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New Tank Innovation Makes Small Natural Gas Vehicles Attractive
9 Mar, 2007 10:31 am
Technology uses corncobs to create space-saving briquettes for low-pressure tanks.
A development in natural gas technology will make it possible to create a space-saving low-pressure tank that could revolutionize the capacity of natural gas to power vehicles, especially smaller cars.
“Natural gas is a promising fuel because it’s clean-burning, and most of it can be produced domestically in the U.S.,” said Peter Pfeifer, MU professor of physics and principal project leader. “Our new technology makes it possible to move natural gas forward as the potential fuel of the future.”
Current natural gas vehicles use bulky high-pressure tanks that must be cylindrical in shape and take up a small car’s premium cargo space, such as the trunk. The MRI-MU team’s innovation makes it possible to store natural gas in a smaller, low-pressure tank that can be made in rectangular form and mounted under a car’s floor. Making this possible is an MU discovery that fractal pore spaces (spaces created by repetition of similar patterns at different levels of magnification) are remarkably efficient at storing natural gas.
Researchers have developed a way to “bake” ground corncobs into carbon briquettes that contain these fractal pore spaces. The walls of the nanoporous carbon adsorb methane molecules as a high-density fluid, and the strong attractive force in the narrow pores lowers the energy of the molecules so that they can be packed more closely than in the absence of the carbon. This makes it possible to create a low-pressure natural gas tank.
“The research partnership here exemplifies how scientists from very different fields can work together to conduct truly fundamental research in new materials with the explicit goal of having the results of the research solve problems for people,” said MU Chancellor Brady Deaton.
Pfeifer said the MRI-MU tank reaches the U.S. Department of Energy’s (DOE) target for the first time. The briquettes can store 180 times their own volume of natural gas, or 118 grams of methane per liter of carbon, at 500 pounds per square inch (35 atmospheres); the best previous carbon could only store 142 times its own volume at 500 psi pressure.
“We hope that this will lead to the design of low-pressure tanks that will solve the cargo space problem posed by high-pressure tanks,” Pfeifer said.
The pickup truck fitted with a prototype tank has been on the road since mid-October. Researchers are collecting data to evaluate the mileage per fill-up, pressure and temperature of the tank during charging/discharging; charging/discharging rates under various fueling/driving conditions; and longevity of the carbon briquettes.
“Having a prototype of this technology operating in the day-to-day work environment is significant,” said James L. Spigarelli, president and CEO of Midwest Research Institute. “Although the team’s work is not yet complete, this technology development comes at a fortuitous time as many researchers strive to find multiple alternatives to address the nation’s energy challenges.”
According to a DOE publication, using natural gas instead of traditional fuels results in a reduction of carbon monoxide and nitrogen oxides, smog-producing gases, by more than 90 percent and 60 percent, respectively, in light-duty applications. Carbon dioxide, a greenhouse gas, is reduced by 30 to 40 percent. Compared to commercial diesel engines in medium- and heavy-duty applications, natural gas engines can reduce carbon monoxide and particulate matter by more than 90 percent and nitrogen oxides by more than 50 percent. Also according to DOE publications, only 15 percent of the natural gas used in the U.S. in 2004 was imported, and most imports came from Canada.
Natural gas is cheaper than gasoline and diesel on an energy-equivalent basis, Pfeifer said. In June 2006, the national average cost of compressed natural gas was 94 cents cheaper than gasoline on an energy-equivalent basis, according to the Clean Cities Alternative Fuel Price Report.
This project was funded by a $600,000 grant from the National Science Foundation’s program Partnerships for Innovation. Additional funds totaling more than $400,000 came from MU, MRI, the U.S. Department of Energy and the U.S. Department of Education.
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Yesterday I was on a Lecture made by Professor Ildo Sauer, the actual Director of the gas sector of Petrobras and he has mentioned that solutions for low pressure tanks would increase substantially the use of gas in people's cars in the world, especially in Brazil. This innovation based on fractal structure will certainly contribute to minimize global changes in a near future.
[Response] That would be fantastic. But the storage capacity does not increase linearly with pressure. For example, an increase of pressure from 500 psi to 1000 psi does increase the storage capacity, but not by a factor of two. For details and graphs, see http://all-craft.missouri.edu/research_development/Presentation.Burress.APS.Denver.CH4.070306.pdf Peter Pfeifer