|
|
| Fig. 1: International space Station. The solar arrays shine brightly as they receive sunlight. [2] (Courtesy of NASA) |
The International Space Station (ISS), orbiting the Earth at an altitude of around 400 kilometers, serves as humanity's only space outpost. Launched in 1998, with an investment of $150 billion to manufacture, the station has provided a crucial platform for humans to experiment with space. The station allows the understanding of the physical and psychological effects of long-term space travel which will be necessary to know when planning for future missions to the Moon and Mars. At its core, the ISS is a colossal research station, spanning over 100 meters, and has many electronics aboard that must be powered. With resupply missions only every 3 months, the ISS takes advantage of renewable energy sources it can harness from the Sun.
The ISS derives its energy from the Sun. The ISS employs autonomous power functions such as an array pointing algorithm to track the sun over orbit. This allows the station to optimize its orientation at all times to maximize the amount of sunlight being absorbed.
The station orbits Earth every 90 minutes, spending 45 minutes in sunlight and 45 minutes in darkness. This allows a consistent source of power from the sun, which supports the ISS continuously. Additionally, sunlight is unobstructed - there are no atmospheric or weather conditions such as clouds that can block the sun from the ISS's solar panels. The prominent solar arrays can be seen in Fig. 1.
The ISS energy power system aboard the ISS has both a US and Russian segment. The US system consists of a 120-Volt dc network. The Russian system consists of a 120-Volt dc system as well as a 28-Volt system that interfaces with the US. [1] The ISS has 4 major solar arrays that contain 262,400 total solar cells and cover an area of 2,500 square meters. The ISS is 150 million kilometers away from the Sun. At its distance from the sun, the panels receive 1.367 kilowatts per square meter. When the station is in the sunlight, the station stores 60% of its energy in its batteries. The energy that the solar arrays generate is stored in 24 batteries that each house 38 lightweight Nickel Hydrogen cells. [2]
These batteries power the station when it is not in direct sunlight. From 2019 to 2021, astronauts underwent spacewalks to replace the original batteries as they reached their expiration date. The astronaut maintenance of the station ensures that the ISS remains reliable.
As humans venture further away from the Earth, the question of powering our equipment will always loom large. Despite the harsh conditions of space, energy is not an issue for the astronauts aboard the ISS. As seen with the ISS, solar power serves as a reliable source of energy that powers all of the scientific experiments as well as sustains the daily lives of astronauts. As humanity establishes a multiplanetary species, we will build on the principles that allow the ISS to harness star power to survive and thrive in space.
© Shay Nair Sharma. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] E. B. Gietl et al., "The Electric Power System of the International Space Station - A Platform For Power Technology Development," 2000 IEEE Aerospace Conference Proceedings, IEEE 878364, 25 Mar 00.
[2] E. Huckins and P. Ahlf, "Space Station Power Requirements and Issues," IEEE Aerosp. Electron. Syst. 9, No. 12, 3 (1994)