Professor Slocum showing President Obama a rough prototype of a system to store wind energy in deep ocean water in 2009.
Zany, quirky, enthusiastic. There are many ways to describe the personal style of mechanical engineering professor Alexander Slocum. And he embraces them all. As a teacher and researcher, he uses what he calls his pinball-like focus and his passion for mechanical engineering to inspire students and tackle some of the biggest challenges in energy, medicine, and precision engineering. “I would probably be classified as ADHD++ because my mind moves so fast between so many different things,” he says. “But I also have the discipline to focus for hours when the right idea warrants it.”
Slocum is a self-described “gizmologist” and a lover of all manner of machines, from giant wind turbine towers to equipment that grows carbon nanotubes. With his colorful wardrobe, he’s a recognizable figure around campus, and he participates actively in student life, often cooking pasta dinners for freshmen in the Experimental Study Group. As a professor, he exemplifies MIT’s motto of mens et manus, or mind and hand, by teaching students to combine intellectual inquiry with hands-on engineering and design.
It’s his research in renewable energy, though, that’s recently gotten the most attention outside MIT. This spring, Slocum coauthored a paper in Proceedings of the IEEE describing a utility-scale energy storage system based on large underwater concrete spheres and floating wind turbines. When Barack Obama visited MIT in 2009 to deliver a speech on energy, Slocum, in one of his trademark Hawaiian shirts, demonstrated the concept to the president using a toy wind turbine and large jars filled with sand and water. Since then, the work has advanced to the point where Slocum and colleagues have had discussions with a large engineering and construction firm on how it might be possible to manufacture the massive structures. Slocum estimates it would take five to 10 years to commercialize the idea, which he calls the Ocean Renewable Energy System.
Floating wind turbines would be moored with cables to a network of 20,000-ton spheres 25 to 30 meters in diameter, or about the size of the dome at MIT. To store excess energy not sent to the grid, the turbines would operate pumps to evacuate water from the spheres. When power was needed, water would flow into the spheres, causing the pumps to run in reverse and act as generators.
Developing inexpensive ways to store large amounts of energy on the electricity grid would allow wind farms and solar installations, which normally are intermittent sources, to deliver power on demand as fossil-fuel and nuclear plants do now. Slocum’s design is a twist on conventional pumped hydropower, currently the most cost-effective and widespread storage method. Pumped hydropower technology sends water uphill to a reservoir and releases it to generate power during peak times. Instead of relying on gravity by storing the water in a mountaintop lake, Slocum’s concept harnesses the water pressure at hundreds of meters of ocean depth to power the electricity generator. The concrete spheres that hold the water also serve to anchor the turbines.
If it works, the impact could be dramatic. The wind over deep waters represents a massive yet largely untapped resource. Slocum’s paper estimates that 1,000 turbines, placed out of sight about 30 to 50 kilometers offshore with anchoring spheres 600 meters below the surface, could supply as much power as a nuclear plant. Today’s pumped hydropower systems typically deliver hundreds of megawatts of power for six to 10 hours. Though deploying turbines in deep water would be more expensive than placing them near shore, Slocum and his colleagues estimate that the Ocean Renewable Energy System could be price-competitive with pumped hydro—and a large-scale deployment with 1,000 turbines could store up to five gigawatts of power for as long as 12 hours. The researchers have already built a prototype system with a 30-foot-high tower and off-the-shelf pumps and other components.
Storage is one of the toughest problems in energy, which is why it has attracted thousands of scientists and entrepreneurs. Although still a research project, the Ocean Renewable Energy System is impressively well thought out, says Haresh Kamath, the program manager for energy storage at the Electric Power Research Institute (EPRI). “With this concept, it is more of an engineering challenge rather than a materials or fundamental science challenge,” he says.
The project showcases Slocum’s affinity for “symbiotic design,” or solving multiple problems at once. In addition to providing energy storage and acting as anchors, the spheres would be made of concrete that can contain significant amounts of fly ash, a waste product of coal power plants. The system could also benefit local ecosystems by encouraging growth of bottom-dwelling life. And in a speech to top Japanese officials, Slocum argued that a deep-sea wind farm near the shuttered Fukushima nuclear power plant could provide new jobs for local fishermen, who can no longer fish there because of radiation. They could help install the systems, perform maintenance, and monitor the impact on the ecosystem.
In a separate research effort, Slocum led the design of a system in which the heat from solar concentrators is stored in large pools of liquid salt. A number of large-scale concentrated-solar plants already use molten salt; it stores the sun’s heat and, through a heat exchanger, converts water into steam to generate electricity in a conventional steam turbine. In these systems, the salt is heated as it circulates through tubes, but Slocum proposes a different method. Drawing on research from the 1970s, his technology would beam sunlight directly into a large volume of molten salt, eliminating the network of pipes and pumps that tend to be the weak points in traditional concentrated-solar power systems.
Slocum’s wind and solar storage systems face enormous hurdles before they can go beyond the design and small-scale prototype phase. At the most basic level, the floating turbines the Ocean Renewable Energy System requires for capturing wind over deep waters are still being tested and have yet to be commercialized. And it’s notoriously difficult to model the economics of energy storage without real-world demonstration systems, which can be hard to fund, says EPRI’s Kamath.
Slocum isn’t daunted. Of course there are lots of things to figure out, he says, but big challenges like going to the moon require years of persistence and “parallel thinking,” or working on many problems simultaneously. The floating wind turbines, for instance, are already being developed by others; multi-hour underwater energy storage could help accelerate their adoption. “When you have two problems at once that kind of depend on each other, they catalyze each other,” he says. “I hypothesize you often end up with a better solution for both by thinking of them as a system.”
That emphasis on systems thinking, spanning everything from product design to manufacturing, accompanies Slocum into the classroom, too. In his Precision Machine Design class, 2.75, doctors come in and present specific challenges to student teams. The students then design and make a proof-of-concept machine that not only solves a clinician’s specific problem but can also be made economically. “When you think about manufacturing and deployment [as you design], you end up inventing more stuff that goes back to the beginning, and you end up inventing a better machine,” Slocum says. Since he made medical devices the focus of 2.75 in 2004, the class has helped generate many peer-reviewed papers, about a dozen patent applications, and a few spin-off companies, such as Rest Devices, a Boston startup that makes shirts with embedded sensors to monitor sleep.
The class is notable because it combines lectures on theory with hands-on work making prototypes, says Tohru Yagi, a visiting Fulbright scholar from the Tokyo Institute of Technology in Japan, who has spent the last year in Slocum’s Precision Engineering Research Group (PERG) lab. “What he does is very analytical and also systematic, and it can be applied to any industry, not only in engineering,” he says. Indeed, Slocum has extensive experience with industry and has been involved in spin-off companies, most recently the startup Keystone Tower Systems, which developed a way to make wind turbine towers at lower cost by using less steel.
Slocum himself is a lifelong tinkerer, carpenter, and furniture maker. He joined the MIT Hobby Shop, the Institute’s wood and metal workshop, as a student in 1978 and now chairs its oversight committee. He’s not afraid to get dirty with hands-on work himself. Postdoctoral associate Nevan Clancy Hanumara, SM ’06, PhD ’12, who co-teaches the 2.75 class, says he once bumped into Slocum at a Chicago hotel where Hanumara was attending a conference and found the professor, in town for an industry visit, covered in grease. Asked what happened, Slocum said, “I must have climbed into a machine.”
Slocum’s enthusiasm for his work tends to rub off on the students in his lab. He tries to motivate them by kindling their own passions and giving them ownership of their projects. “As long as your interests have some kind of relevance, some practical application, he’s all for it,” says doctoral student and Slocum lab member Nikolai Begg ’09, SM ’11, a medical-device engineer who won the Lemelson-MIT Collegiate Student Prize this year. “It’s great to be able to pursue what you want to do and study. He doesn’t have a big personal agenda.” Slocum was named the Massachusetts professor of the year in 2000, one of a number of awards he has received.
One thing that makes Slocum a particularly effective professor is that he mixes his enthusiasm for engineering with humor. When he taught the long-running design and manufacturing class 2.007, students got a dose of his playful style on the first day. As he pulled out materials available to make that semester’s project, he demonstrated the relative strength of objects with his body: he bent metal shafts over his neck, pressed metal sheets across his torso, and delivered fake karate chops on wood boards with a loud shriek. During the final competition between student-made robots, he did the lively play-by-play commentary as if he were calling a wrestling match, shouting lines like “This is where physics meets the carpet!” In celebrating the winners of what he calls this “geek-alicious” event, Slocum has been known to lift students up with a giant bear hug or hoist them on his shoulders for a victory lap. And whether he’s holding court in a lecture hall or talking one on one, goofy one-liners pepper his speech. (One example, on the perils of linear thinking: “While we’re busy analyzing our dinner jacket, we don’t realize that our pants are on fire.”) Asked how old he is, Slocum quips: “Too young to worry about it.”
But his expertise in serious matters is recognized at the highest levels. When the federal government scrambled to stem the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, Slocum, who worked in offshore oil drilling during graduate school, was among Energy Secretary Steven Chu’s select group of science advisors. He played an essential role in the response by developing a fix when the hydraulic lines that allow engineers to control underwater remote-operated vehicles were severed. Last year he was invited to Japan, where he advised officials on how the energy from the nuclear plants shuttered after Fukushima could be replaced by diverting a portion of the country’s auto manufacturing capacity to develop offshore wind.
Slocum is known for packing a huge amount of activity—including triathlon training—into his days. Yet he recently took on another responsibility, at the White House’s Office of Science and Technology Policy. As the assistant director for advanced manufacturing, he will be what he calls a “geek in residence,” charged with helping to launch a number of advanced manufacturing centers. The position is a good fit with his “design for manufacturing” philosophy.
In the PERG lab, Slocum emphasizes a multidisciplinary approach and real-world practicality. During design reviews, researchers get feedback from engineers in completely different fields from their own, such as surgical instruments, drug manufacturing, oil extraction, and cancer detection. To get a better grip on how industry works, he’s taken lab members on tours of many different companies, including aerospace production facilities.
As a lab director, Slocum fosters a collegial atmosphere by inviting researchers to his 300-acre farm in New Hampshire, where he grows fruit and raises sheep, alpacas, and chickens. During these social outings, he makes sure that everyone has a job, whether it’s gathering wood for the fire or going along on turkey hunts. “It’s like a snapshot of his life—everyone’s working and having fun with their own role,” says PERG alumnus Daniel Codd, PhD ’11, who is now trying to secure funding to commercialize the molten-salt energy storage system he worked on with Slocum as a student. “He’s good at getting people around him to rally around something greater.”
Greg Tao ’10, who won the 2.007 robotics competition in 2008, admires Slocum’s ability to excel not only in so many intellectual pursuits but also as an athlete. “You can do a lot more than just being a good academic—he really embodies that,” he says.
For Slocum himself, dividing his attention among many interests apparently works: there are dozens of patents issued or pending with his name on them. He could easily jump from academia to work as chief scientist at a technology startup or other commercial venture. But that appears unlikely to happen. His ties to the Institute run deep: he’s spent nearly all his adult life at MIT, and his three children—all sons—have enrolled as students (two have already graduated and one is there now). More important, his role allows him to pursue his passions in mechanical engineering design. “Every three years, I try like hell to get out of here,” he says. “But I keep coming back because it’s so much fun.”