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The stratospheric airship is a type of aerostat that uses solar energy as its power source and can fly continuously for months or even years in near space. The rapid and accurate prediction of the output power of its solar array is the key to maintaining energy balance and extending flight time. This paper establishes an online learning model for predicting the output power of the solar array of stratospheric airships. The readings of radiometers arranged on the surface of the airship are used as features for training the model. The parameters of the model can be updated in real-time during the flight process without retraining the entire model. The effect of radiometer placement on the model accuracy was also analyzed. The results show that for the continuous flight of 40 days, the online learning model can achieve an accuracy of 88% after training with 10 days of flight data and the accuracy basically reaches its highest level after 20 days. In addition, placing the radiometers at the four corners of the array can achieve a higher prediction accuracy of 95%. The online model can also accurately identify and reflect the effect of module efficiency attenuation or damage and maintain high accuracy. [ABSTRACT FROM AUTHOR]

Solar array is essential for converting sunlight energy to electricity and ensure normal operation of propellers, payloads and avionics of stratospheric airship. Apart from electrical energy, excess solar irradiation is transformed to heat load on the airship, seriously affecting the pressure balance and structural integrity. However, the investigation of insulation layers between solar cells and airship film are rare. This paper aims to maximize the output energy of solar array through optimizing the configuration of insulation layers. The energy model and heat transfer model are established. Based on the theoretical model, the influence of insulation parameters on the output energy of solar array and differential pressure are studied. The energy acquirement and differential pressure have negligible change when increasing the thermal conductivity and thickness of insulation substrate in the same proportion. The thermal impedance as the ratio of thickness to thermal conductivity is firstly adopted to describe the configuration of insulation structure. The optimal thermal impedance can be obtained based on flight missions considering airspeeds, latitudes and dates. The output energy can be maximized while keeping the differential pressure within limited range with the optimal thermal impedance. The result provides a conducive reference for the preparation of solar powered airship. [ABSTRACT FROM AUTHOR]

Stratospheric airships with a solar array have demonstrated overwhelming superiority in many aspects, such as earth observation, meteorological survey, and communication relay. The solar array supplies sufficient power for the airship to be in flight for months, but excessive heat is also transferred to the airship, causing high overpressure of inner gas. However, the optimal arrangement of the insulation layer on the airship has not been investigated. The theoretical method, including the geometry, thermal, and energy models, is developed and validated. The distribution of the temperatures and power of the solar cells, with different installation angles on the curved surface, is investigated. The thickness of insulation layer has a significant effect on the solar output power and internal pressure of the airship. An optimized configuration of the insulation structure is proposed, in order to improve the total output energy of solar array. The optimized configuration of insulations helps to reduce the structural mass by 24.9% and increase the payload mass by 9%. Moreover, the optimized arrangement improves the output energy of solar array in a year, and the maximum improvement is 8.2% on the winter solstice. The work displays the optimization of the thermal insulation layer for the stratospheric airship with a solar array, in order to improve the everyday energy acquirement during flight in a year. [ABSTRACT FROM AUTHOR]

Abstract High-altitude solar powered scientific balloon can be powered by thin-film solar panel mounted on the balloon. The temperature change of solar panel might have significant influence on the thermal performance of the balloon, which is closely related to the superheat and overpressure of balloon. The thermal model of solar powered scientific balloon was presented to investigate the thermal performance and compare with unpowered balloon. A user define function program in computational fluid dynamic software was developed based on the model. The effects of layout parameter and area of solar panel on the thermal performance of solar powered balloon were also analyzed. The results show that the temperature of envelope and internal helium of solar powered balloon is much higher than that of unpowered balloon during the daylight, and the maximum velocity of internal helium is decreased with the existence of solar panel. Moreover, the increase of the height and area of solar panel would result the raise of temperature and pressure of internal Helium, but the helium velocity and the flow distribution were hardly changed. The present work may be used to guide the design of solar energy system and the thermal control of scientific balloon. Highlights • The thermal performance of high-altitude solar powered scientific balloon is initially analyzed. • The effects of the layout parameter and area of solar panel on the thermal performance of balloon are studied. • A UDF program in CFD software is developed based on the thermal model of scientific balloon. • The superheat/overpressure of high-altitude balloon may be exacerbated with the existence of solar panel. [ABSTRACT FROM AUTHOR]

The solar array layout is one of the critical factors affecting the output performance of a solar array on a stratospheric airship. Optimizing the layout to improve output energy per day is very important for a long endurance vehicle, but the research about this subject is rare. This paper outlines a numerical method based on a rotating model of a stratospheric airship to optimize the solar array layout. Combined with the solar radiation model, the solar array layout optimization model applying genetic algorithm is developed using a MATLAB computer program in this paper. Compared with the design parameters of three stratospheric solar-powered airships, the theoretical model is proved to be feasible. In the course of the study, the effects of the starting point and the central angle of solar array are discussed in detail. In addition, the optimal results of the solar array layout for four common situations are investigated using the method. The results indicate that this method is helpful in the preparation stage for installing large area flexible solar arrays. [ABSTRACT FROM AUTHOR]

Solar energy is a key factor for high altitude airships to achieve long endurance flight. In order to receive more solar energy and improve the endurance performance of airships, this paper presents a multidisciplinary design methodology to obtain an optimal configuration of the high altitude airship considering the energy optimization. First, a parameterized shape of the airship is proposed and the aerodynamic characteristics are obtained and integrated through a kriging model. Then the solar radiation and photovoltaic (PV) array models are introduced and validated by a ground experiment. After elaborating the structure, propulsion and energy subsystems, an external-internal loop optimization process is carried out to minimize the total weight considering the maximum solar power from PV array. The result of the multidisciplinary design shows an obvious increase on the received solar energy to 3.36 GJ compared with 0.45 GJ for the traditional design, which has a great potential to save the weight of the PV array laid on the airship surface. Further, the effects of the latitudes, dates and wind conditions on airship endurance performance are analyzed and in order to achieve long endurance flight, an adaptability discussion is carried out through a multi-objective optimization process. The result indicates that the improved design has a higher adaptability ratio in different environments compared with the single input design. It suggests that an adaptability design of high altitude airships might be an effective approach in airship engineering applications. [ABSTRACT FROM AUTHOR]

The increasing application of hybrid airships which have been recently proposed as high altitude platforms, makes it necessary for research into the thermal performance of such airships that possess a photovoltaic module array(PVMA). In this study, a simplified thermal model of a high-altitude hybrid airship with a PVMA, was proposed that included direct solar, infrared, reflected, and scattered radiation and convective heat transfer. Based on computational fluid dynamics(CFD), a simulation methodology, using a user defined function(UDF) program, was introduced to investigate the PVMA's thermal effects on the hybrid airship. A ground experiment was also performed to validate this numerical method's effectiveness. Further simulations and discussion of temperature and velocity distributions of the hybrid airship's internal helium were conducted. The results showed that the PVMA atop the hull had large effects on the hybrid airship's thermal performance. The temperature distribution of the envelope varied greatly during the day and night because of the PVMA's influence as well as the internal helium flow. In addition, forced convection had little influence on the PVMA's output performance, which was analyzed in detail. [ABSTRACT FROM AUTHOR]

The high altitude solar-powered airships have been proposed for use as long endurance platforms, for a variety of military and civilian applications. The challenges of perpetual endurance flight require the airship to generate sufficient power over a wide range of operational latitudes so that the aerial vehicle can keep station through high wind events and maintain persistence. This paper provides a theoretical approach to analyzing the perpetual endurance performance of a high altitude solar-powered airship. According to the features of stratospheric airship and the theoretical model, a custom tool is developed using MATLAB computer program when the airship operates in the cruise condition. The effects of the operational latitudes, wind velocities and solar array areas on the energy ratio are numerically investigated in detail, and the required areas of solar array under the conditions of different minimum energy ratio were discussed. The results showed that the solar-powered airships faced severe operational limitations at high latitudes in the winter, especially in the high wind. In addition, a case study was analyzed to demonstrate the effectiveness of this approach to predicting the perpetual endurance region. The results demonstrated that the theoretical approach suggested a pathway towards planning the flight date and location for an airship. [ABSTRACT FROM AUTHOR]

This paper aims to develop a high-altitude solar-powered hybrid airship, which combines aerodynamic lift and buoyancy with buoyancy force and cruises continuously. A multi-lobed configuration is employed and the solar irradiance and photovoltaic array model are proposed. After introducing all the parts mass of the hybrid airship and design procedure, an optimal problem with the constraint of energy and the equilibrium between buoyancy and weight are proposed. Through a hybrid optimization search method, the solution is obtained and the sensitivities of geographical location and seasons are discussed. The results show a comprehensive influence of the constraint both in latitude and wind field environment. [ABSTRACT FROM AUTHOR]