Search Results (942)

Seaweeds are valuable marine resources rich in polysaccharides and polyphenols. Carbon dots (CDs) from Gracilaria salicornia (GS-CDs), Halymenia dilatata (HD-CDs), Sargasum polycystum (SP-CDs), Spatoglossum asperum (SA-CDs), Ulva lactuca (UL-CDs), and Caulerpa peltata (CP-CDs) were synthesized by a hydrothermal process and characterized by FTIR, XPS, and SEM-EDX. All the CDs had sizes less than 10 nm with spherical morphology and various functional groups. UL-CDs showed the strongest UV-A blocking efficacy via the measurement of light transmission (p < 0.05). HD-CDs exhibited the highest DPPH-RS-A (148.32 ± 1.51 μmol TE/L) and FRA-P (717.24 ± 7.87 μmol TE/L), whereas SA-CDs had the highest ABTS-RS-A (1043.40 ± 3.00 μmol TE/L). HD-CDs had antifungal activity against both Aspergillus flavus and Aspergillus parasiticus. All CDs suppressed the proliferation of both pathogenic and spoilage bacteria; however, high MIC values indicated the limited antibacterial effectiveness. CDs up to 500 mg/L maintained cell viability greater than 80% towards normal BJ cells. When SA-CDs (500 ppm) were incorporated into peeled and deveined Pacific white shrimp (Litopenaeus vannamei), lipid peroxidation during 10 days of refrigerated storage was retarded, as evidenced by lower PV, TBARS, and greater PUFA retention than the control and ascorbic acid-treated samples. Heat map and PCA analyses revealed that lipid oxidation was governed by CD type and storage time. Full article

The electrification of residential demand through electric vehicles (EVs), heat pumps (HPs), photovoltaic (PV) systems, and battery energy storage systems (BESSs) creates new congestion challenges in low-voltage (LV) grids. This study evaluates a transparent, deterministic, and real-time-capable rule-based energy management system (EMS) for curative thermal congestion management within a §14a EnWG-oriented setting. The EMS is implemented in MATLAB/Simulink and tested on a representative four-feeder LV network supplying 56 households. Congestion is detected from maximum phase root-mean-square currents using conservative transformer and feeder thresholds. After a threshold is reached, the EMS first activates available BESS support and then applies simultaneous feeder-wide EV limitation, batched round-robin curtailment, or staged feeder-wide reduction toward $4.2$ kW. In the uncontrolled case, the Feeder 3 and transformer overload areas are $62.84$ Ah and $48.50$ Ah, respectively. All controlled scenarios remove at least 98.70% of the feeder overload and eliminate the transformer overload within the reported numerical precision. The batched strategy requires $328.54$ Ah of cumulative feeder-current reduction, compared with $977.34$ Ah for simultaneous control and $816.00$ Ah for staged control, and achieves the highest feeder-relief efficiency. It therefore provides a balanced trade-off between congestion relief and intervention intensity for the investigated deterministic case. Full article

Building-integrated photovoltaics (BIPVs) can expand the available photovoltaic area on buildings, especially in dense urban contexts with limited roof surfaces. For transparent-envelope applications, such as photovoltaic shading devices (PVSDs) and semi-transparent photovoltaic glazing (STPV), PV-yield assessment is particularly challenging because PV elements also function as part of the building envelope. Their energy yield depends on multiple interacting factors: irradiation, orientation, shading, incidence-angle effects, operating temperature, and, for STPV, glazing thermal behavior. In early-stage building design, however, these effects must be assessed while system characteristics are still evolving, and detailed product or module data are often unavailable. To address this gap, this study develops and evaluates an EnergyPlus-based approach for PV-yield assessments for transparent-envelope BIPV applications. The approach replaces fixed PV efficiency with a time-dependent effective efficiency that accounts for incidence-angle reflection and temperature-related efficiency losses. It is evaluated through a cross-tool comparison with established PV-yield assessment tools. For PVSD, the comparison separates unshaded conditions, louver self-shading, and urban-context shading. For STPV, it includes an analysis of the PV cell-temperature estimation and the link between electricity generation and glazing heat balance. Results show that PVSD yield differences are mainly governed by shading representation, while STPV results are more sensitive to cell-temperature assessment than to thermal coupling effects. Overall, the approach provides a consistent basis for comparing PVSD and STPV yield under early-stage input constraints, while including selected AOI- and temperature-related efficiency effects. Full article

As rooftop photovoltaic (PV) systems are increasingly deployed on taller buildings and across a wider range of building applications, localized overheating or initial fires caused by electrical faults, combustible roof-covering materials, or maintenance-related ignition sources may affect PV modules and contribute to subsequent fire spread over the rooftop system. In this study, a full-scale fire experiment was conducted on a flat-laid rooftop PV system using a nominal 100 kW n-heptane pan fire as a controlled localized external fire source to investigate the fire development and escalation mechanism of the system. The results show that the fire hazard was first and primarily concentrated in the confined under-panel space: the average cavity peak temperature of the ignited array reached 684.0 °C, with a local maximum of 853.4 °C, both significantly higher than the maximum upper-surface center temperature of 370.7 °C. The involvement of the waterproofing membrane in combustion was the key amplifying mechanism driving the transition from localized heating to a sustained high-temperature event; the average cavity temperature exceeded 500 °C after 234 s and remained above this threshold for approximately 201 s, with an average cavity heat accumulation index of 178.1 × 10³ °C·s. Compared with the lower upper-surface center measuring points, hazardous temperatures beneath the modules were reached earlier by 149, 193 and 247 s at the thresholds of 50, 100 and 200 °C, respectively. Under the tested configuration, these findings provide engineering insights for fire-risk identification, early monitoring, and fire-safe design of flat-laid rooftop PV systems in high-rise building applications. Full article

Photovoltaic–thermal (PVT) collectors co-generate electricity and heat—natural front ends for thermochemical energy storage (TCES)—provided the heat transfer fluid stays above the reactor’s desorption temperature. Using an eight-node model of a 0.6834 m² collector at 8.64° N whose thermal core is partially validated against measured data from the same tropical–coastal site (rooftop PV module temperature, RMSE 3.8 °C; prototype absorber-to-water heat transfer, RMSE 1.3 °C), flow-regulated to the ≈95 °C SrCl₂/NH₃ desorption threshold, we quantify the energy and exergy delivered for charging under tropical–monsoon intermittency. The 95 °C setpoint operation, the ≈5.3 h charging window, and all reported exergy yields are simulated: the built prototype delivered hot water peaking at 79 °C and did not reach the 95 °C setpoint. On a measured clear-sky day (clearness index K_t = 0.52), the collector yields 1.38 kWh of energy but only 0.43 kWh of exergy (first-law efficiency ≈ 38%; gross exergy efficiency ≈ 13%); across a 30-seed synthetic-intermittency ensemble, the exergy yield is 0.678 kWh at ≈14% gross exergy efficiency (≈52% combined first-law efficiency). In both cases, the thermal stream dominates the energy output while the electrical stream dominates the exergy output—on the sunlit day, the exergy is about 80% electrical—because 95 °C heat carries a Carnot factor (exergetic quality factor, 1 − T_a/T₇, at the instantaneous ambient dead state) of only ≈0.18 and an integrated Bejan/Kotas thermal-exergy quality of only ≈0.09. The controller holds the outlet within 1.4 K of the setpoint for ≈5.3 h, whereas no fixed flow in the 0.5–5.0 L min⁻¹ range ever reaches it: feedback control is a structural enabler, not an optimisation. On overcast days, the threshold is never reached and charging heat collapses to zero, leaving a PV-only generator. Exergy delivery is nonetheless nearly controller-independent: the accumulated exergy delivery deficit after a 50% irradiance drop is 937 kJ, a controller-independent value changing only 1.3% across a systematic 4 × 4 gain sweep (K_p 0.33–2.7×, K_d 0.25–5× of nominal), and predictive control improves it by ≤1%. For PVT–TCES at this scale, the decisive lever is deployability, not control sophistication. Full article

To enhance the thermal performance of a Stirling air conditioner, this study applies Schmidt-based dimensionless analysis to systematically investigate the influence of key structural parameters on its cooling and heating characteristics. A dimensionless thermodynamic framework is established under the ideal isothermal assumptions of the Schmidt model to investigate the effects of temperature ratio, swept volume ratio, dead volume ratio, and phase angle on a Stirling system. The results indicate that increasing the temperature ratio enhances the thermodynamic driving potential; however, excessive temperature ratios introduce stronger irreversibilities, resulting in saturation or even degradation of effective cooling performance. The dimensionless cooling capacity increases significantly with phase angle, rising from 0.25 at α = 50° to 0.65 at α = 120°, while heating capacity peaks at α ≈ 71.6° with ε_e = 0.18. The p–v diagram analysis reveals optimal work output at α ≈ 75°, where the cycle area reaches 20.8, representing a 44.4% increase from the value at 15°. Performance saturation occurs at τ > 3 and κ > 6 for cooling and beyond κ > 4 for heating. Within the assumptions of the ideal Schmidt model, the results suggest that medium-to-high temperature ratios (τ ≈ 3–4) combined with moderate swept volume ratios (κ ≈ 6–8) provide the optimal balance between thermodynamic performance and structural compactness; these parameter combinations should be regarded as theoretical design references for ideal operating conditions rather than directly applicable engineering optimization guidelines. Full article

This study investigates shading technologies used to protect vertical green façades (VGF) from excessive solar exposure and climate-related stresses. A scoping review of 176 publications from the past decade was conducted, focusing on innovative materials and components applied in adaptive and passive shading systems relevant to Central and Southern European climates (BSh, Csa, Csb, Cfa, Cfb, Dfb). Only technologies that reached at least the prototype or small-scale trial stage were included. The review identifies several categories of emerging adaptive solutions—such as smart materials, pneumatic systems, PCM-integrated, PV-integrated, algae-based, hygromorphic, electro-optic, fluidic, and mechanical or mechatronic devices—which show potential to improve microclimatic regulation and user comfort, though their long-term durability and integration with VGFs remain insufficiently documented. Advances in digital fabrication and optimisation support the development of high-performance passive elements, while experimental and simulation studies indicate that dynamic shading can offer promising outcomes across diverse climatic contexts. To strengthen the plant-centred perspective, each shading category is evaluated through four criteria: PAR transmission, microclimatic regulation, evapotranspiration behaviour, and integration constraints. Climate projections suggest that radiation and heat stress may increasingly challenge certain VGF species in warmer regions, highlighting the need for shading strategies aligned with plant requirements, local conditions, user needs, and long-term maintenance. Full article

Under extreme high-temperature conditions, heat accumulation in rooftop photovoltaic (PV) arrays can substantially reduce PV conversion efficiency and output power. To improve the thermal and power-generation performance of rooftop PV systems, this study developed a computational fluid dynamics (CFD) model for a rooftop PV array and validated it using field measurements from Chongqing, China. The relative root mean square errors (rRMSEs) between simulated and measured backsheet temperatures at the three measurement points were 6.31%, 7.52%, and 8.45%, respectively, indicating acceptable model accuracy. The effects of mounting height, tilt angle, and front-to-rear row spacing on PV backsheet temperature, conversion efficiency, and output power were then investigated. A central composite design (CCD) within response surface methodology (RSM) was used to establish regression models linking the design variables to the objective functions. Finally, an NSGA-III-based multi-objective optimization framework combined with TOPSIS was used to identify the optimal configuration. For the rooftop PV array studied under extreme summer conditions in Chongqing, the TOPSIS-selected compromise solution corresponded to a mounting height of 0.90 m, a tilt angle of 15.63°, and a front-to-rear row spacing of 2.96 m. Compared with the original configuration, the optimized passive installation geometry reduced the peak PV backsheet temperature by 2.3 °C without active cooling, water consumption, or additional energy input. Under the same meteorological and irradiance conditions, this temperature reduction increased conversion efficiency by 0.5% and output power by 0.4%. Detailed inter-row short-wave shading and electrical mismatch were not explicitly modeled. Therefore, the row-spacing effect mainly reflects changes in ventilation and module temperature under the same irradiance input. The proposed framework provides a practical reference for installing and optimizing rooftop PV arrays in hot-climate regions. Full article

Partial shading is one of the main factors that degrade the output performance and operational reliability of photovoltaic (PV) arrays. It not only causes power loss and multi-peak P–V characteristics, but also induces current mismatch, reverse bias, and local hotspot formation. In this study, an electro-thermal PV module model under partial shading conditions is developed and validated, and an improved sparrow search algorithm (ISSA) is proposed for maximum power point tracking (MPPT) of PV arrays under static and dynamic complex operating conditions. The electrical model is established based on the single-diode model with irradiance, temperature, and Bishop reverse bias corrections, while the thermal model considers solar absorption, heat generation, convection, radiation, and heat conduction. The coupled model is validated against published experimental and numerical results. The predicted peak hotspot temperature is 111.9 °C, corresponding to a relative error of 2.7%; the average absolute errors of current and voltage are 0.20–0.25 A and approximately 0.3 V, respectively, and the maximum relative error of peak temperature is 3.7%. Based on the validated model, a MATLAB/Simulink MPPT platform is constructed to compare particle swarm optimization (PSO), the standard sparrow search algorithm (SSA), and the proposed ISSA. The results show that SSA achieves better global tracking performance than PSO under severe partial shading and dynamic irradiance transitions. Furthermore, by introducing Tent chaotic initialization and random walk perturbation, ISSA significantly improves the convergence speed and reduces steady-state power fluctuation while maintaining high tracking efficiency. Under static shading conditions, ISSA reduces the convergence time from 0.44 s to 0.25 s, 0.24 s to 0.15 s, and 0.44 s to 0.26 s for light, moderate, and severe shading cases, respectively. Under dynamic conditions, ISSA also shortens the post-transition convergence time and suppresses output power oscillation. These results demonstrate that the proposed ISSA-based MPPT method is suitable for PV arrays operating under partial shading and dynamic weather conditions. Full article

Solar energy has become one of the most important renewable energy sources for reducing dependence on conventional fossil-based energy systems. Rooftop photovoltaic (PV) installations play a key role in the expansion of solar energy, particularly in tropical countries such as Vietnam. This study experimentally investigates the effects of roof material, rear ventilation gap, PV technology, solar irradiance, and wind speed on the power conversion efficiency (PCE) of rooftop PV modules under tropical climatic conditions in Ho Chi Minh City, Vietnam. Three roof types (concrete, tiled, and corrugated metal), three rear ventilation gaps (10, 30, and 50 cm), and two PV technologies (monocrystalline and polycrystalline) were evaluated under real operating conditions. The results indicate that increased module temperature significantly reduces power output and PCE, even under high solar irradiance. PV modules installed on corrugated metal roofs exhibited the highest operating temperatures and the lowest efficiencies, whereas concrete and tiled roofs provided more favorable thermal conditions. Increasing the rear ventilation gap enhanced convective cooling, with the 30–50 cm configurations showing superior heat dissipation compared with the 10 cm configuration, particularly for corrugated metal roofs. The experimentally determined heat transfer coefficient ranged from 23.48 to 67.64 W m⁻² K⁻¹, exceeding the theoretical wind-based coefficient (16.86–17.22 W m⁻² K⁻¹), thereby indicating the contribution of mixed convection, radiative exchange, and roof–module thermal interactions. Monocrystalline modules consistently achieved slightly higher efficiencies than polycrystalline modules. The findings provide practical guidance for optimizing rooftop PV installations and improving energy yield in tropical climates. Full article

Energy industrial zones can act as a transformative model for industrial decarbonization by integrating renewable energy infrastructure directly with industrial production. By combining energy industrial zones with the energy community framework and peer-to-peer (P2P) energy trading, this study proposes a pathway toward 100% renewable energy sources. The model was tested using a techno-economic assessment applied to the Bravar-Jasenice case study in Croatia featuring 12 MW of solar PV, 10 MW of wind power, and a 9.3 MW biogas cogeneration plant. This integrated approach can achieve 80–90% energy self-sufficiency and reduce electricity expenditures for participating enterprises by approximately 15%. Furthermore, the system facilitates an annual reduction of roughly 20,000 tonnes of CO₂ emissions, thus directly supporting European Green Deal objectives. The study also highlights the potential for industrial symbiosis, including green hydrogen production, data centre integration, and waste heat recovery. Ultimately, the proposed framework provides a robust strategy for enhancing industrial competitiveness and ensuring energy security through localized, sustainable energy management. Full article

The practical performance of building-integrated solar systems in cold climates is strongly governed by temperature-grade matching between solar energy output and space-heating demand. However, year-round field evidence comparing solar thermal collectors, photovoltaic systems, and photovoltaic/thermal systems under the same building, climatic, and heating-network boundary conditions remains limited. This study conducted a year-round field evaluation of solar collector (SC), photovoltaic (PV), and photovoltaic/thermal (PVT) systems installed in an office building in Tianjin, China. Continuous operating data collected from November 2022 to October 2023 were used to assess seasonal thermal output, electricity generation, effective heat supply, solar utilization efficiency, carbon reduction, and payback period. During the heating season, SC exhibited the strongest direct-heating capability among the investigated systems, delivering 817.50 MJ/m² of useful heat. In contrast, under the investigated system configuration without heat-pump assistance, the outlet temperature of the PVT subsystem remained below the 45 °C direct-heating threshold, and its thermal output could not be directly utilized for winter space heating. This result is specific to the investigated operating conditions and does not exclude the potential application of PVT systems coupled with heat pumps or low-temperature heating terminals. During the non-heating season, the investigated PVT subsystem simultaneously produced electricity and usable low-temperature heat, with heat and electricity accounting for 61.3% and 38.7% of its useful output, respectively, indicating its potential for combined energy harvesting. Under the investigated climatic, system, cost, and energy-demand conditions, the entropy-weighted TOPSIS assessment ranked SC highest when non-heating-season heat demand was present, whereas PV was more suitable when such heat demand was absent. Furthermore, a demand–output matching method was developed to support SC/PV area allocation for different building types. Under the investigated climatic and energy-demand assumptions, the recommended PV area ratios were 54.5%, 67.4%, and 79.7% for residential, office, and commercial buildings, respectively. These results provide field evidence for effective heat evaluation, temperature-grade matching, and component selection in solar-assisted heating systems for cold-climate buildings. Full article

This proof-of-concept study proposes a photovoltaic transparent vacuum insulation panel (PV-TVIP) and evaluates its heat transfer and power generation characteristics with increased temperatures, and light transmission characteristics for visible light and ultraviolet wavelengths. The study was conducted with a climate-controlled chamber mimicking the common temperature range of Sapporo, Japan. The average TVIP heat flux was measured to be 65–75 W/m² with a U-value of 1.95–2.3 W/(m²∙K). Compared to earlier measurements to see the effect of seasonal atmospheric conditions to the quality of the TVIP, it was determined that the TVIP manufactured during winter conducted less heat, assumed to be caused by decreased humidity. Placing the PV between the TVIP and a glass pane increased the operating temperature by 26.06 °C and decreased power generation by 13%. Afterwards, the transparency of the TVIP and PV-TVIP were measured under a bright light therapy lamp, showing that TVIP reduced the amount of most visible light wavelengths by 50% and the PV-TVIP by 90%. UV radiation was respectively reduced by approximately 78% and 100%. The results show that while PV-TVIP shows potential as a BAPV window retrofit solution, its manufacturing requires optimized, low-humidity conditions during all phases of the manufacturing process. Full article

The intensification of the urban heat island effect poses a critical threat to the preservation and habitability of compact historic districts. The Alameda de Hércules in Seville exemplifies this vulnerability, where the intersection of heritage protection and extreme Mediterranean summers limits conventional climate adaptation. This study conducts a multi-temporal evaluation of the square’s climate resilience, spanning from its configuration prior to major 21st-century renovations to its current state and future projections, proposing future interventions. By integrating advanced microclimatic simulation and high-fidelity energy modeling, the research assesses a dual-function strategy: the improvement of the thermal environment while implementing non-intrusive photovoltaic pavements (PVPs) for energy generation. Environmental parameters, including air temperature, mean radiant temperature (MRT), and the universal thermal climate index (UTCI), were analyzed alongside the renewable energy potential of the site’s mobility infrastructure. Four heritage-sensitive interventions were tested: PV-integrated bicycle lanes, shading canopies, reflective pavement, and permeable paved grass. The results demonstrate that the canopies and paved grass zones can lower surface temperature up to 3.7–4.3 °C, reduce UTCI stress up to 2.3–3.0 °C, and decline MRT up to 10.6 °C. These values correspond to the maximum reductions achieved in specific zones. However, the PVP can locally increase surface temperature by about 4.7 °C and the reflective pavements increase MRT by around 10.4 °C, while generating an estimated annual energy yield of 174.19 MWh. The analysis under future climate projections suggests that these strategies remain equally effective under future scenarios. These findings confirm that PV-integrated urban surfaces offer a viable, reversible, and replicable approach to retrofitting historic public spaces, harmonizing climate-adaptive cooling with decentralized energy production without compromising the site’s cultural significance. Full article

Amid the global drive for carbon peaking and carbon neutrality, integrating renewable energy into building energy systems to mitigate photovoltaic (PV) intermittency and realize low-carbon energy supply has become a critical research frontier. This study proposes a novel dual-storage renewable energy system integrating solar energy storage system (SES), hydrogen energy storage system (HES), and an alkaline fuel cell (AFC). The model was validated using a two-story single-family residence as the case study, with residential load profiles and Xi’an’s climatic conditions considered under real-world scenarios. An adaptive energy management strategy is developed to dynamically coordinate PV utilization, hydrogen dispatch, and grid interaction, while recovering AFC waste heat to enhance overall efficiency. Targeting minimized lifecycle cost (LCC) and levelized cost of energy (LCOE), the GenOpt multi-objective optimization model optimizes key design parameters. Key results show 74.2% annual renewable energy penetration, 68.5% carbon reduction versus conventional systems, and robust seasonal operation: PV dominates summer supply (81.3% self-sufficiency), while AFC compensates in winter (62.4% hydrogen contribution). The system reduces annual grid dependence by 43.7% with a minimum LCOE of ~12.9 USD/MWh, bridging technical feasibility and economic practicality to provide actionable insights for building-scale renewable integration. Full article