Alta Devices’ record-setting solar cell has just begun a one-year test by NASA in the latest Materials International Space Station Experiment (MISSE-X) flight investigation, launched in November on board the NG CRS-10 mission. NASA is testing Alta Devices solar technology at the Space Station in order to evaluate the technology for future NASA low-Earth orbit missions, including powering CubeSats, a trending, small, inexpensive satellite design.
The goal of the MISSE-X test is to evaluate new solar cell and package technologies in support of future NASA missions requiring solar cells with high efficiency, high packing density, and very low mass, the agency says. After one year of exposure, the solar cells will be returned to NASA and Alta Devices for evaluation, the company says.
NASA and Alta Devices have developed scientific models to simulate how the solar cells may be affected by their on-orbit exposure, and the final sample evaluation will allow the teams to refine their models, enhancing the accuracy of predictions related to solar cell and package performance in future, longer missions, the company says.
The High Efficiency, Low-Mass Solar Cell Systems experiment with the Alta Device cells “exposes candidate solar cells to the space environment. In addition, thin polymeric films, developed as cover slide materials for these solar cells, are exposed as separate samples, to measure atomic oxygen erosion yield and transmission changes due to ultraviolet radiation. The test results will be especially important for the design of small but highly capable spacecraft needed to explore our solar system,” NASA says.
Since 2001, NASA’s MISSE series has tested some 4,000 material samples and specimens — from lubricants and paints to fabrics, container seals and solar cell technologies — to demonstrate their durability in the punishing space environment, NASA says.
Flown 220 miles above Earth, fixed to the exterior of the International Space Station for periods of up to four years, these innovative experiments endured extreme levels of solar and charged-particle radiation, atomic oxygen, hard vacuum, temperature extremes and contamination, giving researchers unprecedented insight into developing durable materials for spacecraft, flight hardware and even astronaut clothing, NASA explains.
Alta Devices set a new 29.1% solar efficiency record in November with its single junction gallium arsenide solar cells in a test with analytics lab Fraunhofer ISE CalLab, in Germany. This is the seventh consecutive time, dating back to 2010, that Alta Devices has achieved this record, and the milestone is the thirteenth cell or module solar efficiency world record achieved by Alta Devices, the Sunnyvale-based company says.
Alta Devices CEO Jian Ding, commented on December 12 that, “NASA’s interest in Alta’s record-setting performance demonstrates that our technology withstands some of the most challenging environments endured by autonomous systems in space, high altitude, and on land. Our continued commitment to innovation enables Alta to remain an industry leader in producing state-of-the-art lightweight, flexible, and highly efficient solar cells.”
The record cell technology is based on Gallium arsenide, which has several unique characteristics including high efficiency, excellent UV and radiation resistance, flexibility, and low weight. Alta chose to focus on gallium arsenide because of its intrinsic efficiency advantages, as well as its ability to generate electricity at high temperatures and in low light, the company says. “With its latest record-setting conversion efficiency, Alta’s gallium arsenide solar technology is ideally suited to powering products that need autonomous power such as small satellites, unmanned aerial vehicles (UAVs), and autonomous vehicles,” the company asserts.
Traditional silicon and Gallium arsenide (GaAs) solar cells both are relatively expensive to produce. To avoid this cost, Alta invented a manufacturing technique that develops extremely thin layers of GaAs about one micron thick; for comparison, a human hair is approximately 40 microns thick. This technology can offer power to weight ratios exceeding 1 kW/kg, the company says.
“By utilizing a very thin layer of material with the highest energy density possible, the amount of material needed is low. Therefore potential system costs can be dramatically reduced,” the company adds. “Whether it’s coiled carbon fiber booms, flat-packed, polymer-based accordion arrays, or even inflatable structures, our solar technology allows creative design approaches for maximizing power,” Alta concludes.
Alta Devices recently launched its Gen4 AnyLight solar technology, a fourth-generation technology resulted in a 160% upgrade in power-to-weight ratio over its third-generation technology.