A new analysis by scientists at the University of California, Berkeley, states that the high efficiency, lightness and flexibility of the latest solar cell technology, photovoltaics could provide all the power needed for a long Mars mission, or even a permanent settlement there.

Most scientists and engineers thinking about the logistics of living on the surface of the Red Planet have assumed that nuclear power is the best alternative, largely because of its reliability and 24/7 operation. Over the past decade, miniaturized Kilopower nuclear fission reactors have advanced to the point where NASA sees them as a safe, efficient and abundant source of energy and key to future robotic and human exploration.

Solar energy, on the other hand, must be stored for use during the Martian night, which is about the same time as on Earth. And on Mars, the power generation of solar panels could be thwarted by the all-encompassing and ubiquitous red dust. So much so that the nearly 15-year-old Opportunity rover, powered by NASA's solar panels, stopped working after a massive dust storm on Mars in 2019.

The new study, published this week (April 27, 2022) in the journal Frontiers in Astronomy and Space Sciences, uses a systems approach to compare these two technologies head-to-head for an extended six-man mission involving 480 days on Mars before returning to Earth. This is the most likely scenario for a mission, reducing the transit time between the two planets while extending the time on the surface beyond a 30-day timeframe.

Astronauts traveling to Mars will need to minimize the weight of the power system they take with themselves from Earth. If the planned settlement is in the yellow area of ​​this flattened Mars chart, photovoltaics would be the best choice. Also shown are the locations of previous missions to Mars, including the Jezero Crater (upper right), which NASA's rover Perseverance is currently exploring. (Graphic work: Anthony Abel and Aaron Berliner, UC Berkeley)

If the weight and efficiency of solar panels are taken into account in the analyzes in question, it was claimed that solar energy in the settlement, which covers almost half of the Martian surface, is comparable to or better than nuclear, as long as that daytime energy produces hydrogen gas, which is used in fuel cells to power the colony at night or during sandstorms.

Aaron Berliner, a UC Berkeley bioengineering PhD student and one of the first authors of the paper said, "Photovoltaic power generation combined with certain energy storage configurations is better than nuclear fusion reactors (contrary to what has been repeatedly suggested in the literature) over more than 50% of the planet's surface, particularly in regions around the equatorial band. puts on a performance.” said.

The study brings a new perspective on Mars colonization and provides a roadmap for deciding which technologies to use when planning manned missions to other planets or moons.

“This paper takes a global perspective on what power technologies we have, how we can deploy them, what are the best use cases for them and where they fall short,” he said. Department of Chemical and Biomolecular Engineering. “If humanity collectively decides we want to go to Mars, such a systems-level approach is necessary to do it safely and to minimize cost ethically. We decide what technologies we will use, which places on Mars we will go, how we will go and who we will bring. We want to make a clear comparison between the options when we give."

Longer missions require more power

In the past, NASA's estimates of the power needs of astronauts on Mars have often focused on short-term stays that do not require power-hungry processes to grow food, build construction materials, or produce chemicals. But leaders of companies building rockets that can now go to Mars, including NASA and SpaceX CEO Elon Musk and Blue Origin founder Jeff Bezos, are calling for consideration of long-term, extraplanetary settlements, larger and more, and more reliable power sources. they are expressing.

Illustration of a conceptual fission surface Kilopower system on the Moon.

(Image courtesy of NASA)

The challenge is that all of these materials have to be transported from Earth to Mars at a cost of hundreds of thousands of dollars per kilo, which makes low weight trips necessary.

One of the key needs is power for biomanufacturing facilities that use genetically engineered microbes to produce chemicals, including food, rocket fuel, plastic materials, and medicines. Abel, Berliner, and the paper's co-authors are members of the Center for Biological Engineering in Space (CUBES), a multi-university group that makes tweaks to microbes using synthetic biology's gene insertion techniques to supply the materials needed for a colony.

But the two researchers discovered that without knowing how much power would be available for an extended mission, it was impossible to assess the practicality of many biomanufacturing processes. So they began to build a computerized model of the various power supply scenarios and possible power demands, such as habitat maintenance involving temperature and pressure control, fertilizer production for agriculture, methane production for rocket propellants to return to Earth, and bioplastic production to produce spare parts.

There were photovoltaics with three power storage options versus a Kilopower nuclear system. Two different techniques for producing hydrogen gas from batteries and solar energy - electrolysis and photoelectrochemical cells from which direct energy is obtained. In later cases, the hydrogen is pressurized and stored for later use in a fuel cell to generate power when solar panels are not available.

Only electrolytic photovoltaic power (using electricity to split water into hydrogen and oxygen) could compete with nuclear power: It proved more cost-effective per kilogram than nuclear, at nearly half the planet's surface.

The main criterion was weight. The researchers assumed that a rocket carrying the crew to Mars could carry a payload of about 100 tons, excluding fuel, and calculated how much of that payload would need to be allocated to a power system for use on the planet's surface. A trip to and from Mars will take approximately 420 days (210 days each way). Surprisingly, they found that the weight of a power system would be less than 10% of the overall payload.

For example, they calculated that for a landing site near the equator, the weight of solar panels plus hydrogen storage would be about 8.3 tons, versus 9.5 tons for a Kilopower nuclear reactor system.

The designed model also specifies how to tune photovoltaic panels to maximize efficiency for the different conditions that will occur at sites on the Martian surface. For example, latitude affects the intensity of sunlight, while dust and ice in the atmosphere can cause light to be emitted at longer wavelengths.

Advances in Photovoltaics

Photovoltaics are now highly efficient at converting sunlight into electricity, but the top performers are still expensive, Abel said. But the most important innovation is a light and flexible solar panel on the outgoing rocket that simplifies storage and reduces shipping costs.

People on Mars will only need to use the raw materials available; - water ice, atmospheric gases, Martian soil and sunlight - everything one would need to survive. Researchers like at CUBES are working on ways to turn these raw materials into food, medicine, fuel and building materials. This flowchart shows how in situ sourcing (ISRU – In-Situ Resource Utilization) transforms raw materials into a form that can be used to synthesize food and drugs (FPS – Food Pharma Systems) and produce biopolymers (ISM) for use by the team. Waste is collected and reused (loop closure or LC) to maximize efficiency and reduce the cost of supply logistics from Earth. (Image: Aaron Berliner and Davian Ho, UC Berkeley)

“Anything on your roof, with steel construction, glass support, etc. Silicon panels won't compete with the new and improved nuclear, but newer lightweight, flexible panels will suddenly really, really change this conversation, Abel said.

He also noted that the lighter weight means more panels can be transported to Mars, providing a replacement for any failed panel. While kilowatt nuclear plants provide more power, less is needed, so if one goes down the colony loses a significant portion of its power.

Berliner, who also holds a degree in nuclear engineering, entered the project with a bias towards nuclear energy, while Abel, whose undergraduate thesis was about innovations in photovoltaics, was more in favor of solar energy.

"I really feel like this article stems from a healthy scientific and engineering disagreement over the merits of nuclear and solar power, and that it's really just us trying to understand and settle a bet," Berliner said. He said and continued: “I think I lost based on the configurations we chose to post this. But of course it's a happy loss."

Other co-authors of the paper are Mia Mirkovic, a researcher at the Berkeley Center for Sensors and Actuators at UC Berkeley; William Collins, professor of earth and planetary science at UC Berkeley and senior scientist at Lawrence Berkeley National Laboratory (Berkeley Lab); Adam Arkin, CUBES director, and Dean A. Richard Newton Memorial Professor of Bioengineering at UC Berkeley; and Douglas Clark, Gilbert Newton Lewis Professor in the Department of Chemical and Biomolecular Engineering and dean of the College of Chemistry. Arkin and Clark are also senior faculty members at Berkeley Lab.

The work was funded by graduate research fellowships from NASA (NNX17AJ31G) and the National Science Foundation (DGE1752814).

Levent Aslan,

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