Search Results (452)

This study numerically investigates the capability of cylindrical phase change material (PCM) encapsulations to attenuate inlet-temperature fluctuations in water as the heat transfer fluid (HTF). A sinusoidal inlet profile with a 20 K amplitude is imposed, and melting and solidification are modeled using the enthalpy–porosity method. The analysis begins with a single encapsulation, which reduces the outlet temperature amplitude by 45.06%, and extends to three, nine, and 15 cylinders in aligned and staggered arrangements. Increasing the cylinder count enhances fluctuation reduction but with diminishing returns, as the HTF thermal energy reaching downstream cylinders decreases. Spatial arrangement is equally important: a staggered array of nine encapsulations achieves a 65.91% reduction, surpassing a 15-cylinder aligned configuration (65.80%), while the highest reduction, 73.01%, is obtained with a 15-cylinder staggered configuration. Across all configurations, the outlet fluctuation reduction follows a single near-linear relationship with the total melted PCM mass (R² = 0.96), across cylinder count and arrangement, identifying melted mass as a controlling parameter for fluctuation mitigation rather than the cylinder-averaged liquid fraction. These results indicate that the total melted PCM mass is a practical criterion for comparing PCM encapsulation configurations, while the arrangement remains a distinct factor. Full article

This paper investigates the use of a hybrid renewable heat-supply system based on photovoltaic–thermal collectors, an industrial heat pump, thermal energy storage, and electrical energy storage for a small- to medium-scale district-heating network. A dynamic lumped-parameter model was developed and applied to hourly data from an existing network. The photovoltaic–thermal collector model accounts for low-temperature operation, wind effects, precipitation, and condensation-related heat gains, while the heat pump is represented using compressor performance characteristics under variable source and sink temperatures. The analysis focuses on whether the proposed configuration can meet summer heat demand and reduce reliance on a conventional peak or backup source during shoulder periods. The results show that, during an extended non-heating season, the system can supply approximately 90–100% of the district-heating demand while maintaining a daily mean coefficient of performance in the range of approximately 2.0–3.1. The photovoltaic–thermal field and electrical energy storage do not provide full electrical self-sufficiency, but they reduce grid electricity import; in July and August, the electricity autarky coefficient is approximately 48–49%. The results indicate that the proposed system can serve as a seasonal renewable heat source for district heating. Further refinement of the configuration, operating setpoints, and control strategy could improve its shoulder-season performance. Full article

Converter-dominated power systems increasingly require flexible resources that can support frequency while preserving a physically interpretable energy trajectory. Thermal-energy-storage (TES)-based virtual energy storage systems (VESSs) can shift electrical demand within thermal-energy and comfort constraints, and have therefore attracted extensive interest. However, existing studies commonly coordinate requested or normalized power without fully connecting it to actuator execution and the electrical-to-thermal energy path. Command-level sharing cannot be directly equated with executed physical power, and controller storage cannot be combined with joule-valued hardware energy without dimensional separation. Therefore, this paper proposes a physically coupled and energy-traceable virtual asynchronous machine (VAM) control method for TES-based VESSs. First, a loss-resolved averaged model establishes the point-of-common-coupling (PCC)–converter–DC-link–actuator–TES physical chain and separates the hardware Hamiltonian from the dimensionless control Lyapunov function. Second, a neighbor-coupled marginal controller is embedded in a command–projection–execution chain so that frequency regulation and weighted sharing are evaluated using the executed service. Third, a constraint-handling mechanism combines directional headroom gating, actuator saturation and ramp limits, thermal comfort bounds, and request-inactive state reset to maintain executable trajectories under the declared constraints. Simulations under a sustained $120\mathrm{kW}$ disturbance show that primary-only control retains a $-0.08883\mathrm{Hz}$ steady-state offset, whereas the proposed nominal case restores frequency. In the constrained case, the 30 s terminal trend remains above the prescribed limit, while both terminal windows of the 60 s run satisfy the restoration criterion; the final-window mean error and dimensionless eligible-unit sharing spread are $-6.317\times {10}^{-5}\mathrm{Hz}$ and $6.564\times {10}^{-5}$, respectively. The model-internal electrical–thermal balance achieves a dimensionless relative RMS residual of $6.2361\times {10}^{-8}$. Because the PCC voltage/current pair is reconstructed from the same power source, this residual quantifies model-internal consistency rather than independent measured closure. These results demonstrate constrained frequency restoration, executed-power coordination, and energy traceability within the averaged-model scope. Full article

Decarbonizing industrial heating in cold climates remains challenging due to high thermal demand and strong seasonal variability. While the existing literature predominantly relies on steady-state or isolated component analyses, this study introduces a novel, multi-scale dynamic modeling framework. This framework evaluates the annual transient performance of an integrated renewable architecture. The proposed system couples a building-envelope Transpired Solar Collector (TSC) with a series-connected Photovoltaic Thermal/Solar Thermal (PVT-ST) array. Computational Fluid Dynamics (CFD) is employed to resolve the localized convective heat transfer within the TSC. Subsequently, a data-driven clustering methodology scales these transient results into a comprehensive annual system-level simulation featuring sensible Thermal Energy Storage (TES). The results demonstrate robust performance under Canadian winter conditions. The TSC maintains stable thermal efficiencies between 50% and 60%, peaking at over 64%. Annually, the integrated dual-source system delivers 229.7 MWh of useful thermal energy to offset primary fossil fuel consumption. Furthermore, the analysis identifies 128.76 MWh of seasonal surplus capacity. This underscores the critical necessity of dynamic TES integration. Ultimately, this framework establishes a highly defensible, predictive methodology for designing and implementing synergistic solar thermal networks for industrial decarbonization. Full article

Historic buildings represent a substantial share of the European building stock. However, their energy retrofit is heavily restricted by conservation principles that often exclude conventional insulation systems. In this context, phase change materials (PCMs) incorporated into lime-based mortars have emerged as a potentially compatible solution, combining latent heat storage capacity with the compatibility traditionally associated with aerial lime, the binder of reference in conservation practice. In some cases, natural hydraulic lime and hydrated lime are also used in heritage conservation applications. The aim of this study, therefore, is to provide a systematic review of peer-reviewed articles published between 2010 and 2026 that illustrate the use of PCM-containing lime mortars applied in historic buildings. The analysis examines PCM types, incorporation methods, thermal and mechanical behavior, durability, and compatibility with conservation requirements. The reviewed studies demonstrate that the incorporation of PCM generally reduces internal thermal fluctuations in buildings along with capillary water absorption. Durability investigations indicate improved resistance to freeze–thaw cycles and salt crystallization of mortars containing such PCMs. However, durability was investigated in less than 20% of the studies reviewed. Lime mortars show a consistent reduction in compressive strength as the PCM content increases; on the other hand, hydrated lime mortars can also offer increases in strength. Although the reviewed studies focused on applications in historic buildings, the reversibility of the intervention and its compatibility with historic substrates was not assessed according to the standards required for the conservation of cultural heritage. This gap represents the main limitation of the research conducted. Full article

Thermal energy storage (TES) is essential for improving the flexibility and efficiency of renewable and industrial energy systems. This study experimentally compares sensible and latent heat storage using basalt aggregate and an encapsulated phase change material (PCM), specifically 60 wt.% NaNO₃–40 wt.% KNO₃, as packed-bed materials under elevated-temperature operating conditions. Tests were conducted in an air-based TES rig at air flow rates of 60–120 kg/h, with packed bed temperatures exceeding 400 °C. Key parameters included temperature profiles, thermal power, energy storage, and recovery during charging and discharging phases. The results indicate that increasing the air flow rate accelerated thermal front propagation and improved charging and discharging power, but did not proportionally increase stored or recovered energy. The basalt bed achieved recovered volumetric energy densities of 108–160 MJ/m³ at about 150 °C and 351–405 MJ/m³ above 320 °C. The encapsulated solar salt bed reached higher values, from 412–508 MJ/m³ near 290 °C to 523–626 MJ/m³ at higher temperatures. Both materials showed high TES efficiencies, in the range of 80–94%. Encapsulated PCM significantly increased energy storage density in packed-bed TES systems, while basalt aggregate provides higher short-term thermal power output. Full article

To alleviate grid peak-shaving pressure from high-penetration renewable energy integration, coupling thermal energy storage (TES) with coal-fired power plants is an effective approach for enhancing operational flexibility. This paper systematically investigates the peak-shaving performance of a coal-fired unit integrated with molten salt storage and heat pump storage systems, focusing on load response characteristics, peak-shaving capability, and the influence of discharge strategies on thermodynamic performance under various rated turbine heat acceptance (THA) conditions. The results indicate that, under identical peak-shaving capacity, the molten salt system exhibits greater storage capacity, which increases with rising THA levels, whereas the heat pump storage capacity remains largely THA-independent. Regarding discharge strategies, replacing high-pressure extraction steam achieves the fastest ramp rate and largest incremental power output, introducing steam into the intermediate-pressure cylinder yields the slowest response but highest round-trip efficiency, and replacing low-pressure extraction steam delivers the smallest peak-shaving capacity and lowest round-trip efficiency. Although TES integration slightly reduces thermal efficiency due to heat exchange losses, this trade-off is justified by significant flexibility improvement, demonstrating clear engineering value for high-renewable grids. Full article

This study presents an ideal-cycle thermodynamic analysis of an advanced compressed air energy storage (A-CAES) system with single thermal energy storage (TES) and an external heat boost. The additional heat is represented by a solar heat source, although the analysis is equally applicable to other forms of externally supplied thermal energy. Following the classical thermodynamic approach used for ideal cycles such as the Brayton, Otto and Diesel cycles, the objective is to establish analytical relationships and performance bounds for the integrated system rather than to model a specific engineering configuration. Three principal performance measures are examined: the electrical round-trip coefficient of performance (CoP), the marginal thermal coefficient of performance associated with external heat addition, and the overall second-law efficiency. Closed-form analytical expressions are derived for these quantities under idealised but still practically relevant assumptions. The analysis identifies distinct operating regimes governed by the level of external heat input and establishes analytical transition conditions between them. It is shown that external heat addition can substantially increase the round-trip coefficient of performance and lead to high marginal heat-utilisation effectiveness. A rigorous upper bound on the second-law efficiency is also obtained from a complete-cycle exergy analysis, demonstrating consistency with the laws of thermodynamics. The results provide analytical insight into the fundamental thermodynamic structure of solar-assisted A-CAES systems and establish performance bounds that are independent of any particular engineering implementation. Full article

To improve the flexibility and carbon reduction performance of coal-fired power plants, a solar-aided power generation (SAPG) system integrated with parabolic trough collectors and thermal energy storage (TES) was proposed and investigated using a combined Aspen Plus and System Advisor Model (SAM) framework. Two different integration schemes, namely SAPG-1 and SAPG-2, were evaluated under 100%, 75%, and 50% load conditions with a solar multiple of 2 and a TES duration of 6 h. The thermodynamic, economic, and environmental performances of the systems were comprehensively analyzed. The results show that TES significantly improves solar energy utilization, annual solar contribution, and system dispatchability. Compared with SAPG-2, SAPG-1 demonstrates superior thermodynamic and economic performance due to its lower boiler heat demand and more effective feedwater integration. At full load, the solar contribution of SAPG-1 with TES reaches 16.04%, while the annual solar energy production increases to 190.35 GWh with a capacity factor of 21.75%. In addition, TES integration effectively reduces the levelized cost of electricity and shortens the payback period under both CO₂ pricing and non-CO₂ pricing scenarios. The proposed SAPG framework demonstrates considerable potential for enhancing renewable energy utilization, operational flexibility, and economic feasibility in large-scale solar–coal hybrid power generation systems. Full article

Industrial processes consume large amounts of thermal energy, while many recoverable heat streams remain unused because heat sources and sinks differ in time, temperature level, power demand, and operating schedule. Thermal energy storage (TES) can decouple heat supply from heat demand and support waste heat recovery, peak-load reduction, process heat electrification, and flexible operation of continuous, batch, and intermittent processes. This narrative review assesses industrial TES from a process integration perspective rather than from a storage-material perspective alone. Sensible, latent, thermochemical, sorption-based, hybrid, and steam-based storage systems are compared with respect to delivery temperature, storage duration, charging and discharging power, response time, heat losses, reliability, integration complexity, and techno-economic feasibility. Sector-specific opportunities are discussed for the iron and steel, cement, ceramics, chemical and petrochemical, pulp and paper, and food and beverage industries. The review shows that deployment is constrained less by the availability of storage concepts than by heat exchanger limitations, inconsistent Key Performance Indicator (KPI) definitions, unclear system boundaries, scarce long-term operating data, and insufficient coupling with pinch analysis, heat exchanger network design, control, and safety requirements. A practical technology-selection workflow and a research roadmap are proposed for scalable, reliable, and economically viable industrial TES deployment. Full article

Thin-film solar cells (TFSCs) remain a cornerstone of the global transition toward renewable energy, characterized by consistent reductions in manufacturing costs and steady gains in power conversion efficiency. In addition to electricity generation, TFSCs play an important role in advanced solar thermal cooling, heating, and energy storage systems, where their tunable optical absorption, low thermal mass, and flexibility enable integration with photovoltaic–thermal (PV/T) collectors, thermally driven cooling cycles, and hybrid thermal–electrical storage architectures. This paper provides a comprehensive review of prominent TFSC technologies, including copper indium gallium selenide (CIGS), cadmium telluride (CdTe/CdS), amorphous silicon (a-Si), copper zinc tin sulfide (CZTS), organic photovoltaics (OPVs), and metal halide perovskite solar cells (PSCs), with a focus on their material structures, performance specifications, and current efficiency benchmarks. Compared to state-of-the-art reviews, this article distinguishes itself by addressing next-generation innovations, cross-domain solar thermal–photovoltaic applications, and economic analysis. Specifically, the integration of machine learning and simulation-based material dynamics is examined to accelerate material discovery, process optimization, and the characterization of novel TFPV components relevant to coupled thermal–electrical energy systems. Furthermore, the study explores how additive manufacturing is transforming the industry through the development of high-efficiency electrodes, electrohydrodynamic atomization for thin-film deposition, and the fabrication of flexible solar arrays suitable for thermally integrated and building-scale energy systems, including space applications. By integrating advancements in module efficiency, scalable manufacturing approaches, and techno-economic analysis, this paper positions TFSCs as sustainable, resource-abundant technologies essential for next-generation solar thermal cooling, heating, and energy storage infrastructures. Full article

This study focuses on optimizing backfill materials to enhance the heat transfer performance of ground heat exchangers (GHEs) in ground source heat pump (GSHP) systems. A series of composite phase change material/original sand soil (CPCM/OSS) backfill materials was prepared using capric acid–myristic acid/expanded graphite (CA-MA/EG) at mass ratios of 5%, 10%, 15%, and 20%. Thermal conductivity testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), laboratory heat transfer tests, and 3D numerical simulations under typical intermittent summer conditions were systematically conducted. The results show that thermal conductivity, specific heat capacity, and thermal storage coefficient all increase with rising moisture content and CPCM dosage. The newly developed CPCM/OSS backfill material significantly improves the heat transfer performance of GHEs. Comprehensive thermophysical characterization indicates that the 10 wt% CPCM sample is the optimal formulation. Laboratory tests demonstrate that, relative to pure OSS backfill, the 10 wt% CPCM-doped CPCM/OSS raises the average soil temperature by approximately 2.5–2.8 °C. Numerical simulations over three consecutive days show that, relative to pure OSS backfill, the 10 wt% CPCM-doped composite enhances the heat exchange capacity per linear meter of the GHEs by 8.8%. The newly developed CPCM/OSS backfill material significantly improves the heat transfer performance of GHEs. It provides a feasible material solution and technical reference for GSHP system design. Full article

Hyperloop transport operates in a low-pressure environment in which convective heat transfer is strongly limited, making conventional air-based cooling ineffective. One promising thermal management approach is therefore to absorb the waste heat generated during travel in a thermal energy storage (TES) system and dissipate it during stops. In this context, latent heat storage based on water–ice systems is particularly attractive because of its high energy density and nearly constant-temperature heat absorption. However, experimental validation of such systems beyond laboratory scale is still lacking. This study therefore investigated a large-scale direct contact latent heat storage (DCLHS) system for Hyperloop thermal management, using water as heat transfer fluid and ice as phase change material. The system was evaluated for two ice morphologies, crushed ice and ice block, under both constant and time-variant cooling power profiles representative of Hyperloop operation. The objective was to assess thermal performance, exergy efficiency, and hydraulic stability at application-relevant scale, and to identify morphology-dependent trade-offs relevant for system integration. The results show that the large-scale system can operate reliably under dynamic loads and that upscaling leads to smoother thermal behavior and reduced boundary effects. Crushed ice demonstrated superior thermal responsiveness, maintaining outlet temperatures close to the phase change temperature and achieving exergy efficiencies up to 0.72 at cooling powers up to 3.8 kW while enabling stable operation at 15 °C. In contrast, the ice block configuration provided higher volumetric energy density but exhibited delayed thermal response and required substantially higher mass flow rates, which limited operation to approximately 25 °C and reduced exergy efficiency to 0.03–0.35. Overall, the results show that large-scale DCLHS is a feasible option for Hyperloop thermal management, while also revealing that system behavior at larger scale is strongly influenced by storage morphology. Full article

Decarbonizing HVAC in hot–arid regions is challenging for natatoriums because year-round cooling must be delivered alongside stringent dehumidification and occasional heating under high ambient temperatures. In this paper, a fully renewable system has been developed and evaluated for an indoor swimming pool located in Abu Dhabi with a 679 m² swimming pool hall designed to accommodate 200 pool users. The hybrid system includes a high-temperature linear Fresnel reflector (LFR) solar field, stratified thermal energy storage (TES), a single-effect LiBr–H₂O absorption chiller for cooling, a water-to-water heat pump as a backup system for the stability of cooling and heating rates, and a photovoltaic (PV) system to offset the ancillary equipment power input of the hybrid system. The system performance was simulated and validated by using hourly data from Abu Dhabi. Optimization of design/operation parameters was carried out by a multi-objective genetic algorithm to achieve the maximum coefficient of performance (COP) and the minimum levelized cost of cooling (LCOE). The initial COP and LCOE were 0.701 and 0.037 $/kWh, respectively. They were optimized to 0.825 and 0.0254 $/kWh, respectively. The annual energy balance revealed a synergistic operation of the solar field, TES, and heat pump. The lifecycle assessment was utilized to compare the proposed hybrid system with the conventional vapor-compression systems in terms of energy, cost, and CO₂ emissions, in which the proposed system proved superior over conventional systems with a positive net present value (NPV) and net zero carbon emissions. Full article

This study analyzes the impact of thermal and electrical storage solutions coupled with Photovoltaic (PV) and Concentrating Solar Power (CSP) plants, proposing an innovative model to test a Hybrid Energy Storage System (HESS). The work presents an innovative Mixed Integer Linear Programming (MILP) model to determine the optimal configuration and operational strategy of a HESS within a grid-connected Microgrid (MG). The research focuses on the synergistic integration of PV with Lithium-ion Electrical Energy Storage (EES) and CSP with Thermal Energy Storage (TES). The MG includes dynamic residential, commercial, and hospital loads. The MILP model is optimized over a 24 h horizon across four season-representative days, utilizing a multi-criteria objective function that balances economic performance and CO₂ emissions via a weighting factor ω ∈ [0, 1]. Three distinct CSP options such as Parabolic Trough Collectors with varying Heat Transfer Fluids (molten salt or thermal oil) and TES types (direct and indirect dual-tank, or Phase Change Material) are analyzed, each coupled with a Rankine or Organic Rankine Cycle. Key constraints address energy balances, component efficiencies, power limits, and storage dynamics. The comprehensive results identify the most suitable technology portfolio mix and optimal hour-by-hour operational rules, providing transparent decision-making criteria based on storage size, process temperatures, and specific demand profiles. Full article