In this paper, an updated review of the state of technology and installations of several energy storage technologies were presented, and their various characteristics were analyzed. The analyses included their storage properties, current state in the industry and feasibility for future installation. The paper includes also the main characteristics of energy storage technologies suitable for renewable energy systems.In this paper, an updated review of the state of technology and installations of several energy storage technologies were presented, and their various characteristics were analyzed. The analyses included their storage properties, current state in the industry and feasibility for future installation. The paper includes also the main characteristics of energy storage technologies suitable for renewable energy systems.••Energy continues to be a key element to the worldwide development. Due to the oil price volatility, depletion of fossil fuel resources, global warming and local pollution, geopolitical tensions and growth in energy demand, alternative energies, renewable energies and effective use of fossil fuels have become much more important than at any time in history,. Current and future markets in fossil fuels are subject to volatile price changes in oil and natural gas. National and international energy/environmental crises and conflicts are combining to motivate a dramatic paradigm shift from fossil fuels to reliable, clean and efficient fuels. Using renewable energy sources seems a promising option; however, there are still some serious concerns about some renewable energy sources and their implementation, e.g. (i) capital cost and (ii) their intermittent nature in power production,,,. Renewable energy resources such as wind and solar energies cannot produce power steadily, since their power production rates change with seasons, months, days, hours, etc. The cost issues depend mainly on how research and development can be successfully carried out in these areas. Extensive public and private researches and development efforts to achieve technological breakthroughs are required to bring these technologies to commercial maturity. Therefore, in order for the renewable energy resources to become completely reliable as primary sources of energy, energy storage is a crucial factor,. Essentially, energy from th. Thermal energy storage (TES) is widely recognized as a means to integrate renewable energies into the electricity production mix on the generation side, but its applicability to the demand side is also possible,. In recent decades, TES systems have demonstrated a capability to shift electrical loads from high-peak to off-peak hours, so they have the potential to become a powerful instrument in demand-side management programs. Thermal storage is a technology that ensures energy security, efficiency and environmental quality.The thermal energy storage (TES) can also be defined as the temporary storage of thermal energy at high or low temperatures. TES systems have the potential of increasing the effective use of thermal energy equipment and of facilitating large-scale switching. They are normally useful for correcting the mismatch between supply and demand energy. Certainly, TES is of particular interest and significance in using this essential technique for solar thermal applications such as heating, hot water, cooling, air-conditioning, etc., because of its intermittent nature. In these applications, a TES system must be able to retain the energy absorbed for at least a few days in order to supply the energy needed on cloudy days when the energy input is low,.The basic principle of a TES system is the same for all the applications: energ. Fossil fuels have two important characteristics in addition to being concentrated sources of energy. They are energy stores and they are readily transportable. This means that the fuels may be stored until such time as they are required and may be transported by rail, road or pipeline to where they are to be used. By contrast, most of the renewable (except for biomass and hydro) cannot be stored and cannot be transported to the place of use, except by first converting them to electricity. Electricity is the most versatile and preferred form of energy for many applications and therefore it is not surprising that renewable energies and electricity generation are so intimately bound together. Electricity is readily transmitted over long distances and distributed to consumers by cable, but there is often the problem of matching the supply to meet the demand. This calls for the development and application of systems for the efficient storage of electricity.Electric energy storage is the capability of storing energy to produce electricity and releasing it for use during other periods when the use or cost is more beneficial. An electrical energy storage unit can participate in electricity markets in a number of ways, depending on its energy storage and delivery characteristics. Electrical energy storage includes all the technologies and systems where the external interface is electrical. The electrical interface is a. Each storage technology has unique characteristics and is different in terms of its appropriate application field and energy storage scale. A comprehensive analysis of each storage technology needs to be performed before a decision can be made about the storage technology that is most suitable. From a user point of view there are both technical and commercial criteria for selecting the most suitable technology,,,,, :••Energy and power densityThe power density (W/kg or W/litre) is the rated output power divided by the volume of the storage device. The energy density is calculated as a stored energy divided by the volume. The volume of the storage device is the volume of the whole energy storage system.••Self-dischargeThere.
