Press room – Why are there no photovoltaic panels in the dune business?

In short, can you describe this planet Arrakis from the work of S.F. Dune?

Just like the earth,
Arrakis has a sun called Canopus. It is a giant blue star that actually exists – it is located in the constellation Karina. It has the advantage of being larger than the Sun because its radius is about 70 times larger. Since it has a temperature of 7,500 degrees Kelvin, it is also 15,000 times brighter. This suggests that Arrakis should be farther from its star (about 120 times) from Earth than from the Sun, but nonetheless it hasA large amount of sunlight. Taking into account the characteristics of the star and its distance from Arrakis, we can estimate this quantity at about
1000 watts per square meter on the ground. By comparison, in France, on a very sunny summer day, you can reach 800 watts per square meter. But receiving light is one thing, and knowing how much to collect is another.

And this is where the issue of photovoltaic panels comes into play?

In fact. To fully understand the problem, you have to understand how photovoltaic (PV) panels work.
The latter absorbs solar energy and converts it into electric current. Photovoltaic panels consist of photovoltaic cells consisting of a semiconducting material (on Earth, silicon) whose electronic structure consists of two layers. One of these layers, called the conduction layer, contains no electrons, while the second, the valence layer, contains. When photons of sunlight hit this material, the electrons “jump” from one layer to another, allowing an electric current to flow.

On Earth or on Arrakis, the received light contains
Photons Of all colors, including
Some of them are absorbable by a semiconductor material, others do not.

How many of them will be accommodated? It depends
Absorption threshold of the selected substance : If this threshold is low, a large number of photons will be absorbed and the electric current generated will be large but the voltage will be low, which will give low electric power (because energy is equal to the product of density by voltage). On the contrary, a high threshold will only absorb photons of sufficiently high energy: the voltage will be strong but not the current, nor the force for it. So the idea is to define the threshold that allows the maximum power to be obtained, for a given light spectrum. It is a compromise to be found, located between these two extremes, and bears the name
d’optimum de Shockley-Queisser.

What does this settlement consist of and how is it critical for the installation of PV panels on the Arrakis?

This compromise depends on the spectrum of the light received (which in turn depends on the temperature of the star). And therefore ,
On Earth, the optimum limit is infrared, around the wavelength of 1100 nm, giving a maximum efficiency of 30%. However, a semiconductor material whose threshold is closest to this value is
silicon Very abundant on Earth (especially in the form of silica found in sand). The sand that Arrakis also has in abundance… Except that
toThe Canopus spectrum turns blue compared to the Sun And it contains fewer low-energy particles than the sun. The yield is higher (about 33%) but
The optimum limit is about 850 nm (between visible and infrared). Silicon is no longer the most appropriate material in this case:
Gallium or indium may be more suitable. However, it is far from abundant in silicon, as it is not found in sand. Both are already present in very small amounts in the natural environment – in particular, indium.

And light is not the only parameter to take into account, temperature also plays a role, just like sometimes stormy weather on the planet?

completely. In Arrakis, it is hot, with a temperature of about 60 degrees Celsius. However, heat reduces the efficiency of the panels by about 0.5% per degree.
It’s a little counter-intuitive, but an area that is very sunny but extremely hot won’t necessarily produce more solar electricity than a less sunny but cooler area.
Finally, in fact, The devastating Coriolis storms hitting the planet will severely destroy solar panels It will be necessary to mobilize a large part of the power produced by the board just to clean it. All these issues, along with others such as storing the electricity produced in this way (to be able to use it when night falls), are thus several hypotheses that can explain the lack of PV panels on the Arrakis.

Arrakis is a planet with a particularly hostile desert environment: extremely high temperatures, scorching sun, devastating sandstorms … not to mention terrible sand worms. © CEA/Getty Images

Other energy sources are rare and precious on this planet. To make the most of every available liter of water, in particular, the inhabitants of Arrakis, Fremen, have developed collections,
distillates, making it possible to recycle nearly 95% of the water obtained from bodily fluids.

Finally, there is
Precious spices, which can only be harvested from the surface of the Arrakis, and indispensable to navigators on their interstellar voyages – not to advance their ships, but instead to give them the capabilities needed for any intergalactic movement.

In your book, other aspects of the work are mentioned. Can you say a few words about it?

In the book I edited, the idea was to talk about Frank Herbert’s work and the planet Arrakis as richly as possible. So many disciplines were called, physics of course, but also chemistry (to talk about spices), biology (in order to understand the life cycle of sandworms), as well as philosophy, linguistics, politics, sociology or literature. This was the least discussed work that science fiction author Laurent Ginfort classified in the “worlds of books” category.