Nav: Home

Scientist devises a solar reactor to make water and oxygen from moon rocks

October 26, 2017

Thorsten Denk's paper Design and Test of a Concentrated Solar Powered Fluidized Bed Reactor for Ilmenite Reduction was presented at the 23rd Annual SolarPACES Conference in Chile. (Thorsten Denk - Presentation (pdf)

Working over a ten year period at the Plataforma Solar de Almeria (CIEMAT) Denk has designed and built a device to make enough oxygen and water for 6 to 8 astronauts, powered by a thermal solar reactor. In 2017 it completed a six-month test run.

The idea is not new; just the implementation.

"From the beginning people were thinking this probably has to be done with a solar furnace, because on the Moon there is not very much to heat a system that you can use; photovoltaics with electricity or a nuclear reactor or concentrated solar radiation," said Denk, who has experience in concentrating solar and in particles engineering.

"After the Apollo missions, scientists had a lot of ideas of how to make oxygen on the Moon, because every material that you bring from Earth costs money. For every kilogram of payload you need hundreds of kilograms of fuel."

Denk's simple solar reactor could chemically split water from lunar soil, and electrolysis could then split the H2O into oxygen and hydrogen. But few other attempts used solar reactors, and ones that did had flawed designs, due to undersizing the solar concentrator to heat the reactor - and none exceeded bench scale.

"Mine is the real size you would build on the Moon to make oxygen for a crew of six or eight, so there's no upscaling needed later. I have also extended my use of fluidized beds. It's not only the reactor itself, but it is also the supply lines and the removal pipe for the particles," said Denk of his fluidized bed solar reactor design. In a fluidized bed reactor, particles behave like liquid.

"It looks just like boiling liquid. If you look up close you see it move very wildly and the same thing happens with fluidized particles. So you have very good mixing and very good contact between the particles and the gas. The result is a very homogeneous temperature and efficient chemistry," he explained.

The regolith would need pre-treatment to smooth the particles out, because unlike rounded particles weathered by atmosphere and water on Earth, lunar regolith particles are strange shapes with sharp edges, as there's no atmosphere on the Moon to wear them down. Pretreating them "round" then sieving for the correct fraction of the grain size would be critical for the safe operation of the fluidized bed reactor.

Denk was initially inspired by a NASA Centennial challenge in 2008 for oxygen from Moon rock. "They put all the questions that they have but they have no money to answer them to the public and if you succeed you can win $2 million." The weight limit was so low, 50 kg, that NASA's challenge expired with no takers. Denk's can process 25 kg of particle load in less than an hour and currently weighs 400 kg. He thinks he can reduce the weight.

But, ten years later, he has met the two other conditions: that it could produce 2.5 kg of oxygen in four hours, and that electricity use should not surpass 10 kW. The chemical reaction is mostly powered by the solar reactor, and would use less than 5 kW of electricity, mostly for the second step; splitting oxygen from hydrogen with electrolysis.

He has demonstrated the first step, making 700 g of water in one hour - which would enable making 2.5 g of oxygen in 4 hours using electrolysis, a proven technology, but that will need additional funding.

Water produced in a solar reactor for the MoonWith the successful test of this solar reactor design, Denk has achieved the first step, creating H2O on the Moon using solar thermal energy. For the second step, solar electrolysis would break the H2O into hydrogen and oxygen.

His process uses ilmenite (TiO3), an iron oxide found in the "dark" areas of the Moon. It would be dug up by a small robot and carried to the reactor. Denk likes the Rassor digging robot, with opposing rotating drums that prevent it from propelling off-surface by the force of digging in lunar gravity (one-sixth Earth gravity).

How this would split H2O and oxygen from lunar soil:

The chemical reactions to make oxygen and water would involve one import from Earth, hydrogen; but just initially.

"The hydrogen would be just for the first few hours. Then that would be recycled with the electrolyzer," he explained. "Even if you bring hydrogen from Earth and get oxygen from the Moon for making rocket fuel, you save nearly 90% of the weight. Hydrogen is the lightest element. Oxygen is much heavier."

He described the two-step process:

The main component is the iron-titanium oxide - ilmenite (FeTiO3). To remove the oxygen, you add hydrogen so it becomes water. H2O comes out of the first step. FeTiO3 + H2 + solar heat ? Fe + TiO2 + H2O

The second step is in an electrolyzer using the product water from the reactor. The water is split to produce hydrogen and oxygen. H2O + electric power ? H2 + ½O2

The oxygen is the product and the hydrogen gets returned to the process.

The Moon's ideal solar resource

The Moon has ideal conditions for making solar fuels, because chemical reactions to split oxygen and hydrogen require very high temperatures, and work best when they are continuous. The Moon's annual normal solar irradiation is nearly 6,000 kWh per square meter per year, and lunar days are 14 earth-days long; 354 hours.

"Daylight is 2 weeks without interruption, and then you have the same half-month of dark as night. So if you need three hours to turn it on, it's not a big problem. There is no atmosphere on the Moon, and there is no weather, no clouds, so you really can operate from sunrise to sunset at full power for each half-month," Denk said.

Concentrated solar furnaces (see Task II), are able to achieve very high temperatures. But at above 1050°C, the Moon's regolith particles tended to gum up the works by glueing together; a process called sintering.

"The chemical reaction starts to be working from 800°C but sintering starts to be a problem at 1,050°C degrees, so my goal was not to surpass the 1000°C," he explained. "I achieved a bit more than 970°C and the maximum was hardly above 1000°C. So I had a temperature in the bed of not more than 30° up and down, for the highest possible average temperature without sintering."

With the successful test of this solar reactor design, Denk has achieved the first step, creating H2O on the Moon using solar thermal energy. For the second step, solar electrolysis would break the H2O into hydrogen and oxygen.
Original Article:

23rd Annual SolarPACES Conference Presentation:

Full Paper:

ORESOL - Release of Oxygen from Lunar

Regolith using Concentrated Solar Energy

Participants: CIEMAT-PSA (E)

Contacts: Thorsten Denk,

Funding: EC 6th Framework Programme ERASTAR

Regions (CA-515793- ERA-STAR REGIONS), ESP2007-29981-E.

Duration: September 1, 2014 - August 31, 2017

Conclusion from paper:

"A concentrated solar powered fluidized bed reactor for the reduction of ilmenite (FeTiO3) with hydrogen (H2) at up to 950°C was designed, built, and successfully tested. All primary testing objectives were accomplished. The basic operation parameters, especially the main fluidized bed gas flow, were determined. Continuous particle feed and removal was demonstrated. A maximum bed temperature of 977°C was achieved. The desired chemical reaction was carried out, converting up to 56% of the hydrogen into water with the oxygen being extracted from the ilmenite mineral. It arose during the tests that the system is also able to extract very efficiently the crystallization water in the minerals, thereby making it suitable for water extraction on Mars. Nevertheless, many possible improvements were identified. For the short term, they include a higher hydrogen flow, a better water separation, a better gas distributor in the main fluidized bed, the installation of thermal insulation under the aperture cone, and the use of particles with a smaller grain size. Depending on the results, measures must be taken to improve the quality of the product water to make it suitable for the decomposition into hydrogen and oxygen in an electrolyzer. Another high priority task is the development of a lightweight foldable and/or inflatable concentrator system [6]. The achieved data suggest a diameter between 4 and 5 meter. For the long term, the adaption to the lunar environment will be a major challenge. This includes vacuum of space, reduced lunar gravity, properties of the real lunar soil, and identification of ilmenite-rich spots on the Moon.


This work has been funded by the Spanish Ministerio de Ciencia e Innovación, ref. ESP2007-29981-E. Our special gratitude goes to all staff of PSA helping in the development of this work, especially José Galindo for his outstanding work keeping running the PSA solar furnaces, the remainder of the solar furnace staff, and the instrumentation group. Moreover, the authors thank the Tioxide company for ceding the particles used for this work.


Related Hydrogen Articles:

Paving the way for hydrogen fuel cells
The hype around hydrogen fuel cells has died down, but scientists have continued to pursue new technologies that could enable such devices to gain a firmer foothold.
Keeping the hydrogen coming
A coating of molybdenum improves the efficiency of catalysts for producing hydrogen.
Hydrogen bonds directly detected for the first time
For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope.
Argon is not the 'dope' for metallic hydrogen
Hydrogen is both the simplest and the most-abundant element in the universe, so studying it can teach scientists about the essence of matter.
Metallic hydrogen, once theory, becomes reality
Nearly a century after it was theorized, Harvard scientists have succeeded in creating metallic hydrogen.
From theory to reality: The creation of metallic hydrogen
For more than 80 years, it has been predicted that hydrogen will adopt metallic properties under certain conditions, and now researchers have successfully demonstrated this phenomenon.
Artificial leaf goes more efficient for hydrogen generation
A new study, affiliated with Ulsan National Institute of Science and Technology has introduced a new artificial leaf that generates hydrogen, using the power of the Sun to mimic underwater photosynthesis.
Hydrogen from sunlight -- but as a dark reaction
The storage of photogenerated electric energy and its release on demand are still among the main obstacles in artificial photosynthesis.
New process produces hydrogen at much lower temperature
Waseda University researchers have developed a new method for producing hydrogen, which is fast, irreversible, and takes place at much lower temperature using less energy.
Hydrogen in your pocket? New plastic for carrying and storing hydrogen
A Waseda University research group has developed a polymer which can store hydrogen in a light, compact and flexible sheet, and is safe to touch even when filled with hydrogen gas.

Related Hydrogen Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...