Solar Energy最新文献

Volumetric solar thermal receivers are composed of semi-transparent media that are irradiated from the top and absorb solar radiation directly. Previous theoretical studies have suggested that these receivers can capture a high percentage of the incoming energy by eliminating temperature differences between the absorber and the heat transfer fluid. However, the complex interaction between radiation-induced natural convection and volumetric heating which governs the receiver thermofluid behavior has never been experimentally investigated. We present a comprehensive experimental study in which these interactions are investigated from a design perspective. A 6.5 kW solar simulator is installed in a beam-down configuration, and molten nitrate salts are used as base fluids to replicate real-life conditions. Key receiver parameters, namely the fluid absorption coefficient, receiver height, surface emissivity, input flux and heating time are varied experimentally to investigate their influence on operating regime transitions and capture efficiency. Receivers dominated by natural convection are shown to achieve capture efficiencies up to 20 times higher than those dominated by conduction. The ${\chi }^2$ goodness-of-fit test is employed to demonstrate that theoretical predictions regarding the receiver physics are reasonably accurate and existing models can be effectively used for design optimization. Finally, a proof of concept for chloride salts-based high-temperature volumetric receivers is presented. The design insights obtained from the experiments are summarized as design guidelines for future commercial scale-up.

In this study, the efficacy of a single pass, single glazed, five different types of absorber plate incorporated solar air heater (SAH) was experimentally examined in outdoor test conditions on alternative days. The experiment was carried out for flat plate solar air heater (FPSAH) and staggered arranged dimple imprinted absorber plate solar air heater (SDPSAH) maintained at four different pitch ratios (P_t/P_l: 1.0, 1.11, 1.25, and 1.67) by varying the air mass flow rate (m_a) from 0.01-0.05 kg/s (corresponding Re range: 1971.66–10466.45). The results show that the performance of both FPSAH and SDPSAH improves when the m_a increases. For the tested range of m_a, SDPSAH outperforms FPSAH regardless of pitch ratio. SDPSAH, with a pitch ratio of 1.25, on the other hand, has a greater air temperature difference, efficiencies, heat removal factor, collector efficiencies, and averaged Nusselt number (Nu_avg) while having a lower global heat loss coefficient and top loss. The Nu_avg of SDPSAH at a pitch ratio of 1.25 is 1.01–1.17, 1.16–1.24, 1.26–1.57, and 1.44–1.88 times higher than SDPSAH at pitch ratios 1.0, 1.11, 1.67, and FPSAH, respectively. The higher averaged friction factor (f_avg) of 0.0443 is attained for SDPSAH at a pitch ratio of 1.25 due to the presence of the largest number of dimples. The η_th and η_d of SDPSAH at a pitch ratio of 1.25 are 34.5 and 35.5 % higher than those of FPSAH. The global heat loss coefficient of SDPSAH at pitch ratios 1.11, 1.0, and 1.67 is 1.05–1.84, 1.09–2.15, and 1.11–2.92 times higher, respectively, than that of SDPSAH at a pitch ratio of 1.25.

The cooling system of a data center accounts for a significant part of its energy consumption, and the adoption of solar energy can reduce its power demand from the grid. This paper investigated the optimal configuration of a grid-connected PV power supply system to a data center’s centralized water-cooling system. Firstly, mathematical models for photovoltaic panels and storage batteries were established. Then, two operating strategies were proposed, respectively, for two systems with and without storage batteries, and the supply–demand matching performances were studied. With storage batteries, mismatch problem between electricity generated by photovoltaic panels and electricity consumed by the water-cooling system can be significantly improved. Utilization ratio of electricity generated by photovoltaic panels was increased by up to 27.64 % in the discussed typical days. Annual utilization of electricity generated by photovoltaic panels can also be significantly increased, especially when heat dissipation density is small. Lastly, the optimal configurations were discussed. To reduce carbon emission, number of battery groups were recommended for different heat dissipation density and number of photovoltaic panels. Full life-cycle carbon reduction ranged from 1.77 to 3.71 tCO₂/m² and carbon emissions reduced from 14.23 to 62.14 % as compared with the traditional system. As for the economic performance, the recommended number of photovoltaic panels are 798, 1330 and 1589 for heat dissipation density being 500, 800 and 1100 W/m², respectively. While the recommended number of batteries was 0 if unit price of batteries is higher than 11.1 ten thousand yuan/group.

This study discusses solar irradiance variability in the spatial and temporal domains for the active use of solar energy. The spatial domain was calculated using the difference between one location and another in a focused small tile area. The principal component analysis (PCA) was used for this analysis in the spatial and temporal domain. The Umbrella Effect Index (UI) was calculated to determine the probability of an umbrella effect event within a specific time range. This study discusses solar irradiance variability using solar irradiance data analyzed every 10 min from high-temporal observations of geostationary satellites in the Asia-Pacific region. This study shows that solar heterogeneity around the Asia-Pacific ranges from 0–135 W/m² with a high tendency in the area around the equator and highlands. In addition, this study also shows that the Asia Pacific region has umbrella effect events of approximately 50–2224 h/year with an index ranging approximately 0–0.34. This study presents the annual analysis and seasonal trends of solar irradiance variability over the entire study area. Determining seasonal trends is important because electricity demand fluctuates significantly as seasons progress. An integrated analysis of heterogeneity and UI revealed trends in spatiotemporal variations in solar irradiance. This approach provides useful information for optimizing and managing the locations for installing solar power plants. Moreover, an evaluation of existing solar power plants is presented. Evaluations based on spatiotemporal data reveal impossible characteristics using traditional approaches that use long-term simple averages or typical solar irradiance data. This research shows the distributed photovoltaic (PV) system in wide area can increase the stability of solar energy supply to the grid.

Solar photovoltaics (PV) and other clean energy technologies are increasingly being deployed as an environmentally responsible and economic approach to energy system decarbonization. The shift from fossil fuel-centric to material-centric equipment has also shifted the consideration and management of environmental and societal impacts across the technology life cycle. Societal desire to reduce raw material needs, mitigate supply chain social and governance challenges, and take advantage of the reuse and recycling capabilities of materials has enhanced interest in regenerative economic models, called circular economies (CEs). A recent critical review documented that solar PV is on a “path towards increased circularity,” but the need remains to expand activities beyond recycling to a broader set of environmental and policy activities to fully realize the benefits [1,2]. Thus, the goal of this research roadmap is to facilitate and accelerate the transition to a solar PV CE by 1) highlighting current opportunities for PV value chain stakeholders to adopt circular strategies and 2) assessing research and development (R&D) needs that can be addressed in the short term to advance a CE for the solar industry.

The development of remarkably resourceful, effectively phase stable, and highly crystalline-minimal defect perovskite (PVT)-based solar cells (PSCs) is extremely needful for the existing energy requisites. The strategy of incorporating appropriate dopants such as metal cations/anions into inorganic PVT lattices has been recognized as a successful methodology to attain aforesaid PSCs. On that account, this analysis reveals the implication of rubidium (Rb)/ acetate (Ac) (cation/anion) co-doping upon cesium (Cs)-based, bromine (Br)-rich PVT: CsPbIBr₂ against undoped equivalent. The thorough numerical study on recommended structure: FTO/SnO₂/CsPbIBr₂/CuAlO₂/Ag specifying recombination profiles and performance parameters with respect to layer parameters of PVT absorber and charge transport layers conveyed supreme behavior from co-doped devices. It is evidenced that highest efficiency of 16.79 % is accomplished from Rb/Ac co-doped PSC for PVT electron mobility of 25 cm²V^-1s⁻¹. The work reveals the progress in photovoltaic characteristics of inorganic PSCs through the involvement of multi-source co-doping.

In this work, numerical and experimental analyses of a new model of circular solar air heater are carried out to examine the effect of employing vortex flow inside the air vessel of collector for convection enhancement. In three-dimensional numerical CFD-based analysis, the COMSOL Multi-physics is used to solve the flow equations for the turbulent forced convection airflow and conduction equation for the solid parts of the solar heater at different air mass flow rates in the range of 0.003 to 0.012 kg/s. In the calculation of turbulent stresses and heat fluxes, the RNG $\kappa -∊$ turbulence model is employed. The surface to surfaces (S2S) radiation model is used to consider the radiations emitted by the hot surfaces in collaboration with the energy equation. For validation, the theoretical findings are evaluated against the experiment. For the studied test cases with different values of solar irradiation and air mass flow rate, thermal efficiencies of up to 80 % are found. In comparison to the conventional rectangular-shaped solar air heaters with smooth ducts, more than 100 % increase in the value of thermal efficiency is delineated from the theoretical and experimental findings. This gain is attributed to the unique flow pattern in the developed solar collector.

A saline-alkali water distillation system by reflection enhanced solar heating is proposed to treat the saline-alkali soil washing water. In this system, the heat concentration collector employs heat collecting plate to receive solar radiation energy, and converges to small-area steam generating tube through efficiently heat transfer. Without expensive optical tracking equipment, the system also employs an external reflector to reflect the solar radiation to the surface of the heat concentration collector. Thereby the energy flow density is further increased, and the useful energy and vaporization intensity is promoted. The latent heat of the steam is reused by heat recovery to enhance the energy utilization efficiency. The optimal inclination angles of reflector in different seasons and system performance were theoretically calculated. In the spring equinox, summer solstice, autumn equinox, and winter solstice, the optimal inclination angles of the reflector were 30°, 45°, 30°, and 15°, respectively. The freshwater production, useful energy, and heat recovery efficiency of the system were investigated by experiments. The daily freshwater production of the system was 17.04 kg, and the maximum production rate was 3.44 kg/h. The reflector increased the useful energy and freshwater production of the system by 33.68% and 35%, respectively. With heat recovery, the initial temperature of the saline-alkali water was increased to 53.8 °C and the freshwater production was increased by 13.16%.

Passive daytime radiative cooling presents a promising avenue for revolutionizing cooling solutions by reflecting sunlight and radiative heat to outer space without consuming energy. Previous studies often focus on a single temperature scenario, neglecting the complexity of real-world applications in which the target object may have heat sources. Here, we have successfully prepared a Cooling Paint for Multi-Temperature Scenarios (CPMTS) by incorporating nanometer boron nitride into the photocured monomer Tricyclodecane Dimethanol Diacrylate (DCPDA). CPMTS exhibits excellent broadband thermal emittance (∼0.955), reflectance (∼0.778, from 300 nm to 2.5 μm), and thermal conductivity (∼0.51 W m⁻¹ K⁻¹). Notably, it achieves a maximum cooling of 20.1 °C and 8.8 °C under ∼790 W m⁻² and ∼507 W m⁻² of solar irradiation in the absence and presence of a 1 W heat source continuously heating, respectively. Continuous and significant radiative cooling performance has been observed on cloudy days or at night. CPMTS shows excellent radiative cooling performance in practical application scenarios. Excellent ageing resistance, adhesion, stability, and color matching ability make CPMTS expected large-scale application through spray or brush. This research provides a potential solution for cooling in real-world diverse temperature scenarios. The obtained radiative cooling coatings demonstrate scalability and durability in practical applications.

Herein, we employed Density Functional Theory (DFT) to comprehensively investigate pristine γ-CuI properties under two computational schemes: Generalized Gradient Approximation (GGA) and GGA + Hubbard correction. Structural stability is rigorously assessed through ground state energy optimization, complemented by a meticulous examination of elastic constants to confirm mechanical stability. Later on, we analyzed the electronic properties, as well as the optical properties, incorporating parameters such as the extinction coefficient that was low and refractive index that was high in the IR and visible regions. Notably, γ-CuI exhibits low reflectivity and absorption in the critical regions of interest. Our findings demonstrate that γ-CuI can serve as a cost-effective Hole Transporting Material (HTM), effectively reducing optical losses in perovskite solar cells.