Earth's Best Friends

by Eileen McCluskey

Cars whisper down highways getting 100 miles to the gallon. Corn has its old job back—feeding humans and animals at reasonable prices—as non-competing and plentiful biofuels are easily produced from reapers' refuse. Automobiles weigh far less than their predecessors, with bodies and many components made from light, strong, recycled aluminum—just one reason for their impressively meager fuel requirements. This vision should cruise into reality within the next handful of years, thanks to WPI researchers working at the forefront of the sustainable energy field.

Fluid Vision

James Van de Ven, assistant professor of mechanical engineering and advisor to WPI's new Mechanical Energy and Power Systems (MEPS) laboratory, specializes in efficient energy conversion and storage, and drives a vision toward better cars.

In MEPS, Van de Ven and a team of graduate students use data acquisition equipment, a hydraulic test stand, prototyping parts, and other tools to create such devices as a power-dense, liquid-piston Stirling engine with a high-speed on-off hydraulic valve. "We're attempting to revolutionize mobile power and hydraulic power," says Van de Ven.

This revolutionary hydraulic hybrid engine will combine the quiet operation of the Stirling engine (invented in 1816 to create power from any heat source) with the power density and flexibility of hydraulic machinery, which is used primarily in industrial equipment, agriculture, and construction.

The liquid piston, an idea developed by WPI's James Van de Ven, may make Stirling engines more efficient and less complex, paving the way for their use in applications like hydraulic hybrid vehicles.

At the engine's heart is the liquid piston, an idea Van de Ven hit upon while pondering how to most efficiently heat and cool the gas in the Stirling engine's expansion and compression chambers. "The liquid piston will decrease the complexity and vastly increase the efficiency of the Stirling engine; these have been its biggest drawbacks," he says. He also seeks to control the hydraulics with a rapidly switching on-off valve, as is done with electrical systems, to dramatically improve efficiency over conventional hydraulic valve control. He is aiming for a valve that cycles on and off 100 times per second.

When complete, says Van de Ven, "A hydraulic hybrid vehicle with a Stirling engine will release and store energy very quickly, providing the ability to rapidly accelerate using a small, lightweight mechanism." Indeed, hydraulic hybrids will offer 10 times more power density than today's hybrids, such as the Toyota Prius, which uses a combination of an internal combustion engine and a battery-powered electric motor. "The hydraulic hybrid completely changes how you look at the power train. The engine can be downsized and run more efficiently, while the hydraulic system manages the high power spikes required in stop-and-go traffic."

fuel tank indicator Hydraulic hybrids will cost far less than electric hybrids and last much longer, Van de Ven says. While an electric battery costs consumers about $4,000 and lasts up to 10 years, hydraulic hybrid accumulators should cost a small fraction of their electric counterparts, using technology that has routinely run for 25 to 30 years in construction vehicles and other heavy machinery. Fuel economy estimates are also notable. While the Prius gets 48 miles per gallon in city driving, the hydraulic hybrids will get 80 to 100, he says.

Perhaps most important, Van de Ven estimates a short timeline. "We'll see a liquid piston Stirling engine as a practical prototype within five or six years," he says. "To get there, we need to determine how the liquid columns will behave in the engine at high frequencies. We also have to determine what materials to use, not only the liquid for the pistons, but also materials for the engine."

Watch a video about reserch at WPI on sustainable energy.

Melt Versus Smelt

Diran Apelian

Diran Apelian is throwing all this weight into research and advocacy "to reduce our carbon footprint, through sustainable production of materials and materials substitution."

Diran Apelian will likely prove a valuable ally in Van de Ven's materials quest. Apelian, Howmet Professor of Mechanical Engineering, founded WPI's Metal Processing Institute (MPI), an industry-university alliance with centers in metal casting, powder metallurgy, heat treating, and thermal processing that is supported by about 110 corporations and private foundations, and the federal government.

"We'll see big fuel savings by manufacturing cars using lighter-weight materials like aluminum and magnesium."
- Diren Apelian

Apelian, who is also president of the international Minerals, Metals, and Materials Society (TMS), specializes in aluminum and magnesium. His pioneering work in solidification processing, molten metal processing, and filtration of metals, among many other areas, has been repeatedly recognized with top awards and honors in his field. "I'm a heavyweight player in the light metals world," he says with a laugh.

Apelian is throwing all this weight into research and advocacy "to reduce our carbon footprint through sustainable production of materials and materials substitution," he says. "The materials science and engineering research agendas in the U.S. over the last 40 to 50 years have been defense-centric, rather than focused on societal needs. Defense is very important, but we need a balance to ensure that basic human needs are being addressed."

Apelian's own research focuses on solutions to the energy-hogging aluminum production process. Aluminum must be extracted from bauxite via electrolysis, and aluminum smelters use such prodigious amounts of electricity that they are typically built near large power stations. Recycling aluminum, by melting and reshaping it into new products, requires 94 percent less electricity. "We're developing processes to use a heck of a lot less energy," Apelian says. "It's a good idea, and it has to happen."

To render aluminum recycling even more appealing to businesses, Apelian seeks to put the shine on his ideas with X-ray fluorescence, which permits quick and accurate sorting of aluminum cast-offs (beverage cans, siding for houses, power-train components) by their alloys, and laser-induced breakdown spectroscopy, which analyzes the precise makeup of the component elements in liquid metal, allowing each batch to be fine-tuned for its intended purpose. "It's like cooking," Apelian says. "Depending on the product you're casting, you may need to add a bit more of one alloy or another."

Laser-induced breakdown spectroscopy can analyze the precise makeup of the component elements in liquid metal, allowing each batch to be fine-tuned for its intended purpose.

All this happens in mini-mills, innovations developed by the steel industry 30 years ago to increase efficiency and save energy. Apelian notes that MPI industrial partners, such as Waste to Energy in Bedford, Mass., and ERCO Corporation in Albany, N.Y., have committed to the project. "We have a major proposal out to the Department of Energy to build the future aluminum mini-mills."

Automobiles will certainly benefit from greater availability of recycled, recast aluminum. "We'll see big fuel savings by manufacturing cars using lighter-weight materials like aluminum and magnesium," notes Apelian. For every 10 percent reduction in vehicle weight, fuel consumption drops by five to six percent.

It Takes Guts (and Termites)

Like his colleagues, Alex DiIorio seeks bold new ways to improve the planet's prospects. As director of the Bioprocess Center in the WPI Life Sciences and Bioengineering Center at Gateway Park, DiIorio works to identify novel micro-organisms—fungi and bacteria in the guts of termites and other wood-eating insects—that he has altered genetically, enhancing their abilities to convert cellulose and other plant matter to sugars. The work is funded by California-based EdenIQ, which invests in finding more effective and efficient ways to create ethanol from plant materials that are not needed for human or animal nutrition.

All this happens in mini-mills, innovations developed by the steel industry 30 years ago to increase efficiency and save energy. Apelian notes that MPI industrial partners, such as Waste to Energy in Bedford, Mass., and ERCO Corporation in Albany, N.Y., have committed to the project. "We have a major proposal out to the Department of Energy to build the future aluminum mini-mills."

"We're developing a cocktail of enzymes to break down the materials," explains DiIorio, "essentially mimicking the processes you see in nature." Once he selects the most effective microorganisms for the job, DiIorio harnesses them to produce glucose in vast quantities, which can be fermented into ethanol using an industrial process that is simple and economical enough to place this form of the fuel on a level economic playing field with that made from corn or sugar cane.

"We carefully monitor the batches for proper oxygenation and other key issues so we end up with glucose and not fungal soup."

As he shifts his strains into large (1,000-gallon) bioreactors, DiIorio says, "we carefully monitor the batches for proper oxygenation and other key issues so we end up with glucose and not fungal soup." He expects to have this ramped-up system operating within a year. In the end, all agricultural waste—whether corn husks, melon rinds, or other refuse—will be fair game for this new ethanol production process.

Alex DiIorio uses enzymes derived from those found in the guts of wood-eating insects to break down cellulose into sugars that can be fermented to produce ethanol.

Additional Readings

Materials and society: Challenges and the TMS response
Apelian, D., and W. Hunt, JOM, vol. 60, no. 2, 2008.

Development of a hydro-mechanical hydraulic hybrid drive train with independent wheel torque control for an urban passenger vehicle
Van de Ven, J., M. Olson, and P. Li, proceedings of the International Fluid Power Exposition, Las Vegas, Nev., 2008.

"Right now we're sending $700 billion overseas each year to pay for our energy needs," says DiIorio of his inspiration to improve ethanol production. "The solution to our problems is the combination of ethanol, solar, wind, and other renewable sources of power. We can solve this problem in this country. I want to play a role in that solution."

All this happens in mini-mills, innovations developed by the steel industry 30 years ago to increase efficiency and save energy. Apelian notes that MPI industrial partners, such as Waste to Energy in Bedford, Mass., and ERCO Corporation in Albany, N.Y., have committed to the project. "We have a major proposal out to the Department of Energy to build the future aluminum mini-mills."

Though working in disparate areas toward common goals, DiIorio and his colleagues find plenty of fuel for hope. As Van de Ven says, "Doing this research gives me hope that we can curb energy consumption and put the brakes on global warming before it's too late."

Another Road to Sustainability

Rajib Mallick, associate professor of civil and environmental engineering, thinks one answer to our energy needs may be right under our feet. He is studying the potential for extracting energy—as hot water and electricity—from sun-baked asphalt. Working with Novotech Inc. of Acton, Mass., and Sankha Bhowmick at UMass Dartmouth, Mallick's team found that asphalt absorbs considerable heat that can be transferred to water with heat exchangers just below the surface. This technique could reduce the urban heat-island effect significantly. They've also identified additives and coatings that boost blacktop's heat-absorbing ability. Someday the idea could transform the nation's bounty of parking lots into solar collectors.