**2. Literature review**

Although fossil fuel complete our desire of electricity but on the other hand these are destructing the planet, so now day's renewable energy resources including hydroelectric, geothermal, solar thermal, biofuels, biomass, wave, tidal, and wind are being used to generate electrical power. More importantly, wind and solar are more developed due to their environment friendly characteristics [7]. There is uncertainty in the output of solar and wind or it can be said that their output is not constant, and depend on season whether it is sunny days or cloudy and also the location for proper required wind speed. This uncertainty in output of these renewable energy resources result in the requirement of energy storage devices for the reliability and improvement in economy of power system [8]. Major problem associated for renewable energy resources is the inconsistent power output, that can easily be reduced and solved using battery energy storage technology, along with that it result in decarburization of energy mix and mitigation of CO2 emission, and global warming effects. BESS can easily be adopted in off grid as well as in on grid system, also at any location in the power system from generation to consumer. Batteries installed at solar photovoltaic PV and wind power plant allow owners to store the energy when energy prices are low or there is inexpensive and uneconomic to supply to grid, and can be released to use during high prices time. Batteries installed with PV system and wind generator at household level increase self-produced and self-consumption electricity, a household PV system with battery system result in increment of selfconsumed energy about 30% without storage to 60–70%, along with that efficiency is increased and also additional power requirement from grid is decreased [9].

Now a day most of the storage in every country is the pumped hydro storage with the capacity of 200 MW, about 25 MW of electrical power is generated using pumped hydro storage plant, out of that 22 MW is being generated in United States. These plants are basically used during peak demand time, also providing water for the nuclear and steam power plant to enhance their performance efficiency and frequency control and regulation [10]. Another bulk storage technique in which air is compressed at the time of low demand with low energy prices, and during peak hour power can be generated at low cost with respect to stand alone gas turbines [11]. Because of new technology in concentrated solar thermal power system and photovoltaic system, demand of energy storage system is increasing in offshore platforms, and telecommunication installations (which are remote area power supply system), mobile applications, emergency backup, gird connected renewable power plants, and stressed electricity supply system [12].

This study shows the renewable energy generation and energy storage analysis in the Finland, It is committed that by year 2050 greenhouse effects will be reduced to 80–97% as compared to year 1990 [13]. Finland is dominating on run of river hydropower with limited capacity of 5.5Twh approximately, during months of December–April in winter season water is stored in reservoir and in summer season, that stored water is used to generate electrical power [14]. It is examined that

### *The Role of Energy Storage with Renewable Electricity Generation DOI: http://dx.doi.org/10.5772/intechopen.96114*

energy storage technologies can play an important role for getting proper benefit of solar resources, along with that gas storage, thermal energy storage, stationary batteries and power to gird technologies are also discussed [15]. Solar photovoltaic and wind are variable sources of power generation; about 70% of total energy generation is being generated using these technologies, about 51% of renewable energy generation is stored and 47% is directly utilized [16]. This study is about United states, inspite of knowing the benefits of energy storage technologies, only 2.5% of total electric power of United States is being stored (out of that most part is hydro pumped storage system), which is about 10% of Europe and 15% of Japan energy storage [17]. About 99% of worldwide storage capacity of 127000 MW is pumped storage, at second compressed air storage with capacity of 440 MW. Electrochemical energy storage has lot of system friendly characteristics i.e. high round trip efficiency, no any pollution, flexible energy and power characteristics, long life and low maintenance. Because of compact size of batteries, these are suitable for distributed locations, also can reduce variation in output voltage of solar PV and wing power plants [18]. From this study it is estimated to increase the renewable generation around 60–80% by the year 2030, which is currently about 20% of total generation of the country; at same time, high cost of battery and un availability of suitable location will result in the limited installment for compressed air energy storage and pumped hydro storage technologies [19].
