Download or read book Steady State and Time Dependent Compressed Air Energy Storage Model Validated with Huntorf Operational Data and Investigation of Hydrogen Options for a Sustainable Energy Supply written by Friederike Kaiser and published by Cuvillier Verlag. This book was released on 2020-12-17 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind power and photovoltaic energy play a significant role in sustainable energy systems. However, these two renewable energy sources do not generate electrical energy on demand and are subject to natural fluctuations. Thus, the need for compensatory measures arises. Compressed air energy storage power plants (CAES) are a possible solution to providing negative and positive control energy in the electric grid. However, in contrast to other energy storage devices such as pumped hydro energy storage or batteries, the storage medium compressed air hardly contains any energy (or more precisely: enthalpy). Yet, compressed air storage allows the operation of highly efficient gas turbines, which are not only particularly fast available but also achieve better efficiency than combined cycle power plants used today, as illustrated by the example of the modern gas and steam power plant Irsching with ηtc = 60%from 2011 compared to the 20 years older McIntosh CAES with ηtc = 82.4 %. In this thesis, the calculation methods for the thermodynamics of the CAES process are presented and validated by measured data from the operations of the CAES power plant Huntorf. Both the steady state and the dynamic (time-dependent) analyses of the process take place. The characteristic value efficiency is discussed in detail, since numerous different interpretations for CAES exist in the literature. A new calculation method for the electric energy storage efficiency is presented, and a method for the calculation of an economically equivalent electricity storage efficiency is developed. Consideration is given to the transformation of the CAES process into a hydrogen-driven and, thus, greenhouse gas-free process. Finally, a model CAES system is tested in a 100 % renewable model environment. Consequently, it can be stated that in the steady-state thermodynamic calculation in particular, the consideration of realistic isentropic efficiencies of compressors and turbines is essential to correctly estimate the characteristic values of the process. Furthermore, a steadystate view should always be accompanied by dynamic considerations, since some process characteristics are always time-dependent. The simulation shows that by mapping transient operating conditions, the overall efficiency of the system must be corrected downwards. Nevertheless, in the model environment of a 100 % renewable energy system, it has been shown that a CAES is a useful addition that can provide long-term energy storage.
Download or read book Proceedings of the International Renewable Energy Storage Conference IRES 2022 written by Peter Schossig and published by Springer Nature. This book was released on 2023-05-25 with total page 585 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an open access book.Energy storage systems are the key to the successful energy transition to full renewable energy supply and are more relevant today than ever before. They address numerous challenges of the energy transition at once: stabilise the electricity grids, support the shutdown of power plants, make regionally generated electricity available locally and compensate for fluctuations in renewable energy generation. For more than 15 years now, EUROSOLAR has dedicated the annual International Conference on Renewable Energy Storage (IRES) to this important topic. The conference, which has been organised in partnership with Messe Düsseldorf since 2015, addressed the current state of research and the social, political and legal framework conditions of energy storage technologies from 20 to 22 September 2022, as part of its exhibitions on decarbonised industries.In up to three parallel series of lectures, experts from science, practice, politics and society focused on the current state of knowledge about energy storage.In recent years, more than 4000 visitors attended Energy Storage Europe, the predecessor of Messe Düsseldorf’s decarbXpo and IRES, each year. In plenary sessions, topic-specific lecture series and discussion rounds, around 150 lectures were presented including a large poster exhibition.We look forward to welcoming you to the 17th IRES in 2023.
Download or read book Investigation of Energy Storage Options for Sustainable Energy Systems written by Mehdi Hosseini and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Storage Systems written by United States. Department of Energy. Division of Energy Storage Systems and published by . This book was released on 1979 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design and Optimization of a Small Compressed Air Energy Storage System for Isolated Applications written by Hanif SedighNejad and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a variety of practical and theoretical CAES systems are reviewed in order to show the current status of the available CAES systems. Then a small scale compressed air energy storage for small isolated wind based hybrid energy system is introduced and discussed. In order to develop a cost-effective renewable based hybrid energy system, this research investigates the optimization of each component of the system from the wind turbine to the load to deliver the required energy in the most efficient way. After finding the general control strategy for energy harvesting from the wind, the control strategy based on predictive initial working condition of the air vane motor is investigated through practical tests. A control path is developed using the implemented air motor steady state operation based on its manufacturer datasheet, and it is used to supply a fixed amount of power to the grid. A new criterion for evaluation of different energy storage system with identical power rating and storage capacity is proposed and examined during a case study and the performance of pumped hydro, battery and compressed air energy systems are compared based on the total shortage time and total fuel consumption of backup diesel generators. The Monte Carlo simulation was used in order to regenerate the wind speed data with 10 minute resolution to represent more accurate variable wind speed. The proposed Harvested Energy Index (HEI) showed the ability of energy storage systems with low efficiency in utilizing excess wind energy and reach their storage capacity. Based on the obtained results, a novel general control concept for such systems is proposed and its steady state simulation results are discussed.
Download or read book Handbook of Energy Storage written by Michael Sterner and published by Springer. This book was released on 2019-09-27 with total page 821 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors of this Handbook offer a comprehensive overview of the various aspects of energy storage. After explaining the importance and role of energy storage, they discuss the need for energy storage solutions with regard to providing electrical power, heat and fuel in light of the Energy Transition. The book’s main section presents various storage technologies in detail and weighs their respective advantages and disadvantages. Sections on sample practical applications and the integration of storage solutions across all energy sectors round out the book. A wealth of graphics and examples illustrate the broad field of energy storage, and are also available online. The book is based on the 2nd edition of the very successful German book Energiespeicher. It features a new chapter on legal considerations, new studies on storage needs, addresses Power-to-X for the chemical industry, new Liquid Organic Hydrogen Carriers (LOHC) and potential-energy storage, and highlights the latest cost trends and battery applications. “Finally – a comprehensive book on the Energy Transition that is written in a style accessible to and inspiring for non-experts.” Franz Alt, journalist and book author “I can recommend this outstanding book to anyone who is truly interested in the future of our country. It strikingly shows: it won’t be easy, but we can do it.” Prof. Dr. Harald Lesch, physicist and television host
Download or read book Energy Storage Systems Volume I written by Yalsin Gogus and published by EOLSS Publications. This book was released on 2009-09-30 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy Storage Systems theme is a component of Encyclopedia of Energy Sciences, Engineering and Technology Resources which is part of the global Encyclopedia of Life Support Systems (EOLSS), an integrated compendium of twenty one Encyclopedias. The Theme is organized into six different topics which represent the main scientific areas of the theme: The first topic, Rationale of Energy Storage and Supply/Demand Matching is devoted to the discussion of essential concepts and the most important aspects of the optimization, establishment and operation of energy storage systems based on six cases as examples. The succeeding four topics are Storage of Thermal Energy; Mechanical Energy Storage; Storage of Electrical Energy; Storage of Chemical Energy and Nuclear Materials. Each of these consists of a topic chapter emphasizing the general aspects and various subject articles explaining the back ground, theory and practice of a specific type of energy storage of that topic. The last topic is transport of energy with emphasis on hydrogen as future energy carrier. It contains detailed review of other modes of energy transport and discussion of environmental effects. Fundamentals and applications of characteristic methods are presented in these volumes. These two volumes are aimed at the following five major target audiences: University and College Students, Educators, Professional Practitioners, Research Personnel and Policy Analysts, Managers, and Decision Makers and NGOs.
Download or read book Extensible Modeling of Compressed Air Energy Storage Systems written by Siddharth Atul Kakodkar and published by . This book was released on 2018 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a growing number of renewable energy sources that can supply power to the electrical grid. These renewable sources of energy are intermittent in nature and therefore the transition from using fossil fuels to green renewables requires the use of energy storage technologies to maintain and regulate a reliable supply of electricity. Energy storage technologies play a key role in allowing energy providers to provide a steady supply of electricity by balancing the fluctuations caused by sources of renewable energy. Compressed Air Energy Storage (CAES) is a promising utility scale energy storage technology that is suitable for long-duration energy storage and can be used to integrate renewable energy (such as Wind energy) to the electrical grid. CAES technologies can be broadly classified into 3 types: Diabatic-CAES (D-CAES), Adiabatic-CAES (A-CAES) and Isothermal-CAES (I-CAES). The author first performs a review on the different types of energy storage available today and a literature review on of CAES system level models, Turbomachinery models, and cavern models. After the gaps in literature are identified, the author then develops a flexible and extensible model of an A-CAES system, which can be used a CAES plant designer to obtain a first order thermodynamic evaluation of a particular plant configuration. The developed model is scalable, modular and can be connected to a control strategy. The model is able to capture time dependent losses and part load behavior of turbomachinery. The modeling methodology is focused around keeping the model extensible, i.e. components and their fidelity can be easily altered for the model's future growth. The components modeled are the compressor, the turbine, the induction motor, the generator, and a thermal energy storage device to the make the CAES plant adiabatic. The model is created using the Matlab/Simulinkʼ software, which is commonly used tool for modeling. The A-CAES plant model was simulated for 23.3 hours comprising of 12.47 hours of charging using a mass flow rate of 107.5 kg/s, 8 hours of storage and 2.83 hours of discharge using a mass flow rate of 400 kg/s. The maximum and minimum cavern pressures were 72 bar and 42 bar respectively. The obtained round trip efficiency is 76.24%. Additionally, the turbine start-up time was found to be 760 seconds. The compressor train average efficiency was calculated as 70%, the expansion train average efficiency was calculated as 81% and the TES efficiency was calculated as 91%. The models simulated the behavior of an A-CAES plant accurately with the compressor and turbine showing a close resemblance to their performance maps. The results indicate that Adiabatic-CAES is a promising and emerging technology. However, further research and development is required beyond this thesis; specifically, in the area of thermal energy storage and management. Finally, the author makes recommendations on how to further improve upon the achieved objectives in this work.
Download or read book Modeling of Compressed Air Energy Storage for Power System Performance Studies written by Ivan Calero and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the effective integration of large renewable generation for grid scale applications, pumped-storage hydro and Compressed Air Energy Storage (CAES) are currently economically and technically feasible alternatives to properly manage the intrinsic intermittency of energy sources such as wind or solar, with CAES being less restrictive in terms of its location. Furthermore, the relative fast response, and the possibility of physically decoupling the charging and discharging drive trains interfacing the grid through synchronous machines make CAES a suitable asset to provide ancillary services in addition to arbitrate, such as black start, spinning reserve, frequency regulation, and/or voltage regulation. Nevertheless, although the economic value of CAES having multiple stream revenues has been studied in the context of planning and operation of power systems, the actual impact of CAES facilities on the electrical grids have not been properly addressed in the literature, in part due to the lack of suitable models. The existing CAES models proposed for power system studies fail to represent the dynamics, nonlinear relations, and physical restrictions of the main mechanical subsystems, by proposing simplifications that result in unrealistic dynamic responses and operating points when considering the entire CAES operating range, as is required in most ancillary services or during grid disturbances. Furthermore, the detail of these models and the controls used are inconsistent with the state-of-the-art modeling of other storage technologies such as batteries and flywheels. Hence, in order to bridge the gap in CAES modeling and control, this thesis propose a comprehensive physically-based dynamic mathematical model of a diabatic CAES system, considering two independent synchronous machines as interface with the grid, which allows simultaneous charging and discharging of the cavern, such as the recently inaugurated 1.75 MW CAES plant in Goderich, Ontario. Detailed and simplified models are proposed based on the configuration of the Huntorf plant, in Germany, which is one of the only two existing large CAES facilities currently operating in the world. The system modeled comprises a multi-stage compressor with intercoolers and aftercooler, driven by a synchronous motor in the charging stage, an underground cavern as storage reservoir, a multi-stage expander with a recuperator and reheater between stages, and a synchronous generator in discharging mode, such as the aforementioned small CAES Ontario plant. The proposed thermodynamic-based dynamic models of the compressors and expanders allow calculating internal system variables, such as pressures, temperatures and power, some of which are used as controllable variables. Furthermore, different approximations to model the nonlinear relations between mass flow rate, pressure ratio, and rotor speed in the CAES compressors and expanders, determined by so called "maps", are proposed based on Neural Networks and physically-based nonlinear functions; these constrain the operation of the turbomachinery, but are usually ignored in existing models. A control strategy for active and reactive power of the CAES system is also proposed. The active power controller allows primary and secondary frequency regulation provision by the turbine and compressor. Special controllers are proposed to restrict the charging and discharging power of the turbine and compressor, to avoid pressure ratios that violate the restriction imposed by the cavern pressure. A surge detection controller for the compressor, and a controller that regulates the inlet temperature at each expansion stage are also presented, and these controls are complemented by a state of charge logic controller that shuts down the compressor or turbine when the cavern is fully charged or runs out of air, respectively. A coordinated droop-based reactive power control is also proposed for the parallel operation of the two synchronous machines, which is used to provide voltage regulation assuming both machines operate synchronized with grid. Finally, the implementation of a block-diagram based CAES model for transient stability studies in the DSATool's TSAT® software is presented, based on a generic model architecture of the different CAES system's components and their interrelations. The performance of the proposed models, with different levels of detail, are examined in various electrical system studies. First, the potential of a CAES system to provide primary and secondary frequency regulation in a test power system with high penetration of wind generation is evaluated in Simulink®, where the proposed CAES models are also compared with existing models. The voltage regulation, oscillation damping capability, and frequency and transient stability impact of CAES are also studied in a modified WSCC 9-bus test system using TSAT®. It is demonstrated that CAES is more effective than equivalent gas turbines to regulate frequency and voltage and damp low frequency oscillations, with the simultaneous charging and discharging operation significantly reducing the frequency deviation of the system in the case of large power variations in a wind farm. Furthermore, the effects on the overall frequency regulation performance of incorporating detailed models for some of the CAES components, such as expansion air valve, compressor and turbine maps and associated controls is also assessed, demonstrating how modeling these sub systems restricts the CAES response, especially in charging mode. Finally, the effect of the stage of charge control on the frequency stability of the system for different cavern sizes is investigated, concluding that if the power rating of the CAES system is large enough, small cavern sizes may not allow proper provision of frequency regulation.
Download or read book Compressed Air Energy Storage written by David S-K. Ting and published by IET. This book was released on 2021-10-29 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: A systematic overview of the state of Compressed Air Energy Storage (CAES) technology, covering the key components and principal types of systems in the order of technical maturity: diabatic, adiabatic, and isothermal. Existing major systems and prototypes and economics are also addressed.
Download or read book Project Summary Data Thermal and Mechanical Energy Storage Program written by United States. Department of Energy. Division of Energy Storage Systems and published by . This book was released on 1979 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Economic and Technical Feasibility Study of Compressed Air Storage written by General Electric Company. Research and Development Center and published by . This book was released on 1976 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Powering the Future A Comprehensive Guide to Energy Storage written by Charles Nehme and published by Charles Nehme. This book was released on with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Powering the Future: A Comprehensive Guide to Energy Storage is a book that delves into the critical role of energy storage in shaping the world's energy landscape. In an era where the demand for reliable and sustainable energy is constantly increasing, energy storage has emerged as a transformative solution to overcome the challenges of intermittency, grid stability, and the integration of renewable energy sources. As the global community faces the pressing need to transition towards a low-carbon economy, energy storage has emerged as a key enabler, facilitating the effective utilization of renewable energy resources. From batteries to pumped hydro, flywheels to compressed air, and emerging technologies like hydrogen storage, this book explores the diverse array of energy storage technologies and their applications across various sectors. In these pages, we aim to provide readers with a comprehensive understanding of energy storage and its vast potential to revolutionize the way we generate, distribute, and consume energy. We delve into the underlying principles, technical aspects, and challenges associated with energy storage systems, while also exploring the economic, environmental, and societal implications of widespread adoption. Written by a team of experts from diverse backgrounds in energy, engineering, and sustainability, this book aims to bridge the gap between academic knowledge and practical insights. We have strived to present the information in a manner that is accessible to both technical and non-technical readers, allowing anyone with an interest in the future of energy to engage with the subject matter. Throughout the chapters, we draw upon real-world examples, case studies, and the latest research to illustrate the current state and future prospects of energy storage. From large-scale grid-level applications to decentralized solutions for off-grid communities, we explore how energy storage is reshaping industries, revolutionizing transportation, empowering individuals, and driving innovation in ways previously unimaginable. It is our hope that this book serves as a valuable resource for policymakers, industry professionals, researchers, students, and anyone seeking a comprehensive guide to energy storage. By delving into the intricacies of this rapidly evolving field, we aspire to inspire new ideas, facilitate informed decision-making, and foster a collective commitment towards a sustainable energy future. We invite you to embark on this journey into the world of energy storage, as we uncover the untapped potential that lies within, and illuminate the path towards a cleaner, more resilient, and efficient energy system. Charles Nehme
Download or read book Compressed Air Energy Storage CAES RAM written by Harry W. Brown and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressed Air Energy Storage (CAES) technology represents an economically attractive and technically proven approach to obtaining overall cost-effectiveness in power generation. A key to realizing the load-leveling benefits offered by CAES is the achievement of good reliability, availability, and maintainability (RAM) performance by the system and its components. With this in mind, the Electric Power Research Institute (EPRI) sponsored the development of RAM models of the three generic types of CAES units: salt caverns, rock caverns, and aquifers. The objectives in developing these models were to evaluate the expected RAM performance of design alternatives, to investigate trade-offs among design parameters affecting RAM, and to develop an analysis tool for use by utilities interested in building CAES plants. This paper presents the generic models developed by ARINC Research Corporation, together with some initial evaluation results.
Download or read book Steady State Analyse of Existing Compressed Air Energy Storage Plants written by Friederike Kaiser and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hybrid Thermal and Compressed Air Energy Storage System HT CAES Thermodynamic Analysis and Thermoeconomic Optimization written by Sammy Houssainy and published by . This book was released on 2017 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Global warming concerns, volatile oil costs, and government incentives are leading to increased interest in the adoption of renewable energy sources. However, the integration of renewable sources in our existing infrastructure is challenging, as renewable generation is unpredictable and intermittent by nature. Energy storage compensates for the inherent intermittency of renewable energy sources, by storing energy during surplus power production periods and discharging the stored energy during low production periods. Compressed Air Energy Storage has received much attention as a viable solution due to its economic feasibility, low environmental impact, and large-scale capability. However, conventional CAES systems rely on the combustion of natural gas, require large storage volumes, and operate at high pressures, which possess inherent problems such as high costs, strict geological locations, and the production of greenhouse gas emissions. Through this research, a novel and patented hybrid thermal-compressed air energy storage (HT-CAES) design is investigated as a possible solution. The HT-CAES system allows a portion of the available energy, from the grid or renewable sources, to operate a compressor and the remainder to be converted and stored in the form of heat, through joule heating in a solid-state sensible thermal energy storage medium. The hybrid design has the beneficial effect of mitigating the shortcomings of conventional CAES systems and its derivatives by eliminating combustion emissions and reducing storage volumes, operating pressures, and costs. Therefore, the hybrid system provides flexibility of adjusting to a myriad of storage volumes based on available geological restrictions. Additionally, The hybrid system possesses a wide range of possible operations, without a compromise in its storage capacity, which may prove useful as we move towards a sustainable future. An ideal HT-CAES system is investigated and the thermodynamic efficiency limits within which it operates have been drawn. The efficiency of the HT-CAES system is compared with its Brayton cycle counterpart, in the case of pure thermal energy storage (TES). It is shown that the efficiency of the HT-CAES plant is not theoretically bound by the Carnot efficiency and always higher than that of the Brayton cycle, except for when the heat losses following compression rise above a critical level. The results of this work demonstrate that the HT-CAES system has the potential of increasing the efficiency of a pure TES system, executed through a Brayton cycle, at the expense of an air storage medium. Subsequently, a realistic and irreversible hybrid configuration is presented that incorporates two stages of heating through separate low-temperature and high-temperature thermal energy storage units. A thermodynamic analysis of the HT-CAES system is presented along with parametric studies, which illustrate the importance of the operating pressure and thermal storage temperature on the performance of the storage system. Realistic isentropic component efficiencies and throttling losses were considered. Additionally, two extreme cavern conditions were analyzed and the cyclic behavior of an adiabatic cavern was investigated. An optimum operating pressure resulting in maximum roundtrip storage efficiency of the hybrid storage system is reported. Additionally, a modified hybrid design is investigated that includes a turbocharger in the discharge process, which provides supplementary mass flow rate alongside the air storage. This addition has the potential of drastically reducing the necessary storage volume and pressures, thus further increasing the operational flexibility of the system. The results of this work provide an efficiency and cost map of the HT-CAES system versus both the operating pressure and the distribution of energy, between thermal and compressed air storage. The results of this work illustrate and properly quantify a tradeoff that exists between the HT-CAES system cost and performance. Both roundtrip energy and exergy efficiencies are quantified, presented, and compared. Lastly, a local optimum-line of operation, which results in a local maximum in efficiency and a local minimum in cost, is presented. The HT-CAES system is also investigated and optimized based on a minimum entropy generation criteria. Regenerative and non-regenerative configurations are examined. It is illustrated that an HT-CAES system designed based on a minimum entropy generation objective may be at a lower energy and exergy efficiency, and lower output power, than otherwise achievable. Therefore, in the case of a hybrid energy storage system, minimization of entropy generation does not always coincide with minimization of energy losses. Only under certain conditions does the point of minimum entropy generation coincide with maximum energy efficiency. Specifically, this occurs only when the input energy, thermal energy storage mass, specific heat, and temperature swing, are a constant. Similarly, only in the specific case where the total input exergy is a constant, does minimum entropy generation coincide with maximum exergy efficiency. Lastly, an exergy analysis of the hybrid system is presented. The calculated and normalized exergy destruction maps provide a means of comparing the component exergy destruction magnitudes for assessing and pinpointing the sources of largest irreversibilities. In addition to the exergy destruction, the exergetic component efficiencies are also presented and compared. Both component exergy destruction and their exergetic efficiencies demonstrate that the largest source of avoidable exergy destruction results from the irreversibilities associated with throttling and the irreversibilities associated with mixing losses within the air storage medium.
Download or read book Application of Phase Change Material to Improve Adiabatic Compressed Air Energy Storage System written by Erwan Adi Saputro and published by . This book was released on 2019 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of renewable energy, such as wind and solar, has significantly increased in the last decade. However, these renewable technologies have the limitations of being intermittent; thus,storing energy in the form of compressed air is a promising option. In compressed air energy storage (CAES), the electrical energy from the power network is transformed into a high pressure energy through a compressor. When the demand for electricity is high, the stored high pressure air is used to drive a turbine to generate electricity. The advantages of CAES include high energy density and quality, but the efficiency is relatively low (about 50%) since a significant amount of the compression energy is lost as heat. Additionally, in the expansion process, this technology would require a non-renewable source of energy for heating the air to prevent frosting. To overcome this drawback, an adiabatic CAES (ACAES) system has been proposed by applying methods of storing the generated heat during compression. The generated heat during compression is stored in the specific thermal storage system and is utilised to heat up the air during the expansion process. This method eliminates or limits the use of extra energy to heat the expanded air, usually needed in CAES system, which enhances the efficiency of the system by up to 70%. However, there are still challenges related to the selection of the thermal energy storage (TES) system needed in this application.The thermal storage material should have large storage capacity and should be able to store/release the heat rapidly during compression and expansion. For that reason, this thesis aims to develop a new method for the ACAES system using microcapsule of phase change material (PCM) for thermal storage. The use of PCM is selected since it has high latent heat of melting and hence is able to store a large amount of heat within a narrow change of temperature.The microcapsules are not only needed to contain the PCM but also to provide the large surface Philoarea needed for the heat to be stored in or released from it at a very high rate. In addition, a specific goal of this research is to develop a model for a small ACAES, which requires solving energy equations in both air and container wall and validate the model experimentally. A small CAES system has been designed for experimental purposes to validate the conceptual model. During the compression stage, the compressed air is stored into a 2L cylinder at 200 bar, while during the expansion stage, the compressed air is released to the environment. The results show that at the beginning of compression the air temperature rises from approximately 17°C to over 60°C, while it drops to -20°C during expansion. The previous model is further improved to account for the presence of PCM microcapsules and then validated experimentally. In the presence of PCM microcapsules (Micronal® DS 5038X), the air temperature rises from 24°C to around 50°C during compression, which is lower than without PCM, since PCM absorbs some of the heat and stores it in the form of latent heat. While in expansion, the minimum temperature drops to only -2 °C compared to -20°C when operated without PCM, which indicates that PCM has efficiently transferred its stored heat to the air. The effect of compression on physical and thermal properties of PCM microcapsules are investigated by comparing their characteristics before and after compression and for a number of cycles. Since air compression could crack the shell of the microcapsule, a metal-coating process, well-described in the thesis, is applied to prevent cracking of the polymer shell of the microcapsules and to improve their stability. Also to have a better understanding, two different PCMs are applied in this research: Micronal® DS 5038X and Microtek 24D, together with Microtek 24D metal-coated. All PCM microcapsules used in this research are analysed using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscope (SEM), before and after 20 compression-expansion cycles. The results show that Micronal® DS 5038X has a better stability than Microtek 24D since these microcapsules are lumps of very small capsules. The performance of Microtek 24D is improved when metal coating is applied to the capsule. The results disclosed in this thesis indicate that PCM microcapsules are able to successfully store the heat generated during compression and release it during expansion at a very high rate due to their large surface area. The developed model has successfully predicted both air and cylinder’s wall temperature during compression and expansion processes.
