Anthony J. Colozza

Design of a GaAs/Ge solar array for unmanned aerial vehicles

Unmanned aerial vehicles (UAV) are being proposed for many applications including surveillance, mapping and atmospheric studies. These applications require a lightweight, low speed, medium to long duration airplane. Due to the weight, speed, and altitude constraints imposed on such aircraft, solar array generated electric power is a viable alternative to air-breathing engines. Development of such aircraft is being funded under the Environmental Research Aircraft and Sensor Technology (ERAST) program. NASA Lewis Research Center (LeRC) is building a solar electric airplane to demonstrate UAV technology. This aircraft utilizes high efficiency Applied Solar Energy Corporation (ASEC) GaAs/Ge space solar calls. The cells have been provided by the Air Force through the ManTech Office. Expected completion of the plane is early 1995, with the airplane undergoing flight testing using battery power.

Evaluation of Convective Array Cooling for a Solar Powered Aircraft

A general characteristic of photovoltaics is that they increase in efficiency as their operating temperature decreases. Based on this principal, the ability to increase a solar aircrafts performance by cooling the solar cells was examined. The solar cells were cooled by channeling some air underneath the cells and providing a convective cooling path to the back side of the array. A full energy balance and flow analysis of the air within the cooling passage was performed. The analysis was first performed on a preliminary level to estimate the benefits of the cooling passage. This analysis established a clear benefit to the cooling passage. Based on these results a more detailed analysis was performed. From this cell temperatures were calculated and array output power throughout a day period were determined with and without the cooling passage. The results showed that if the flow through the cooling passage remained laminar then the benefit in increased output power more than offset the drag induced by the cooling passage.

Development and operation of a photovoltaic power system for use at remote Antarctic sites

A photovoltaic power system, designed and built at the NASA Lewis Research Center, has successfully operated over for two summer seasons at a remote site in Antarctica, providing utility-type power for a six-person field team. The system was installed at the Lake Hoare site for approximately five weeks during late 1992, put into storage for the Antarctic winter, and then used again during the 1993 season. The photovoltaic power system consists of three silicon photovoltaic sub-arrays delivering a total of 1.5 kWe peak power, three lead-acid gel battery modules supplying 2.4 kWh, and an electrical distribution system which delivers 120 Vac and 12 Vdc to the user. The system worked extremely well in providing quiet, reliable power. The experience gained from early system demonstrations such as this should be beneficial in accelerating the transition toward future PV systems in Antarctica and other similar areas.