Search Results (675)

Standalone solar chemical heat pumps (SCHPs) have attracted increasing attention as promising technologies for utilizing renewable solar thermal energy for heating and cooling applications. However, residential deployment remains challenging because reducing collector area and installation space generally leads to a decline in thermochemical storage performance. In particular, practical design guidelines for minimizing system size while maintaining performance under moderate solar irradiation conditions such as in autumn have not been sufficiently established. In this study, a standalone CaSO₄ solar chemical heat pump driven solely by solar thermal energy and a photovoltaic-powered heat exchange medium (HEM) circulation system was experimentally investigated. First, the influence of HEM flow rate on sensible and thermochemical heat storage was evaluated using a baseline configuration equipped with two solar collectors. Subsequently, the collector area was reduced by employing a single collector. Finally, the apparatus layout was optimized through adjustment of the collector tilt angle for autumn operation in Japan and reduction in piping length by vertically installing the CHP unit. The results showed that increasing the HEM flow rate enhanced heat transfer and promoted the dehydration reaction of CaSO₄. Under the optimum condition, a conversion of approximately 93% and a chemical heat storage capacity of 537 kJ were achieved. Furthermore, the optimized layout significantly reduced thermal losses and improved solar energy utilization. Although the collector area was reduced by 50%, the optimized Type 3 configuration achieved a chemical heat storage capacity of 462 kJ, corresponding to 84% of that of the baseline system. In other words, a 50% reduction in collector area resulted in only a 16% reduction in heat storage capacity. These results demonstrate that system-level optimization can substantially mitigate the performance loss associated with collector downsizing. The proposed configuration provides a practical pathway toward compact residential SCHPs with reduced installation space requirements while maintaining high thermochemical heat storage performance. Full article

Increasing the share of renewable energies is a key challenge in residential heating systems, particularly when available solar heat cannot be effectively stored or used. This study examines a façade-integrated Multifunctional Building Part (MBP) incorporating a phase change material (PCM), with a hydronic circuit designed for active thermal charging and renewable heat integration. The PCM-enhanced MBP enables direct charging of latent thermal storage through a hydronic circuit and provides an active envelope-based approach for storing renewable heat and supporting space heating. The PCM behaviour was experimentally verified at the component level using the SmallHouse IV demonstrator, and the resulting model was subsequently integrated into the International Energy Agency Solar Heating and Cooling (IEA SHC) Task 32 single-family reference building for seasonal numerical simulations under selected climatic conditions. The building-level assessment considers the conventional reference building, the hydronically activated MBP without PCM, and the PCM-enhanced MBP, thereby distinguishing the overall effect of the MBP from the additional contribution of latent thermal storage. The results demonstrate a progressive improvement in renewable heat utilization and electrical energy performance from the reference building to the hydronically activated MBP and, under favorable climatic conditions, to the PCM-enhanced configuration. In Stuttgart, the MBP reduced electrical energy demand from 1719.7 to 1255.6 kWh, with a further reduction to 962.0 kWh after PCM integration. Correspondingly, solar thermal utilization increased from 1194 kWh for the reference building to 2756 kWh with the MBP and 3999 kWh with PCM. Across Stuttgart, Madrid, and Kabul, the additional PCM integration reduced electrical energy demand by 23–69% and increased solar thermal utilization by 22–45% relative to the MBP without PCM. In contrast, under the investigated Moscow climate, PCM integration increased electrical energy demand by 9.6% and reduced solar thermal utilization by 6.9%, indicating a deterioration in simulated system performance. Overall, the results indicate that the performance of PCM-based thermal storage within the building envelope is highly dependent on the interaction between heating demand, renewable heat availability, and the opportunities for latent heat charging and discharging. The study highlights the potential of component-verified PCM-enhanced and numerically investigated hydronically activated building components for climate-adaptive renewable heat utilization in residential building. Full article

Energy piles are multifunctional deep foundations that structurally support buildings while enabling heat exchange between the superstructure and shallow subsurface. It is crucial for the wider use of energy piles and thus reliance on clean, renewable shallow geothermal energy for supplemental space heating and cooling to understand thermal and combined thermo-mechanical load transfer. To this end, previously developed and successfully validated analytical solutions are transformed into a unified dimensionless form, and the minimum set of controlling composite parameters is identified through rigorous application of the Buckingham Π theorem. A multifaceted solution space is explored through a sensitivity analysis performed across a wide range of controlling parameters and under different boundary conditions. The results show that the mechanisms of load transfer for thermal and mechanical loads are inherently different. In a very stiff soil, mechanical load is supported by the soil, while thermal load generates significant stress in the pile. Thus, the thermo-mechanical stress response is dominated by the thermal response. In a very soft soil, mechanical load is supported by the pile while stresses generated by thermal load are negligible. Thus, the thermo-mechanical stress response is dominated by the mechanical response. Full article

Existing and prospective maritime carbon-pricing regimes, together with uncertain renewable generation, complicate the low-carbon operation of shipboard integrated energy systems (SIES), particularly when network voltages and coupled electrical, heating, and cooling demands must be coordinated. To address this problem, this paper develops a two-stage robust optimization framework for day-ahead unit commitment and dispatch of diesel generators, renewable energy sources, energy storage, alternative maritime power, and carbon capture systems. A shipboard-adapted second-order cone programming (SOCP) DistFlow formulation combines an impedance-ratio-dependent operational security margin with node-specific voltage envelopes. The resulting min–max–min problem is solved by column-and-constraint generation with Big-M linearization. Case studies on a 20-bus shipboard microgrid demonstrate that the framework maintains nodal-voltage feasibility under the modeled worst-case deviations and provides a favorable robustness–cost trade-off. In out-of-sample tests, no infeasible robust realization is observed among the sampled scenarios, whereas the deterministic schedule exhibits infeasibility. Under the assumed capture efficiency, carbon capture also substantially reduces net emissions relative to the no-capture case. The proposed framework supports network-feasible, low-carbon day-ahead scheduling under renewable-generation and multi-energy-load uncertainty without altering the voyage plan. Full article

Zero-carbon industrial parks (ZCIPs) must balance renewable supply, carbon emissions, and multi-energy reliability. This study examines capacity planning for a ZCIP connected to an external concentrated solar power (CSP) plant through a green power direct-connection contract. The contract gives the park bounded scheduling rights over its offtake and allows thermal energy storage (TES) charging or discharging within an agreed operating envelope; the CSP operator retains physical control of the plant. A tri-objective model minimizes annual cost, net accounted carbon emissions, and a representative-day supply adequacy deficit for electricity, heat, and cooling. Four seasonal typical days are used, and the problem is solved by an improved MOPSO. Under equal evaluation budgets, the improved algorithm achieves the highest mean HV and lowest mean IGD. CSP direct connection raises the hypervolume from 5.871 × 10⁹ to 7.838 × 10⁹; allowing electricity sales raises it from 4.563 × 10⁹ to 8.508 × 10⁹. Two stress cases, the maximum electricity-load day and maximum residual-load day, are evaluated using the fixed compromise configuration under a normal grid-connected boundary. The results support ZCIP planning and green power direct-connection policy design. Full article

This narrative review examines the design of power electronics for deep-sea energy and industrial systems, where converter performance is constrained by electrical demands and prolonged exposure to pressure, seawater, temperature cycling, and limited maintenance access. Targeted, non-systematic literature searches covering studies available through September 2026 were used to connect offshore renewable generation and hydrogen production, sub-sea distribution and motor drives, and autonomous underwater vehicle (AUV) power and charging. The review organizes published evidence around converter topology, semiconductor and passive-component selection, switching and conduction losses, insulation coordination, thermal paths, protection, and environmental qualification. It identifies distinct design priorities: high-voltage insulation and fault isolation for sub-sea distribution; continuous-current capability and ripple control for hydrogen interfaces; and compact conversion, energy budgeting, and misalignment-tolerant charging for AUVs. Hydro-static pressure and sealing alter heat-transfer and insulation boundaries, while vibration, corrosion, and cycling create interacting failure pathways. Consequently, efficiency or power-density figures measured under different electrical loads, pressure conditions, cooling arrangements, and test duration cannot be ranked directly. A mission-specific design and verification pathway is proposed, beginning with explicit operating boundaries and component-level screening, followed by combined-stress tests, converter prototypes, and system-level trials. The proposed pathway also incorporates monitoring, maintainability, and life-cycle assessment. Published demonstrations substantiate individual technical options, but they do not establish a universally optimal architecture or long-term sub-sea reliability. Future studies should report comparable measurement boundaries, failure criteria, and exposure histories so that converter designs can be evaluated against the demands of their intended missions under repeatable, application-relevant conditions and declared measurement uncertainty. Full article

Achieving the European Union’s (EU) climate neutrality targets requires residential buildings to reduce operational carbon emissions, while increasing on-site renewable generation. However, the relative contributions of rooftop photovoltaic (PV) systems with battery storage and heat pump (HP) retrofits have not been comprehensively evaluated for representative French single-family house typologies. This study assesses two representative French detached-house typologies, Mozart (single-storey) and Puccini (two-storey), across four climatic zones (Paris, Lyon, Brest, and Nice) using a scenario-based dynamic simulation framework. Three retrofit scenarios were developed from prototype models of each building typology: (i) a baseline configuration with existing electric radiators, (ii) rooftop distributed PV systems combined with battery storage, and (iii) PV–battery systems combined with the replacement of the existing heating systems by water-to-air HPs. Performance was evaluated using energy, carbon, economic, and grid-dependency indicators, including the self-consumption ratio (SCR), self-sufficiency ratio (SSR), grid import dependency ratio (GIDR), operational carbon emissions (OC), levelized cost of energy (LCOE), and carbon emission reduction (CER). The results show that Scenario 2 (PV–battery systems) reduces OC relative to the baseline and achieves SSR values of approximately 36.21–50.62%, while grid-import dependency remains high because of the seasonal mismatch between PV generation and winter heating demand. Replacing the existing electric radiators with water-to-air HPs reduces heating electricity demand but does not uniformly reduce total annual electricity consumption. For Puccini, energy consumption in Scenario 3 is higher than in Scenario 2 in Paris, Lyon, and Nice because cooling and additional heat pump system loads—including fans, pumps, heat rejection, and supplemental electric heating—offset the heating savings. However, houses in the Mediterranean climate zone perform best overall, whereas those in oceanic climates require more careful system design. These findings emphasize the importance of retrofit strategies and financial support that are sensitive to both typology and climate, to support effective progress towards EU climate neutrality. Full article

Ground source heat pump (GSHP) systems play a pivotal role in the decarbonization of heating, ventilation, and air conditioning systems. However, their long-term performance depends heavily on operational control strategies capable of addressing system dynamics, varying load conditions, and the increasing integration with renewable and distributed energy resources. Data-driven methods have emerged as promising approaches for improving the operational flexibility, efficiency, and sustainability of GSHP systems. Existing review studies mainly focus on predictive modeling and provide limited systematic analysis of the interactions among predictive modeling, control, and optimization, particularly in hybrid and networked energy systems. This review shows recent advances in data-driven approaches for GSHP operational control. The reviewed studies demonstrate that data-driven control strategies can improve operational performance and enable real-time decision-making under dynamic conditions, particularly when predictive models are integrated with first-principles models and optimization algorithms. Beyond conventional standalone applications, this review highlights the transition toward hybrid GSHP configurations and integrated energy systems, including fifth-generation district heating and cooling networks. Within these systems, operational objectives shift from maintaining local ground thermal balance and maximizing equipment efficiency to achieving coordinated energy exchange, load flexibility, economic performance, and carbon-aware network operation. Despite substantial methodological advances, challenges related to data quality, boundary uncertainty, model transferability, and computational scalability continue to limit large-scale deployment of data-driven control strategies. Finally, future directions for developing intelligent, interpretable, and scalable data-driven control frameworks for next-generation low-carbon buildings and district energy systems are outlined. Full article

Solar energy has become one of the most promising renewable energy sources owing to its wide availability and relatively low initial cost for energy conversion. Among the various technologies, photovoltaic (PV) systems represent one of the most effective approaches for harnessing solar energy through the photovoltaic effect. Nevertheless, a key limitation affecting the large-scale deployment of PV systems is their sensitivity to operating temperature. Heat accumulation can reduce electrical performance, accelerate degradation, and create spatial temperature non-uniformity across the module surface. In this context, thermal symmetry refers to a balanced and spatially uniform temperature distribution across comparable regions of a PV module; improved thermal symmetry can reduce local hot spots and thermal gradients that adversely affect reliability. Existing literature on PV cooling places insufficient emphasis on the standardization of critical parameters required to evaluate and compare different cooling techniques under consistent operating conditions. Therefore, this study reviews recent advancements in passive, active, and hybrid PV cooling and proposes a common comparison framework covering temperature reduction, electrical performance, auxiliary energy consumption, net energy benefit, economic considerations, environmental requirements, climate suitability, maintenance, scalability, and technology maturity. Particular attention is given to the distinction between gross performance improvement and net benefit in active cooling systems, for which pumps and fans may consume part of the additional generated energy. The analysis indicates that PV cooling technologies still face critical challenges, including high costs, maintenance demands, incomplete reporting of parasitic energy use, and reduced or variable performance under extreme environmental conditions. The review concludes with recommendations for standardized testing, climate-adaptive design, improved thermal uniformity, and transparent reporting of net system performance. Full article

Given that fixed energy tariffs and demand-response compensation rates cannot adequately capture temporal variations in source-load conditions across multi-park integrated energy systems, this study develops a coordinated optimization approach driven by load-pressure-based dynamic pricing. First, the original electric, thermal, and cooling load profiles are evaluated together with the day-ahead forecasts of wind and photovoltaic generation. These data are then converted into five pricing indicators: net electric load pressure, thermal load pressure, cooling load pressure, renewable energy output level, and the peak-valley period factor. These multidimensional source-load indicators are further translated into time-varying electricity and heat tariffs, together with compensation rates for shifting and curtailing electric, thermal, and cooling demands. Second, a coordinated scheduling model is formulated for interconnected energy parks that integrates renewable generation, shared energy storage, multi-energy conversion devices, electricity transfers among parks, and power exchanges between each park and the distribution grid. The objective function accounts for the emission-related costs arising from grid electricity procurement and natural gas use. Once obtained, the dynamic price signals are introduced into the scheduling stage as fixed inputs, enabling the simultaneous coordination of equipment operation, shared storage charging and discharging, electricity transfers among parks, and multi-energy demand response. Following linearization, the scheduling problem is converted into a mixed-integer linear model, which is implemented in YALMIP and solved by CPLEX without iterative price updates. The numerical results indicate that the resulting energy tariffs and demand response incentives vary with the predicted day-ahead source-load state and encourage flexible electric, thermal, and cooling demands to be redistributed across the scheduling horizon. Shared energy storage and inter-park electricity exchange redistribute the equivalent net-load profile and contribute to peak-load regulation, while wind power is coordinately allocated among direct park supply, storage charging, and export to the distribution grid. The electricity, heat, and cooling power balances of all parks are maintained, verifying the feasibility and coordination capability of the proposed method. Full article

The increasing penetration of renewable energy requires coal-fired power plants to operate with greater flexibility, while deep load reduction and frequent load variations challenge combustion stability, efficiency, and equipment reliability. High-temperature solid-particle thermal energy storage (TES) offers a promising approach to decouple boiler heat supply from turbine power demand. This review compares particle heating, discharging, transport, and system-integration strategies and relates reported findings to key design and operational constraints. Solid-particle storage media can operate over a wide temperature range of approximately 200–1200 °C; silica sand can withstand temperatures up to about 1200 °C and alumina approximately 1100–1200 °C, substantially exceeding the typical operating range of nitrate molten salts (<600 °C). This broad temperature tolerance provides favorable thermal matching with high-temperature boiler flue gas. Direct flue-gas heating shortens the heat-transfer pathway and reduces intermediate heat-transfer stages, although its effects on boiler heat distribution and downstream heating surfaces require careful evaluation. Moving-bed discharging can provide continuous thermal output, while gravity-driven high-temperature transport combined with mechanical lifting after particle cooling can reduce the demand for high-temperature moving components. Based on these findings, a conceptual configuration integrating direct flue-gas heating, particle sensible-heat storage, moving-bed discharging, and temperature-segmented circulation is proposed. Future studies should focus on system-level efficiency, dynamic response, and load-following capability. Preliminary calculations for a 600 MW subcritical unit at 30% THA load show that particle-storage integration increases the boiler outlet flue-gas temperature by only about 1 °C, indicating no apparent increase in low-temperature corrosion risk under the investigated condition. Full article

AI data centers raise concerns about electricity consumption and costs, water shortages, and air pollution, as AI, machine learning, cloud computing, and high-performance computing rapidly increase electricity demand and thermal loads. This study develops an integrated framework for a large-scale, solar-assisted AI data center in Granbury, Texas, combining high-efficiency liquid cooling, heat-exchanger optimization, solar photovoltaic (PV) generation, and grid electricity. A MATLAB-based thermal and energy model was developed to evaluate GPU workloads, IT power consumption, cooling demand, coolant and air temperatures, pumping and fan power, Power Usage Effectiveness (PUE), and water consumption. Heat-exchanger performance was evaluated as a function of coolant velocity and channel gap, and single-objective optimization using Sequential Quadratic Programming (SQP), Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) was compared with multi-objective optimization using Non-dominated Sorting Genetic Algorithm II (NSGA-II). The baseline 1.30 MW IT system achieved an average IT load of approximately 910.26 kW, daily facility energy consumption of 28,590.96 kWh, and a PUE of approximately 1.31 while maintaining acceptable coolant and air temperatures. Heat-exchanger analysis revealed a strong trade-off between thermal compactness and hydraulic efficiency. The minimum-pumping configuration occurred at a coolant velocity of 2.0 m/s and a 20 mm gap, requiring 0.0508 MW of pumping power and 1218.3 kWh/day, but also requiring 43,170 heat-exchanger modules. SQP, GA, and PSO produced similar system-level energy performance but different hydraulic configurations, whereas NSGA-II provided a broader set of Pareto-optimal solutions balancing cooling electricity, water flow, heat-exchanger area, infrastructure requirements, and solar capacity. A modular PV configuration with 69 rows, a 30° tilt angle, and a ground coverage ratio of approximately 0.655 was also developed for integration with a 500 MW-scale data-center campus. The results demonstrate that coordinated optimization of cooling, heat exchangers, renewable generation, battery storage, and grid interaction can provide a practical pathway toward energy-efficient, water-conscious, grid-resilient, and lower-carbon AI data centers. Full article

Much of the existing Mediterranean building stock was constructed before the introduction of modern seismic and energy-performance standards and therefore requires sustainable rehabilitation addressing both structural vulnerability and poor energy efficiency. Moreover, the marked variability in seismic hazard and climatic conditions across the region calls for assessment methods capable of evaluating retrofit effectiveness under different environmental conditions. This study introduces a multi-site assessment framework for evaluating integrated seismic and energy retrofit solutions, including passive control systems—tuned mass damper, tuned mass damper inerter and base isolation—integrated with energy-oriented interventions, employed at roof or ground level, aimed at improving envelope performance or providing on-site renewable energy generation. The framework is applied to a representative three-story reinforced-concrete residential building with masonry infill walls and no thermal insulation, considering three Mediterranean sites with different seismic and climatic conditions. The structural response is simulated through a nonlinear finite element model employing lumped plasticity hinges for reinforced concrete members and infill walls. Dynamic building energy analyses are performed through simulations by means of the transfer function method, with hourly time steps and typical meteorological year. The structural and energy responses are synthesized through properly defined integrated performance indicators, which allow for comparative assessment of alternative retrofit strategies according to different design priorities. The results show that retrofit effectiveness is site-dependent. Base isolation provides the greatest structural improvement, whereas the performance of roof-level control systems varies with seismic hazard and spectral characteristics. From an energy perspective, cool roofs, green roofs and insulated ground-floor slabs modify heating and cooling demands by improving specific components of the building envelope but provide only moderate reductions in overall primary energy consumption. Conversely, photovoltaic roofs generate on-site renewable electricity and produce the best energy performance. The tuned mass damper inerter configuration combined with a photovoltaic roof achieves the most favorable integrated performance when equal importance is assigned to structural and energy objectives. The proposed framework supports the development of holistic, regionally adaptable strategies aimed at enhancing the safety, sustainability and efficiency of Mediterranean buildings. Full article

Passive cooling strategies are essential to curbing the growing air-conditioning demand of dwellings in warm–humid regions. This work presents a Computational Fluid Dynamics (CFD) study, carried out with the open-source code OpenFOAM, of a passive system that couples an earth–air heat exchanger (EAHE) with a solar chimney (SC) serving a room-representative cavity, i.e., the coupled EAHE–SC device is analyzed together with the room it conditions. The methodology was built progressively: (i) a transient conduction sub-model (laplacianFoam) characterized the thermal inertia of the soil around the buried duct; (ii) a parametric study of eight coupling geometries identified the best relative position of the EAHE and the SC; (iii) three configurations—the complete system, the EAHE + cavity system, and the bare cavity—were solved under identical numerical conditions with the buoyancy-driven solvers of OpenFOAM and the k–$\epsilon$ turbulence model with the Boussinesq approximation; and (iv) the complete system was evaluated for a representative hot and a representative cold design day through a section-based post-processing of the ventilation and thermal-energy indicators. Over the four-day period simulated, the soil behaved as a stable thermal reservoir with no depletion. At the design condition, the complete system reached a mean cavity temperature of 33.2 °C, 8.32 air changes per hour (ACH) and 67.0 W of thermal power removed from the cavity, against 34.4 °C, 2.01 ACH and 4.56 W for the bare cavity; coupling the chimney raised ventilation by 94.8% and 313.9% relative to the EAHE-only and bare-cavity cases, respectively. The design-day comparison showed a marked climate-dependent response: on the hot day the EAHE dominated (air cooled by 5.75 °C, 2.51 ACH), whereas on the cold day the exchanger remained nearly neutral ($+0.19$ °C) and ventilation dropped to 0.69 ACH, lowering the cavity temperature to 24.1 °C. The results indicate a complementary, mutually reinforcing behavior—the coupled system removes more heat and renews more air than either device does on its own—for the design conditions analyzed. Full article

Freshwater scarcity remains a major challenge across many African regions, particularly in remote and arid areas where access to centralized water infrastructure and reliable energy resources is limited. In this context, humidification–dehumidification (HDH) desalination represents a promising decentralized solution for sustainable freshwater production due to its low operating temperature, simple design, and compatibility with renewable energy systems. However, the efficiency of conventional HDH systems is often constrained by passive condensation processes that are highly sensitive to ambient climatic conditions. This study presents a numerical investigation of an innovative HDH desalination system integrating active thermoelectric condensation using Peltier cooling modules. The proposed system operates in a closed-loop water circulation, open-air configuration and incorporates dual evaporators and a coaxial air–water heat exchanger to improve heat recovery and thermal efficiency. The system is designed to be powered by solar photovoltaic energy, making it suitable for decentralized and off-grid applications in water-stressed regions. A comprehensive numerical model was developed using MATLAB to simulate the system performance under various climatic conditions. Simulation results demonstrate that the active condenser significantly improves freshwater productivity compared to conventional passive configurations. Under hot and dry climatic conditions (38 °C and 45% relative humidity), the system achieved a maximum freshwater production corresponding to a 57% improvement compared to a conventional single-evaporator HDH system and a 22% increase relative to a passive-condenser configuration with heat recovery. In addition, the thermoelectric condenser maintained stable condensation performance under highly humid conditions, ensuring improved operational reliability and resource efficiency. The findings highlight the potential of combining renewable energy, heat recovery, and active thermoelectric cooling to develop sustainable and energy-efficient desalination technologies adapted to African environmental conditions. The proposed system contributes to decentralized water production, environmental sustainability, and the strengthening of climate-resilient water solutions for vulnerable communities. Full article