We had not yet set foot on the Moon when American engineer Peter Glaser proposed launching solar panels into space. The idea was brilliant: photovoltaic panels would capture the Sun’s energy uninterrupted by clouds and send it back to Earth in the form of microwaves. Glaser died in 2014, but his idea persists and we are closer to making it a reality.
Commercially viable solar farms in space. Producing lightweight, low-cost solar panels that can generate power in space for years is possible, according to new research from the Universities of Surrey and Swansea in the United Kingdom.
The researchers came to this conclusion after analyzing the results of an experiment that, although designed to last for one year, has been operating for seven years aboard a small satellite in Earth orbit. The findings, published in the journal Acta Astronautica, could pave the way for creating commercially viable solar farms in space.
38,000 test orbits. In the first study of its kind, the researchers placed thin photovoltaic cells called Thin-Film Solar Cell (TFSC) aboard the British satellite AlSat-1N. The experiment was launched into space in sun-synchronous orbit on September 26, 2016, and has been generating power ever since. More importantly, the thin photovoltaic film has withstood solar radiation and the harsh thermal conditions of the vacuum after 38,000 revolutions around the Earth.
“We are very pleased that a mission designed to last one year is still working after six,” said Craig Underwood, lead author of the study, in a University of Surrey press release. “These detailed data show that the panels have withstood radiation and their thin-film structure has not deteriorated in the harsh thermal and vacuum conditions of space.”
Technology. On the one hand, researchers at Swansea University’s Solar Energy Research Center developed a very thin photovoltaic film from cadmium telluride. Such films cover a larger area, are lighter and more flexible, and have a significantly lower cost per watt than current photovoltaic cells, making them capable of generating more power with a lower initial investment.
Four prototypes of these films were launched into space aboard the AlSat-1N satellite, a collaboration between the Algerian Space Agency and the UK Space Agency. The films were deposited directly onto ultrathin glass designed to withstand space. Scientists at the University of Surrey were responsible for designing the instruments that would measure the solar panel’s performance in orbit.
Exceeding expectations. The four cells demonstrated sustained light-harvesting performance. Their peak output was 16 mW at a solar flux of 124.2 mW per square centimeter and at a temperature of 10 ºC, an efficiency of 13%. Then that efficiency dropped to 8% due to a decrease in cell filling, which the researchers attributed to the scattering of gold atoms from the rear electrical contacts.
The most important fact, the researchers insist, is that the cells demonstrated exceptional resistance to ionizing radiation, making them ideal for long-duration missions in space. The cells remain operational with no signs of delamination or significant deterioration, and the data collected show high mechanical and thermal robustness.
A low-cost option. Not only because these films are more efficient than other technologies, but also because they are very flexible and lightweight, making them easy to transport into space and reducing the cost of launch.
“This ultra-low mass solar cell technology could lead to the deployment of large, low-cost solar power stations in space to bring clean energy back to Earth, and we now have the first evidence that the technology works reliably in orbit,” Underwood said.
An opportunity to be exploited. Although power production from the cells in this experiment became less efficient over time, the researchers believe their findings prove that solar-powered satellites work and could be commercially viable. “There is no technological barrier with the right market incentive,” say the study authors.
The most obvious advantage of solar farms in space is that there are no clouds: satellites spend more time in sunlight. Another advantage that cannot be overlooked is that terrestrial solar panels have to be cleaned, which entails maintenance costs and water consumption that can be enormous depending on the size of the installation.
As the growing demand for space launches and the growing demand for power converge, these promising advances in space-targeted solar cell technology destined for space such as this seem to come at just the right time. However, there are still problems to be solved to make Peter Glaser’s idea a reality.