Development and Testing of New Thin-Film Solar Cell (TFSC) Technology: Flight Results from the AlSAT-1N TFSC Payload

The increasing power demands of spacecraft payloads, and the future prospect of space based solar photovoltaic (PV) power stations, mean that there is an emerging requirement for large area solar arrays that will provide far greater power (kWpeak) than is currently available. To be practical, such arrays will need to use solar cells which have a much higher specific power (i.e. power per unit mass) and a much lower cost per watt than current space-rated solar PV technologies. To this end, the Centre for Solar Energy Research (CSER) at Swansea University, the Surrey Space Centre (SSC) and the Department for Mechanical Sciences at the University of Surrey, have been working on a new solar cell technology, based on thin film cadmium telluride (CdTe), deposited directly onto ultra-thin space qualified cover glass. This offers a potentially high specific power, low-cost technology with the added benefit of allowing a high degree of solar array flexibility for improved stowage volume and novel deployment strategies. Cells based on this innovative solar cell architecture have been manufactured and tested under a three year UK Engineering and Physical Science Research Council (EPSRC) funded project, with the result that highly efficient (for their class) cells were produced, which passed mechanical, thermal and ionising radiation tests with great success. Whilst this work was in progress, an opportunity to fly test cells on the joint Algerian Space Agency – UK Space Agency AlSat-1N Technology Demonstration CubeSat arose, and a successful bid was made to fly a payload capable of characterising the cells in orbit, via an automatic Current-Voltage (I-V) measurement circuit. The resulting Thin Film Solar Cell (TFSC) payload, comprising four test cells, was integrated onto AlSat-1N at Surrey, and launched from India into a 661 km × 700 km, 98.20° Sun Synchronous orbit on 26th September 2016. This paper describes the new cell technology, the pre-flight ground testing, the flight payload, and the first flight results of thin film CdTe solar cells flying on an international 3U CubeSat technology demonstrator. Keywords: (Thin-Film Solar Cells, CubeSat, Technology Demonstration)