Status of Photovoltaic Power Technology

The status of photovoltaic power technology is reviewed primarily from the viewpoint of current and future applications of the technology to the exploration and utilization of space. The photovoltaic solar cell has been the electric power workhorse throughout the first decade of the space age. The technology has shown steady improvement in reliability, increased efficiency, reduced cost, increased power per unit of hardware weight and ability to withstand extremes of the space environment. New developments are underway to increase solar cell and array size, to reduce stowage volume during boosting into orbit and to improve resistance to space radiation and thermal cycling. Silicon cell electrical contacts and interconnections, low energy proton damage to small exposed cell areas and instability of CdS thin film solar cells are examples of problems receiving attention at this time. The ongoing development of large, 2500–3000 ft², solar cell arrays to power the planned Apollo Applications Telescope/Workshop Cluster demonstrates the growing confidence in the ability of photovoltaic power to handle space missions of the future. As photovoltaic technology advances and economic conditions change, the solar cell may well find large scale terrestrial markets.