Energy storage is a vital component in the chain of production-distribution-consumption of energy, even more so if the energy comes from a source that is intermittent and/or is not controllable as is the case with for example solar energy and wind energy. For many people, the term energy storage is the storage of electricity in batteries, as it is the most commonly found way of storing energy. In addition to classic batteries, there are other energy storage alternatives from a primary source for later use. The most valuable forms of energy storage are the ones that can both take over and release the energy on demand, in the form of electricity, such that, in the end, the electrical energy is transformed into thermal or mechanical energy. In stationary applications, energy can be stored in various forms such as batteries, ultracapacitors, or tanks of hydrogen, water, and different types of materials. This chapter will evaluate each form of energy storage.
TopIntroduction
In recent years there has been a major worldwide concern for the change the source of energy from fossil fuels to renewable sources. The end user (be it a home or industrial user) has changed his profile in terms of energy consumption. The need for energy storage will certainly grow substantially. This is not just due to the natural growth of all the technologies in which storage is an important component, but also to important changes in the energy production and utilization landscape (Robert A. Huggins, 2016).
An important objective in the European Strategic Energy Technology Plan (SET Plan) is energy efficiency and decarbonization. This objective is attempting to be reached using research and innovation in production and storage of renewable energies (e.g. solar, wind, geothermal, hydro, hydrogen). Due to these SET Plan objectives, Energy Storage Systems are an important factor in meeting Europe's need for clean and efficient energy.
The trend being set is the usage of renewable sources everywhere, however these sources are not able to deliver constant 24/7 energy (e.g. Photovoltaic plant on a cloudy day or a non-windy day for wind turbines). Another present issue is that the increased number of devices electrically connected to the grid, including stationary applications, highly increase the chances of causing an imbalance. At the same time, the price of energy is varying in different power markets. In a scenario with the possibility of the main source having a power failure due to lack of constant generation, the need for a backup solution greatly increases. These four issues (Smoothing the flow of power; Increasing utilization of power-generation, transmission and distribution assets; Smoothing out the costs, and necessity of a backup solution) have the same valid answer: energy storage.
Historically, companies, grid operators, independent power providers, and utilities have invested in energy-storage devices to provide a specific benefit, either for themselves or for the grid. As storage costs fall, ownership will broaden and many new business models will emerge. (P. D’Aprile, J. Newman, D. Pinner, 2016)
New technologies and new materials for energy storage are presented every day. Their purpose is to increase efficiency, life-time, and to provide environmentally-friendly solutions.
According to the European Market Monitor on Energy Storage (EMMES), installed energy storage will grow up to 5.5 GWh. (EMMES, 2019) Figure 1, shows the growth of electrical, electrochemical and mechanical storage, from the year 2016 until now, with a prediction for year 2020 (with the exception of pumped hydro storage).
Figure 1. Electrical energy storage capacity annually installed (MWh)
As the level of electrification increases, in parallel with the increasing number of decentralized energy sources, it raises the question of the technical flexibility of the systems of electricity supply, storage and distribution. stationary applications storage capacity can integrate variable sources of renewable energy.
Energy storage systems (for both stationary and mobile applications) must provide maximum benefit to the end-users of electricity and must be accepted by the electricity industry. Therefore, in order to achieve these two most important objectives, economic factors, technical factors, research and design factors for energy storage applications must always be taken into consideration. It is clear that each storage application will have its own specifications, but these three interrelated factors must lead to a global-scale spread of the proposed application and, ultimately, to its grid-integration use.
The usual method of storing energy for stationary applications is in pumped hydro, and its represented in 2018 around 94% of all storage systems. But EU is also focusing on other storage systems for stationari applications (batteries and hydrogen). The most important key issue factors regarding the batteries storage systems are: raw materials, battery cell manufacturing, reaserch and inovation, qualified human resources. In 2017 Commission created the European Battery Alliance to follow up these major key factors along with other secondary key factors.