Thirty years ago, a pair of chemists made headlines around the world with their claim that they had achieved “cold fusion”: the production of energy using the same nuclear reaction that powers the sun, but at room temperature. If confirmed, the discovery could have transformed the global energy landscape overnight—but the chemists' findings weren't readily replicated.
Swiftly labeled a lost cause by mainstream physics, attempts to spark cold fusion are now once again heating up, thanks to a stealth effort by the U.S. tech giant Google.
In a review paper published in Nature on Monday, U.S. and Canadian researchers funded by Google publicly unveiled their efforts to reassess cold fusion. Like many other outside researchers, the Google team hasn't found evidence of the phenomenon as originally described. However, since 2015, their efforts have yielded three preprints and 10 peer-reviewed publications, including the latest review, that are offering new insights into key materials and that have improved measurement techniques at high temperatures and pressures.
With these advances in hand, the team says that there's much more basic science to do—research that likely hasn't gotten done because of its relation to cold fusion.
“That is why we got involved, [and] that’s actually the work we are continuing to do,” says team member Yet-Ming Chiang, a materials scientist at MIT. “This project is by no means over. There’s lots of ongoing work we're interested in doing.”
Though the work may well raise eyebrows, Google was aware of the risks. Two of the review's coauthors, Google engineers Ross Koningstein and David Fork, have argued that to deliver meaningful innovation in the energy sector, 70 percent of research funding should flow to core technologies, 20 percent should be dedicated to cutting-edge research, and 10 percent should back high-risk ideas that just might work—like cold fusion.
Whether their experiments yield an energy breakthrough, the research team hopes they've provided cover for young researchers and government funding agencies to reconsider this area of science with an open mind.
“The timing is really good for this,” says lead author Curtis Berlinguette, a chemist at the University of British Columbia. “I’m just really excited to show the younger generations of scientists it’s okay to take risks—to take the long shots.”
Sparking a controversy
Nuclear fusion occurs when pairs of light nuclei fuse together to form a nucleus of net lighter mass, releasing huge amounts of energy as described by Einstein's iconic equation E = mc2. Inside the sun, hydrogen atoms fuse to produce helium and energy. If successfully harnessed on Earth, fusion could provide humankind with abundant, emissions-free energy—a huge boon to efforts to combat climate change. (As a byproduct, fusion on Earth might also help to address a global helium shortage.)
But getting fusion to work on Earth is tricky, since it's hard to get two nuclei close enough to combine; atomic nuclei are positively charged, so they fiercely repel one another, a hurdle known as the Coulomb barrier. Crossing this barrier and realizing fusion power is possible at high densities and temperatures, if the nuclei are confined for a sufficiently long time. But to achieve these conditions, scientists seem to need large, expensive machines and huge amounts of initial power. The interior of ITER, a fusion reactor being built in France, will need to reach 270 million degrees Fahrenheit to ignite fusion—a full ten times hotter than the sun's core.
“What nature does with the enormous force of gravity in the sun's core is what mankind has been trying to do under controlled conditions in the laboratory,” says physicist Amitava Bhattacharjee, the head theorist at the Princeton Plasma Physics Laboratory, one of the leading fusion research groups in the U.S.
“For the last 60 years we’ve been at this, and I think the progress has been enormous,” he adds. “But we still continue to have a challenge to make nuclear fusion power inexpensively available to people.”
But what if cleverly structured materials could somehow lower the energy needed for fusion? That's what chemists Martin Fleischmann and Stanley Pons at the University of Utah thought they had achieved. The duo ran electricity through a rod of palladium in so-called heavy water, a form of water where the hydrogen atoms are replaced with hydrogen's heavier sibling deuterium.
At a press conference on March 23, 1989, Fleischmann and Pons announced that their setup emitted hundreds of times more heat than the chemistry could account for. Their interpretation: Deuterium nuclei within the palladium were fusing. The news made headlines around the world. Had humankind's energy woes been solved once and for all?
“It got us [physicists] all really excited,” Bhattacharjee says. “Imagine if this were true, how wonderful it would be, how simple this would be. This would be a lot of people’s dream.”
But for many, excitement quickly gave way to skepticism. Early outside attempts to replicate the results didn't turn up massive amounts of heat, nor did the setup appear to yield many high-energy neutrons, a signature of conventional nuclear fusion.
“In March 1989, everybody jumped on this topic, even serious fusion physicists (like me),” Hans-Stephan Bosch, the head of the Wendelstein 7-X fusion experiment at the Max Planck Institute for Plasma Physics, writes in an email. “However, we didn’t find any positive result confirming their claims. Therefore we finished our work, published it, and closed the topic. My impression is that most physicists and chemists did the same, regarding cold fusion as an 'interesting' episode.”
Ever since, cold fusion largely served as a parable on the perils of irreproducibility. But a small group of researchers and enthusiasts has remained convinced that the phenomenon is real and nuclear in nature, though not necessarily the same thing as fusion. This scientific circle still does experiments and reports its results in its own meetings and journals, though it has shed the “cold fusion” name for low-energy nuclear reactions, or LENR.
“It was never all the way gone, but also never quite developing the way other scientific fields typically do,” says David Kaiser, a science historian at MIT who has written on the cold-fusion community. “I found that interesting; it was a kind of shadow community with different communal characteristics, let alone intellectual claims.”
For a time, Matt Trevithick was part of the club. He had first heard of cold fusion while a student at MIT, and from 2004 to 2005, Trevithick worked for Spindletop, a company that helped with LENR research. So when Trevithick eventually ended up on Google's research team as a program manager, he resolved to revisit the nagging question.
“The story [of cold fusion] was decided in a matter of months, and nothing in science is decided that quickly,” he says. “That’s what stayed in my craw for all these years.”
Battery of tests
By April 2015, Trevithick had identified candidate researchers for the project and invited them to Google's California campus. None of the researchers knew each other well; it became a day-long guessing game for each to decipher why they had been invited.
“I’m not gonna lie, there were awkward moments,” Trevithick says.
The researchers then had several months to brainstorm experiments, which they collectively whittled down to three priorities. From the beginning, the researchers agreed to rigorously check their work and publish all their results—even when the work came up empty.
The first major experiment aimed to address a key claim within the cold fusion community: If enough deuterium atoms are electrically crammed into a piece of palladium—at least seven for every eight palladium atoms—the device gives off excess heat. But as the researchers soon realized, packing palladium full of deuterium is extremely difficult, and so is measuring it.
In the past, researchers had measured palladium's deuterium content by tracking changes in its electrical resistance. But when the Google team tried the technique, they noticed errors. So they came up with a new measurement technique: shining x-rays through the palladium to directly see how much the loaded metal had swelled.
The team's second agenda tested whether heating hydrogen with various powdered metals triggers fusion, yielding heat and fusion byproducts. Italian cold-fusion proponents have made the claim since the 1990s, including Andrea Rossi, the colorful inventor of the E-Cat, a device that Rossi claims is a LENR reactor.
But when researchers tried to replicate Rossi's claims, they realized their tools could easily give inaccurate results at the required temperatures and pressures. So Berlinguette and his students built four of the world's most precise calorimeters, devices that measure the heat given off by reactions taking place within them. They then ran 420 separate trials of the experiments—and none of them clearly yielded excess heat. The team will detail their tests in a forthcoming arXiv preprint, Trevithick says in an email.
The third experiment followed up on results reported by Los Alamos National Laboratory in the 1990s: that an electrified palladium wire surrounded by a cloud of electrically charged deuterium made certain fusion byproducts, specifically an excess of a heavy, radioactive sibling of hydrogen called tritium.
When Lawrence Berkeley National Laboratory physicist Thomas Schenkel and his team tested the claim, they didn't find a spike of excess tritium. But while fusion reactions are still extremely rare at low energies, they found that fusion occurred a hundred to 160 times more frequently in their experiment than they expected. Schenkel's team describes the early results in a preprint posted to the arXiv.
“When I see a factor of a hundred discrepancy between my data [and] established theory, that usually means it's interesting,” he says. “I feel I’d like to poke into that.”
In store for the future
Now that the team has publicly unveiled its efforts, Chiang says that the team wants to couple his lab's work with Schenkel's device, with the goal of creating a “reference experiment” for other labs to also advance research into lower-energy nuclear physics.
So far, Trevithick says, Google has spent $10 million on the effort since 2015, and funding persists through the end of 2019. Trevithick stresses that cold fusion represents just one sliver of Google's energy research, which includes working with the traditional fusion company TAE Technologies. Regardless of Google's future investments, the researchers it has supported say they're interested in continuing the work on its basic scientific merits.
And if they or others eventually make new, disruptive discoveries in science and engineering by pursuing less conventional avenues, Bhattacharjee would welcome the effort.
“I'm not addressing in particular whether [cold fusion] is one such candidate, but I generally am for trying out different things,” he says. “And that was the really exciting part of the Pons-Fleischmann experiment. It's really interesting that they dared.”
Then again, Bhattacharjee is a veteran of the effort to bring the sun to earth—and he knows how hard it is to play the role of Prometheus.
“A lot of intelligent people have been at it for a while, and the reason why they have made a lot of progress and still haven't solved it is because it is a very, very hard problem,” he adds. “It may very well be the hardest science and engineering problem we have ever undertaken.”
Editor's note: This piece has been updated to clarify Trevithick's position at Google and the number of published studies the research program yielded.