A researcher from German research institute Forschungszentrum Jülich has investigated for the first time the possibility of designing a Dyson sphere utilizing photovoltaic modules. A Dyson sphere is a theoretical artificial megastructure built around a star that can collect all of its radiant energy. If ever built, similar megastructures could provide huge amounts of energy for interstellar space travel and large-scale technological endeavors.
In the study “The photovoltaic Dyson sphere,” published in Solar Energy Materials and Solar Cells, its author, Ian Marius Peters explained that the Dyson sphere concept was invented by science fiction author Olaf Stapledon in 1937.
“I started this study out of curiosity, and there were several aspects of this that I found intriguing,” he told pv magazine. “I have an affinity with science-fiction concepts, and given my background in PV, the idea to use solar panels for a Dyson sphere seemed obvious. I was surprised that I found nothing on it in the scientific literature.”
Peters acknowledged that he also addressed this work with sense of humor. “A Dyson sphere is a project of a scale that is, at least today, absurd and comical, but it’s fun to think about. A Dyson sphere is exciting. But a Dyson sphere also symbolizes unintended consequences like the ones we currently strive to avoid, such as climate change. So it serves as a commentary on our contemporary global situation.”
Peters stressed that the theory behind the Dyson sphere concept is relatively simple, as it is a detailed balance consideration, so all the equations can be found in textbooks. “The thrill of it to me was that these theoretical concepts can be used to cover something as fantastic as a Dyson sphere. I ran into some geometric calculations that were difficult at one point, but in the end all relevant questions can be resolved by considering conservation of energy.”
Another interesting aspect, according to Peters, is the materials availability discussion. “We often discuss the question if we have enough material to build enough solar cells in the world for our current purpose, so the question if there is enough material to build a Dyson sphere imposed itself on me,” he explained. “I started looking into what materials are there in the solar system, and I found would there be enough. I believe that there are several routes one could imagine to gather enough material to actually build this system. I hope that this will reflect on the material availability discussion we currently have.”
Peters is also convinced that constructing a Dyson sphere would have substantial implications for life on Earth. “A large space project like a Dyson sphere demands that we manage its impact on our own environment,” he also stated. “So, before thinking about such an enterprise, we need to resolve the consequences of our actions here.”
In the proposed Dyson sphere system configuration, photovoltaic modules are expected to act as a grey body that partially absorbs incident electromagnetic radiation, with their operation relying on the balance of absorbed and emitted radiation. This grey body should then be coupled to a black body outside for temperature control, which would help maintain the sphere's temperature low enough not to impact PV efficiency.
“The highest conversion efficiency of such a sphere was found to be for a material with a band gap of around 1.3 eV,” the paper reads. “At an extension of one astronomical unit, the sphere would reach a radiative efficiency limit of 25% while assuming a temperature of around 400 K.”
However, the researcher found that decreasing temperatures may lead to an increase in the extent of the Dyson Sphere, which would in turn add more costs for growing material demand. As a result, he suggested first designing a partial sphere with limited extension, and then developing a planetary temperature control system.
“As an example, it was estimated that a partial Dyson Sphere, or Dyson Swarm, covering 22% of the sphere surface at an extension of 2.13 AU would require 1.3 × 1023 kg of silicon, and would allow to harvest 4% of the sun’s energy, while increasing temperature on Earth by less than 3 K,” he also explained. “This increase, incidentally, is similar to our current global warming trajectory.”
Peters also concluded that a photovoltaic Dyson sphere with an extension beyond Earth's orbit would not endanger life on Earth while maintaining suitable temperatures for photovoltaic efficiency.
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