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| Fig. 1: Energy consumption per year [1] (Image source: T. Wooldridge) |
Global energy supply, and thus consumption, continues to grow every year as seen in Fig. 1, with the exception of 2020 due to the global pandemic and quarantine. With the recent advancements of large language models and AI, the energy demands to operate these systems have grown exponentially. The yearly energy consumption in 2024 was nearly 600 exajoules (EJ), with the largest contribution to energy production being oil and natural gas. [1]
Because humanity still generates the majority of its energy from fossil fuels, greenhouse gas emissions continue to rise each year. With the increasing demand for energy, along with the increase in emission regulations, a clean energy source is needed.
One possible theoretical solution to humanity's energy crisis would be the Dyson Sphere/Swarm with its ability to harness the full solar power of a star.
Dyson Spheres are a technology consisting of countless solar cells surrounding a star, fully harnessing the star's solar energy. Freeman Dyson, a renowned mathematician and physicist, proposed this idea in 1960 in a magazine article titled Search for Artificial Sources of Infrared Radiation.
The Dyson Sphere is fundamentally possible to construct, although a solid monolithic sphere would be inherently unstable. Gravitationally, the solid structure would not be able to remain centered on the star without active control. Additionally, the mechanical stress experienced by the structure would need to be communicated through the Young's modulue E of roughly the value
where G is Newton's constant, $ρ= 2000 kg m-3 is the density of the shell, and ΔR = 10 m is the shell's thickness. This value is about E ≈ 1013 GPa. If the structure were to be made form the strongest known material, carbyne (E = 4631 GPa), it would still fall short of the Young's Modulus requirement by nine orders of magnitude. [2,3]
This effectively rules out the possibility of having one coherent megastructure or sphere and starts the discussion of having a swarm of countless smaller orbiting satellites to harness the star's solar energy. An array of over a billion small solar satellites orbiting a celestial body is the most practical version of a Dyson Sphere. They would be scalable, fault-tolerant, serviceable, and compatible with known or foreseeable technologies.
To build such an array, advanced robotic automation is required. As suggested by Smith, construction and launch of these satellites should be done on Mars. [4] Mars is an ideal Dyson Swarm site because of its vast number of desirable resources for this project like silicon, metals, and glass, as well as its close proximity to Earth compared to other celestial bodies in the solar system.
Each small satellite would be equipped with photovoltaic cells, primarily made from silicon, to collect solar radiation from the sun and directly convert it to energy. According to the solar cell efficiency tables, there is a maximum solar cell efficiency of 30.2%. [4] Here, an average efficiency of 21% is used for solar radiation to electricity, where the range of efficiencies for the swarm is 21% before the distance factor is applied. At the average distance from Mars to Earth of 1.5 AU, the efficiencies drop to 6.12%. [5] At the maximum efficiency of 6.12%, 3.57 terawatts of energy consumption, an intensity of solar irradiation for Mars of 387 W/m2, and an average solar panel area of π × 100 m2 (10 meter radius), the number of satellites needed comes out to be around 479 million according to the above equation. [1,4]
Here N is the number of satellites, I is the solar irradiation, η is the efficiency of a single solar satellite, and A is the average area of a solar cell.
Finally, there is the issue of power transportation from one celestial body to another. There are several ways this can be accomplished: using modern day power transmission cables, using a high-powered laser, or using far-field radiative wireless power transfer. [4] Using modern day power transmission cables would be a vast engineering challenge as there is no way to hold them in place in deep space. Additionally, each cable can transmit a finite amount of energy without melting, making this the least feasible option. A high-powered laser could be used to transmit large quantities of energy in short periods of time, but would require several receiver outposts to ensure minimal power losses. Diffraction spreading of the beam over large distances would cause substantial power posses without focusing lenses oriented along the beam path. This, again, proves to be a problem in deep space without there being a foundation to fix the structure too. Using radiative wireless power transfer can be done by using rectifying antennae that consist of flat transmitting and receiving antennae. These antennae are made using dipole antennae. Using this technology, the Dyson Swarm would be able to transmit the solar energy harnessed from Mars' orbit and send it to ground control on Mars and Earth given all satellites are perfectly aligned.
The over-a-billion satellites being perfectly aligned in deep space is a vast assumption in this scenario. In order for the satellites to have correctional capabilities, they will have to be launched with enough fuel on board for long term orbit correction. With the sheer scale of this project, having enough weight of fuel on each satellite is impossible. Overall, the outcome of a Dyson Swarm with currently available technology would be a monumental increase in the space debris orbiting Mars. It would successfully dwarf the amount of total space debris and satellites currently orbiting Earth, at around 52000 objects. [6]
There is an increasing need for greater clean energy production in the world today. With the advancement of technology, specifically AI and its incorporation in everyday life, the energy demand is projected to grow exponentially. These grand increases in energy demands call for a source of energy that has low greenhouse gas emissions yet is still able to keep up with the energy requirements. A long-studied option to solve this energy crisis is the construction of a Dyson Swarm around a nearby celestial body to collect the needed energy from the sun. This would produce energy several orders of magnitude greater than that of the current energy consumption in a year. However, the construction of such a megastructure comes with several inherent design, engineering, and logistical problems. With the current advancement of technology, humanity is still several generations from being able to accomplish such a feat. Although if humanity was brass enough to try and construct a Dyson Swarm, there would surely be a higher chance extraterrestrial life notices the billion-large pile up of space junk around Mars. Perchance then they may take pity on us and gift a fully operational Dyson Swarm system, thereby confirming Humanity's step up on Kardashev's scale.
© Thomas Wooldridge. 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] "BP Statistical Review of World Energy 2022," British Petroleum, June 2022.
[2] J. T. Wright, "Dyson Spheres," Serb. Astron. J. 200, 1 (2020).
[3] S. Kotrechko et al., "Mechanical Properties of Carbyne: Experiment and Simulations," Nanoscale Res. Lett. 10, 24 (2015).
[4] M. Green and K. Emery, "Solar Cell Efficiency Tables," Prog. Photovolt. 1, 25 (1993).
[5] J. Smith, "Review and viability of a Dyson Swarm as a form of Dyson Sphere," Physica Scripta 97, 122001 (2022).
[6] P. Anz-Meador, J. O. Jacobs, and J.-C. Liou, "History of On-Orbit Satellite Fragmentations, 16th Edition," U.S. National Aeronautics and Space Administration, NASA/TP-20220019160, December 2022.