Thermal Energy Storage Components Research Articles

Advanced eco-friendly power and cooling cogeneration-thermal energy storage utilizing phase change materials and chemisorption in renewable-based configurations

Increasing the reliability, stability, and safety of renewable energy systems depends on the integration of energy storage systems in order to balance energy production and demand. This research introduces an innovative system that combines a chemisorption unit, a phase change material (PCM)-based thermal energy storage (TES) mechanism, and a solar thermal unit with Linear Fresnel Reflectors (LFRs), tailored for residential usage. The system’s performance and dynamics are examined using TRNSYS and MATLAB software tools. Within this system, electricity is produced via a turbine propelled by the pressure differential created by chemical reactions within a chemisorption unit. Concurrently, cooling was facilitated through the ammonia evaporation process within an evaporator. At heat source temperatures between 100–200 °C, the system achieved a maximum electricity output of 2,718.9 W and a cooling rate of 14,601.5 W. The energy efficiency peaked at 46.32 %, and exergy efficiency at 40.78 %. The thermal energy storage component, with a volume of 1.5 m3, achieved a maximum storage capacity of 253.7 kWh. The study shows that higher heat source temperatures enhance production capacity but reduce the coefficient of performance (COP) for cooling by approximately 25 %. Overall, the system demonstrates significant potential for improving the efficiency and reliability of renewable energy systems.

Evaluation of the thermal capacity of cement-based thermal energy storage components. A case study

In this paper, we evaluate the heat capacity performance of cement-based heat exchangers for thermal energy storage and analyze their structural integrity under elevated temperatures. Fluid flow is modeled using the Navier-Stokes equations, conservation of mass, and energy. The response of the cement-based material is modeled considering thermomechanical coupling, obtaining the temperature profile within the thermal energy storage. This study allows us to observe the thermal energy storage capabilities for different thermal energy storage designs: plain concrete and concrete with nanoparticles of SiO2. Finally, we use our model for the evaluation of the concrete thermal energy storage component, which has been previously functionalized for use in low to medium temperature ranges (i.e., 100 °C to 400 °C).

Numerical Study on Peak Shaving Performance of Combined Heat and Power Unit Assisted by Heating Storage in Long-Distance Pipelines Scheduled by Particle Swarm Optimization Method

Thermal energy storage in long-distance heating supply pipelines can improve the peak shaving and frequency regulation capabilities of combined heat and power (CHP) units participating in the power grid. In this study, a one-dimensional numerical model was established to predict the thermal lag in long-distance pipelines at different scale levels. The dynamic response of the temperature at the end of the heating pipeline was considered. For the one-way pipe lengths of 10 km, 15 km and 20 km, the response times of the temperature at the distal end were 2.33 h, 2.94 h and 3.54 h, respectively. The longer the flow period, the further the warming-up time is delayed. An optimization scheduling approach was also created to illustrate the peak shaving capabilities of a CHP unit combined with a long-distance pipeline thermal energy storage component. It was demonstrated that the maximum heating load of the unit increased up to 503.08 MW, and the heating load could be expanded in the range of 17.88 MW to 203.76 MW at the minimum electric load of the unit of 104.08 MW. Finally, the particle swarm optimization method was adopted to guide the operating strategy through a whole day to meet both the electric power and heating power requirements. For the optimized case, the comprehensive energy utilization efficiency and the exergy efficiency increase to 64.4% and 56.73%. The thermal energy storage applications based on long-distance pipelines were simulated quantitively and proved to be effective in promoting the operational flexibility of the CHP unit.

Techno-economic assessment of the solar-assisted heat pump latent heat thermal energy storage system for water heating

A novel solar-assisted heat pump heating system including the latent heat thermal energy storage component that enables flexible switching between different connection modes was developed in this study to provide a cost-effective and energy-efficient solution for hot water supply. The feasibility, energy efficiency, and economic performance of the system under different design parameters and operation modes were evaluated via the experimental validated numerical model of the heating system. The end-user loads and meteorological parameters highly affected the system performance under the same design scheme. The optimal system configuration and component size for promoting renewable energy penetration and decreasing electricity cost were further determined. A certain increment in the collection area substantially benefits system performance, resulting in an approximately 56.6 % reduction in energy consumption. The larger capacity of the heat pump reflects a slight improvement in the system performance; however, it would require a longer payback period. Compared with the single solar and air heat source, the energy consumption of the hybrid heat source system declined by 26.6 % and 68.0 %, respectively. The system implementing the demand-side management proved to be a more profitable solution, exhibiting a low carbon emission of 188.1 kg, significant potential to flatten peak load, and a large lifecycle cost saving of $1834.64.

Energy distributing and thermodynamic characteristics of a coupling near-isothermal compressed air energy storage system

Intermittent renewable energy generation systems bring serious adverse impacts to the stable operation of the grid. In this regard, large-scale compressed air energy storage (CAES) systems with the potential to serve as long-term could be a solution for their optimal utilization. However, in a conventional CAES, most of the electricity is transformed into heat which passed into heat exchange mediums leads to serious heat transfer losses. In this study, a novel CAES system employing a Kalina cycle to effectively utilize the pre-compression heat in a near-isothermal compressed air process, is proposed and its holistic dynamic model is developed and presented for a deeper understanding of performance. The results showed that a near-isothermal compression undertakes the responsibilities of storing pressure potential energy, and the adiabatic pre-compression process helping in raising the inlet pressure of the liquid piston is primarily for storing thermal energy. In addition, the Kalina cycle working in the adiabatic pre-compression process achieves a 2.7 % improvement in the electrical efficiency. The thermal energy storage temperature was highlighted as the key factor in the energy allocation among the Kalina cycle, the thermal energy storage component, and the energy releasing sub-system in the proposed system. Through a systematic analysis of the proposed system performance, the highest electrical efficiency attained was 65.1 % with a 353 K storage temperature.

Component-based modeling of ground-coupled seasonal thermal energy storages

Seasonal thermal energy storages are considered a central element of modern, innovative energy systems and help to harmonize fluctuating energy sources. Furthermore, they allow for an improved coupling between the electricity and heating sectors. Despite recent improvements of planning processes and enhanced models, significant discrepancies between projected and measured heat losses were revealed. Additional shortcomings of available tools relate to limitations in specifying geometry, internal design, or physical processes. Addressing these drawbacks, this study employs a revised, alternative approach by using a flexible, component-based, model (“STORE”). It allows variable flexible parameterizations to study diverse design scenarios. After introducing relevant seasonal thermal energy storage components, processes and mechanisms, datasets, and evaluation techniques, a plausibility test is presented that applies a common thermal energy storage model for benchmarking. In a test study, the re-use of a circa 1,000 m3 large swimming pool is simulated. STORE is used to investigate performance trends caused by different designs (e.g., insulation thicknesses, materials at individual interfaces). For the plausibility test, the results show a high degree of coverage and good applicability. Further, the results of the test study show a storage efficiency of 12.4% for an uninsulated base case, which can be improved to 69.5% in case of the most complex, highly insulated configuration. Critical trends are revealed, covering reduced peak capacity levels (26.5 to 23.5 MWh) and raised average filling temperatures (39.1 to 45.2 °C). Improved long-term behavior involves reduced environmental impacts due to reduced heating of the ambient soil (+7.9 K compared to +14.1 K after 2 years). General conclusions reveal that an optimal design should initially focus on an external cover of soil and top insulation. However, evaluations should base on multiple parameters depending on the target criteria. This is where the present model is highly useful. The capability of STORE to rapidly analyze a plethora of scenarios proves its high applicability for optimizing the planning processes of seasonal thermal energy storage projects.

Flow models of perforated manifolds and plates for the design of a large thermal storage tank for district heating with minimal maldistribution and thermocline growth

Large water tanks are used as thermal energy storage components in district heating systems to store sensible heat produced by intermittent energy sources and to decouple the production of thermal energy from its demand. Good thermal stratification is crucial for energy storage efficiency, thus flow maldistribution and mixing of water layers at different temperatures should be minimized. This paper proposes an innovative internal flow distribution configuration for a large-size thermal energy storage, and develops new simplified analytical models for the choice of its design parameters. In the novel configuration, water is injected into (and collected from) the cap volumes of the tank by flowing radially inward (outward) through several small orifices of a peripheral toroidal manifold. Two horizontal perforated plates cover the full cross sections downstream of the manifolds and rectify the vertical flow, thus reducing mixing. Uniform perforation pitch was analytically demonstrated to be the most reasonable solution both for the toroidal distributors and for the rectifying plates. A 1D model was developed to predict the time evolution of the vertical temperature distribution in the tank. The turbulence-related parameters that could not be inferred from the existing fluid-mechanics literature were initially estimated with CFD simulations. The results of CFD-calibrated model were then compared to experimental data obtained from a full-scale large water-tank facility recently built in Brescia according to the proposed design. After a re-calibration of the exponent defining the decay of homogeneous turbulence downstream of the perforated plates, good agreement was found between measured and predicted vertical temperatures. With the novel inlet design, a thermocline of about 0.5 m is established immediately downstream of the perforated plate, and remains practically constant along time. The model is important to minimize and control the thermocline thickness so as to maximize the recoverable thermal energy, not only at the tank design stage but also to identify optimal loading and unloading protocols.

A Hybrid Bimodal LSTM Architecture for Cascading Thermal Energy Storage Modelling

Modelling of thermal energy storage (TES) systems is a complex process that requires the development of sophisticated computational tools for numerical simulation and optimization. Until recently, most modelling approaches relied on analytical methods based on equations of the physical processes that govern TES systems’ operations, producing high-accuracy and interpretable results. The present study tackles the problem of modelling the temperature dynamics of a TES plant by exploring the advantages and limitations of an alternative data-driven approach. A hybrid bimodal LSTM (H2M-LSTM) architecture is proposed to model the temperature dynamics of different TES components, by utilizing multiple temperature readings in both forward and bidirectional fashion for fine-tuning the predictions. Initially, a selection of methods was employed to model the temperature dynamics of individual components of the TES system. Subsequently, a novel cascading modelling framework was realised to provide an integrated holistic modelling solution that takes into account the results of the individual modelling components. The cascading framework was built in a hierarchical structure that considers the interrelationships between the integrated energy components leading to seamless modelling of whole operation as a single system. The performance of the proposed H2M-LSTM was compared against a variety of well-known machine learning algorithms through an extensive experimental analysis. The efficacy of the proposed energy framework was demonstrated in comparison to the modelling performance of the individual components, by utilizing three prediction performance indicators. The findings of the present study offer: (i) insights on the low-error performance of tailor-made LSTM architectures fitting the TES modelling problem, (ii) deeper knowledge of the behaviour of integral energy frameworks operating in fine timescales and (iii) an alternative approach that enables the real-time or semi-real time deployment of TES modelling tools facilitating their use in real-world settings.

Experimental investigation of a passive type solar still with double wedge shape glass cover

Solar thermal energy-based desalination systems such as solar stills deliver fresh distilled water at zero carbon emission levels. In this paper, passive type solar still with double wedge shape glass cover is experimentally investigated for its performance, and economics factor is analyzed. This new design solar still model is Twin Wedge Solar Still (TWSS). The economics of the system concerning cost per litre is also presented. The performance of TWSS is weighed against that of a Conventional Solar Still (CSS) in this study. The novel glass cover shape design of the TWSS increases the condensation surface area, increasing the condensation rate, thus enabling the TWSS to deliver 2.68 L of fresh distilled water per m2 area of the solar still. The CSS yielded only two-third of TWSS for the same constraints, thus making TWSS 51.5% more efficient than CSS. The economic analysis shows that TWSS possess a lesser cost per litre rate (0.028 $/l) than CSS, which aids it to achieve a shorter payback period (one year for TWSS). The simple and symmetrical design of the TWSS makes it more advantageous than other unique and new design solar stills. As a future study, the integration of thermal energy storage components in the basin structure is proposed to increase the vaporation rate of the TWSS.

A New Methodological Approach for the Evaluation of Scaling Up a Latent Storage Module for Integration in Heat Pumps

A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of this paper is to identify some key aspects to be considered when scaling up the module from lab-scale to full-scale using different performance indicators calculated in both charge and discharge. Different normalization methods were applied to allow an appropriate comparison of the results at both scales. As a result of the scaling up, the theoretical energy storage capacity increases by 52% and 145%, the average charging power increases by 21% and 94%, while the average discharging power decreases by 16% but increases by 36% when mass and volume normalization methods are used, respectively. When normalization by the surface area of heat transfer is used, all of the above performance indicators decrease, especially the average discharging power, which decreases by 49%. Moreover, energy performance in charge and discharge decreases by 17% and 15%, respectively. However, efficiencies related to charging, discharging, and round-trip processes are practically not affected by the scaling up.

Thermal Spray Processes in Concentrating Solar Power Technology

Solar power is a sustainable and affordable source of energy, and has gained interest from academies, companies, and government institutions as a potential and efficient alternative for next-generation energy production. To promote the penetration of solar power in the energy market, solar-generated electricity needs to be cost-competitive with fossil fuels and other renewables. Development of new materials for solar absorbers able to collect a higher fraction of solar radiation and work at higher temperatures, together with improved design of thermal energy storage systems and components, have been addressed as strategies for increasing the efficiency of solar power plants, offering dispatchable energy and adapting the electricity production to the curve demand. Manufacturing of concentrating solar power components greatly affects their performance and durability and, thus, the global efficiency of solar power plants. The development of viable, sustainable, and efficient manufacturing procedures and processes became key aspects within the breakthrough strategies of solar power technologies. This paper provides an outlook on the application of thermal spray processes to produce selective solar absorbing coatings in solar tower receivers and high-temperature protective barriers as strategies to mitigate the corrosion of concentrating solar power and thermal energy storage components when exposed to aggressive media during service life.

Numerical Investigation of Latent Thermal Storage in a Compact Heat Exchanger Using Mini-Channels

This paper aims to numerically investigate the thermal enhancement of a latent thermal energy storage component with mini-channels as air passages. The investigated channels in two sizes of internal air passages (channel-1 with dh = 1.6 mm and channel-2 with dh = 2.3 mm) are oriented vertically in a cuboid of 0.15 × 0.15 × 0.1 m3 with RT22 as the PCM located in the shell. The phase change is simulated with a fixed inlet temperature of air, using ANSYS Fluent 19.5, with a varying number of channels and a ranging air flow rate entering the component. The results show that the phase change power of the LTES improves with by increasing the number of channels at the cost of a decrease in the storage capacity. Given a constant air flow rate, the increase in the heat transfer surface area of the increased number of channels dominates the heat transfer coefficient, thus increasing the mean heat transfer rate (UA). A comparison of the channels shows that the thermal performance depends largely on the area to volume ratio of the channels. The channel type two (channel-2) with a slightly higher area to volume ratio has a slightly higher charging/discharging power, as compared to channel type one (channel-1), at a similar PCM packing factor. Adding fins to channel-2, doubling the surface area, improves the mean UA values by 15–31% for the studied cases. The variation in the total air flow rate from 7 to 24 L/s is found to have a considerable influence, reducing the melting time by 41–53% and increasing the mean UA values within melting by 19–52% for a packing factor range of 77.4–86.8%. With the increase in the air flow rate, channel type two is found to have considerably lower pressure drops than channel type one, which can be attributed to its higher internal hydraulic diameter, making it superior in terms of achieving a relatively similar charging/discharging power in exchange for significantly lower fan power. Such designs can further be optimized in terms of pressure drop in future work, which should also include an experimental evaluation.

Thermal and mechanical properties of building external walls plastered with cement mortar incorporating shape-stabilized phase change materials (SSPCMs)

Phase change materials (PCMs) have been widely proven to provide thermal energy storage (TES) capacity in building systems. However, some potential problems associated with the incorporation of PCMs in building materials may cause uncertainty about their real performance. Among such problems, the leakage possibility of PCMs in the molten state has been greatly addressed in the literature. In this regard, this study is aimed to evaluate the mechanical and thermal behavior of a shape-stabilized PCM (SSPCM) as a TES component in the conventional wall system of buildings in Iran. For this purpose, PEG 600 was shape-stabilized in the porous structure of the silica fume as the supporting material using the vacuum impregnation method. The SSPCM was further employed to prepare cement mortars for plastering masonry brick wall specimens. The mechanical experiments on the SSPCM-incorporated mortars indicated satisfactory results to be used as the finishing plaster for masonry walls. Moreover, a novel experimental setup was utilized to perform thermal performance test on the wall specimens plastered with SSPCM-incorporated mortar under ambient temperature conditions of two different cities. Accordingly, the developed SSPCM exhibited the promising potential to provide TES capacity in external masonry wall systems by reducing the peak temperature as well as mitigating indoor temperature fluctuations.

Evaluation of the State of Charge of a Solid/Liquid Phase Change Material in a Thermal Energy Storage Tank

Monitoring of the state of charge of the thermal energy storage component in solar thermal systems for space heating and/or cooling in residential buildings is a key element from the overall system control strategy point of view. According to the literature, there is not a unique method for determining the state of charge of a thermal energy storage system that could generally be applied in any system. This contribution firstly provides a classification of the state-of-the-art of available techniques for the determination of the state of charge, and secondly, it presents an experimental analysis of different methods based on established sensor technologies, namely temperature, mass flow rates, and pressure measurements, tested using a lab-scale heat exchanger filled with a commercial phase change material for cooling applications. The results indicate that, depending on the expected accuracy and available instrumentation, each of the methods studied here can be used in the present application, the deviations between the methods generally being below 20%. This study concludes that a proper combination of two or more of these methods would be the ideal strategy to obtain a more reliable and accurate estimation of the state of charge of the latent heat thermal energy storage.

Development of polyurethane foam incorporating phase change material for thermal energy storage

The major aim of the present study is to improve the thermal characteristics of polyurethane foams (PUFs) that have been almost exclusively used for thermal insulation purposes but can also play a role in potential thermal energy storage components as a matrix material.To overcome the low thermal conductivity of the of PUFs matrix, a synthesized phase change material (PCM) based on paraffin and calcium carbonate (CaCO3) has been developed to enhance the thermal conductivity and thus achieve a more effective charging and discharging process. The synthesized PCM (PCM@CaCO3) exhibited a good phase change performance with significant thermal storage capacity and thermal stability compared to commercial based PCM (PCM@BASF).Different PUFs formulations incorporating PCM (PCM@CaCO3 and PCM@BASF) were used to produce PUFs panels (rigid and soft PUFs panels). The thermal conductivity of the PUFs panels was measured using the transient plane heat source method (HotDisk Analyser, TPS 2500 S) and the thermal flux metre method (steady-state method). The results obtained revealed that, regardless of the method used, the thermal conductivity profile has a similar increasing trend before and after the bounds of the PCM phase change transition zone, whilst during PCM phase transition both methods showed a decreasing trend of the thermal conductivity as the temperature increased.In addition, this work presents and discusses the limitation of the HotDisk method to analyse panels composed by multilayers.

Experimental study on performance of square tube absorber with phase change material

The intermittent nature of solar radiation has decreased the performance efficiency of solar heaters. Integrating the solar heater with thermal energy storage component could increase its performance effectively. In this article, an investigation on the effect of phase change material (PCM) as the thermal energy storage component on the performance of square aluminum tube was carried out experimentally. In the first phase, the temperature behavior of square aluminum tube with two types of PCM, namely, generic plant‐based PCM (A2) and paraffin wax (A3), was compared with square aluminum tube without PCM (A1). In the second phase, the performance of square aluminum tube was investigated with different paraffin wax masses of 38 g (B1), 48 g (B2), and 58 g (B3). Based on the result, the A3 tube configuration performed better than A1 and A2 tube configurations with higher heat gain rate (0.08°C/s) and lower heat discharge rate (−0.04°C/s). The B2 tube configuration was found to have maximum heat gain of 3.73 kJ with higher heat discharge rate as compared with other square tube configurations. The average temperature difference between internal and external surface tube of B2 was lower (4.3°C) leading to higher average temperature difference at ambient temperature of 25.3°C. Instantaneous efficiency of the tube B2 is higher than the B1 and B3 tube configurations by 16% and 26%, respectively. The result suggests that the insertion of paraffin wax inside the square absorber tube improves the temperature response of the absorber in the situation of intermittent solar radiation.

Composite phase change materials for thermal energy storage: From molecular modelling based formulation to innovative manufacture

Thermal energy storage (TES) has a crucial role to play in conserving and efficiently utilising energy, dealing with mismatch between demand and supply, and enhancing the performance and reliability of our current energy systems. A competitive TES technology requires a number of scientific and technological challenges to be addressed including TES materials, TES components and devices, and integration of TES devices with energy networks and associated dynamic optimization. This paper concerns mainly about TES materials challenges with a specific focus on using shape stable composite phase change materials (CPCMs) for medium and high temperature application. The paper first briefly reviews the state-of-the-art development of materials research for thermal energy storage. The focus is then on CPCMs for medium to high temperatures applications, covering materials screening, formulation based on molecular modelling validated at a different length scale through experiments, formulation based on chemical and physical compatibility, and manufacture of material modules via innovative use of conventional powder technology. The properties of the materials and materials modules are characterised and analysed with an aim to establish property-structure relationships. This includes a particularly interesting aspect of the motion of PCM and nanoscale objects with the PCMs for heat transfer enhancement during thermal cycling, which explains the mechanisms of the encapsulation of PCMs in the composite.

Heat transfer performance of thermal energy storage components containing composite phase change materials

This study concerns about the heat transfer behaviour of composite phase change materials (CPCMs) based thermal energy storage components. Two types of components, a single tube and a concentric tube component, are designed and investigated. The CPCMs consist of a molten salt based phase change material, a thermal conductivity enhancement material (TCEM) and a ceramic skeleton material. A mathematical model was established to model the heat transfer behaviour. The modelling results were first compared with experiments and reasonably good agreement with the experimental data was obtained, demonstrating the reliability of the model. Extensive modelling studies were then carried out under different conditions. The influence of thermoproperties, surface roughness and size of the CPCMs as well as heat transfer fluid (HTF) velocity were examined. The results show that the thermal contact resistance between the CPCMs should be considered. Increasing the mass fraction of TCEMs and thickness of CPCMs as well as the HTF velocity intensifies the heat transfer behaviour of component. The concentric tube based component offers a better heat transfer performance compared with the single tube based component, with the total heat storage and release time ∼10 and 15% shorter, respectively, for a given set of conditions.

Thermal energy storage: Challenges and the role of particle technology

Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage (TES) has a pivotal role to play in the energy chain and hence in future low carbon economy. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including TES materials, TES components and devices, and integration of TES devices with energy networks and associated dynamic optimization. This paper provides a perspective of TES technology with a focus on TES materials challenges using molten salts based phase change materials for medium and high temperature applications. Two key challenges for the molten salt based TES materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials consist of a phase change material, a structural supporting material, and a thermal conductivity enhancement material. The properties of the supporting material could determine the dispersion of the thermal conductivity enhancement material in the salt. A right combination of the salt, the structural supporting material, and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. Understanding of the structure–property relationships for the composite is essential for the formulation design and fabrication of the composite materials. Linking materials properties to the system level performance is recommended as a key future direction of research.

Simulated Performance of Packed Bed Solar Energy Storage System having Storage Material Elements of Large Size - Part I

Packed bed or rock bed is very commonly known thermal energy storage component for solar air heaters. The major concern for design of packed bed energy storage system is to maximize the heat transfer with minimum pressure drop or pumping power. Under the given operating conditions, system parameters could affect heat transfer and pressure drop in the bed considerably. An attempt has been made to report the simulated performance of a packed bed solar energy storage system. Large size storage material elements of five different shapes have been used to carry out the present simulation study. Nusselt number and friction factor correlations reported by the authors under previous experimental study have been utilized to analyze the packed bed energy storage system for a range of system and operating parameters. Performance of the system has been evaluated based on temperature distribution, thermal energy stored and available energy stored in the bed, energy consumption by fan to propel air through the bed and thermal efficiency of the collector as a function of system and operating parameters. In present part of the paper, various component models of packed bed solar energy storage system and development of computer program have been reported. Results of simulated system performance have been reported and discussed in Part-II and III of this paper.