Experimental Investigation of a Sensible Thermal Energy Storage System
01 Jan 2021-pp 365-382
TL;DR: In this paper, the secondary heat thermal energy storage (SHTES) system of an in-house solar air tower simulator (SATS) is investigated, which uses hot air as heat transfer fluid and magnesium silicate pebbles as the storage material.
Abstract: Solar energy is a promising renewable source to support the growing energy demand. Sensible heat thermal energy storage (SHTES) is widely used, in practice, to supply the stored energy, in off-solar hours. These systems can be built using locally available and environment friendly materials. However, a good design as well as proper choice of materials is essential to construct an efficient and economical system. In this work, the secondary SHTES system of in-house solar air tower simulator (SATS) is investigated. The system uses hot air as heat transfer fluid and magnesium silicate pebbles as the storage material. The function of the secondary TES here is to store the waste energy from the hot air after it exits the solar convective furnace (SCF). The charging and discharging of the TES system are studied experimentally. It is observed that the secondary TES performance is satisfactory and serves as a proof of concept for future development.
TL;DR: In this article, the state of the art of phase change materials for thermal energy storage applications is reviewed and an insight into recent efforts to develop new phase change material with enhanced performance and safety.
Abstract: Phase change materials (PCMs) used for the storage of thermal energy as sensible and latent heat are an important class of modern materials which substantially contribute to the efficient use and conservation of waste heat and solar energy. The storage of latent heat provides a greater density of energy storage with a smaller temperature difference between storing and releasing heat than the sensible heat storage method. Many different groups of materials have been investigated during the technical evolution of PCMs, including inorganic systems (salt and salt hydrates), organic compounds such as paraffins or fatty acids and polymeric materials, e.g. poly(ethylene glycol). Historically, the relationships between the structure and the energy storage properties of a material have been studied to provide an understanding of the heat accumulation/emission mechanism governing the material’s imparted energy storage characteristics. This paper reviews the present state of the art of PCMs for thermal energy storage applications and provides an insight into recent efforts to develop new PCMs with enhanced performance and safety. Specific attention is given to the improvement of thermal conductivity, encapsulation methods and shape stabilization procedures. In addition, the flame retarding properties and performance are discussed. The wide range of PCM applications in the construction, electronic, biomedical, textile and automotive industries is presented and future research directions are indicated.
TL;DR: In this article, the authors provide a review of solar collectors and thermal energy storage systems, including both non-concentrating collectors and concentrating collectors, in terms of optical optimisation, heat loss reduction, heat recuperation enhancement and different sun-tracking mechanisms.
Abstract: Thermal applications are drawing increasing attention in the solar energy research field, due to their high performance in energy storage density and energy conversion efficiency. In these applications, solar collectors and thermal energy storage systems are the two core components. This paper focuses on the latest developments and advances in solar thermal applications, providing a review of solar collectors and thermal energy storage systems. Various types of solar collectors are reviewed and discussed, including both non-concentrating collectors (low temperature applications) and concentrating collectors (high temperature applications). These are studied in terms of optical optimisation, heat loss reduction, heat recuperation enhancement and different sun-tracking mechanisms. Various types of thermal energy storage systems are also reviewed and discussed, including sensible heat storage, latent heat storage, chemical storage and cascaded storage. They are studied in terms of design criteria, material selection and different heat transfer enhancement technologies. Last but not least, existing and future solar power stations are overviewed.
TL;DR: Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation as discussed by the authors.
Abstract: Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation TES systems are used particularly in buildings and in industrial processes This paper is focused on TES technologies that provide a way of valorizing solar heat and reducing the energy demand of buildings The principles of several energy storage methods and calculation of storage capacities are described Sensible heat storage technologies, including water tank, underground, and packed-bed storage methods, are briefly reviewed Additionally, latent-heat storage systems associated with phase-change materials for use in solar heating/cooling of buildings, solar water heating, heat-pump systems, and concentrating solar power plants as well as thermo-chemical storage are discussed Finally, cool thermal energy storage is also briefly reviewed and outstanding information on the performance and costs of TES systems are included
TL;DR: A chronological review of the volumetric receivers of most interest for electricity production, identifying their different configurations, materials and real and expected results, and pointing out their main advantages and conclusions based on the multitude of international and national projects reports and references.
Abstract: Deployment of the first generation of grid-connected plants for electricity production, based on Solar Thermal Power Plants with Central Receiver System technology using large heliostat fields and a solar receiver placed on the top of a tower, is currently being boosted by the first commercial plants in Spain, PS10, PS20, and Gemasolar. Therefore one of the main goals of solar technology research is the study of existing receivers and development of new designs to minimize heat losses. In this context, volumetric receivers appear to be the best alternative to tube receivers, mainly due to their functionality and geometric configuration. They consist of a porous material that absorbs concentrated radiation inside the volume of a structure and transfers the absorbed heat to a fluid passing through the structure. Solar radiation is first converted into thermal energy or chemical potential, and then at a later stage, into electricity. This volumetric receiver technology has been under development since the early 1990s in various research and development projects. This paper is a chronological review of the volumetric receivers of most interest for electricity production, identifying their different configurations, materials and real and expected results, and pointing out their main advantages and conclusions based on the multitude of international and national projects reports and references. This study also deals with other important issues surrounding the volumetric receiver, such as the basic plant configuration, flow stability phenomenon and the main problems of a windowed design for pressurized receivers.
TL;DR: In this article, high-temperature thermal storage in a packed bed of rocks is considered for air-based concentrated solar power plants, and the unsteady 1D two-phase energy conservation equations are formulated for combined convection and conduction heat transfer, and solved numerically for charging/discharging cycles.
Abstract: High-temperature thermal storage in a packed bed of rocks is considered for air-based concentrated solar power plants. The unsteady 1D two-phase energy conservation equations are formulated for combined convection and conduction heat transfer, and solved numerically for charging/discharging cycles. Validation is accomplished in a pilot-scale experimental setup with a packed bed of crushed steatite (magnesium silicate rock) at 800 K. A parameter study of the packed bed dimensions, fluid flow rate, particle diameter, and solid phase material was carried out to evaluate the charging/discharging characteristics, daily cyclic operation, overall thermal efficiency and capacity ratio.