Single Phase Change Materials Research Articles

Energy assessment of a sliding window integrated with PV cell and multiple PCMs

Windows often serve as a thermal weak point between a room's interior and the outside world. As such, we are exploring a new design for a sliding window that integrates both multiple phase change materials (PCMs) and photovoltaic (PV) cells. During the day, the PV cells produce electricity, which can be used in the building during the night. The sliding mechanism introduces several innovative features: use the PV-PCM glass unit (as the external sliding layer) or a standard glass unit (the internal sliding component). The PV-PCM window also can be used as a sliding light shutter or curtain. The PV cell in the proposed design is operated in the closed and open case due to the sliding design. We compared the thermal performance of a single PCM type (either RT-35or RT-27) with a combination of multiple PCMs (RT-35-RT27). Further, we evaluated various thickness combinations of the multi-PCM configuration (RT-35-RT27), including 2.5mm–7.5mm, 5 mm–5 mm, and 7.5 mm–2.5 mm, to identify the best-performing setup. Over the course of a day, the multi-PCM setup (RT-35-RT27) maintains a consistently lower average interior wall temperature than using a single PCM. Among the configurations tested, the 5 mm–5 mm multi-PCM setup (RT-35-RT27) emerged as the most effective, displaying steadier results than the other variations. Compared to a standard single glass pane, the proposed PV-PCM window reduced the highest interior wall temperature by up to 46 % when employing multiple PCMs. As a result, we advocate for the adoption of this innovative sliding window in future building designs.

Mathematical model of the solar combined cycle power plant using phase change materials in thermal energy storage system (Thermodynamic analysis)

This research presents a novel mathematical framework for optimizing solar combined cycle power plants, with a particular emphasis on the exergy analysis of various superheating heat exchanger configurations used in thermal energy storage. The importance of phase change materials (PCMs) in improving the thermodynamic efficiency of solar combined cycle power plants is emphasized in this study. The investigation includes three configurations, two with a single PCM and one with two PCMs. The use of PCMs is intended to increase storage density, reduce volume, and maintain consistent temperatures, thereby favoring latent energy storage. The model developed evaluates exergy efficiency and output temperature profiles during the charging and discharging processes. The results show that the single PCM configuration has an impressive charging efficiency of 93.12 %, reaching an output temperature of 371 °C in 8 h. The two PCM configurations, on the other hand, achieve even higher efficiency at 94.89 % during charging, with an output temperature of 367 °C over a slightly longer 10-hour period. This comparison emphasizes the benefits of using two PCMs, demonstrating increased exergy efficiency and a marginal increase in output temperature over a single PCM setup. Furthermore, a comparison of the outcomes resulting from the use of a single type of PCM in exchangers reveals that the disparity in PCM melting temperatures causes only minor variations in the system's efficiency. The findings emphasize the significance of optimal PCM utilization for efficient solar energy retention, particularly during periods of low radiation.

Analytical modeling of phase change in a composite wall comprising two distinct phase change materials in series

Most of the past literature on solid-liquid phase change heat transfer modeling focuses on a single phase change material (PCM), whereas, a sandwich of two or more PCMs arranged in series may be of interest in several applications. The modeling of heat transfer and phase change in such a system is complicated by the presence of multiple phase change fronts propagating at the same time. This work presents a theoretical analysis of the problem of melting of a two-PCM stack being heated from one end. Depending on whether the lower-melting PCM is located next to or away from the heat source, two distinct cases are considered. The propagation of the phase change fronts in each case is divided into several stages, each of which is characterized by a distinct phase change and/or sensible heating processes. The transient temperature field in each stage is determined in the form of infinite series solutions, and the propagation of phase change front over time is then determined using energy conservation at the phase change interface. In this manner, explicit expressions are derived for the time taken for each layer to completely melt. Results are shown to be in good agreement with finite-element simulations, and with the exact Stefan solution under special conditions. Key non-dimensional parameters that influence the nature of the two-PCM phase change process are identified, and their impact on phase change performance is analyzed. Quantitative predictions are presented for the conditions under which both PCMs finish melting at the same time, which is a favorable outcome for efficient energy storage.

Dual-sided melting of a one-dimensional composite wall comprising two distinct phase change material (PCM) layers

Past literature on theoretical modeling of solid-liquid phase change heat transfer mostly addresses a single phase change material (PCM), whereas, a series combination of two or more PCMs is often used in practical applications. This work presents an approximate analytical model for the melting/freezing of a one-dimensional composite of two PCMs being heated/cooled from both ends. It is shown that up to three phase change fronts may simultaneously exist in this problem. In addition to direct melting/freezing from the respective walls, it is shown that each PCM may also melt/freeze due to heat transfer through the other PCM. Using a quasi-stationary assumption, temperature field during the multi-stage phase change process is approximated by solving a multilayer transient thermal conduction problem using eigenfunction expansion. Good agreement with numerical simulations, and with the Stefan solution for a special case is demonstrated. The impact of key non-dimensional parameters on performance metrics including total time for phase change is determined. A quantitative prediction of conditions leading to the thermodynamically favorable situation of simultaneous completion of phase change of two commonly used PCMs is carried out. This work improves the theoretical understanding of phase change in composite PCMs, leading to optimization of practical thermal systems.

Reduced Graphene Oxide/Cellulose Sodium Aerogel-Supported Eutectic Phase Change Material Gel Demonstrating Superior Energy Conversion and Storage Capacity toward High-Performance Personal Thermal Management.

By virtue of their capacity to absorb and release energy during the phase change process, phase change materials (PCMs) are ideal for personal thermal management (PTM). The combination of reduced graphene oxide/cellulose sodium aerogel (rGCA) and lauric acid/myristic acid binary eutectic phase change gel (LMG) creates a composite phase change material that possesses outstanding photothermal conversion capabilities, electro-thermal conversion capabilities, energy storage capabilities, and shape-stable performance. The results showed that rGCA had a maximum adsorption efficiency of 99.7% with a melting latent heat of 124.6 J g-1. The high absorption rate of rGCA to LMG is a result of the capillary force, pore characteristics, hydrogen bonding, and the π-π interaction. Notably, rGCA and LMG composite material (rGCG) exhibited an excellent photothermal conversion efficiency of 96.5% and electro-thermal conversion of 82.3%. Results indicate that binary eutectic phase change materials are more suitable for temperature regulation than single phase change materials, making them more suitable for PTM. It is anticipated that the innovative thermal comfort solution, which provides thermal shielding, thermal energy storage, self-supporting characteristics, and wearability, will offer new possibilities for the next generation of wearable PTMs.

Numerical Investigation of Thermal Energy Storage Systems for Collective Heating of Buildings

This study aims to investigate and identify the most effective thermal energy storage (TES) system configuration for the collective heating of buildings. It compares three TES technologies, i.e., sensible, latent, and cascade latent shell and tube storage, and examines their respective performances. A fast and accurate lumped thermal dynamic model to efficiently simulate TES system performances under different operation conditions is developed. The validation of this model’s accuracy is achieved by aligning numerical findings with data from prior experimental studies. Key findings indicated that the latent and cascade latent shell and tube storage systems demonstrate superior thermal energy storage capacities compared to the sensible configuration. Using a single-phase change material (PCM) tank increases the duration of constant thermal power storage by about 50%, and using a cascade PCM tank further enhances this duration by approximately 65% compared to the sensible TES case. Moreover, the study revealed that adjusting the PCM composition within the cascade TES significantly influenced both thermal power storage durations and pumping energy consumption. In summary, the recommended cascade PCM configuration for collective heating of buildings offers a balanced solution, ensuring prolonged stable thermal power production, elevated HTF outlet temperatures, and improved energy efficiency, presenting promising prospects for enhancing TES systems in district heating applications.

Performance investigation and optimization of latent heat exchanger with pin fins based on non-uniform deployment strategy

Latent heat storage technology is an essential way of efficiently utilizing industrial residual heat, which helps to the objective of carbon neutrality in all countries. In this work, latent heat exchangers with pin fins are numerically investigated based on non-uniform deployment strategy and then optimized according to response surface method. The influences of rotation angle, non-uniform fin pitch, non-uniform fin length and combination of phase change materials with different melting temperatures on thermal storage performance are studied. Results show that the increment of rotation angle facilitates the reduction of complete melting time, and the optimal angle accelerates the melting speed by 10.3% compared to the 0° angle. The arrangements of gradually decreasing fin pitch and gradually increasing fin length along flow direction of heat transfer fluid improve the heat storage performance, which can reduce the complete melting time by 7.3% and 22.2% respectively, compared to the uniform arrangement. The multiple phase change materials latent heat exchanger with high melting temperature phase change material placed in high temperature region and low melting temperature phase change material in low temperature region can make better utilization of heat from heat transfer fluid, which can improve the melting speed by 16.8% compared with the single phase change material latent heat exchanger. The optimized latent heat exchanger based on response surface method reduces the complete melting time by 23.4% compared to the original model. In conclusion, the heat storage performance of latent heat exchanger with pin fins effectively improved by adopting the non-uniform deployment strategy.

The Influence of Composition Ratio on the Thermal Performance Parameters of Eutectic Phase Change Materials: Experimental Research and Theoretical Prediction

Eutectic phase change material (EPCM), compared with single phase change material (PCM), is widely studied by many scholars due to its flexibility in practical engineering applications by the characteristic of changing phase change temperatures. However, there is still a lack of theoretical prediction research on the thermal performance parameters of EPCM. The existing theories about EPCM are unable to accurately predict its thermal performance parameters, which increases the difficulty of selecting the composition ratio of EPCM and affects its practical application. Based on a background of the accurate prediction of EPCM thermal parameters, 12 binary EPCMs, and 7 ternary EPCMs are prepared by mixing capric acid, n-octanoic acid and tetradecane with different proportions, respectively. By using the cooling curves and DSC test, the variation patterns in thermal performance parameters of EPCMs are studied. After comparing various thermodynamic models, the Schrader model was selected and combined with experimental results to compare and calculate the experimental and theoretical values of thermal performance parameters. The results show that the binary PCM reaches the minimum eutectic point of 1.42 °C at a mass ratio of 0.33:0.67 for capric acid to n-octanoic acid, while the ternary PCM reaches the minimum eutectic point of 0.34 °C at a mass ratio of 0.231:0.469:0.3 for capric acid, n-octanoic acid, and n-tetradecane. The latent heat of a EPCM is between the lowest and highest values of the latent heat of the constituent components, and its value increases with the enhancement of the overall thermal storage density of the material. The modified Schrader equations can effectively predict the phase change temperatures and latent heats of EPCMs at different composition ratios. The equation has a fitting accuracy of over 0.986 and a bias error of less than 6%, demonstrating excellent accuracy and providing a reliable theoretical basis for the proportion design and thermal parameter prediction of EPCM in actual engineering applications.

A new thermal management figure of merit for design of thermal energy storage with phase change materials

Phase Change Materials (PCMs) are frequently employed in thermal management of systems with high heat fluxes because their high latent heat of phase change limits transient temperature rises and damps temperature fluctuations. In general, detailed numerical analysis is used to design such systems. However, for an efficient thermal design process, it is desirable to have an analytic method to perform a quick quantitative comparison between all the available PCMs considering potential design configurations. The previously developed Figure of Merit (FoMc) for PCMs only depends on the thermophysical properties of the PCM and does not account for other relevant information such as geometry, melting temperature, and boundary condition. In the present work, we develop a novel performance factor (f) that works in conjunction with the material property based FoM to gauge the performance of different PCM-based thermal management systems (TMSs). The performance factor f is based on the characteristic timescales for thermal diffusion and thermal storage in a PCM system. First, this work demonstrates the range of applicability of our new FoM (fFoMc) for various PCMs (3 metallic, 4 organic, and 3 inorganic materials) across different geometrical and boundary configurations. The PCM performance is evaluated using transient numerical simulations with the metric of the maximum temperature rise in the domain after a fixed heating time. For a single PCM in different geometries, the maximum temperature rise decreases with increased f. For a general PCM-based TMS (i.e., a random combination of PCM, geometry, and boundary condition), the maximum temperature rise generally decreases with increasing the newly proposed FoM (fFoMc). Second, we extend the analysis to a composite PCM (an aluminum foam impregnated with organic PCM) to estimate the optimum porosity (ϕopt) for different geometric configurations. The analytically estimated ϕopt agrees well with the values calculated from optimizing detailed finite element simulations. Furthermore, this approach can explain the effect of expected duration of the PCM use on the ϕopt value using the proposed FoM. Overall, the proposed approach can identify the best performing geometrical configuration for a certain PCM or shortlist best performing PCM for a given setup of PCM-based TMS without detailed numerical simulations, making the design process more efficient.

Numerical study on thermal resistance of PCMs incorporated in novel roof structures against energy loss

Incorporating Phase Change Materials (PCM) into building enclosures is one of the passive techniques to improve thermal comfort and reduce energy costs. The present study is dedicated to the assessment of various configurations of PCM incorporation in a roof structure in order to evaluate their impact on thermal resistance and consequent reduction in energy losses. Several arrangements of the PCM and brick are tested: small PCM blocks distributed through the structure, multiple long PCM blocks distributed horizontally or vertically, single PCM block occupying either the right half or the left half, and single PCM block occupying the top half or bottom half. The equations governing the flow and thermal transfer in the PCM, as well as heat transfer in the plaster and brick, are defined and derived in the non-dimensional form. The hydro-thermal behavior of the melting PCM is assessed in the different configurations and for two values of Rayleigh number. The results indicate that for low Ra, the highest thermal resistance is obtained when a single PCM block is located at the top of the cavity and separated from the hot source by brick. For high Ra, the maximum resistance is found when the PCM is placed in multiple vertical blocks. Putting the PCM in multiple horizontal blocks or in small blocks does not change the PCM melting when Ra is varied. In all cases, the fastest PCM melting is obtained when the PCM block is close to the hot source and is either in one single block or in multiple vertical blocks.

Adaptive machine learning based control of multi-temperature, multi-module latent thermal storage ensembles

Phase change material thermal energy storage systems can be used to alleviate disparities in renewable energy supply and demand. Performance of such systems can be enhanced using a cascade of multiple phase change materials but efficiency benefits currently rely on precise optimization of design parameters. Therefore, there is motivation to develop storage technologies which provide greater flexibility for applications with dynamic operating conditions. In this study, a novel system is proposed called a multi-temperature, multi-module ensemble which consists of multiple phase change materials combined in series and parallel configurations. The system is optimized and controlled by an artificial neural network trained using a multi-objective optimization scheme. The performance for the novel system is compared to two baseline systems: a single phase change material system and a cascaded system. Across a wide range of fixed operating conditions, the results show that the ensemble reduces the rate of exergy destruction by 60% compared to the single module system and achieves a 10 °C improvement in performance for matching target outlet temperature compared to the cascaded system. Over a dynamically changing load profile, the results show that the multi-temperature, multi-module ensemble with artificial neural network controller is the preferable design as it achieves the excellent exergy efficiency of a cascaded system while maintaining the flexibility needed to respond to dynamically changing operating conditions. Furthermore, this novel approach widens the potential applications of latent thermal energy storage by providing a means to standardize manufacturing to drive down system cost and allowing the system to adapt to unforeseen design parameters.

Thermal analysis of a cascaded latent thermal storage tank in a solar domestic water heating system

AbstractTo enhance the thermal characteristics of a solar collector storage system, this study investigates the performance of a rectangular thermal energy storage (TES) tank by incorporating cascade phase change materials (cascade‐PCMs). Three different commercially available PCMs (RT44HC, RT54HC, and RT62HC) with distinct melting temperatures are employed. These cascade‐PCMs are utilized as slabs in vertical rectangular modules, which are integrated into the water TES tank. The heat transfer fluid (HTF) in the flat‐plate solar collector captures solar energy and transfers it to the TES tank, where it is stored as latent thermal energy. A two‐dimensional (2D) numerical model, utilizing the enthalpy‐porosity approach and conservation equations, is developed to analyze the melting and heat transfer processes within the TES tank. The model is validated against previous experimental and numerical data. Performance evaluation of the cascade‐PCMs tank is conducted during a 9‐h charging period (from 8:00 am to 5:00 pm) under Marrakesh weather conditions in Morocco. An optimization study is carried out to determine the optimal height of each cascade‐PCM. The results suggest that an optimal design with heights of 23, 16, and 11 cm for RT44HC, RT54HC, and RT62HC respectively, offers improved melting and storage quality. The thermal characteristics of the TES tank incorporating cascade‐PCMs are compared to those of a TES tank filled with a single phase change material (single‐PCM) during the charging period. The findings indicate that the cascade‐PCMs achieve complete melting, while the single‐PCM only reaches a melting fraction of 0.903 at the end of the charging process. Furthermore, the optimal configuration of the cascade‐PCMs storage tank exhibits slightly higher sensible and latent thermal energy storage capacity compared to the single‐PCM tank. The combination of the solar collector with the cascade‐PCMs storage tank results in a 3.47% higher average collection efficiency when compared to the single‐PCM tank.

Self-Adaptive Multistage Infrared Radiative Thermo-Optic Modulators Based on Phase-Change Materials

Phase-Change Materials (PCMs) are widely applied in dynamic optical modulation due to the dramatic changes in their complex refractive index caused by temperature variation. As the functionality varies, the application of a single PCM cannot meet the compact, efficient and broadband needs of optical modulators. In this work, we combine vanadium dioxide (VO2) and a chalcogenide (Ge2Sb2Te5 (GST) or In3SbTe2 (IST)) to obtain a VO2–GST/IST multiple-stack film that is optimized by a genetic algorithm. This film has a wide spectrum and high modulation properties with three self-switchable modes varied by temperature, including transmission, absorption and reflection. The optimal results are an average normal transmittance, absorbance, and reflectance of 0.76, 0.91, 0.86 in 3–5 μm and 0.72, 0.90, 0.90 in 8–14 μm under different temperature ranges. The film enhances the transmission and absorption properties due to the formation of anti-reflective coating and Fabry–Perot resonance. Compared with GST, the film maintains high reflectance due to the metal-like interface reflection of crystalline IST, which exhibits metallic properties. For different polarization states, the film demonstrates great directional insensitivity when the incidence angles vary from 0° to 60°. The designed self-adaptive multistage infrared radiative thermo-optic modulator has promising implications for optical fuse, fiber-optic communication and energy storage fields.

Optimal design and thermal performance study of a two-stage latent heat thermal energy storage technology for heating systems

Power-to-heat coupled with latent heat thermal energy storage can improve the economy and flexibility of heating systems and also is one of the key technologies used for promoting the balance between power grid supply and demand. However, the existing latent heat thermal energy storage heating systems are primarily based on a single-stage device filled with a single phase change material. Their exergy and energy utilization efficiencies are limited. Moreover, it is difficult to apply the existing multistage devices filled with cascaded phase change materials to building heating because of their small capacity. Therefore, in this study, a novel two-stage latent heat thermal energy storage device was developed. First, a numerical simulation method was used to optimize the cascade mode and select phase change material. Second, experiments were conducted to determine how the flow rate, inlet temperature, and number of stages of the devices affected the thermodynamic performance. Finally, heating effects were investigated. Compared with the single-stage device, the total heat storage and release of the two-stage device increased by up to 53.0% and 66.3%, respectively. The most noteworthy finding was that the thermal performance of the device was significantly improved by increasing the flow rate of the heat transfer fluid only when the flow regime changed from laminar flow to critical flow or from critical flow to turbulent flow. In addition, the two-stage device can support a 3.0-kW heat demand for 7.2 h. This study provides theoretical guidance for engineering applications of cascaded latent heat thermal energy storage heating systems.

Numerical analysis of borehole heat exchanger using a single shape-stabilized phase change material in heating and cooling seasons

Borehole heat exchanger (BHE) plays a key role in ground source heat pump (GHSP) and underground thermal energy storage for heating and cooling, which can backfill with phase change material (PCM) to enhance its thermal performance. In this study, a novel PCM-grouted BHE which can run in both heating and cooling seasons by using a single shape-stabilized PCM (SSPCM) is presented and investigated, and the phase change hysteresis (PCH) of SSPCM is detected and applied to achieve the all-seasons run. A heat transfer model considering PCH for U-type BHE was established to evaluate the thermal performance of the novel BHE. And four kinds of backfill materials were concerned and compared to investigate the effect of initial temperature, and pipe spacing on the performance of the BHE and its characteristics of intermittent operation. The results show that octadecane SSPCM with PCH showed the best comprehensive performance in the two seasons with an energy storage rate of 68.9 W/m in heating and 75.9 W/m in cooling, presenting 21.4 % higher than BHE with conventional backfill material. Mean COP during cooling can be improved by 3.61 % when the thermal conductivity increases from 0.5 W/(m·K) to 2 W/(m·K). It also reveals that the selection of PCM for different regions depends on the ground initial temperature.

A novel liquid air energy storage system integrated with a cascaded latent heat cold thermal energy storage

Liquid air energy storage system (LAES) is a promising Carnot battery's configuration that includes thermal energy storage systems to thermally connect the charge and discharge phases. Among them, the high grade cold storage (HGCS) is of paramount importance due to the waste cold recovery of the liquid air regasification process. As of now, most of the literature studies on LAES designed to store the cryogenic energy using sensible heat material and only few works (including one recently carried out by the authors) proposed the implementation of phase change materials (PCMs) as alternative promising solution. This paper goes a step further numerically investigating a novel configuration of the HGCS system utilizing a cascade of multiple PCMs in place of the single PCM HGCS. By enhancing the thermal buffer effect typical of PCM media, the cascaded HGCS augments both the capacity ratio of the charge phase (0.87 vs 0.81) and the utilization factor of the discharge phase (0.87% vs 0.80%). As a result, the novel LAES system based on cascaded PCMs is capable to achieve a liquefaction specific consumption of 0.27 kWhe/kgLA, increasing thus the liquefaction performance of the single PCM HGCS by 6%.

Dynamic ionic crosslinking, graft polyethylene glycol-based polymeric phase change materials networks with ultrahigh latent heat efficiency and recycling ability

Polymeric polyethylene glycol (PEG)-based phase change materials (PCMs) present the intrinsic shape-stable essence, tunable phase change properties and mechanical strength, yet most of polymeric PCMs present a relatively low latent heat density (<120 J/g) and efficiency (<0.7), non-recycling ability resulting from the covalent crosslinking structure. Herein, the graft PCMs (GPCMs) with graft PEG side chains were synthesized via the dynamic ionic crosslinking reaction of carboxyl-functionalized graft PEGs and citric acid as the carboxyl co-donors with divalent zinc cations. The phase change and rheological properties of the GPCMs can be readily tuned by the length of PEG side chains and the loading content of citric acid. The highest latent heat density and efficiency of the GPCMs reach up to 155.0 J/g and ∼1, respectively, resulting from the synergistic effect of the ionic bonding and graft PEG side chains. The GPCMs present the shape-stable solid-solid phase transition behavior, high thermal reliability and stability, photothermal properties by compositing carbon black and excellent solvent-induced dissolving ability resulting from the nature of dynamic ionic crosslinking. The design of dynamic ionic crosslinking GPCMs structure will provide a robust, versatile access to the combination of high latent heat density and efficiency, high mechanical strength, recycling ability in a single organic PCMs.

Preparation and characterization of binary eutectic phase change material laden with thermal conductivity enhancer for cooling steel slag asphalt pavement

The active asphalt pavement cooling strategy using phase change material (PCM) is crucial for mitigating urban heat island impacts and reducing high-temperature rutting distress. However, most PCM-incorporated pavements use single pure PCM for temperature regulation, resulting in either a discrepancy between phase change temperature and pavement rutting sensitive temperature or a low phase change enthalpy. Moreover, their unacceptable low thermal conductivity can dramatically lower the PCM thermal performance in cooing asphalt pavements. This study aimed to develop a novel PCM-incorporated cooling asphalt pavement, which consists of a binary eutectic mixture of fatty acid PCMs (palmitic acid (PA) and stearic acid (SA)), a supporting material (waste steel slag aggregate (SSA)), and a thermal conductivity enhancer (TCE, Nano Al2O3). The PCM composite of PA-SA was screened out first based on a binary eutectic system. The composite phase change steel slag aggregate (CPC-SSA) and the TCE-based CPC-SSA asphalt mixture were then designed and developed with three types of TCEs. The performance tests were finally conducted to examine the thermal and rutting resistance performance of the PCM-incorporated asphalt pavement. The test results showed that the pavement incorporated with the PCM composite of PA-SA and Nano Al2O3 is capable of effectively cooling asphalt pavement and alleviating its high-temperature rutting distress. The findings of this study are expected to promote sustainable resource utilization and cooling strategies developed for the mitigation of high pavement temperature distresses and urban heat island impacts.

Techno-Economic Assessment of Residential Heat Pump Integrated with Thermal Energy Storage

Phase change material (PCM)-based thermal energy storage (TES) can provide energy and cost savings and peak demand reduction benefits for grid-interactive residential buildings. Researchers established that these benefits vary greatly depending on the PCM phase change temperature (PCT), total TES storage capacity, system configuration and location and climate of the building. In this study, preliminary techno-economic performance is reported for a novel heat pump (HP)-integrated TES system using an idealized approach. A simplified HP-TES was modeled for 1 year of space heating and cooling loads for a residential building in three different climates in the United States. The vapor compression system of the HP was modified to integrate with TES, and all heat transfer to and from the TES was mediated by the HP. A single PCM was used for heating and cooling, and the PCT and TES capacity were varied to observe their effects on the building’s energy consumption, peak load shifting and cost savings. The maximum reduction in electric consumption, utility cost and peak electric demand were achieved at a PCT of 30 °C for New York City and 20 °C for Houston and Birmingham. Peak energy consumption in Houston, New York City, and Birmingham was reduced by 47%, 53%, and 70%, respectively, by shifting peak load using a time-of-use utility schedule. TES with 170 MJ storage capacity allowed for maximum demand shift from on-peak to off-peak hours, with diminishing returns once the TES capacity equaled the daily building thermal loads experienced during the most extreme ambient conditions.

Annual Thermal Management of the Photovoltaic Module to Enhance Electrical Power and Efficiency Using Heat Batteries

Several studies state that phase change material (PCM) improves the electrical power and efficiency of the photovoltaic (PV) module. To find the suitable PCM for tropical climatic conditions, multi-PCMs are examined simultaneously with melting temperatures of 31 °C, 35 °C, 37 °C, and 42 °C. In this study, PCM containers are integrated behind the PV module with a thickness of 50 mm. The performance of the multi PV-PCMs is monitored year-round and compared with PV-noPCM. The experimental results show that the selected four PCMs performed the cooling process autonomously in all the climates, such as PCM with a melting temperature of 37 °C and 42 °C enhanced the higher cooling rate in summer, and the same PCMs failed to achieve a higher cooling rate in winter. The lowest temperature drop was noted for pre-monsoon and monsoon seasons due to the low irradiance. On the other hand, the highest temperature drop of 16.33 °C is observed for pre-summer (March) and 15.7 °C, and 17.14 °C for summer (April) as compared to PV-noPCM. The results of the present investigation highlight the requirement for choosing the proper PCM melting temperature based on optimal year-round performance. Further, it is recommended that a single PCM melting temperature for cooling the PV modules year-round in tropical climates is inappropriate, and instead, a cascaded structure with different PCM melting temperatures is recommended.