The concept of this artist depicts astronauts and human habitats on Mars. Credit: NASA
Photovoltaics may be more practical for long stays on Mars thanks to today’s lightweight, flexible solar panels.
According to a new study by researchers at the University of California, Berkeley, the high efficiency, lightness and flexibility of current solar cell technology means photovoltaics can provide all the electricity needed for a long expedition to Mars or even a permanent settlement on the Red Planet.
Most scientists and engineers who have looked at the logistics of life on the surface of Mars believe that nuclear energy is the best option, thanks in large part to its reliability and 24/7 performance. Kilopower’s miniature nuclear fission reactors have improved over the past decade to the point where NASA sees them as a safe, efficient and abundant source of energy, as well as a key to future robotic and human research.
Solar energy, on the other hand, must be stored for use at night, which lasts approximately the same time on Mars as on Earth. And the persistent red dust that covers everything on Mars could limit the production of energy from solar panels. After a huge dust storm on Mars in 2019, the nearly 15-year-old solar-powered rover of NASA Opportunity stopped working.
Artistic depiction of a Martian biomanufactory with a crew powered by photovoltaics and capable of synthesizing food and pharmaceuticals, producing biopolymers and recycling biological waste. Credit: A work by Davian Ho
A new study, published April 27, 2022, in the journal Frontiers in Astronomy and Space Sciences, uses a systematic approach to compare these two technologies directly to a six-man extended mission to Mars involving a 480-day stay on the planet before to return to Earth. This is the most likely scenario for a mission that reduces the time spent passing between the two planets and prolongs the time on the surface beyond the 30-day window.
Their analysis found that for settlements over almost half of Mars’ surface, solar energy is comparable to or better than nuclear, if you consider the weight of solar panels and their efficiency – as long as some daily energy is used to produce hydrogen gas. for use in fuel cells to feed the colony at night or during sandstorms.
“The production of photovoltaic energy, combined with certain configurations for storing energy in molecular hydrogen, surpasses fusion reactors over 50% of the planet’s surface, mainly in these regions around the equatorial belt, which is in stark contrast to what is being offers again and again in the literature, which is that it will be nuclear energy, “said Aaron Berliner, a doctoral student in bioengineering at the University of California, Berkeley, one of the two first authors of the study.
Astronauts traveling to Mars will have to minimize the weight of the energy system they take with them from Earth. Photovoltaics would be the best choice if their planned settlement is in the yellow zone of this flattened map of Mars. Also on display are locations from previous missions that landed on Mars, including Jezero Crater (top right), which NASA’s Perseverance rover is currently exploring. Credit: Image by Anthony Abel and Aaron Berliner, UC Berkeley
The study provides a new perspective on the colonization of Mars and provides a roadmap for deciding which other technologies to use when planning manned missions to other planets or moons.
“This paper takes a global look at available energy technologies and how we can implement them, what are the best uses for them and where they are lacking,” said co-author Anthony Abel, a graduate of the Department of Chemical and Biomolecular Engineering. . “If humanity collectively decides that we want to go to Mars, this kind of system-level approach is necessary to achieve it safely and minimize costs in a way that is ethical. We want to have a clear comparison between the options, whether we decide which technologies to use, which places to go to Mars, how to go and who to bring.
Longer missions have greater energy needs
In the past, NASA’s assessments of the energy needs of astronauts on Mars have usually focused on short stays that do not require energy-hungry processes for growing food, building materials or producing chemicals. But while NASA and the leaders of companies that are now building rockets that can go to Mars – including Elon Musk, CEO of SpaceX, and Jeff Bezos, founder of Blue Origin – are talking about the idea of long-term settlements outside the planet, more large and more reliable energy sources must be considered.
The complication is that all of this material has to be transported from Earth to Mars at a cost of hundreds of thousands of dollars per pound, which makes low weight essential.
The people of Mars will have to use the only available raw materials – water ice, atmospheric gases, Martian soil and sunlight – to do everything necessary to survive. Researchers like CUBES, based at UC Berkeley, are working on ways to turn these raw materials into food, medicine, fuel and structural materials. This flowchart shows how the use of in situ resources (ISRU) turns raw materials into a form that can be used for food and pharmaceutical synthesis (FPS) and biopolymer production (ISM) for crew use. Waste is collected and reused (loop closure or LC) to maximize efficiency and reduce logistics costs for supplies from Earth. Credit: Illustration by Aaron Berliner and Davian Ho, UC Berkeley
One of the key needs is power for bio-production facilities that use genetically modified microbes to produce food, rocket fuel, plastic materials and chemicals, including medicines. Abel, Berliner, and co-authors are members of the Center for the Use of Biological Engineering in Space (CUBES), a multi-university effort to tune microbes using synthetic biology gene insertion techniques to deliver the necessary supplies to the colony.
However, the two researchers found that without knowing how much power will be available for an extended mission, it is impossible to assess the practicality of many organic production processes. So they set out to create a computerized model of different power supply scenarios and likely energy needs, such as habitat maintenance – which includes temperature and pressure control – agricultural fertilizer production, methane production to return rocket fuel to Land and production of bioplastics for the production of spare parts.
Against the Kilopower nuclear system were photovoltaics with three energy storage options: batteries and two different techniques for producing hydrogen gas from solar energy – by electrolysis and directly from photoelectrochemical cells. In the latter cases, the hydrogen is pressurized and stored for later use in a fuel cell for energy production when the solar panels are not.
Only photovoltaic energy with electrolysis – which uses electricity to separate water into hydrogen and oxygen – was competitive with nuclear energy: it turned out to be cheaper than a kilogram of nuclear energy on almost half the planet’s surface.
The main criterion was weight. Researchers have suggested that a rocket carrying a crew to Mars could carry a payload of about 100 tons without fuel, and have calculated how much of that payload will have to be spent on an energy system to use the planet’s surface. The journey to and from Mars will take about 420 days – 210 days in each direction. Surprisingly, they found that the weight of the energy system would be less than 10% of the total payload.
For a landing site near the equator, for example, they estimated that the weight of the solar panels plus hydrogen storage would be about 8.3 tons, compared to 9.5 tons for the Kilopower nuclear reactor system.
Their model also specifies how to adjust the photovoltaic panels to maximize efficiency under different conditions on Mars objects. Latitude affects the intensity of sunlight, for example, while dust and ice in the atmosphere can scatter longer wavelengths of light.
Progress in photovoltaics
Abel said photovoltaics are now very effective in converting sunlight into electricity, although the best manufacturers are still expensive. The most important new innovation, however, is a lightweight and flexible solar panel, which makes storing the outgoing rocket easier and transport costs lower.
“The silicone panels you have on your roof, with a steel frame, glass pad, etc., just won’t compete with the new and improved core, but the newer lightweight, flexible panels suddenly really, really change that conversation,” said Abel.
He also noted that less weight means more panels can be transported to Mars, providing a backup for any panels that are damaged. Although kilowatt nuclear power plants provide more power, less is needed, so if one falls, the colony will lose a significant portion of its power.
Berliner, who also holds a degree in nuclear engineering, joined the project with a penchant for nuclear energy, while Abel, whose bachelor’s thesis was on new innovations in photovoltaics, was more on solar energy.
“I feel that this document really stems from a healthy scientific and engineering disagreement about the merits of nuclear versus solar energy, and that it’s really just a matter of us trying to understand and settle the pledge,” Berliner said. “Which I think I lost, based on the configurations we chose to publish this. But it’s a happy loss, for sure. “
Reference: “Photovoltaic-powered energy production can help explore man on Mars” by Anthony J. Abel, Aaron J. Berliner, Mia Mirkovich, William D. Collins, Adam P. Arkin and Douglas S. Clark, April 27, 2022, Frontiers in Astronomy and Space Science.DOI: 10.3389 / fspas.2022.868519
Other co-authors of the article are Mia Mirkovic, a researcher at UC Berkeley at Berkeley Sensor and …
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