Carbon Nanotube-based Batteries for HEVs

Oil import numbers for February have been released by the federal government's Energy Information Agency, which follow the recent trend, and the data shows that the U.S. is importing nearly 60 percent of its oil consumed and that about 70 percent of that supply is utilized for gasoline in cars, light trucks, and SUVs, and diesel for heavy-duty trucks like 18-wheelers and refuse/recycling trucks. In February, the U.S. imported 322 million barrels of petroleum at a total cost of $24.6 billion, keeping the country on track to spend approximately 1/3 of a trillion dollars for the domestic gasoline and diesel supply. Energy independence and its inherent national security and economic benefit will require a portfolio of solutions including possibly: natural gas, biofuels and advanced hybrid electric vehicle technology (HEVs), which favors lithium-ion (Li-ion) battery technology.

The United States Environmental Protection Agency (EPA) has announced a partnership this month between the manufacturers of Li-ion batteries together with the EPA and university scientists, and non-governmental organizations, in order to help the manufacturers develop environmentally-friendly manufacturing and material choices. This Design for the Environment (DfE) partnership emphasizes the application of nanotechnology and targets companies which produce Li-ion batteries that incorporate carbon nanotubes. Nanotechnology is being applied towards numerous areas of alternative energy including: energy-efficient solid-state lighting, hydrogen fuel cells, solar cells, and biofuels- among others.

The DfE plan focuses on identifying the materials or processes within a product's life cycle that possess the greatest risks to the public health or the environment. In addition, this life-cycle analysis will promote nanotechnology innovations in advanced batteries that result in reduced greenhouse gas emissions. It is expected that this partnership will have a completed report by 2011 including information on how to improve the extraction, manufacturing and disposal practices of the toxic materials used in the Li-ion battery industry. Similar surveys of best practices are necessary for the solar cell industry as well, which deals with toxic substances in certain cases.

It was published recently in Popular Science that MIT scientists under the direction of Michael Strano have shown how carbon nanotubes can channel a ring of heat that creates electrical current carrying about 100 times as much energy per unit of weight when compared with a Li-ion battery. Carbon nanotubes are submicroscopic structures of carbon just a few billionths of a meter in diameter, which can conduct both electricity and heat; however, after their discovery at Rice University in the early 1990s, they have been limited to mere niche commercial applications such as tips for atomic microscopes.

The MIT group coated the carbon nanotubes with reactive fuel that produces heat by decomposition initiated by a laser beam or high-voltage sparks, which generates a fast-moving heat wave that travels through the nanotube's hollow cylinder 10,000 times faster than in the reactive fuel itself. The fast-moving heat produced a localized temperature of 4,940 deg. F and pushed electrons along the tube, creating a measurable direct electrical current.

Some semiconductor materials can also produce an electric current when heated, but the carbon nanotube experiments defy predictions according to thermoelectric calculations noted by the MIT group. The possibility of creating substantial energy on this scale is being considered for new ultra-small electronic devices the size of peas such as implantable medical and sensor microchips. The main focus of this group's research is to improve the efficiency of this effect and reduce resulting waste energy given off as heat and light. Silicon nano-wire structures developed by other research groups are another major related application for improving upon Li ion battery performance for HEVs and even 3rd generation solar cells, for that matter.

Numerous federal funding grants over the last decade have advanced the field of nanotechnology, which is being applied to the nation's thrust into alternative energy that is subsequently being propelled by record-levels of funding, typically allocated by the U.S. Department of Energy- in order to spur new areas of research for solving future energy problems.

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