The implementation of organic phase change materials (PCMs) in several applications such as heating and cooling or building comfort is an important target in thermal energy storage (TES). However, ...one of the major drawbacks of organic PCMs implementation is flammability. The addition of flame retardants to PCMs or shape-stabilized PCMs is one of the approaches to address this problem and improve their final deployment in the building material sector. In this study, the most common organic PCM, Paraffin RT-21, and fatty acids mixtures of capric acid (CA), myristic acid (MA), and palmitic acid (PA) in bulk, were tested to improve their fire reaction. Several flame retardants, such as ammonium phosphate, melamine phosphate, hydromagnesite, magnesium hydroxide, and aluminum hydroxide, were tested. The properties of the improved PCM with flame retardants were characterized by thermogravimetric analyses (TGA), the dripping test, and differential scanning calorimetry (DSC). The results for the dripping test show that fire retardancy was considerably enhanced by the addition of hydromagnesite (50 wt %) and magnesium hydroxide (50 wt %) in fatty acids mixtures. This will help the final implementation of these enhanced PCMs in building sector. The influence of the addition of flame retardants on the melting enthalpy and temperatures of PCMs has been evaluated.
The main economic activities in rural areas of Ecuador are agriculture and livestock rearing, with water being the primary resource for these activities. Approximately 3% of the rural population ...lacks access to the conventional electrical grid, so photovoltaic pumping systems can fulfil the need to capture and distribute water without emitting greenhouse gases. This research aims to study the appropriate technologies to develop a photovoltaic pumping system for future implementation in rural areas of Ecuador, based on a centrifugal pump, induction motor, variable speed drive, and powered by a photovoltaic array. Simulink/MATLAB R2019B is used for system modelling and simulation. Additionally, two maximum power point tracking methods are studied, the perturb and observe algorithm and the artificial neural network algorithm. The simulation results show that when using the artificial neural network maximum power point tracking technique, the system performs better, being faster in transitions and presenting fewer oscillations in the steady state. The EN50530 standard is also employed to test the performance of the maximum power point tracker, and as a result, the artificial neural network-based algorithm achieves the highest efficiency of 99.5%. Finally, it is shown how the automatic regulation of speed allows adjustment of the pumping capacity in response to variations in irradiation and temperature. Even in unfavourable levels of irradiation and temperature, the water supply is not interrupted, and the pump capacity is adjusted to the maximum power supplied by the photovoltaic array.
Phase change materials (PCMs) based thermal energy storage (TES) has proved to have great potential in various energy-related applications. The high energy storage density enables TES to eliminate ...the imbalance between energy supply and demand. With the fast-rising demand for cold energy, cold thermal energy storage is becoming very appealing. In this paper, a review of TES for cold energy storage consisting of various liquid-solid low-temperature PCMs has been carried out. The classification of the PCMs is briefly introduced. Recent approaches to optimizing the properties of PCMs, particularly to remedy the poor thermal conductivity, leakage of liquid PCMs and the high degree of super-cooling, which limits the cold applications of TES, have also been reviewed. Methods for increasing the thermal performance including using composite PCMs and solid mesh are compared. Both modelling and experimental research on cold energy storage devices have been examined. The current cold energy storage applications including air conditioning, free cooling, etc. have been summarised. Compared with previous reviews, this work emphasises the cold energy storage applications instead of the materials aspects. The main challenges and approaches to cold thermal energy storage from the perspective of the engineering applications have been identified. Recommendations for future low charging rates and device design methodology are proposed.
•Recent approaches to optimizing PCMs properties have been reviewed.•Both modelling and experimental researches on cold energy storage devices have been examined.•Main challenges and approaches on cold thermal energy storage engineering applications have been identified.•Recommendations on low charging rate issue and device design methodology have been proposed.
Researchers have sought for standards, methodologies and procedures to properly measure the thermal properties of Thermal Energy Storage (TES) materials. Among them, thermal conductivity plays a key ...role in the TES system design as it dictates the charging/discharging dynamics of a TES system. The lack of thermal conductivity measurement's standards led to a large extent of discrepancies in terms of measurement method, measurement equipment, and sample preparation as reported in this review. Such discrepancies create uncertainties in the thermal conductivity values, which results in misleading interpretation that will be later used by other researchers for comparison purposes. This is particularly important when thermal properties are strongly linked to complex nano and micro scale materials structure. This review paper was motivated by the need of filling the gap in the literature when assessing the thermal conductivity measurements used for TES media. To that end, steady-state methods and transient methods have been reviewed by its device (commercial or own-developed), sample size, accuracy, repetitions, measurements time, etc. The outcomes of this study are threefold: regarding TES media, not all three TES technologies have been studied at the same extent; just few papers have been reported on thermochemical storage, being phase change materials and sensible the most studied; Regarding thermal conductivity techniques, transient plane source, laser flash apparatus and transient hot wire are the most used, whereas modulated DSC and 3ω the least; And lastly, regarding the measurement procedure, the data is widely spread especially for accuracy, sample size and repetitions within the same material/technique. Overall, TES community have many challenges to face in the future to converge on a common agreement aiming comparable results among studies. That means optimized sample preparation and method procedure across the different techniques achieving high accuracies for the different TES materials.
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•TES system design depends on accurate thermal conductivity versus temperature data.•Thermal conductivity reliable data are essential for TES materials selection.•There are no standards for TES materials thermal conductivity measurements.•The data reports the advantages, disadvantages and uncertainties of the procedures used in literature.•Scientific community must normalize procedures; define sampling methodology and equipment.•This review provides researchers a framework for standardising the measurement protocol.
This article aims to provide a comprehensive review of the latest work on structurally stabilised composite phase change materials (SSCPCMs) for thermal energy storage, with a specific focus on the ...manufacturing technologies and the associated skills. SSCPCMs have attracted significant attention in recent years given their advantages of small volume changes, reduced phase segregation and corrosion, and improved thermal conductivity. The review covers SSCPCMs with different types of matrices, including ceramic, carbonic, metallic, and polymeric. Unlike previous reviews, this work pays a specific focus on the fabrication methods and the impact of preparation parameters on the properties of SSCPCMs, aimed to understand the current knowledge gap in the manufacturing processes and to promote the scale-up production of the SSCPCMs. To this end, knowledge databases on key preparation parameters were established from literature for three manufacturing routes: impregnation, mix-sintering, and hot-melt extrusion. Such databases provide a guidance for academic researchers and engineering practitioners to select optimal fabrication parameters for their designed SSCPCMs. The work also leads to the establishment of relationships between the fabrication parameters and material performances based on the databases. Furthermore, the manufacturing readiness level of various energy storage technologies were reviewed, which is an important indicator to evaluate the manufacturing maturity.
•Methods for manufacturing SSCPCMs for TES technology have been reviewed.•Manufacturing methods include impregnation, mix-sintering, hot-melt extrusion and other methods.•Knowledge databases on key preparation parameters were established.•Correlations between manufacturing and material properties were discussed.•Manufacturing readiness levels of various energy storage technologies were reviewed.
•A novel hybrid system is proposed in this paper: 3 in 1 TES.•3 in 1 is a synergistically entanglement of sensible, latent and thermochemical heat.•In the system the main fundamental challenges of ...each technology are surpassed.•PCM helps to maintain the physical integrity during cycles.•TCM/PCM pair provides a cost-extensive storage media that can store up to 2 GJ∙m−3.
Thermal energy storage (TES) technologies have been traditionally classified into sensible, latent and thermochemical categories. TES needs significant research efforts to address some fundamental challenges to reach its full potential. The hybridisation of TES technologies provides potentially a highly effective solution to the challenges. We present here a new concept, the 3 in 1 system, examining the feasibility, and the applied aspects of the newly proposed technology. The 3 in 1 system integrates the three known thermal storage methods of sensible heat, latent heat and thermochemical based TES into one system, providing three different operational configurations with cascading, charging integrated and discharging integrated working conditions. These different configurations offer controllability of TES charge/discharge processes while enhancing system-level efficiency. The proof of concept consists of a co-working matrix of a polymer as the phase change material (PCM), high-density polyethylene, and one of the most studied thermochemical material (TCM), MgSO4·7H2O. The feasibility of the composite containing 80–90 wt% of TCM was studied, over 15 cycles, for mechanical integrity, stability, energy stored and reaction kinetics. The results show that the system has a great potential for storing heat, up to 2 GJ∙m−3 and offers a wide working temperature range, from 30 °C to ∼150 °C. The combination of the PCM/TCM pairs give the composites mechanical integrity while accommodating the volume change and maintaining the structural stability during thermal cycling. This novel idea addresses some key technology gaps in TES particularly degradation and hence short life-span of TCM, cost-effectiveness and flexibility of the TCM based technology, thus offers potential paradigm shift to the thermal energy storage technology.
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•Summarizes a wide temperature range of Cold Thermal Energy Storage materials.•Phase change material thermal properties deteriorate significantly with temperature.•Simulation methods ...and experimental results analyzed with details.•Future studies need to focus on heat transfer enhancement and mechanical design.•Analyzes applications with technology readiness and more should be explored.
The energy industry needs to take action against climate change by improving efficiency and increasing the share of renewable sources in the energy mix. On top of that, refrigeration, air-conditioning, and heat pump equipment account for 25–30% of the global electricity consumption and will increase dramatically in the next decades. However, some waste cold energy sources have not been fully used. These challenges triggered an interest in developing the concept of cold thermal energy storage, which can be used to recover the waste cold energy, enhance the performance of refrigeration systems, and improve renewable energy integration. This paper comprehensively reviews the research activities about cold thermal energy storage technologies at sub-zero temperatures (from around −270 °C to below 0 °C). A wide range of existing and potential storage materials are tabulated with their properties. Numerical and experimental work conducted for different storage types is systematically summarized. Current and potential applications of cold thermal energy storage are analyzed with their suitable materials and compatible storage types. Selection criteria of materials and storage types are also presented. This review aims to provide a quick reference for researchers and industry experts in designing cold thermal energy systems. Moreover, by identifying the research gaps where further efforts are needed, the review also outlines the progress and potential development directions of cold thermal energy storage technologies.
•Compatibility of Solar Salt and four metal alloys for CSP plants is studied.•A static corrosion test at 500 °C and in air is performed.•The descaled and gravimetrical corrosion rate methods are ...compared and analysed.•An economical study assessing cost, mechanical properties and corrosion rate is done.•304H and 316L have the best cost-corrosion rate-mechanical properties performance.
One of the main limitations concerning the implementation of heat transfer fluids in Concentrated Solar Power (CSP) plants, are their compatibility with the construction material. Hence, the study of this interaction over cycles is crucial for a proper material selection and life span forecast. In this work, the chemical compatibility of four commonly used metals in CSP plants; low carbon steel-A1045, stainless steel-304H and 316L, and nickel alloy-Inconel 600, with one of the most promising HTFs, Solar Salt, was evaluated. Two different methodologies (gravimetrical and descaled method) were compared and used to characterise the corrosion behaviour depending on the metal coupons analysed, concluding that the best method for most of the metals is the descaled one. The corrosion oxides were also characterized using a combination of different techniques: SEM, EDX, and XRD. Inconel 600 showed the best corrosion resistance among the metals evaluated. However, a further brief economical study concludes that a compromise between the overall metal loss cost per year and the price of the construction material over the lifetime of the plant must be found. The two stainless steels (304H and 316L) were identified as the best performing according to metal loss vs. material price and mechanical properties vs. corrosion rate.
This paper aims to complete and complement the information available on the past trends of thermal energy consumption in residential buildings and its drivers for Europe, as a continent and for the ...different countries. This paper follows the drivers identified in a previous one for the heating and cooling energy consumption, decomposing this energy demand into key drivers based on a Kaya identity approach: number of households, persons per household, floor space per capita and specific energy consumption for residential heating and cooling. Results show that all drivers did follow a consistent trend at global, regional and country level during the studied period of time, but the heating and cooling energy consumption did not follow the same trend if it was considered at global, regional or country level, showing that the energy consumption is very much influenced by all its drivers and does not follow the same trend as the specific energy consumption. Moreover, similar trends for each indicator can be found when evaluated at country or regional level, therefore as expected when aggregating data trends can be seen but details and particularities (both for the different countries and for the different studied years) are lost.
•Past trends of thermal energy consumption in residential buildings for Europe are presented.•H&C energy consumption drivers are identified and quantified.•Number of households, persons per household, floor space per capita and specific energy consumption.•All drivers did follow a consistent trend at global, regional and country level.•H&C energy consumption did not follow the same trend for different levels.
•Several issues must be solved to transfer to the market solid particle CSP plants.•Solid particles combine roles: as TES media and HTF within CSP plants configuration.•Review of operating conditions ...and parameters that make solid particles attractive.•Review about whole system: the storage, heat exchangers and material conveyance.•Solid particle systems can increase heat conversion efficiency to electric power.
Thermal energy constitutes up to 90% of global energy budget, centering on heat conversion, transmission, and storage; therefore, the technology for harvesting solar energy worth to be developed. One of them is the concentrated solar power (CSP) solar towers where sun-tracking heliostats reflect solar radiation to the top of a tower where the receiver is located. The great advantage of CSP over other renewable energy sources is that energy storage is feasible, particularly when the heat transfer fluid (HTF) is also used as thermal energy storage (TES) material which is the case of solid particles. A lot of development efforts are under way for achieving commercial direct solar solid-particle systems. Solid particle systems for transferring high temperature thermal energy are purposed for increasing the efficiency of these systems when converting heat into electric power. This review recapitulates the concept of these systems taking into account the main receiver designs, particle conveyance, particle storage systems and components, the heat exchanger, and the main challenges that must be overcome to split this technology as a commercial one, especially from the materials availability point of view. This review summarizes the actual status of the use of solid particles for TES and as HTF for CSP Tower, and condenses all the available information and classifies them considering the main functional parts and remarking the current research in each part as well as the future challenging issues.
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