energy bursts

Lignite My Fire

Lignite occupies a niche somewhere between hard, black coal and crumbly peat. Pound for pound, lignite has half the energy content of anthracite, and it often has a high moisture content. But while it is far from ideal as fuel goes, it does get burned. In the United States, there are 35 power-generating stations that depend on lignite.

Low-grade lignite in Montana, North Dakota and Texas makes up 10 percent of U.S. coal reserves.

Now lignite may get a leg up. In June, the US Department of Energy kicked off the testing of a new system designed to use waste heat from a power plant boiler to remove moisture from lignite and other soggy coal before burning. The hope is that the drier fuel will burn hotter and cleaner.

The testing project, part of the national Clean Coal Initiative, will be conducted by Great River Energy of Elk River, Minn., at its Coal Creek Station in North Dakota.

First, a prototype module will be designed to dry about one-sixth of the coal fed to a 546-megawatt unit. Once the prototype runs successfully, the company will perform full-scale, long-term operational testing. The coal will be dried to various moisture levels, the full effects of coal drying on plant performance will be measured, and optimum operating conditions will be determined.

North Dakota lignite typically contains about 40 percent moisture. By drying the lignite first, the researchers expect to lower the moisture content by at least 10 percentage points, resulting in an estimated 2.8 percent to 5 percent efficiency improvement in the plant. This could translate into 25 percent less emission of sulfur dioxide, and 7 percent less of mercury, carbon dioxide, nitrogen oxides, and particulates per unit of electricity output.

Home Economical

Seeing images of wood frame houses shattered by hurricanes or flattened by tornadoes may make one long for the security of a sturdy concrete home. But new research suggests that wood houses require less energy over a lifetime than do concrete or steel frame buildings.

Researchers from the Consortium for Research on Renewable Industrial Materials, made up of a number of US universities and research institutes, analyzed the total energy used to manufacture and transport building materials, build a house, maintain it for a 75-year life cycle, then demolish or dispose of it. They found that construction of a typical 2,100-square-foot steel-frame house would use 17 percent more energy than building an identical wood-frame home. A typical concrete-frame house used 16 percent more energy than a matching wood-frame house.

When Abraham Lincoln's family built this log cabin, few greenhouse gases were likely emitted.

The researchers also calculated emissions of carbon dioxide, methane, and nitrogen oxide generated during the life cycles of the houses to determine the potential of different construction materials to affect climate change. The global-warming potential of the steel-frame home was found to be 26 percent greater than that of the wood-frame home; greenhouse emissions of the concrete-frame home were 31 percent greater than those of the comparable wood-frame home.

The houses analyzed shared much of the same building material, such as glass, gypsum, and asphalt, in spite of the differences in their frames. But glass, concrete, and steel require much larger quantities of fossil fuel to produce than do wood products.

Differences in heating and cooling costs are to be assessed in an upcoming study. Perhaps the researchers will take on storm damage as well.

_{Fueled by Flowers}

Nothing says "eco-friendly" like a big, bright sunflower. And now researchers in England think they've discovered a way to make automobiles greener by powering them with hydrogen derived from sunflower seed oil.

Valerie Dupont, an engineer with the University of Leeds in England, and her colleagues have developed a hydrogen generator that processes sunflower seed oil—the kind found on supermarket shelves—together with air and water. The prototype device vaporizes the oil and water, then reforms the mixture with the help of nickel- and carbon-based catalysts to produce carbon dioxide, hydrogen, methane, and carbon monoxide.

The device is compact enough to fit on a standard laboratory bench.

In studies, the researchers achieved a hydrogen purity of 90 percent, which is more efficient than current hydrogen generators that only achieve a hydrogen purity of about 70 percent. The byproducts of the sunflower oil transformation, carbon dioxide and methane, are generated in roughly equal proportions, the researchers say.

Ultimately, the researchers hope that the catalytic reactions will provide enough heat to drive the device. At present, electricity is needed to bring the generator to the correct temperature.

Such a device could one day fit under the hood of a car to generate hydrogen for fuel cells. One of the great stumbling blocks to developing affordable fuel cell-powered cars is the issue of hydrogen storage. Hydrogen can be stored much more densely in the form of vegetable oil than it can as a compressed gas.

_{Cars as Batteries}

Utilities searching for innovative sources of peak power ought to look at their parking lots. Researchers at the University of Delaware and at Green Mountain College in Vermont suggest that electric vehicles could feed the grid while they are parked.

The concept, called "vehicle to grid" or V2G, is derived from the observation that cars used for commuting (as most autos are) spend most of their time sitting parked. The standard operating model for electric vehicles is that they would recharge during the evening, when electricity demand is down. During the day, however, they would sit unused in worksite parking lots.

Willett Kempton of the University of Delaware and Steven Letendre of Green Mountain College say that by adding a few hundred dollars worth of electronics, these sitting cars could be tapped by utilities during peak hours, drawing down individual car batteries by predetermined amounts and crediting car owners for the juice. Since electricity sells for a higher price during peak hours than at nighttime, car owners might profit from the transaction.

Kempton and Letendre estimate that such a scheme, executed on a wide scale, could supply as much as one-fifth of the nation's electricity needs by 2050.

Of course, it seems farfetched to suggest that enough people will be driving electric vehicles for V2G to have an impact, even by 2050. But the researchers say hybrids, which have a large electric component to their drivetrains, could be used as well.

This section was written by Editor Jeffrey Winters.

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