Scientists can now bottle solar energy, turn it into liquid fuel

The barrier to solar energy has always been storage. Now, bottled sunshine has a shelf-life of 18 years.

  • Researchers have invented a liquid isomer that can store and release solar energy.
  • The team has solved problems other researchers have previously encountered.
  • The discovery could lead to more widespread use of solar energy.

In the last year, a team from Chalmers University of Technology, Sweden, essentially figured out how to bottle solar energy. They developed a liquid fuel containing the compound norbornadiene that—when struck by sunlight—rearranges its carbon, hydrogen, and nitrogen atoms into an energy-storing isomer, quadricyclane. Quadricyclane holds onto the energy, estimated to be up to 250 watt-hours of energy per kilogram, even after it cools and for an extended period of time. For use, it's passed through a cobalt-based catalyst, at which point the energy is released as heat. The team's research could be a breakthrough in making solar energy transportable and thus even more usable for meeting real-world energy needs.

What's more, the team has been adjusting the molecular makeup of their fuel so that it doesn't break down as a result of storage and release cycles. It can be used over and over again. "We've run it though 125 cycles without any significant degradation," according to researcher Kasper Moth-Poulsen.

As a result, the scientists envision a round-trip energy system they call MOST, which stands for Molecular Solar Thermal Energy Storage.

The MOST system

(Chalmers University of Technology)

In the MOST system, the liquid runs through a concave solar thermal collector that has a pipe running across its center. The collector focuses sunlight on that pipe, and the fuel running through it, causing the transformation of norbornadiene into quadricyclane. The charged fuel then flows through transparent tubing into storage tanks, or it can be diverted and shipped elsewhere for use. Says Moth-Poulsen in the Chalmers press release, "The energy in this isomer can now be stored for up to 18 years. And when we come to extract the energy and use it, we get a warmth increase which is greater than we dared hope for."

To release the fuel's energy, it's passed through the catalyst in which a chemical reaction occurs to convert the fuel back into liquid whose temperature has been boosted by 63°C or 145°F. So, for example, if the fuel goes into the catalyst at 20°C, it comes out at 83°C. In this form, the fluid can be used for heating a home or business, or be used in any other system reliant on heated liquid. "You could use that thermal energy for your water heater, your dishwasher or your clothes dryer," MIT's Jeffrey Grossman tells NBC MACH. "There could be lots of industrial applications as well."

This last year has been a key time

(Johan Bodell)

Kasper Moth-Poulsen holds the tube containing the MOST catalyst

The first iteration of the Chalmers fuel was revealed about a year ago, and in the intervening months, the researchers have been working toward the robust behavior they're now seeing, even beyond achieving that remarkable 18-year storage potential. "We have made many crucial advances recently, and today we have an emissions-free energy system which works all year around," says Moth-Poulsen.

Though other researchers have experimented with similar uses for norbornadiene, their fuels broke down after just a few cycles before their research was abandoned. Those earlier fuels also didn't hold the energy very long.

The Chalmers team also originally had to mix their isomer with flammable toluene. Now, however, they've worked out a way to use the isomer without dangerous additives.

Storing solar energy

As the world moves to renewable energy, solar energy has proven to be among the most attractive: Sunlight is free and releasing its energy produces no pollution or harmful effects. One remaining limiting factor has been finding ways of storing solar energy that are as clean as solar energy itself. Much work is being down with batteries, but it's difficult to produce power cells without using toxic materials. The MOST system offers an exciting new angle to pursue.

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New fossils suggest human ancestors evolved in Europe, not Africa

Experts argue the jaws of an ancient European ape reveal a key human ancestor.

Surprising Science
  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
  • Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
  • These fossils may change how we view the evolution of our species.

Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.