Medium and high-temperature latent heat thermal energy storage (LHTES) systems with high energy density can manage the intermittency of renewable energy sources. However, some significant challenges ...remain to be addressed. Hence, in this article, a pilot-scale medium-temperature cylindrical LHTES system loaded with 4130 kg phase change material (PCM) and equipped with heat exchanger tubes featuring spiral and H-shaped fins was constructed. The temperature evolution of PCM and various parameters containing charging/discharging time, instantaneous power, accumulated energy, and efficiency under the constant temperature and the step temperatures methods were investigated. The experimental results revealed that the melting of the upper PCM was accelerated by natural convection, whereas the melting of the bottom PCM was slower due to heat conduction. The heat exchange tubes with spiral fins demonstrated better performance during the charging process, whereas those with H-shaped fins performed better during the discharging process. In addition, the LHTES system achieved accumulative energy storage of 993.64 MJ and release of 659.58 MJ with a cycle efficiency of 66.38% under the constant temperature method. However, the accumulative energy storage and release under the step temperatures method were 966.2 and 664.86 MJ, respectively, with a cycle efficiency of 68.81%.
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•Laboratory scale packed bed TES was developed to store heat at medium temperatures.•The new STESM developed from demolition wastes was used as packing material.•Demolition waste as ...STESM was more efficient and cheaper than alternatives.•The results from lab-scale packed-bed with new STESM will be valuable for scaling up.
Thermal energy storage (TES) is essential for cost-effective use of solar energy in industries. The most energy intensive processes in industry operate below 200 °C. This study tested a new sustainable and low-cost sensible thermal energy storage material (STESM) based on demolition wastes in a lab-scale packed bed TES system, specifically built to analyze its performance in industrial solar applications below 200 °C. This system was investigated both experimentally and numerically under different operating conditions. One-dimensional continuous phase model used verified that experimental results were in good agreement with numerical ones during charging and discharging steps. Performance of demolition waste STESM was compared with Therminol 66 synthetic oil as a liquid heat storage media. The maximum system energy efficiency of the packed-bed filled with demolition waste STESM was 67% at charging temperature of 150 °C and superficial fluid velocity of 0.95 mm s−1, while it was 63% for Therminol 66. Packed bed TES system with demolition waste STESM showed good performance up to 180 °C in fully laminar flow regime (Rep < 10) and Bi number < 0.1. The material cost of demolition waste STESM is at least tenfold cheaper than the alternative natural rock based packing materials. Packed bed TES systems using demolition wastes can be recommended for low cost and sustainable solar applications in industry.
Due to humanity's huge scale of thermal energy consumption, any improvements in thermal energy management practices can significantly benefit the society. One key function in thermal energy ...management is thermal energy storage (TES). Following aspects of TES are presented in this review: (1) wide scope of thermal energy storage field is discussed. Role of TES in the contexts of different thermal energy sources and how TES unnecessitates fossil fuel burning are explained. Solar power generation, building thermal comfort and other niche applications of TES are presented. (2) Insight into classes of TES storage materials with details like their physical properties, cost, operational performance and suitability to application requirements is provided. (3) Insight into types of TES systems is presented. TES systems are classified using different types of criteria. Most common TES systems like seasonal TES systems, CSP plant TES systems, TES systems of domestic solar thermal applications, heat and cold storages of building HVAC systems etc are described. Active TES systems like thermocline, packed bed, fluidized bed, moving bed etc are analyzed. Passive TES systems implemented in buildings, textiles, automobiles etc are presented. TES systems operating in cold, low, medium and high temperature ranges are listed. Design parameters, operational issues and cost model of TES systems are discussed.
•Technology, material and research works in thermal energy storage were summarized.•Thermal properties of thermal energy storage materials were presented and analyzed.•Heat storage mechanism and applications based TES systems were shown in detail.•Performance parameters and operational issues based TES systems were discussed.
To meet the global climate change mitigation targets, more attention has to be paid to the decarbonization of the heating and cooling sector. Aquifer Thermal Energy Storage (ATES) is considered to ...bridge the gap between periods of highest energy demand and highest energy supply. The objective of this study therefore is to review the global application status of ATES underpinned by operational statistics from existing projects. ATES is particularly suited to provide heating and cooling for large-scale applications such as public and commercial buildings, district heating, or industrial purposes. Compared to conventional technologies, ATES systems achieve energy savings between 40% and 70% and CO2 savings of up to several thousand tons per year. Capital costs decline with increasing installed capacity, averaging 0.2 Mio. € for small systems and 2 Mio. € for large applications. The typical payback time is 2–10 years. Worldwide, there are currently more than 2800 ATES systems in operation, abstracting more than 2.5 TWh of heating and cooling per year. 99% are low-temperature systems (LT-ATES) with storage temperatures of < 25 °C. 85% of all systems are located in the Netherlands, and a further 10% are found in Sweden, Denmark, and Belgium. However, there is an increasing interest in ATES technology in several countries such as Great Britain, Germany, Japan, Turkey, and China. The great discrepancy in global ATES development is attributed to several market barriers that impede market penetration. Such barriers are of socio-economic and legislative nature.
•The historical development and the current application status of ATES are reviewed.•Worldwide, there are currently more than 2800 ATES systems in operation.•Market barriers for ATES commercialization are discussed for all relevant countries.
•A novel shape stable composite PCM using lauric acid and myristic acid was prepared.•Superior shape stability along with enhanced heating rate is observed.•Improved photothermal conversion ...efficiency and thermal conductivity.•Composite PCM is thermally and physically stable.
Phase Change Materials (PCM) have emerged as one of the potential candidates for solar Thermal Energy Storage (TES) because of their high energy density, low volume change, and easy availability in varying temperature ranges. However, PCM suffers from a few critical drawbacks such as leakage during phase transformation, low thermal conductivity, and poor photothermal energy conversion performance. In this study, shape-stable composite PCM loaded with varying percentages of Graphite (GR) and Boron Nitride (BN) were prepared. Copper foam of 96 PPI was used as 3-dimensional skeleton support to provide shape stability to the eutectic mixture of Lauric Acid (LA)-Myristic Acid (MA). Shape stable composite PCM CF/LA-MA/GR with 0 %, 5 %, 15 %, 25 %, and 35 % of GR and CF/LA-MA/BN with 0 %, 5 %, 15 %, 25 %, and 35 % of BN were prepared and characterized for thermal, physical, and photothermal energy conversion performance. A maximum loading percentage of 67 % of LA-MA in CF without leakage was obtained. The PCM composites show excellent thermal stability at elevated temperatures and suitable TES parameters for solar thermal storage applications. Among all the prepared samples, CF/LA-MA/GR35% shows a maximum rise of 76.1 % in heating rate and 81.2 % in photothermal energy conversion efficiency in comparison with CF/LA-MA/GR0%. In addition, CF/LA-MA/GR35% shows a maximum of 1.08 W/m-K of thermal conductivity at a melting enthalpy of 95.36 J/g. The shape-stable composite PCM shows a stable physical structure along with good surface morphology.
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•A phosphorus-containing flame-retardant PCMs based on MXene was synthesized.•The MXene-based PCMs exhibits excellent thermal stability and thermal cycling reliability.•Improved ...thermal conductivity and good encapsulation effect of PCMs were achieved.•A synergistic flame-retardant mechanism between MXene and phosphorus-containing components in the PCMs were discussed and clarified.
Phase change materials (PCMs) are promising candidates for enhancing the efficiency of solar thermal energy utilization owing to their excellent capacity of storing thermal energy. However, the issues of leakage, poor thermal conductivity, and high flammability have hindered their application. Here, we have successfully designed and prepared flame-retardant PCMs through chemical modification of stearyl alcohol (SAL) with a phosphorus-containing molecule. Form-stable phase change composites were then fabricated through a vacuum impregnation method, where an MXene with a porous architecture serves as the supporting skeleton for PCMs. As expected, benefiting from the high aspect ratio and strong capillary force of the MXene aerogel as well as the interfacial interaction between the PCM molecule and MXene, the resulting MXene-based PCMs (PSM-4) exhibit a large thermal conductivity (0.486 W m−1 K−1) and are form-stable upon heating up to 90°C. Additionally, the combination of phosphorus and MXene further strengthens the flame retardancy of PCMs, e.g., the peak heat release rate and total heat release are reduced by 42.8% and 32.1%, respectively. The improvement of flame retardancy can be assigned to the catalytic charring and barrier effect in the condensed phase as well as to the effect of free radical quenching in the gas phase. Hence, the obtained MXene-based flame-retardant PCMs can be potentially utilized for safe and efficient applications of solar energy storage.
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•A 10 MW/8h PHES system using TES arrays was proposed and studied.•A novel operation mode of the TES array-(temperature complementation) was proposed.•Transient behavior of cyclic ...steady states under four operation modes was observed.•Delivery power variation decreased to 13.2% with the novel operation mode.•Novel operation mode requires low TES reservoir volume and cost.
As a novel physical energy storage technology with energy densities and efficiencies comparable to advanced compressed air energy storage, pumped heat electricity storage (PHES) has attracted significant attention in recent years. Arrayed multi thermal energy storage (TES) reservoirs have promising potential for large-scale TES storage, and the operation modes of TES arrays significantly affect the PHES system which has not been investigated in presented studies. By performing numerical simulations considering coupling dynamics, transient heat transfer, and thermodynamics, the transient behavior of the cyclic steady-state of a 10 MW/8 h Joule–Brayton PHES system under four operation modes including series, parallel, in-sequence, and the innovative “temperature complementation” is investigated in this study. The PHES with series-connected reservoirs arrays has a round-trip efficiency of 64.9% and a delivery variation of 43.1%; these results are better than those obtained under the parallel and in-sequence operating modes of the singular reservoir PHES. Under the innovative “temperature complementation” operation mode, the delivery stability improves further with a variation of 13.2%. The TES reservoirs could be reduced to 1.8 times the minimum volume with a round-trip efficiency of 63%–65%. Such a TES array with the “temperature complementation” operation mode may facilitate the development and application of other fixed TES technologies by providing stable thermal energy delivery.
Designing a cost-effective phase change thermal storage system involves two challenging aspects: one is to select a suitable storage material and the other is to increase the heat transfer between ...the storage material and the heat transfer fluid as the performance of the system is limited by the poor thermal conductivity of the latent heat storage material. When used for storing energy in concentrated solar thermal power plants, the solar field operation temperature will determine the PCM melting temperature selection. This paper reviews concentrated solar thermal power plants that are currently operating and under construction. It also reviews phase change materials with melting temperatures above 300°C, which potentially can be used as energy storage media in these plants. In addition, various techniques employed to enhance the thermal performance of high temperature phase change thermal storage systems have been reviewed and discussed. This review aims to provide the necessary information for further research in the development of cost-effective high temperature phase change thermal storage systems.
•Energy, exergy, environmental & economic analysis of cold thermal storage AC system.•Ice & PCM-TES-based systems at full and partial operating modes using R134a and R717.•Solutions for exergy ...efficiency & total annual cost from genetic algorithm.•Multi-criteria decision-making method- TOPSIS for selection of design point.•Highest exergy efficiency for PCM-TES based system at FOM with R717.
Thermal energy storage can be employed for air conditioning system load management, i.e., load shifting and leveling, to serve the peak electricity demand for the air-conditioning system with high capacity utilization. Ice and phase change material-based thermal energy storage systems were modeled and optimized for air-conditioning applications. The mathematical modeling involved energy, exergy, environmental and economic analysis of both the systems at full and partial operating modes. The system is then optimized for a commercial building to give maximized exergy efficiency and minimized total annual investment and operating cost over five different system temperatures as decision variables. The full operating mode strategy resulted in a higher exergy efficiency for both systems, whereas partial operating mode proved to be a more economical operating strategy. The multi-objective genetic algorithm-based optimization is carried out with two different refrigerants (R134a and R717) in the vapor compression refrigeration cycle of the systems. A single system design point is then selected using a multi-criteria decision-making technique. The electricity consumption while utilizing the thermal energy storage based system was lower as compared to the conventional system for air-conditioning applications. The two modeled systems are compared based on storage media, operating strategies, and the refrigerant used.
