Latent Heat Thermal Storage Using Phase Change Materials (PCM) Aniruthan .M.E
ABSTRACT Department of Mechanical Engineering, Anand Institute of Higher Technology, Chennai.
Various methods are employed in production of energy throughout the globe. Some prove as perennial resource, however many of them undergoes many loses in the intermediate conversion process from initial stage to the final stage of power production. Also supply and demand don’t quite meet their ends often. To reduce this mismatch storage systems are employed in almost all the mechanisms from small flywheels to high efficient storage systems in spacecrafts. Though storage system is a vast medium, thermal energy storage concepts and ideas are presented in this paper. Thermal energy storage is becoming a very attractive means of storing and retrieving thermal energy. TES using Phase changing materials (PCM), pros and cons of using it are discussed here. Since TES is a vast division, this paper doesn’t cover everything but it gives a brief introduction about what is thermal energy storage, its types, methods of storing, and it’s drawbacks . This paper also deals with the processes involved in analyzing those storage systems for its physical property changes using computational fluid dynamics (CFD). Keywords: Thermal energy storage, Heat recovery system, PCM, Latent heat thermal storage 1 Introduction Energy is an important entity for the economic development of any country. Considering the environmental protection and also in the context of great uncertainty over future energy supplies, attention is concentrated on the utilization of sustainable energy sources and the energy conservation methodologies. Concentrated solar thermal power generation is becoming a very attractive renewable energy production system among all the different renewable options, as it has a better potential for dispatch ability. Solar thermal power plants produce electricity in the same way as other conventional power plants, but using solar radiation as energy input. This energy can be transformed to hightemperature steam, to drive a turbine or a motor engine. Mainly, four elements are required in these plants: concentrator, receiver, transport/storage media system, and power conversion device. Of all components, thermal storage is a key component. Dispatching inevitably requires the need for efficient and cost-effective storage systems. Thus storage systems become the key one here. In spite of the advantages the TES provides, it is one of the less developed. Here the concept of thermal energy storage is presented along with its classification, methods, materials, its pros and cons . Also steps involved in analysis for the property changes during the storing and retrieving process is highlighted using computational fluid dynamics (CFD). 2 Energy Storage Energy storage is storing some form of energy so that it can be retrieved and used later. Energy storage device are sometimes called as accumulators. All forms of energy come under one of the following classification: Potential energy, kinetic energy, electrical energy or thermal energy. Each of this energy can be stored with its appropriate type of accumulator. Fig.1 shows variety of energy storage systems . Thermal energy storage is discussed in this document. 2.1 Thermal energy storage Thermal energy storage systems are used to correct the mismatch between supply and demand. A thermal energy unit essentially consists of three important processes: Charging, storing and discharging/retrieving.
Energy Storage System
Mechanical Energy Storage - Hydro storage - Compressed air storage - Flywheels
Chemical Energy Storage
Biological Energy Storage
Magnetic Energy Storage
Thermal Energy Storage - Sensible heat storage - Latent heat storage - Chemical heat storage
- Electrochemical batteries - Organic molecular storage
Fig. 1 Classification of energy storage system 
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Fig. 10. Contours of the melt fraction of PCM for case: (a)
Fig. 9. Velocity contours at different slices (Reproduced from )
∆T = 20 K; (c) ∆T = 30 K. (Reproduced from )
∆T = 10 K; (b)
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5 Conclusion The concept of energy storage is discussed its types, advantage of latent heat storage over the sensible storage, the material used in latent heat storage i.e., phase changing materials (PCM). Some case studies are considered for more knowledge about the PCM concept. Its application in solar thermal storage, use in heat recovery system and numerical analysis of such systems are considered. The important drawback of PCM, its thermal conductivity seems to be a huge hurdle to be applied in common use, besides cost consideration, space availability and the
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