Solar technology, be it residential or commercial, is a common sight across the United States. The distinctive blue and black panels, prominently adorning rooftops across states such as California, New York, and Massachusetts, are instantly recognizable.
However, the subject of space-based solar technology remains an enigma to many, even to those well-versed with its terrestrial counterparts. So, let's delve into the nuances of space-based solar and how it stands apart from the traditional solar technology we're familiar with.
Harnessing Solar Energy in Outer Space
First introduced aboard the Vanguard 1 satellite launched by the U.S. in 1958, solar technology has since undergone significant advancements to cater to the harsh space environment.
The Vanguard 1 Satellite, with its petite photovoltaic cells
The usual monocrystalline or polycrystalline solar panels utilized in residential and commercial premises lack the durability to withstand space's extreme conditions – intense heat and cold, incessant solar radiation. Consequently, the solar technology employed in space exhibits unique features that set it apart from conventional panels.
The Significance of Solar Power for Satellites
The smooth operation of spacecraft and satellites necessitates a substantial amount of energy. Before solar emerged as a feasible power source, batteries served this purpose. But their limitations lay in their finite capacity and the absence of a reliable recharge system, rendering them ineffective once drained.
Pairing solar panels with batteries proved to be an advantageous alternative, supplying a steady flow of renewable energy. Today, solar power energizes the computer and monitoring systems integral to the spacecraft's operation. The ultimate objective, however, is to leverage solar energy for spacecraft propulsion, thereby reducing or eliminating the need for other fuels – a breakthrough that could revolutionize space travel.
The Solar Tech Utilized in Spacecraft
Two types of solar cells are predominantly used in spacecraft:
- Silicon cells encased in thin glass, and
- Multi-junction cells composed of gallium arsenide and other analogous materials.
Silicon cells encapsulated in glass mirror conventional solar panels but feature enhancements to withstand radiation and extreme temperatures. A prime example of this panel type is the International Space Station, which houses the majority of space-based solar panels.
Solar cells composed of gallium arsenide offer superior efficiency, making them the preferred choice when space constraints exist. These panels can achieve efficiency levels around 34%, considerably higher than the 15-20% efficiency of most commercial solar panels.
The Dawn Satellite, equipped with high-efficiency gallium arsenide panels
Furthermore, many space satellites are equipped with solar panels that can track the sun's path, maximizing sunlight absorption. The sun's rays in space are more abundant than on Earth, as there is no atmospheric interference. Approximately 55-60% of solar energy gets reflected or absorbed as it travels through Earth's atmospheric layers of clouds, gases, and dust.
Additionally, the solar panels used in most space satellites feature a folding structure, enabling the panels to expand once the spacecraft is in orbit, a design also used in the International Space Station.
Interestingly, the solar panels in space bypass the need to convert DC electricity into AC, a conversion necessary on Earth because our electronics operate on AC power. However, space-based satellites and spacecraft, not requiring power transmission over large distances, can operate on DC power, reducing the hardware requirements for these systems.
Durable and Efficient – The Hallmarks of Space Solar Tech
While there are many similarities between space-based and terrestrial solar panels - such as the inclusion of conductive material, typically silicon, arranged into arrays - the significant distinction lies in their quality and durability.
Space-bound solar panels must endure intense heat, cold, and radiation, influencing the overall design and build of the hardware. NASA continues to experiment with different semiconductor materials to produce superior solar cells suitable for space. Gallium arsenide is one such example, paving the way for future innovation in space solar technology.