Electric Energy Storage Systems

Fossil or nuclear primary energy sources (PES) have been widely used in energy systems worldwide. The PES are finite and are forecasted to last only for the next 60 (natural gas) or 200 (hard coal) years at today’s level of consumption. However, the consumption of energy has been increasing worldwide for many years. Furthermore, an increase of CO₂ emissions has been observed as a negative result of the increase in consumption, which has become evident from the global warming effect. It has become necessary to define global countermeasures to stabilize the increase in the Earth’s temperature.

Electrical energy storage has been used in powers system since the beginning.

The first power systems were constructed as DC systems and are generally associated with the name Thomas Edison, who founded the General Electric Edison Company in the United States in the late 1880s. The first electric city light was supplied by electricity from a DC generator combined with battery storage. The first large power station used the energy of falling water and converted it into AC electricity [1]. The energy storages (batteries) at that time were a necessary part of the power system and extended the limited supply of power from generators in the night, operating those generators in parallel with batteries that had been charged during the day.

The power-system structure is composed mainly of generation, transmission and distribution. This is also due to the unbundling process which takes place in many countries. Many power networks are unbundled commercially, with a separation of generation from the operation of the network. The power in a traditional power system is produced by a few large power plants located near primary energy sources (e.g., coal mines, water). The power is then transmitted at very high or high voltage for long distances (e.g., 500 km) and, finally, distributed to the end users. Generation is the main part of the power system. More than 50 % of the total costs of the power system are related to generation, which is also responsible for most of the polluting emissions. The general structure of the primary energy sources has changed during the last 30 years (see Fig. 1.2), but still fossil energy dominates the sources with a share of about 80 %.

The modeling of an energy storage system (ESS), as already mentioned in Chap. 2, consists mainly of determining two parameters: the storage power and the storage capacity. After having determined these two parameters, which are based generally on the analysis of specific load curves and a general storage model, an optimal storage technology, considering the economic, technical and ecological criteria (also see the example in Sect. 2.4) can be chosen depending on the application (e.g. power quality and/or energy management) that they need to cover.

Energy storage systems have been instrumental in the modernization of our society. Energy storage systems have been essential for decoupling electricity generation from consumption since electrification began. Their use will grow yet more predominant in the future; the greatest amount of electricity is being generated by volatile renewable-energy sources, such as wind and solar power. This will entail the use of new solutions to optimally decouple the power generated by renewables from the power demanded. Multi-energy systems and virtual-power plants constitute the most promising solutions; both of them employ energy storage systems as well as demand-side and demand-response programs.

Electric vehicles, by definition vehicles powered by an electric motor and drawing power from a rechargeable traction battery or another portable energy storage system recharged by an external source, e.g. residential electrical systems or public electrical grids, are nothing new. Werner von Siemens developed and built his Elektromote in 1882 and Ferdinand Porsche his Lohner-Porsche in 1900, see Fig. 6.2.

The flexibility that Electric-Energy Storage Systems (EES) will bring into the power system, as one of the key technologies which enables the widespread use of intermittent renewable energies and the decoupling of power generation from power consumption, can be used both in terms of power and energy. Such a capability will be beneficial to all the actors in the power system: the generation companies, the system operators (transmission and distribution) and the consumers (see Fig. 7.1). Generally, the benefits of EES from the points of view of utilities, consumers and generation are introduced in Sect. 1.1.2. In this chapter, the economic benefits from the point of view of the market participants will be specified in detail.

A reliable supply of electricity with the requisite high quality to industrial consumers, in particular, is essential for society’s continued development and welfare. The standard DIN 40 041 defines reliability as an entity’s quality in terms of being able to meet the demand for reliability during or after specified time intervals and under specified conditions of use. The electricity supply is considered to be reliable when it continuously meets customer demand (just-in-time), and this must be so while the complete system of primary-energy production, conversion, transport and distribution are always necessarily factored in. Various malfunctions or events characterized by their intensity (insufficient energy) and duration also affect the security of supply in various ways, e.g. affecting varying numbers of consumers. Causes of malfunctions are external, e.g., storms and lightning strikes, terrorism or solar winds, or internal, e.g., planning and design errors or operational errors such as overloaded system components, short circuits caused by incorrect operation, switching surges, and have various points of origin. Statistical data on this are plotted in unavailability graphs, see, e.g., Fig. 8.1. Malfunctions that go undetected or cannot be assigned to any of the predefined groups/criteria are placed under the category “no identifiable cause” [1].