energy densities for example 40 GJ m℗đ for crude oil and coal. Considering these facts energy storage technologies need to have either simi lar technical characteristics or different advantages of an economic or ecologic nature. Electric mobility may it be cars public transportation or any other kind of vehicle is a prime example of direct competition between a storage system and fossil fuels. The storage i.e. the battery is supposed to take in energy from for ecological reasons re newable sources and deliver it whenever the consumer deems fit. At the same time the storage needs to make the consumer physically independent of these energy sources. Besides a purely economic comparison of vehicles fitted with combustion and electric engines environmental issues like air quality might cause a crucial bias toward the ener gy storage. The cost of storage usually adds to the total energy cost. The cost for stored energy must not be significantly higher than the cost of energy supplied directly to the consumer. Prices however fluctuate with actual demand. Storages are economically most attractive when energy can be obtained at low cost and provided at a higher price during a peak in demand. With an increasing share of renewable energy future energy systems will also have an increased need for balancing of supply and demand. Fluctuating renewable energy sources combined with energy storage systems are able to provide demand adapted en ergy. This application will become the most relevant one in the next years.