One approach to enhance the energy efficiency of buildings is the integration of construction materials of latent heat storage biocomposites, which are prepared by vacuum impregnating the phase ...change material into biochar. Biochar is used because it is highly utilized and environmentally-friendly, and the selected phase change materials are fatty acid type which are bio-based material and have a low risk of depletion. Experimental results showed that latent heat storage biocomposite possesses excellent exudation and thermal stability as characterized by 0.1727 W/mK of thermal conductivity comparable to that for a gypsum board, and good chemical compatibility as its amount of latent heat tends to decrease as compared with that of pure phase change material. Results of the numerical analysis showed further that latent heat storage biocomposite efficiently reduced the maximum energy consumption of reference building models by 531.31 kWh per year. Thus, both results validate the claim that latent heat storage biocomposite is a promising building material.
•Latent heat storage biocomposite was prepared from eco-friendly biochar and bio-based phase change materials.•Experiments and numerical analyses were performed.•Integration of latent heat storage biocomposite into building walls reduced annual building energy consumption.•Latent heat storage biocomposites can be used as sustainable building materials.
CSP (concentrating solar thermal power) is emerging as a viable and cost effective solution to renewable energy generation. Molten salts are currently used as heat storage media to enable power ...generation during the night-cycle. Metal hydrides offer the possibility of storing energy with an order of magnitude less raw material than molten salts due to their impressive energy densities. To test the viability of hydrogen storage materials for CSP applications we have designed and constructed a prototype scale apparatus for screening materials under dynamic conditions with active heat extraction. The apparatus is tested with 19 g of well-known MgH2 to assess the viability of the design for screening purposes. The metal hydride is thermally cycled up to 420 °C more than 20 times with a minimal loss in hydrogen capacity. Issues relating to testing on a prototype scale are discussed, where problems with environmental heat loss and powder compaction dominate the performance of the metal hydride in the prototype. Problems with heat loss are inherently minimised on scale-up, leading to thermal behaviour more representative of a full-scale CSP energy storage system.
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•A prototype renewable energy storage system has been designed and tested.•Results indicate the system is feasible and reversible.•The design of the metal hydride vessel is critical to kinetic performance.•Practical issues and design considerations are highlighted.
Renewable energy has become very prominent these days because of its sustainable and environment-friendly nature. The soil heat storage system plays an important role in the long-term storage of ...solar energy to ensure a consistent power supply. The experimental analysis and practical implementation of soil heat storage system are very difficult due to its large size and the simulation-based calculation is also very complex for the entire storage system. In order to reduce the system from the perspective of space and time, this paper has applied a similar function relationship for soil heat storage system and develops the traditional CFD simulation model and similar model. According to the dimensions of similar model, the corresponding experimental setup is constructed and the experimental results of long-term heat storage in the soil are compared with the calculation results of a CFD similar model. The relative error of inlet and outlet temperature difference is measured 10% and the error for soil temperature rise is below 1 °C. The proposed method has reduced the simulation and experimental workload for soil heat storage using similarity theory. Hence, the proposed method has great significance in the research domain of soil heat storage and the application of similarity theory.
Latent heat storage (LHS) is one of the key methods to level renewable energy and utilize waste heat. In this method, heat is stored as latent heat of the phase change material (PCM) during melting. ...Releasing the stored heat in PCM consumes considerable time because the heat release rate is slow when a solidification layer of PCM is formed on the heat transfer wall during the heat release period. The authors have proposed a new mechanism for rapid heat exchange in LHS, i.e., by scraping the solidified PCM layer on the heat transfer wall. In this mechanism, the heat transfer wall is a rotating cylindrical tube to which a fixed blade is attached. During the heat release period, PCM is solidified on the tube, and the solidified layer is immediately removed using the fixed blade. In this study, a laboratory-scale setup with 1 kg of sodium acetate tri-hydrate as PCM was developed, and the effect of rotation rate on the heat release rate was experimentally examined. The results showed that the heat release rate during rotation accelerated by more than 100 times compared with the rate without rotation, and it increased with the rotation rate of the cylindrical tube.
•New concept for heat transfer accelalation in Latent heat storage (LHS) is proposed.•In LHS, heat is stored as latent heat of phase change material (PCM).•Solidified layer of PCM prevents the heat transfer furing heat release period.•The heat release rate is inovatevely accelerated by the scraping the solidified PCM.•The overall heat transfer coefficient in LHS reaches more than 2000 W/m2K.
Composites carbon foams based on sucrose-based char matrix and graphite filler were prepared and characterised with the aim of hosting sugar alcohols as phase-change materials (PCMs) in the context ...of thermal energy storage (TES). Seasonal solar TES demands an excellent undercooling of the molten PCM infiltrated in the foam, so that the heat can be stored as long as possible. The present paper demonstrates how the surface of such composite foams, i.e., comprising two carbon phases of different reactivities, can be modified for promoting undercooling. For that purpose, 8 different hydrophobisation treatments were applied, and the results were compared with those of the non-treated foam, in which heterogeneous nucleation could not be avoided. We show that one kind of functionalisation was successful, i.e., it fully preserved the melting point and the enthalpy of melting of the hosted phase-change material and completely avoided the heterogeneous nucleation of the PCM, while maintaining the thermal conductivity in the range required for this kind of application.
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•Seasonal heat thermal storage (STES) is addressed, based on composite carbon foams.•The latter were hydrophobised by 8 different methods and fully characterised.•Infiltration with sugar alcohols (SA) as phase-change materials was carried out.•Some hydrophobised materials fully prevented the heterogeneous nucleation of SA.•Excellent undercooling was thus evidenced, therefore promoting long-term STES.
In this research article a new modified adsorbent has been presented to be used in thermally driven adsorption systems for renewable energy applications. Bentonite is introduced as a cheap adsorbent ...with high potential for use in heat pumps or chillers driven by renewable energy. A simple acid activation procedure increases the inner surface of the material and also enhances the water adsorption capacity markedly. The raw bentonite is activated with different concentrations (0.2, 0.4, 0.6 mol L−1) of HCl. FT-IR, XRD, N2 adsorption, water adsorption and heat capacity measurements have been carried out for the raw and HCl activated bentonite. The acid activation process increased the surface area of the bentonite from 64 m2 g−1 to a level of 500 m2 g−1. In that respect the maximum adsorption capacity has markedly increased by the acid activation. Experimental and theoretical studies for the adsorption isotherms and kinetics at different adsorption temperatures of water vapor onto 0.6 HCl treated bentonite have been conducted. A simulation for an adsorption cooling system employing treated bentonite has been presented. The performance of the modeled system has been also studied to be driven by low grade heat source temperatures at different operating conditions.
•New material is presented for renewable energy applications.•Bentonite has been activated using HCl.•Physical properties of the activated bentonite have been studied.•Adsorption isotherms and kinetics of the activated bentonite have been studied.•Model of an adsorption cooling system with bentonite has been presented.
Metal oxides are potential materials for thermochemical heat storage via reversible endothermal/exothermal redox reactions, and among them, cobalt oxide and manganese oxide are attracting attention. ...The synthesis of mixed oxides is considered as a way to answer the drawbacks of pure metal oxides, such as slow reaction kinetics, loss-in-capacity over cycles or sintering issues, and the materials potential for thermochemical heat storage application needs to be assessed. This work proposes a study combining thermodynamic calculations and experimental measurements by simultaneous thermogravimetric analysis and calorimetry, in order to identify the impact of iron oxide addition to Co and Mn-based oxides. Fe addition decreased the redox activity and energy storage capacity of Co3O4/CoO, whereas the reaction rate, reversibility and cycling stability of Mn2O3/Mn3O4 was significantly enhanced with added Fe amounts above ~15mol%, and the energy storage capacity was slightly improved. The formation of a reactive cubic spinel explained the improved re-oxidation yield of Mn-based oxides that could be cycled between bixbyite and cubic spinel phases, whereas a low reactive tetragonal spinel phase showing poor re-oxidation was formed below 15mol% Fe. Thermodynamic equilibrium calculations predict accurately the behavior of both systems. The possibility to identify other suitable mixed oxides becomes conceivable, by enabling the selection of transition metal additives for tuning the redox properties of mixed metal oxides destined for thermochemical energy storage applications.
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•Solar thermochemical energy storage via reduction/oxidation of mixed metal oxides.•Co-Fe and Mn-Fe mixed oxides are promising candidates for high-temperature energy storage.•Improved cycling of Mn2O3 between bixbyite and cubic spinel by adding 15–50mol% Fe.•Co3O4 and Mn2O3 reaction temperature and hysteresis gap tuned with Fe addition.•Validation of calculated phase diagram by comparison with experimental results.
Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building ...efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.
•Zeolite was impregnated with PCM using the direct immersion method.•Zeolite has absorbed a high amount of PCM without exhibiting leakage.•The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C.•Cement based mortars were produced with PCM-impregnated zeolite instead of sand.•Mortars has provided sufficient mechanical properties and thermal inertia.
Inorganic salt hydrates, known for their high thermal capacity, are promising materials for large-scale thermal energy storage. This study investigates the potential of salt solution remnants, ...byproducts of green nano-silica extraction from olivine, as a sustainable source for crystallizing magnesium sulfate hydrates. Our primary objectives include analyzing the composition and heat capacity of this salt, which contains minor amounts of iron and nickel. Using Thermal Gravitational Analysis (TGA) and X-ray Diffraction (XRD), we identify primarily Hexahydrite as the recycled salt. The total heat capacity of these recycled salts was 247 J/g-267 J/g. Surprisingly, the thermal behavior deviates from expected salt mixes, challenging assumptions about the influence of iron and nickel on magnesium sulfate. Notably, the obtained recycled salts exhibit a comparable stored energy capacity to analytical grade sulfate salt mixtures.
•Primary salt hydrate generated from sidestream is Hexahydrite.•Thermal behavior of “Crystal Product” does not resemble any of the references.•Phase Change Material behavior is observed with regards to “Crystal Product”.•Primary inclusions do not play significant role in thermal behavior.
This research presents technical and cost-minimised design to decarbonise the heating network by using large-scale heat pump and thermal heat storage. In this paper, real hourly heat-consumption and ...heat-production cost data for the city of Aarhus, Denmark are used for calculating techno-economic feasibility of coupling the heating network with electrical grid. An optimum solution is suggested for the entire network with least amount of backup generation capacity, thermal heat storage capacity, natural gas boiler capacity and levelised cost of energy. Aarhus constitutes 5% of the Denmark's total heat demand and 4% of electrical load demand. This can be fulfilled with 160 MW of rated wind generation capacity, 35 MW of solar PV generation capacity, 45 MW of backup generation capacity, 221 MW of natural gas boiler capacity and 3.4 GWh of thermal heat storage capacity. The levelised cost of energy shows that, the coupling between the electrical grid and heating sector reduces the cost by more than 50% to 45 € /MWh. However, the cost-minimised design is possible with wind/solar mix of 85% and renewable energy penetration of 100%. Sensitivity analysis concedes that, the 100% decarbonisation of heating sector relies heavily upon the cost assumed for wind generation and solar PV generation, instead of the operation and maintenance cost for heat pump. Furthermore, the reduction in cost for wind generation and solar PV generation leads to the decrease in levelised cost of energy. Whereas, the reduction in cost for heat pump, thermal heat storage capacity and natural gas boiler capacity leads to an increase in renewable energy penetration. Sensitivity analysis further reveals that, increasing thermal heat storage capacity and the cost of selling excess renewable energy does not have major impact upon the levelised cost of energy and can be instrumental for the economic viability of fossil-free future.
•The average heat-production cost from combined heat and power plant is 40 €/MWh.•The intra-day heat demand profile coincides with people commute to work.•Energy from heat pump is economical until renewable energy penetration is 130%.•The sector coupling reduces the energy costs by more than 50% to 45 €/MWh.•Excess generation can be sold up to 108 €/MWh without impact on cost of network.
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