Integrated thin-film solar power system

The need for small and lightweight modular power systems is growing rapidly as the space science community continues to move toward smaller and less costly spacecraft (e.g., nanosatellites). Thus the use of lightweight thin-film photovoltaic solar cell arrays for power generation is an attractive possibility. Thin-film lithium ion energy storage with its large power densities and long cycling lifetimes should also prove a valuable resource. The authors have been developing a thin-film device capable of both solar energy conversion and storage. This device combines a thin-film lithium polymer battery with a thin-film solar cell. In a typical satellite application, the solar cell would be used to provide power for the spacecraft and charge the battery during the illuminated portion of the orbit. The battery would then provide the necessary “stay-alive” power for the satellite when in eclipse. The deposition techniques the authors have been using to deposit the component films of this device are inherently scalable. Sectioning the solar cells, varying the series and parallel combinations of the batteries, and adjusting the overall size of the device can be used to fulfill a wide variety of power requirements. The authors discuss the device design and the electrical properties of the component films. The output of the thin-film solar cell under an AMO illumination and the cycling characteristics of the thin-film battery under a low-Earth orbit or LEO (e.g., 55 min. Illumination, 35 min. Eclipse) timing sequence will be presented