Deployable solar panels – in space!

This article highlights the link between solar power as we know it, and the field of space exploration, using examples such as our startup, O’Sol.

If you have been following our journey (if you haven’t, you can subscribe to our newsletter here), you know that O’Sol has been intimately linked to space since its inception. While O’Sol focuses on terrestrial applications, its work is also of interest for space. As part of a project with CNES (the French Space Agency), we are using our expertise of deployable solar panel systems to apply it to satellites. The aim is to use this know-how to increase the power that satellites produce, giving them more possibilities.

Solar photovoltaics and Space

A bit of history: the development of solar panels for space

Solar panel technology was used from a very early stage in the history of space exploration. Since the 60s, satellites have been equipped with solar panels [1]. Due to the constraints that space imposes (weight, volume and resistance restrictions), these solar panels had to be optimised to produce more power for a smaller weight and size.

These constraints were a driving force for the improvement of solar panels, and starting in the 70s, solar panels became efficient enough to be used for terrestrial applications.

A few examples

Vanguard 1, launched by NASA in 1958, was the first satellite to be equipped with solar photovoltaics [2]. It was equipped with six 5-centimeter solar cells. These produced a power of a few milliwatts (1 milliwatt = 0.001 watt), just enough to power a small transmitter.

At the other end of the scale, there is the International Space Station. This space station, which currently orbits the Earth, is powered by large solar arrays which can produce between 84 and 120 kilowatts (1 kilowatt = 1000 watts) of power – enough to power about 20 households. The ISS’ 262 400 solar cells cover an area of 2500 square metres – about the third of a football field. The electricity the solar arrays produce power the ISS’s science instruments and all the equipment needed to keep the astronauts alive [3].

Deployable solar panels

Due to the size constraints inside a rocket, the solar panels used in space are generally deployable. They are folded during launch, but once in orbit, they deploy and start producing electricity. Back on the ground, engineers must be inventive to create deployment systems which maximise the surface of solar panels in orbit while minimising their size inside the rocket.

The Orion spacecraft

One example of deployable solar panels can be found on the Orion spacecraft, jointly designed by ESA (European Space Agency) and NASA. This spacecraft, which is designed for journeys to the Moon and to Mars, is equipped with 4 deployable solar panels which form an X shape, and can produce about 10 kilowatts of power. The 4 panels, which start off stowed along the sides of the spacecraft during launch, open up in orbit to reach a length of 7 metres.

Deployment illustration

Deployable solar panels on nano satellites

As part of a contract for CNES, we at O’Sol are analysing a concept for deployable solar panels for nano satellites. Nano satellites, also known as cubesats, are very small satellites – about the size of a shoe box. They are becoming increasingly common thanks to the miniaturisation of on

Here’s one example of deployable solar panels for nano satellites (source: https://www.clyde.space)

board components and the reduction in launch costs (which are linked to the mass of the satellites sent into space).

The only obstacle to the development of cubesats is power. Due to the mass and volume constraints, their power production and storage options are limited. Usually, the power available to cubesats is of about 10W, less than the power needed by most light bulbs. The problem is the increasingly sophisticated instruments on board nano satellites also require increasing amounts of power. One way to solve this problem is to increase the area of solar panels using deployment systems. This is the rationale behind our project with CNES.

The system we are developing with CNES is based on a flower-shaped deployment, like the one on our terrestrial generator, Kino. Thanks to this innovative system, the area of solar panels can be doubled or even tripled. This is why CNES took an interest in our technology and contracted us to carry out this project: to transfer terrestrial solar panel technology back into space.

 

Sources
[1] http://www2.cnrs.fr/presse/communique/371.htm
[2] https://www.nasa.gov/content/vanguard-satellite-1958
[3]https://www.nasa.gov/mission_pages/station/structure/elements/solar_arrays-about.html
[4]http://blogs.esa.int/orion/2016/03/01/testing-solar-array/