Phase Change Materials For Energy Storage Research Articles

Dynamic 4E (energy, exergy, economic and environmental) analysis and tri-criteria optimization of a building-integrated plant with latent heat thermal energy storage

The buildings energy sector is expected to account for 40% of total world energy consumption and 40% participation on total carbon dioxide emissions, according to the International Energy Agency reports. The present study proposes a novel integrated system to meet all loads of the house's energy requirements. The system employs a heat storage tank rather than pricey batteries, which helps to keep the total cost of the system as low as feasible. Also, the system is developed for an on-grid operation, being capable to sell surplus energy to the grid helping to reduce the payback time. Dynamic modeling is conducted to analyze the system performance to provide heating, cooling and power demands of a case study building, for which two scenarios of with and without Phase Change Material (PCM) incorporation is considered. The influence of critical design factors is investigated, after which a tri-objective optimization is carried out. It was found that, the integration of PCM energy storage would reduce the annual heating and cooling demands of the building by 25.6%. As a result, the exergy efficiency of the proposed system increases by 13 % and the product cost is reduced by 8.57%. Based on the obtained yearly average results, the proposed building energy system yields exergy efficiency, unit product cost, and CO2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh, respectively.

Study on Physicochemical Properties and Potential Applications of Chemically Treated Luffa Sponge Fibers

ABSTRACT To explore and expand the application of luffa sponge (LS) fiber, three methods were used to chemically modify the LS fibers. The nanoindentation (NI) results show that the LS fibers exhibit a high elastic modulus (12.4 GPa) and hardness (0.7 GPa). Upon treating the fibers with 5%NaOH-5%H2O2, the NI hardness of the fibers increases by 14.3%. However, when 10%NaOH-20%CH3COOH (method B) is used, the hardness of the cell walls decreases by 28.6%. In this case, the removal of amorphous substances from the LS fibers and the swelling reaction of the LS cellulose plays a significant role. Three chemical treatments can partially remove the hemicellulose in the LS fiber. 18%NaOH-1.6%CO(NH2)2 (method C) modifies the crystalline structure of the cellulose in the LS fibers. Gas chromatography-mass spectrometry results show that the LS fibers are rich in hexadecanoic acid (14.3%), as well as in substances, such as squalene, oleic acid, and behenic alcohol, which exhibit a high antibiofilm activity. Furthermore, method B increases the total relative content of squalene and squalane in the LS extract by 49.4%; while method C treatment allows LS fibers have the potential to be used to develop phase-change energy storage materials and anti-photoaging discoloration materials.

Bio-based recyclable Form-Stable phase change material based on thermally reversible Diels–Alder reaction for sustainable thermal energy storage

Polymer-based form-stable phase change materials (FPCMs) have attracted much attention due to their excellent shape stability and facileness, low-energy-consumption preparation. However, bio-based recyclable phase change energy storage materials (PCMs), crucial for reducing pollution and sustainable energy storage, have not yet been prepared. Herein, we prepared a novel bio-based recyclable PCM (DGEM-18/FA/MA/xBW), in which a novel epoxy resin (DGEM) was synthesized by using bio-based magnolol and epichlorohydrin, bio-based 2-Furanmethanamine (FA) and C36-alkylenediamines bismaleimide (MA) were used to construct a reversible crosslinked network based on epoxy-amine ring opening and Diels-Alder (D-A) reactions as the supporting frame. And 1-Octadecanethiol (ODT) and bio-based beeswax (BW) with phase change property were introduced into this supporting frame by grafting on the C=C of Magnolol via “thiol-ene” click reaction and physical blending, respectively. The D-A and rD-A reactions proceed at the temperature below 80 ℃ and above 120 °C, respectively, which provides recyclability of the crosslinked network. The ODT and beeswax provide phase change latent heat up to 119.1 J/g for the sample DGEM-18/FA/MA/1.1BW. Furthermore, taking DGEM-18/FA/MA/0.4BW as an example, its shape memory performance has been explored, as well as its potential applications in recyclable thermal management coatings. To the best of our knowledge, this is the first report on the preparation of bio-based recyclable FPCMs.

Energy, exergy, and economic assessment of thermal regulation of PV panel using hybrid heat pipe-phase change material cooling system

There has been a theoretical investigation for energy, exergy, and economic evaluation of thermal regulation of PV panels via an innovative hybrid cooling system of flat heat pipes (HPs) coupled with phase change material (PCM). PV panel dissipates its heat through the HP evaporator while the HP condenser is cooled by PCM. The cooling system performance is investigated for different PCM quantities and types (RT42, RT35HC, and SP31) for summer and (RT21, RT18HC, and SP15-gel) for winter conditions in Egypt. A thorough study and analysis have been conducted for the impact of the cooling system on PV panel's temperature, electric efficiency, output power, PCM energy storage, and system efficiency. The results show that compared with conventional PV, the best PCM type for PV performance in summer is SP31 of 3 cm thickness, which achieves a maximum PV temperature reduction of 20.6 °C with a maximum improvement in PV electric efficiency of 11.5%. SP15-gel of thickness 2.5 cm is the best PCM for winter conditions, achieving 14.1 °C temperature reduction with 7.2% enhancement in PV electric efficiency. The exergy efficiency of the PV panel is higher than in PCM, where it rises as the phase change temperature of the PCM increases. PV maximum average daily exergy efficiency is 13.4% for SP15-gel, compared with 12.71% for conventional PV in winter, while SP31 achieved 12.25%, 1% higher than reference PV in summer. PCM's maximum average daily exergy efficiency is 0.69% and 0.7% for RT42 and RT21 in summer and winter, respectively. The minimum payback period for conventional PV is about 18.01 years, while it is approximately 13.39 years for PV with HP and PCM. The studied cooling system at different PCMs proves its capability to enhance the PV performance with higher energy and exergy efficiencies and lower cost and store the excess heat inside the PCM.

Energy harvesting and storage blocks based on 3D oriented expanded graphite and stearic acid with high thermal conductivity for solar thermal application

Photothermal energy conversion and storage based on organic solid-liquid phase change materials (PCMs) show huge potential in conquering discontinuous solar irradiation. It remains a challenge to fabricate integrated devices that take excellent photothermal conversion, heat transportation and energy storage into account. Here, we construct 3D oriented expanded graphite (EG) by compression induced graphite sheet self-assembly, then load the stearic acid (SA) to form oriented PCMs. The in-plane thermal conductivity, thermal response and energy storage density of 3D oriented PCMs are better than those of non-oriented PCMs under the same graphite mass faction and packing density. When the EG content is 20 wt%, the thermal conductivity of the oriented PCMs is 34.2% higher than that of the non-oriented PCMs and latent heat maintains above 159.36 J/g. We further prepare energy storage bricks and coordinate the heat conduction of oriented EG perpendicular to the axial direction of copper tube. The photothermal energy conversion efficiency of the energy storage brick reaches 95.3%, and the average powers during charging and discharging process are 2.1 kW and 2.4 kW, respectively. The design method for solar energy storage device improves the photothermal conversion efficiency, thermal conductivity and energy storage of PCMs, provides a simple and economical strategy for large-scale photothermal applications.

Experimental study of using system of flat heat pipe-phase change material inclusion heat sink for thermal regulation of simulated PV

ABSTRACT Flat heat pipe (HP)-phase change material (PCM) hybrid system used for thermal regulation of simulated PV is investigated experimentally. Three PCMs; Rubitherm RT-25 H (RT25), Rubitherm RT-35 H (RT35), and Rubitherm RT-44 H (RT44) coupled with the HP are tested for best cooling system. Impact of using one or two heat sinks compared with PCM only is studied. The results show that RT25 achieves lowest PV temperature, while RT44 achieves highest energy storage. Compared to RT25 and RT44, RT35 is considered the best for PV cooling and PCM energy storage. Including heat sinks reduces PV temperature and melting time and increases energy storage rate.

Performance evaluation of a solar air heating system integrated with a phase change materials energy storage tank for efficient thermal energy storage and management

This research aims to manage thermal energy in a solar system to make it more functional due to solar energy variability. A parabolic trough collector (PTC) was integrated with a tank of phase change materials (PCMs) to produce hot air with a temperature close to the PCM melting point over a lengthy period. A comprehensive computational fluid dynamic (CFD) model was developed for the system. After model validation, parametric sensitivity analysis was performed and the proper ranges of the effective parameters were attained. Obtained results reveal that the PTC dimensions must be selected based on inlet temperature to the PCM bed as follows that could melt the entire or a part of PCMs. The PTC's length to its aperture ratio, Rl in the range of 0.85–2.25, bed length and diameter greater than 0.9 and 0.35 m, respectively, bed porosity in the range of 0.1–0.5, and inlet air rate in the range of 0.01–0.06 kg/s can satisfy the objectives of the present work. The system can produce up to 1025 m³ of hot air with a temperature of 60 °C and ±2 °C fluctuations during 12.5 h of system operation from the early hours of the day until late at night.

Experimental and computational study of melting phase-change material for energy storage in shell and tube heat exchanger

The preservation of thermal energy is a significant problem that needs to be resolved. In the present energy demand situation, effective storage of available energy will be a technique to manage the gap between the demand and supply. Solar energy is one such energy, which is an easily obtainable and renewable source of energy. Still, the maximum employment of solar energy is not readily possible without the implementation of the thermal energy storage system (TESS). This TESS can be an integral part of solar applications, thus TESS acts as a reservoir of energy to deliver the energy requirement at all times. Hence, it is an appropriate system to unite the energy source, i.e., the sun and the applications. Thus, the TESS is very vital in solar applications. The main objective of this work is to design and analyze the vertical shell and tube type TESS using water as heat transfer fluid (HTF) and paraffin wax RT58 as phase change material (PCM), which is subjected to change its phase at 46 °C to 68 °C from solid to liquid when exposed to higher temperatures, and its operating temperature range is 60 °C to 80 °C. Here, PCM (RT58) is enclosed in the tubes of the shell and tube storage unit. The property of the high specific heat capacity of PCM is tested for utilization of latent heat storage that can be used any time as required. Temperature measurements are taken using a T-type thermocouple along with an indicator and a series of experiments were conducted to study the effects of PCM in TESS. PCM encapsulated heat exchanger performance is investigated for both charging and discharging cycles with 85 °C inlet water temperature and a constant flow rate of 0.04 kg/s. To analyze the melting characteristics of PCM, simulation is carried out using ANSYS Fluent in the workbench, and comparative simulation studies are carried out for quadrilateral and triangular node shapes for better accuracy with experimental data. The heat energy stored in the charging cycle is 302.327 kJ for 100 min duration, and in discharging cycle is 295.8 kJ for 56 min duration. The HTC and Nusselt number were also calculated for both the charging and discharging cycle. It is evident from the present work, that the PCM can act as a better alternate for energy storage medium compared with the present solar energy storage methods, ensuring the correct adaptability of PCM for the particular application. The heat transfer rate can be increased further by using more amounts of different PCM or PCM composite with higher latent heat and also by providing better tank insulation. In future work, emulsification of nanomaterial in the PCM or in the HTF, and implementation of finned tube profile can increase the overall performance of TESS.

Energy saving and CO2 reduction potential of external building walls containing two layers of phase change material

Using two layers of phase change material (PCM) instead of one to improve the thermal energy storage of PCM is a promising way to minimize thermal loads in buildings. This study aimed to maximize the latent heat utilization by splitting the PCM into two layers and adjusting their location and melting temperature. Seven scenarios were created using one or two PCM layers on the inner side, outer side or both sides of an external wall. Energy savings analysis was carried out using a verified numerical model. The results indicated that the monthly optimum PCM melting temperature ranged from 5 °C to 30 °C. Two PCM layers, one on the outside side of the wall with a melting temperature of 17 °C and the other on the interior side with a melting temperature of 25 °C, resulted in higher annual energy savings (17.2%), compared to a single PCM layer (16.8%). With two PCM layers, the energy saving due to latent heat activation increased from 2.5% to 3.2%. Furthermore, this design reduced CO2 emissions by up to 18.4% and caused the surface temperature to approach the comfortable room temperature thereby decreasing thermal loads and improving thermal comfort.

Study on Influencing Factors of Phase Transition Hysteresis in the Phase Change Energy Storage

Phase change energy storage is a new type of energy storage technology that can improve energy utilization and achieve high efficiency and energy savings. Phase change hysteresis affects the utilization effect of phase change energy storage, and the influencing factors are unknown. In this paper, a low-temperature eutectic phase change material, CaCl2·6H2O-MgCl2·6H2O, was selected as the research object, combined with the mechanism of phase change hysteresis characteristics, using a temperature acquisition instrument to draw the step cooling curve. A differential scanning calorimeter was used to measure the DSC (differential scanning calorimetry) curve, and the hysteresis characteristics of phase transformation were studied by factors, such as heat storage temperature, cooling temperature, and cooling rate. The experimental results show that when heating temperature increases by 30 °C, phase transition hysteresis decreases by about 3 °C. The cooling temperature decreased by 10 °C, and the phase transition hysteresis increased by 2.69 °C. This paper provides a new idea for optimizing the properties of phase change energy storage materials and provides a possibility for realizing the parametric control of phase change hysteresis factors.

Parametric optimization of a cesaro fins employed latent heat storage system for melting performance enhancement

The large-scale use of sustainable energy necessitates the use of latent heat storage (LHS). This study aims to increase the melting performance of an LHS system by designing and optimizing the cesaro fins. To examine the melting behaviours of PCM (i.e., RT-82) in a finned LHS system, a 2-D melting heat transfer model is developed and numerically solved. As per literature, there is very literature including the NC (Natural Convection) and represents the coordination in fins, nanoparticles and metal foam. So, the impacts of natural convection, fin arrangement, nanoparticles and metal foam are explored for the Fourier number variations from 0.014 to 0.158 at a constant Stefan number of 0.20. The dynamic temperature distribution, as well as the natural convection and fin arrangement, are investigated to determine how phase change material melts over time by considering the non-thermal equilibrium between metal foam and PCM/nanoPCM. The findings illustrate that natural convection has a significant effect on melting behaviours in the LHTES (Latent Heat Thermal Energy Storage) system, with a 26.8% increase in melting/charging rate as compared to the situation without NC. The LHTES system with improved fin structure (i.e., Type-3) and increased number of fins (i.e., Type-5) configurations have more uniform temperature distribution and a higher melting rate by increasing the heat transfer cooperation between NC and thermal conduction. Low thermal conductivity causes poor performance in PCM (Phase Change Material) energy storage devices. The melting/charging of PCM in an LHTES system is greatly improved in this study by employing a porous metal foam (i.e., copper metal foam) or nanoparticle (i.e., Cu, CuO and Al2O3). The impact of nanoparticle volume fraction and metal foam porosity on the LHTES system's melting/charging performance is also investigated using the enthalpy-porosity technique. According to the results, PCM's melting/charging time is lowered by 63.4% when nanoparticles are mixed in and incorporated with metal foam for the Fourier number varies from 0.014 to 0.158 at a constant Stefan number of 0.20. PCM melting/charging time decreased when the metal foam porosity decreased or increased in the volume fraction of nanoparticles. High porosity metal foams with low volume fractions of nanoparticles can increase melting performance since it assures minimum PCM volume and increases natural convection.

Numerical simulation of the heat storage performance of aluminum/paraffin composite phase change materials

Phase change energy storage materials are widely used in the fields of battery thermal management and solar power generation due to their characteristics of storing and releasing energy periodically. However, their further applications are limited by their low thermal conductivity. The addition of high thermal conductivity foams provides an effective method to address this shortcoming. A three-periodic minimal surface (TPMS) was used to generate an aluminum foam skeleton, and the variation of phase change heat storage of the aluminum/paraffin composite phase change material was numerically simulated based on the pore scale. The results showed that the addition of aluminum skeleton enhanced the heat storage and shortened the melting time, and the melting time of the composite phase change material was shortened by 68%, 75% and 80% when compared with pure paraffin wax at the porosity of 0.90, 0.85 and 0.80, respectively, and the temperature field was more uniform during the heat storage process, The thermal non-equilibrium effect between the aluminum skeleton and the paraffin wax is verified, and the lower the porosity of the aluminum/paraffin composite phase change material, the more obvious this effect is.

A 3D resolved-geometry model for unstructured and structured packed bed encapsulated phase change material system

A 3D numerical model is developed to simulate melting in packed bed encapsulated phase change material (PCM) energy storage systems. The main novelty of the model is that it resolves the arrangement of capsules inside the system for both structured and unstructured packing and thus accurately captures the fluid flow, heat transfer and phase change in the capsules. To create the unstructured arrangement of capsules in the domain a novel dropping and rolling algorithm is implemented. The flow of heat transfer fluid (HTF) outside the capsules as well as the natural convection in the PCM within the capsules is also simulated. Initially, a single capsule study is performed, which shows that both natural convection inside the liquid PCM and forced convection outside the capsule affect the melting characteristics. Subsequently, the model is extended to simulate phase change in multiple capsules in a cubical domain arranged with structured and unstructured packing. The analysis of the effect of capsule arrangement on the melting and energy storage characteristics for both structured and unstructured packing of capsules is performed. Additionally, parametric studies are performed to analyze the effects of capsule size, fluid temperature, and fluid velocity for both types of systems. Simulation results show that the total melting time for unstructured packing is reduced on an average by 23.56% for the 2.5 mm capsules and by 10.14% for the 5 mm capsules as compared to structured packing. The effect of HTF temperature change is more prominent for structured cases, with an increase of 65.8% melting time as compared to 58.4% for the unstructured cases when the HTF temperature is reduced by 20 K. In contrast, the effect of velocity is less significant for the structured cases with a reduction of HTF velocity from 0.1 cm/s to 0.05 cm/s causing an increase of 27.3% melting time for the structured cases and 42.6% for the unstructured cases. The developed model can be used to capture the effect of different arrangements of capsules in encapsulated PCM energy storage systems and thus obtain effective designs for such systems.

Design and preparation of salt hydrate/ graphene oxide@SiO2/ SiC composites for efficient solar thermal utilization

Efficient solar thermal utilization has attracted extensive attention because it effectively alleviates carbon dioxide emissions and environmental pollution. Phase-change material (PCM) energy storage technology has been regarded as the most promising in improving its efficiency. Toward higher energy utilization efficiency, how to realize conversion and storage of solar energy into PCM is becoming progressively important. Herein, we developed low-cost and stable sodium acetate trihydrate (SAT, salt hydrate PCM) with ultra-fast solar energy charging efficiency by integrating photothermal and thermal conductivity materials. Specifically, a graphene oxide@SiO 2 (GS) nanocomposite fabricated by a novel modified Stober method was employed as the nucleating agent and photothermal conversion enhancers for SAT. The supercooling degree of SAT can be reduced to 0.5 °C from 32.0 °C with the addition of 1.0 wt% GS, while the solar energy charging efficiency of SAT was increased by 92.5% when it is synergistically augmented by integrating GS and silicon carbide (SiC) foam. This study results indicate that the prepared SAT-GS-SiC composite with an enthalpy of 193.2 J/g can be potentially used to efficiently utilize solar energy. A novel PCM composite with low supercooling, high thermal conductivity, and photothermal conversion efficiency was facilely synthesized. • Graphene oxide and SiO 2 (GS) composite with excellent photothermal conversion efficiency was synthesized. • Supercooling degree of sodium acetate trihydrate (SAT) could be reduced to 0.5 °C with the addition of 1.0 wt% GS. • Thermal conductivity of SAT improved by 184.5% after integrating GS and silicon carbide (SiC) foam. • Photothermal conversion efficiency of SAT-GS-SiC composites could reach to 92.5%.

The effect of Incorporating phase change materials in building envelope on reducing the cost and size of the integrated hybrid-solar energy system: An application of 3E dynamic simulation with reliability consideration

According to statistics, building energy consumption is responsible for 40% of the world’s energy usage and 40% of the emission. To minimize the enormous damage caused by energy usage in the building sector, many energy storage applications as phase change materials (PCMs) are proposed. Moreover, retaining proficient energy systems to arrange for building energy loads is another essential tactic to diminish energy consumption in the building division. In this research, a new hybrid solar-based energy system is proposed to supply the demands of the building. The system is grid-connected and has two-way interactions with the grid that can sell the electricity to compensate for some of the building bills. The usage of a heat storage tank and not employing expensive batteries in a solar system is another advantage. A two-story building is dynamically simulated in actual weather conditions of Tabriz city with embedded PCM materials in the building façade. Also, the building energy demand and the proposed system recital are systematically compared with and without PCM integration. The results indicated that with the incorporation of PCM energy storage, the building's yearly heating and cooling loads are decreased by 27.4%. Such a reduction of heating and cooling loads, in turn, improves the plant performance by 18.42%, 13.0%, and 28.54%, respectively, in terms of fuel consumption, exergy efficiency, and unit product cost. Moreover, the reliability of heating and power generation is 0.9688, while the reliability of power and cooling generation is 0.9783 on the supply side.

Preparation and properties of lauric acid-octadecanol/expanded graphite shape-stabilized phase change energy storage material

In order to obtain sustainable phase change material (PCM) with excellent thermal properties for building energy conservation, a LA-OD binary eutectic system was designed and prepared by melt blending of lauric acid (LA) and octadecanol (OD). Phase transition temperature (PTT), latent heat (LH) and optimum ratio of LA-OD were determined by theory calculation, step cooling curve and differential scanning calorimetry (DSC) test. LA-OD and EG were combined into LA-OD/EG shape-stabilized phase change energy storage material (SSPCESM) by method of vacuum adsorption. The best ratio of EG to LA-OD is 1:9 under heat treatment experiments. In this case, the pores of EG are almost filled with LA-OD by scanning electron microscope (SEM), and the leakage of LA-OD is well controlled when the phase transition of LA-OD occurs. Thermal storage properties are determined by DSC, the melting point of SSPCESM with the LA-OD (90 wt%) is 36.06 °C, where the corresponding LH value of 176.44 J/g. The molecular characteristics and microstructure of the material were analyzed by Fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), which show that the LA-OD/EG is formed by the physical interaction and no chemical reaction occurs. Heat storage and release time is shortened about 3.7 times compared with no EG, which indicates the thermal conductivity of LA-OD is greatly enhanced by EG. The LA-OD/EG has excellent thermal and chemical stability after 1000 thermal cycles. Moreover, it has good heat resistance when the temperature is less than 132.01 °C by TG test. Expanded graphite (EG) is considered as the adsorption carrier to enhance the thermal conductivity of LA-OD greatly, and to reduce leakage of PCM effectively.

Influence of phase change material encapsulation shape on performance of energy‐efficient roof design

AbstractThe design of passive cooling systems is part of the energy‐efficient building since population growth and indoor requirements in various dwellings are paramount. As a part of passive designs, modifying the conventional roof with phase change materials (PCM) is one of the techniques to control the abnormal changes of the inner surface temperature of the roof. In this aspect, a numerical investigation has been carried out by incorporating the PCM encapsulated pipes in the RCC (reinforced concrete), and a comprehensive analysis has been carried out. Three different shapes are chosen, namely circular, oval, and rectangular oval, to encapsulate the PCM. Diurnal outside changes are considered to envisage the inner surface temperature of the roof. Validation of the literature's experimental results is done before developing a numerical model for the current study. The effect of encapsulated shape on PCM's average temperature, liquid fraction and energy storage has been studied. The inner surface temperature is reduced drastically with the roof consisting of elliptical encapsulated PCM than other designs such as circular and rectangular oval encapsulated PCM. Moreover, the performance of PCM is sensitive to encapsulated shape and location within the system.

Experimental Analysis of Heat Storage and Release of Binary Methanol Aqueous Solution Pulsating Heat Pipe Phase Change Accumulator

To improve the problems of energy shortage and low utilization rate, this paper designed a set of pulsating heat pipe (PHP) devices coupled with phase change energy storage material. Further, the binary methanol-water solution is proposed as a novel experimental filling medium to enhance the heat transfer performance of the device. The fluid flow model of the PHP was analyzed via experiment and simulation. Besides, the heat storage and release performances of the PHP at different flow rates, different heating temperatures, different filling mediums, and different filling ratios are investigated. The results show that when the filling medium (binary methanol-water solution) possesses the filling ratio of 0.6 (methanol and water are each 0.3), the heat source inlet flow is 0.60 m3/h, the heat source heating temperature is 120°C, and the PHP is at the best heat storage performance. During the exothermic process, the lower the initial temperature of cooling water, the higher the heat recovery rate. Thus, it can be concluded that the selection of an appropriate filling medium and the optimal parameters to enhance heat transfer can have a broader application prospect in the field of waste heat recovery.

Enzymatic synthesis of a novel solid\u2013liquid phase change energy storage material based on levulinic acid and 1,4-butanediol

The current energy crisis has prompted the development and utilization of renewable energy and energy storage material. In this study, levulinic acid (LA) and 1,4-butanediol (BDO) were used to synthesize a novel levulinic acid 1,4-butanediol ester (LBE) by both enzymatic and chemical methods. The enzymatic method exhibited excellent performance during the synthesis process, and resulted in 87.33% of LBE yield, while the chemical method caused more by-products and higher energy consumption. What’s more, the thermal properties of the obtained LBE as a phase change material (PCM) were evaluated. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the melting temperature, latent heat of melting, and pyrolysis temperature were 50.51 °C, 156.1 J/g, and 150–160 °C, respectively. Compared with the traditional paraffin, the prepared PCM has a superior phase transition temperature, a higher latent heat of melting, and better thermal stability. The thermal conductivity could be increased to 0.34 W/m/k after adding expanded graphite (EG). In summary, LBE has great potential in the application of energy storage as a low-temperature phase change energy storage material.Graphical

Laboratory Testing of Small Scale Solar Facade Module with Phase Change Material and Adjustable Insulation Layer

Active building envelopes that act as energy converters—gathering on-site available renewable energy and converting it to thermal energy or electricity—is a promising technological design niche to reduce energy consumption in the building sector, cut greenhouse gas emissions, and thus tackle climate change challenges. This research adds scientific knowledge in the field of composite building envelope structures containing phase-change materials for thermal energy storage. In this study, the focus lies on the cooling phase of the diurnal gain and release of solar energy. The experimental setup imitates day and night environment. Six alterations of small-scale solar facade modules are tested in two different configurations—with and without the adjustable insulation layer on their outer surface during the discharging phase. Modules explore combinations of aerogel, air gap, and Fresnel lenses for solar energy concentration. The results allow us to compare the impact of the application of an additional insulation layer at “night” for different designs of solar facade modules. The results show that modules with an air gap provide higher heat gains but do not take full advantage of the latent heat capacity of phase-change materials.