Chinese mitten crab (Eriocheir sinensis) is one of the most popular seafoods in Asian areas. However, the shading from the flexible photovoltaic (FPV) arrays can often affect the pond's environmental conditions and its nutritional quality. This study aimed to evaluate the ecological compatibility of the FPV systems with the pond aquaculture. A systematic analysis was also implemented to clarify their impacts on the pond's physical environment, submerged aquatic vegetation, and cultured organisms. Two treatments were conducted, including the ponds equipped with FPV arrays, and the ponds without photovoltaic facilities as a control (CK). The key environmental factors were determined to be induced by FPV shading, including the light intensity, water temperature, and major water quality. The physiological properties of the dominant submerged macrophyte Elodea nuttallii, the biological performance, and nutritional composition of the Chinese mitten crab tissues were quantitatively evaluated in the culture period. The pond experiment showed that the FPV significantly reduced the underwater light intensity and water temperature (P<0.05), compared with the CK, thereby altering the thermal and light regimes of the pond ecosystem. The light and temperature were combined to regulate the FPV shading. The pond water quality (P<0.05) was significantly improved for the more stable aquatic environment. In the upper water layer, the dissolved oxygen concentration increased by 0.7 mg/L in September. While the ammonia nitrogen concentrations decreased by approximately 0.1 mg/L during August and September, the cyanobacterial biomass was significantly suppressed under FPV shading, with the relative inhibition rates of 18.0% in July and 50.4% in September. In the bottom water layer, the ammonia nitrogen concentrations were consistently reduced by about 0.1 mg/L from July to September. The cyanobacterial biomass exhibited stronger suppression, with the relative inhibition rates of 43.0%, 56.7%, and 60.9% from July to September, respectively (P<0.05). As such, the FPV shading effectively alleviated the eutrophication risks, particularly in deeper water layers. The FPV shading also altered the physiological status of Elodea nuttallii, where the accumulation of the reactive oxygen species was reduced to maintain the basal antioxidant enzyme activities. The stress resistance and physiological stability were enhanced under shaded conditions. At the same time, the ecological function of the submerged macrophytes was also supported in pond systems. In terms of the aquaculture performance, no significant differences were observed between FPV and CK treatments in the hepatopancreas index, gonadosomatic index, condition factor, meat yield, or total edible yield for either male or female crabs (P>0.05). There was no negative effect of the FPV installation on the crab growth, reproductive development, or production efficiency. In nutritional quality, the FPV shading induced moderate but sex-specific changes in certain tissues: The ash content in male gonads decreased by 11.5%, the crude protein content in female gonads increased by 3.0%, and the crude protein content in the hepatopancreas increased by 15.8% in males but decreased by 15.7% in females. While no significant differences were detected in the muscle nutritional composition between treatments (P>0.05). The FPV shading triggered the adaptive nutritional regulation in the Chinese mitten crabs, with the responses between sexes and tissues, without compromising overall flesh quality or edible value. Overall, the FPV arrays effectively improved the pond environmental conditions and ecological stability compatible with the Chinese mitten crab pond culture. The finding can also provide important scientific evidence for the ecological application and optimization of the fish-light complementation in freshwater aquaculture.

Photovoltaic Agriculture Systems (PAS) have emerged as an innovative land-use pattern to balance the synergistic "electricity generation aboveground, and crop cultivation belowground", particularly against the rapidly growing global demand for the renewable energy and intensifying pressure on agricultural land resources. The sSolar photovoltaic power generation can be spatially converged with the conventional agricultural production, theoretically enhancing the comprehensive output per unit land area. Significant promise can be intertwined with the global challenges of energy security, agricultural sustainability, and carbon neutrality. However, the dual-use framework can also introduce the complex ecological compromises. Crucially, the photovoltaic panel deployment on agricultural land can inevitably reshape the sub-panel microenvironments. The solar radiation intensity and its spectral redistribution can reach the crop canopy after modifications. Subsequently, the dynamic soil temperature fluctuations can induce after alterations. The photothermal regimes can directly mediate the critical crop physio-ecological processes, including photosynthesis, respiration, nutrient dynamics, water-use efficiency, as well as ultimately govern the yield formation and quality accumulation. Consequently, the photovoltaic panel deployment density—an important parameter to determine the spatial light heterogeneity—can be precisely regulated on the crop microenvironmental dynamics. A pivotal challenge can remainremains to successfully optimize the PAS configurations for the synergistic maximization of the "power generation-yield-quality" multi-objectives. It is often required for the PAS transitioning to transition from the localized pilot demonstrations toward scalable, sustainable implementation. In the present study, a strategically selected PAS demonstration base was employed in Lishui District, Nanjing, China. The knowledge gap was also proposed to concern the photovoltaic arrays’ impacts on the crop microenvironments. A coverage density gradient experiment was then carried out to capitalize on its standardized single-span photovoltaic support structure (6.8 m). Three treatments were set—50%, 75%, and 100% coverage—alongside an open-field control. The microenvironmental heterogeneity was systematically characterized under spatially discontinuous PV arrays. Two discrete micro-zones were defined within each structural span: the inter-panel zone (receiving greater incident radiation) and the under-panel zone (northern shaded area), in the entire growth cycle of sweet potato. The intensive monitoring was precisely tracked on the solar radiation intensity—including Photosynthetically Active Radiation (PAR)—and soil temperature variations across all zones and controls. An environmental profile was generated after monitoring. Key findings demonstrated that there were the significant effects of the deployment density on microenvironments and crop outcomes. The photovoltaic coverage density was reduced the gradient in the radiation intensity, and then moderated soil temperature profiles. Critically, the full coverage (100%) was significantly reduced the tuber yield and tuber number per plant, highlighting the productivity limitations under maximal shading. Conversely, the semi-coverage (50%) was exerted the comparatively minor yield impacts, indicating a pragmatic threshold for the agricultural viability. Nutritional quality exhibited the compensatory adjustments: the higher coverage densities increased the starch and protein content, while there was the a decrease in the soluble sugar content. Moderate shading shared the beneficial influence on the specific quality indices. The context-responsive photovoltaic layout standards were then established to quantitatively map the response relationships between coverage density and crop performance. The framework was investigated to optimize the PAS implementations. The synergistic land-use innovation can also offer the clean energy production with the agricultural sustainability and nutritional output.

Solar greenhouses have been widely developed in China. Active heat storage walls using air ducts arranged in the walls can improve the walls' thermal performance and indoor temperatures of solar greenhouses. In the present work, three kinds of air duct layouts, namely straight-up-and-down duct (Z), fork-shaped top-in- bottom-out distribution duct (DF), and “±”-shaped top-in-side-out distribution duct (CF) are designed. The effect of the three air duct layouts on the heat transfer and storage characteristics of the back wall is studied using the computational fluid dynamics (CFD) method. Results show that after the same time period, the transferred heat amount in the back wall with duct DF is the largest, while that with duct CF is slightly greater than that with duct Z. The temperature of the back walls with air ducts is higher than that without air ducts. The air duct DF is the optimal among the three kinds of air duct layouts. The greenhouse with the duct DF in the back wall shows the most obviously increased indoor average temperature, the highest temperature at night, and the most uniform temperature.

An agrivoltaic system has been one of the most promising potential sources of clean energy power in green agriculture. Some guidelines have been released to fully meet the requirement of the photovoltaic (PV) modules in agricultural projects. Particularly, it is the high demand for land utilization and mechanization of agricultural production in agrivoltaic systems, such as in Jiangsu and Yunnan provinces in China. Among them, the minimum installation height of PV modules has been standardized to maintain a specific tilt angle. However, the "prioritizing light over agriculture" can often occur during actual production. A large number of PV panels are typically installed on agricultural land in order to ensure the PV power generation in agrivoltaic projects. Furthermore, these PV panels can block the sunlight to form a considerable shading area on agricultural land during the day. This study aims to investigate the effects of shading from PV modules on the internal light environment, shading width, crop yield, and leaf photosynthetic characteristics in the agrivoltaic system. A series of tests were conducted on the agrivoltaic systems at the module installation heights (the vertical distance from the ground to the lower edge of the PV module) of 2.5, 3.2, and 3.9 m in Nanjing City. A systematic measurement was performed on the solar radiation intensity of the planting area under and between the panels inside the PV agricultural system. A quantitative analysis was implemented to calculate the annual variation patterns of the shading width formed by the PV panels. Additionally, there were significant differences in the yield and leaf photosynthetic characteristics of figs (Ficus carica L.) in the planted areas between the modules. The results indicated that the daylighting rate in the planted areas between the panels ranged from 55.4% to 68.9% during the testing period, which was 2.1 to 3.3 times that of the area under the panels. Specifically, the daylighting rate in the areas between the panels decreased at the three heights of PV module installation as the installation height increased, while the area under the panels showed the opposite trend. The shading width caused by the PV modules also increased with latitude and installation height throughout the entire growth period of the figs. Shading from the PV panels led to a reduction in average yield across treatments compared to the CK control, ranging from 19.9% to 48.9%. Additionally, the photosynthetic characteristics of the leaves effectively reflected the yield differences among treatments. A lower installation height of the PV panels can significantly enhance the net photosynthetic rate and stomatal conductance of fig leaves, thereby alleviating the photosynthetic suppression caused by shading. In summary, compared to agrivoltaic systems with panel heights of 3.2 m and 3.9 m, the system with a panel height of 2.5 m offered a better internal light environment and shorter shading width, effectively reducing the decline in fig yield and demonstrating practical value for photovoltaic agricultural projects in various regions.