**7. Challenges and future orientations of EES/the future for energy storage and renewable integration**

As we are moving towards renewable energy for our electricity generation, and also with the development in battery energy storage technology and their life and cost, it is important to say that battery will be an important part of power system in near future. Battery storage system makes the grid to be more flexible and modernize, just like improvement of cycling performance of conventional thermal units at lower prices, coordination of hydro with solar and wind power plants, advancement in control system and communication [47]. With the development in battery energy storage system, their cost and performance characteristics are being improved, that make an important role in their market value. By storing energy using battery storage technology near to the loads transmission and distribution losses reduced, hence system efficiency is increased; stacked services and multiple value streams and services (which are easily monetize able in deregulated markets) are illustrated in **Figure 3**. The energy storage technology has promising application prospect in renewable energy generation grid integration, distributed generation, micro grid,

#### **Figure 3.**

*Multiple value streams of battery energy storage [International Renewable energy agency 2016, Electric power research institute, & US department of Energy] [47].*

transmission and distribution, smart grid and ancillary services. However, the large scale application of energy storage technology still faces challenges both in the technical and economic aspects. For the development in energy storage system, some new break throughs are required in capacity, long-lifespan, low-cost, high-security for electrochemical energy storage, high efficiency. Along with that simulation and operation optimization on storage technology should be focused in order to support theoretical as well as well practical knowledge for projects demonstration for promoting the commercialization and industrial system. At the same time it is necessary to establish a complete and rigorous professional cohesion, reasonable classification, transparency, openness and energy storage standards, which will provide strong support for research and development, production and application of energy storage, and promote the development of energy storage technology and related industries. Currently, lack of policies to support the technology, and high cost and other issues are main challenges for energy storage system in industrial applications. Two aspects should be considered in the future: on the one hand, it is

necessary to propose energy storage system solutions with the participations from electricity users, electrical enterprises, researcher, economical organizations and social originations, and on the other hand, the suitable industry market mechanism and the subsidy policy should be promoted. Researchers should be promoted and encouraged for applications of energy storage in order to provide development model and achieve commercial operation of energy storage.
