Storage Techniques for Solar Thermal Applications Abdullah M. Al-Shaalan and Tauqeer Ahmed Shaikh Electrical Engineering Department, King Saud University, Riyadh, Saudi Arabia Email: shaalan@ksu.edu.sa, shaikhtauqeer.ahmed@gmail.com Abstract—The traditional electricity operation in solar thermal plants is designed to operate on a single path initiating at power plant and executes at the consumer. Due to lack of energy storage facilities during this operation, a decrease in the efficiency is often observed with the power plant performance. This paper reviews the significance of energy storage in supply design and elaborates various methods that can be adopted in this regard which are equally cost effective and environmental friendly. Moreover various parameters in thermal storage technique are also critically analysed to clarify the pros and cons in this facility. Discussing the different thermal storage system, their technical and economical evaluation has also been reviewed. Index Terms—thermal energy storage, sensible heat storage, latent heat storage, thermochemical heat storage I. INTRODUCTION Solar thermal power plants collect and concentrate the sun’s energy to heat through a working fluid that is then used to process heat applications or the generation of electricity. In order for these systems to operate commercially, they must be able to operate during periods of changing levels of insolation and to operate at times that will ensure maximum financial return. This can either be achieved by utilizing existing backup methods, through the use of fossil fuels, or the incorporation of a Thermal Energy Storage (TES) system. The thermal energy storage (TES) can be defined as the temporary storage of thermal energy at high or low temperatures. TES systems also provide an environmentally friendly solution to Solar Power Generating Systems [1]. Energy storage is used in solar thermal energy systems to save the additional energy generated during the times of high solar availability and used in the times of low solar availability (at night or in cloudy weather) which ensures twenty-four hour power generation without using the fossil fuels. However there exists alot of loophole in this facility which results in energy loss and efficiency is decreased. In this paper we have overviewed the applications of TES system and its types. Discussing the thermal storage systems, its technical and economical evaluation has also been reviewed. Manuscript received January 11, 2014; revised July 14, 2014. II. APPLICATIONS OF TES SYSTEMS A single TES system cannot be used to fulfil all the applications. The selection of a TES system is highly dependent upon the stability, low cost, reliability, safety, energy capacity and efficiency of the storage media. Furthermore, theTES system could be classified as low temperature or high temperature depending upon the operating temperature of the storage medium [2]. Some of the key applications of a TES system are: A. Energy Management At night when energy production cost is low, the energy can be generated cheaply and stored to use in the time of costly production or when needed referred as load leveling.Storing for this purpose enables the power generator to conduct workingin a “peaking” mode of operation. B. Buffering Buffering is required in solar thermal power generation to smooth transients and enable a consistent and uninterrupted supply of thermal energy to a heat engine. C. Period Displacement It refers to generating excess energy during daylight hours to enable baseload supply to extend into the non-daylight hours. This can enable 24 hour generation during periods of high insolation. D. Power Quality The stored energy is only applied when needed depending upon the application. So its power quality must be high even when it is applied for seconds or maybe less to assure the stability and continuity of the system energy. E. Annually Averaging During winter, the low radiation of the sun results in low energy generation. So, the large solar plants can use the TES system to store energy to supply it in the time of peak demand or low light. III. TYPES OF THERMAL STORAGE SYSTEMS TES SYSTEMS CAN BE CATEGORIZED AS: Journal of Automation and Control Engineering Vol. 3, No. 3, June 2015 237 ©2015 Engineering and Technology Publishing doi: 10.12720/joace.3.3.237-240 An Overview in Energy Conservation of Thermal