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International Space Station’s Solar Panels Have a No-Fail Mission

Powering a scientific laboratory solely by solar-energy is no-easy task for any facility on Earth. This one is in outer space. And lives depend on it to never fail.

The challenge to power the International Space Station solely by solar array fell to the design team for the craft, a task that came with added burden of knowing that the lives of the crew depended on their success in delivering enough energy to power the laboratory experiments and life support system.

When Space Shuttle Discovery docked with the ISS in May of 2009, the final piece of the long awaited solar panel array had finally reached the station. Each of the eight panels affixed to the station measure 115 feet in length and the whole array covers an acre when placed side-by-side. The delicate nature of the solar array has lead to numerous construction delays as the panels adjust to the environment of space, requiring emergency spacewalks via shuttle crews on two different occasions.

The panels that cover the solar array wings (SAWs) are draped in photovoltaic solar cells capable of delivering a constant DC voltage of 160V per array, that is necessary to power the numerous components of the laboratory equipment, navigational controls and life-support system. Photovoltaic cells are special materials capable of transferring light to energy at an atomic level, a phenomenon first discovered by French physicist, Edmund Bequerel, in 1839.

The millions of solar cells embedded in each array capture 24 kW, an efficiency rate of 14%-statistic on par with the leading industry standard when they were first produced.

Voltage captured by the solar cells is transported down the central shaft of the array into a Sequential Shaft Unit (SSU) that maintains the collected voltage at a steady rate. The power is then sent from the SSU to a set of Nickel-Batteries needed that store power and deliver energy whenever the panels are not in direct sunlight. As the station is upgraded, the batteries will be replaced by a Lithium-ion version similar to the power sources commonly found in laptops, smartphones and tablets. The remaining voltage is passed onto a Main Bus Switching Unit that feeds the power into the station’s main power grid and on to the various pieces of equipment and controls.

The unobstructed view of the Sun provides certain advantages and each of the arrays is equipped with a light sensitive Beta Gimbal that adjusts the angle of the array to achieve the maximum possible exposure to sunlight based on the Sun’s relative position to the Earth depending on the season. Although fragile by nature and design, the solar arrays provide ample power to a station far, far away from any terrestrial power grid.

Jason Taetsch is a freelance content writer with experience in tech writing, blogs, travel writing, pop culture and a range of promotional materials. Jason blogs via

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