Application Advantages of Bifacial Photovoltaic Array on Stratospheric Airship Based on Power-to-Areal-Density Ratio

Stratospheric airships utilize lighter-than-air gas to provide lift, and as a result, airships are generally large in size to meet load capacity requirements. The capacity of an energy system is limited by the energy conversion efficiency of conventional solar cells, thus requiring the laying of a large-scale photovoltaic (PV) array. The large installation area of the PV array not only intensifies the challenges in weight but also faces the problems of current mismatch due to the influence of the curvature of the envelope on irradiation. Bifacial solar cells have great potential for solar-powered aircraft due to their double-sided power generation characteristics. This article innovatively proposes the application of bifacial solar cells on stratospheric airships and analyzes the benefits of bifacial cells in reducing weight and increasing efficiency of energy systems. The rear irradiance and electrical models for bifacial modules are established. Outdoor experiments have demonstrated the feasibility and accuracy of proposed models. The bifacial and monofacial total-cross-tied array outputs of the airship were simulated at different latitudes, seasons, and flight directions. The results show that under the conditions set in this study, the maximum bifacial energy gain of the array is 3.91% and the minimum is 1.39% . The concept of a power-to-areal-density ratio was proposed to evaluate the contribution of bifacial cells to increasing array output and reducing weight. By reducing the cell quantity and increasingthecellgapwidthwhilekeepingthemodulesizeunchanged, the power-to-areal-density ratio of a single module increased from 0.37289 to 0.37926 kW/(kg/m²), which not only maintains the output power at the original level or above but also reduces the weight and improves the utilization efficiency of the bifacial modules.