Mildred Dresselhaus, a professor of physics and electrical engineering at MIT, gave the keynote address at an MIT conference on nanotechnology and energy. Among other science management positions, Dresselhaus chaired a 2003 Department of Energy report called the Basic Research Needs for a Hydrogen Economy.

During her talk, Dresselhaus said there has been progress since the 2003 report was published, but there remain a number of challenges in hydrogen production, storage, and fuel cells , the devices which convert hydrogen to power.

"If we're going to use hydrogen for transportation or other large-scale uses, we are faced with a scale factor--we have to increase production by factors of many to achieve the levels of the energy supply for transportation," she said.

Storage, too, remains a "vexing problem," she said. "Energy density is the biggest challenge," Dresselhaus said. "Even if we address that, we still have a whole bunch of things to do."

For example, work needs to be done in reducing the amount of energy that is released and heat created when transferring hydrogen into a car, for example.

In the short term, most production-related research is focused on using fossil fuels to make hydrogen, which cannot be harvested like fossil fuels.

Longer term, nanostructure materials, used in fuel cell catalysts and other places, could lead to technical breakthroughs, she said.

Echoing the comments of her colleagues at MIT, Dresselhaus said that in the next 50 years new technologies will need to be developed to satisfy growing energy demand and to address climate changes from increased carbon in the environment.

In 2003, the DOE's authors said that a hydrogen-based economy was difficult but achievable, she noted.

"Probably nobody has changed their assessment: the problem is difficult but we are making rapid progress and nanostructures are an important component," Dresselhaus said.

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