Overview of Storage Energy Systems for Renewable Energy System Application A. M. Shiddiq Yunus Mechanical Eng. Department, Energy Conv. Study Prog. State Polytechnic of Ujung Pandang South Sulawesi, Indonesia shiddiq_96@yahoo.com.sg Yassir Al Harby, A. A. Siada, and M. A. S. Masoum Electrical and Computer Eng. Department Curtin University Perth, Western Australia y.alharby1@postgrad.curtin.edu.au Abstract — The integration of renewable energy system into modern power grids has significantly increased during the last decade. Solar and wind energy are the most popular renewable energy sources recently. Solar energy has reached about 17,3 GW in 2010 whilst about 340 TWh of wind energy source has been installed worldwide. In this paper, the overview of updated information regarding proposed storage energy systems for renewable energy is presented. It is useful information for practitioners in considering the possible options of storage energy technologies to be connected with renewable energy sources. I. INTRODUCTION Solar and wind energy resources are today’s two most popular renewable energy resources. They are both environment-friendly and sufficiently available naturally, so their utilization continues to show a significant growth worldwide. Germany currently has 43.5% of the world’s solar peak capacity, with an installed capacity of 17.3 GW by the end of 2010. This is four times more than that of its nearest rivals, Spain and Japan. Despite overall rapid capaci ty growth around the globe, the PV’s power generation share globally is still low, contributing only 0.1% of the world’s total power generation. The total installed peak capacity of wind power generation, on the other hand, has shown immense growth by a record 39.4 GW, reaching 200 GW by the end of 2010. Wind power’s total installed capacity in 2010 was estimated at around 340 TWh. This indicates that about 1.6% of the total electricity generation worldwide is supplied by wind power generation [1]. In this paper, some well-known storage systems that are pervasive in current power systems will be presented. The chapter will also explain their advantages and limitations as well as their applications to renewable energy resources such as PV and wind. Finally, a short summary and comparison will appear in the last section. II. STORAGE SYSTEMS FOR RENEWABLE ENERGY SOURCES The inherent intermittent behavior of renewable energy sources will result in inconsistent power output. Meanwhile, the customer needs the voltage output to be stable, at least within the range of the equipment’s safety margin, and the customer must be able to access power immediately. These needs have made diesel and other conventional constant power output generators the dominant supplies ever sinc e the power generator was introduced in the nineteenth century. After the Kyoto Protocol in 1997 [2], the demand for flexible renewable energy sources has skyrocketed as countries wish to mitigate the adverse environmental effects of conventional energy sources. In response to this demand, all sustainable energy systems must limit their reliance upon conventional resources and increase the engagements of renewable energy resources over the next 20-30 years. Overcoming the uncertain behavior of the renewable energy resources would make this goal feasible. Developers have been revising EST for a few decades, and the technology has become so mature that its storage capacity worldwide is currently the equivalent of about 125 GW. Energy storage in a power syste m can be defined as any installation or method, usually subject to independent control, which is capable of storing energy and using it in the power system when required. Energy storage devices are intended to supply energy when the system is under high demand; they are also designated to save energy during low energy demand. These devices are very important to maintaining the continuity of power supply when the main source of power cannot meet all the power demands. On account of this role, energy storage devices are also considered as back-up power systems. Therefore, devices such as solar panels and wind turbine generators not only run on renewable resources, but also increase the value of electricity generated by backing it up during peak demand periods or during the fluctuations of energy resources. With the proper controller, the natural intermittent characteristic of renewable resources can be smoothed out through energy storage devices . A. Battery Energy Storage System (BESS) The BESS stores energy in a chemical form. When BESS is connected to the power system, it releases energy back into the network whenever there is a demand. Then, BESS recharges when the grid returns to its normal operation. Batteries are considered as very old storage technologies as they were invented roughly one hundred years ago. Therefore, they are well utilized, explored, and tested and have been a highly popular form of energy storage solution since the early twentieth century. Many types of batteries are available in the market, but this chapter focuses on the batteries that store energy in electric power utility applications, and it pays particular attention to their application in renewable energy sources. Unlike other storage systems, BESS has no