Primary and Albedo Solar Energy Sources for High Altitude Persistent Air Vehicle Operation

Abstract

Abstract:A new class of the all electric airship to globally transport both passengers and freight using a 'feeder-cruiser' concept, and powered by renewable electric energy, is considered. Specific focus is given to photo-electric harvesting as the primary energy source and the associated hydrogen-based energy storage systems. Furthermore, it is shown that the total PV output may be significantly increased by utilising cloud albedo effects. Appropriate power architectures and energy audits required for life support, and the propulsion and ancillary loads to support the continuous daily operation of the primary airship (cruiser) at stratospheric altitudes (circa 18 km), are also considered. The presented solution is substantially different from those of conventional aircraft due to the airship size and the inherent requirement to harvest and store sufficient energy during "daylight" operation, when subject to varying seasonal conditions and latitudes, to ensure its safe and continued operation during the corresponding varying "dark hours". This is particularly apparent when the sizing of the proposed electrolyser is considered, as its size and mass increase nonlinearly with decreasing day-night duty. As such, a Unitized Regenerative Fuel Cell is proposed. For the first time the study also discusses the potential benefits of integrating the photo-voltaic cells into airship canopy structures utilising TENSAIRITY ® -based elements in order to eliminate the requirements for separate inter-PV array wiring and the transport of low pressure hydrogen between fuel cells.

On the capabilities and limitations of high altitude pseudo-satellites

“…Following [132], almost 30% of the total incoming radiation is reflected by the clouds (22%), atmosphere (6%) and Earth surface (2.3%). As is described in [124], the cloud albedo depends on the geographic localization in which the measure is made. The cloud concentrations are higher in Northern Europe and the Northern Atlantic (60-80% cover); the opposite is found in regions such as Australia, Central…”

“…Pacific and North Africa. It also depends on the type of clouds, having in ascending order of reflectivity [124]: High types such as cirrus, cirrostratus and cirrocumulus (20%), medium clouds like altocumulus and altostratus (40-56%), low clouds as nimbostratus, stratocumulus and cumulus (60-70%) and cumulonimbus (78-90%).…”

Estudio del sistema motopropulsivo para Pseudo-satélites = Design of the propulsion system for High Altitude Pseudo-Satellites

“…Según datos de Trenberth [41], casi el 30 % de la energía solar que llega a la Tierra es reflejada por las nubes -22 %-, la atmósfera -6 %-y la superficie terrestre -2.3 %. El albedo [42] depende en gran medida de la localización geográfica en la que nos encontremos, junto con la concentración de nubes y el tipo de las mismas. Esta concentración es mayor en el norte de Europa y del océano Atlántico -60-80 %-, mientras que el mínimo se encuentra en regiones como Australia, el Pacífico Central y el Norte deÁfrica.…”

“…No todos los tipos de nubes reflejan lo mismo: clasificándolas de menor a mayor indice de reflectancia [42], tenemos: nubes altas como los cirros, cirroestratos y cirrocumulos -20 %-, nubes de altitud media como altocúmulos y altoestratos -40-56 %-, y bajas nubes como nimboestratos, estratocúmulos, cúmulos -60-70 %-y los cumulonimbos -78-90 %-.…”

“…Dependiendo de la altitud de operación en la estratosfera, el ambiente radiativo hostil puede hacer obligatorio el uso de materiales compatibles que toleren los rayos ultravioletas, el ozono y los gradientes térmicos existentes [42].…”