Energy

Coal as Fuel of the Future

August 31, 2000

Imagine traveling over nine times the speed of sound in a hypersonic aircraft powered by... coal.

It is true that hypersonic flight is being ushered into our future with such aeronautic innovations as NASA's unpiloted X-43 Hypersonic flight vehicle which will ultimately result in larger, manned aircraft with larger engines.

But the major obstacle for such high-speed flight is heat, particularly the amount of heat exposed to an aircraft's engines and the fuel that powers them. While today's jet engines are exposed to heat of roughly 310-320 degrees Celsius (600 degrees Fahrenheit), hypersonic speeds can introduce these engines to temperatures over 480 degrees Celsius (900 degrees Fahrenheit).

Not only is coal-powered flight possible, according to scientists, but it may be available within a few years, according to The Energy Institute at Pennsylvania State University.

X-43A Hypersonic Experimental Vehicle, or "Hyper-X," was developed to fly at speeds from Mach 7 up to Mach 10(Mach 1 represents the speed of sound). Heat associated with such flight can cause problems for conventional jet fuels and coal may hold the answer to the fuel challenge. (Courtesy: NASA)

Funded for over nine years by the US Air Force, research at Penn State University has concluded that coal is more suited for high velocity flight because the conventional petroleum-based jet fuel cannot withstand the intense temperatures associated with supersonic flight. Petroleum-based fuels will breakdown under intense heat, which can be as high as 1,000Sˇ C (about 1,800Sˇ F) in hypersonic flight. These temperatures usually range under 315Sˇ C (about 600Sˇ F) during today's normal jet flights.

"Solid coal itself could not of course be used in these applications, but coal-derived liquid fuels most certainly could be used," said Dr. Harold Schobert, Director of the Energy Institute, in reference to the possibility that coal could become the primary fuel for hypersonic flight.

Coal-based fuels, however, have shown that they can withstand much more intense heat than petroleum fuel, and they have already been put to the test by the Penn State research team. Coal fuel has been subjected to temperatures in excess of 800 degrees Celsius (approximately 1,450 degrees Fahrenheit), and plans are to continue experimenting with higher temperatures. It is expected these fuels will be tested in actual engines by 2005, if not sooner.

Coal Power for the Future

It seems logical that coal would be used as the predominant fuel of the future until other non-petroleum-based substitutes are fully developed. Coal burns cleaner, despite the false image that associates coal with the dingy, smog-choked air of the old coal-burning cities and towns, particularly during the Industrial Revolution. Furthermore, according to The World Coal Institute (WCI), "technologies have been developed to improve the environmental performance of coal-use techniques" and that the efficient burning of coal-based fuels results in the release of fewer pollutants into the atmosphere. All fossil fuels produce greenhouse gases; but, greenhouse gases from coal contribute to less than 20% of any enhanced greenhouse effect.

Currently, coal is the primary source of fuel for electricity generation worldwide, according to WCI. Over 62 % of the world's total coal production is used for about 37% of the world's electricity.

Electricity needs are on the increase worldwide at an alarming pace for cities such as this one in India. India, which derives 75% of it's electricity from coal-based fuel, is the third largest producer of coal.

Other uses for coal are used for steel and cement production, commerce, public services, agriculture and other industries, as well as domestic use. Gas (16%), oil (9%), nuclear (17%), and renewable energy sources (21%) supply the rest of the world's electricity needs.

Total world production of hard coal is about 3,700 metric tons, withChina, the United States, India, South Africa, Australia and Russia topping the list of coal producers. Coal provides the majority of the electricity needs for countries such as Poland (96%), South Africa (90%), China (81%), Greece ((70%), India (75%), USA (56%), and Germany (51%).

If coal-based fuels could be relied on more heavily for domestic and commercial transportation, such as airlines and automobiles, all countries around the world can be confident that their coal-based energy resources would be secured, and dependency on the more centralized petroleum-based production industry would be significantly reduced. According to WCI, this would mean that our energy needs can be assured and prices would remain stable and competitive with other fuels. Scientists have confirmed that there is over 200 years of coal resource availability worldwide, far exceeding current known and available petroleum reserves.

"In terms of BTUs [British Thermal Unit - unit of measurement used to express the heat contained in energy resources] in the ground, there is plenty of coal," said Dr. Schobert. "But the 'killer issue' on coal is that it produces more (carbon dioxide) emissions per BTU of energy than the other major fuels." However, "technologies are available or under development to address (these issues)."

Still coal remains our safest, most viable and dependable energy resource to meet our enormous energy needs. When asked if there any source of energy that could replace coal as our primary energy source within our lifetimes, Dr. Schobert replied, "There is only one: nuclear."

What is Coal?

Over half of the world's coal reserves is of the bituminious variety, such as is being mined here in Queensland, Australia. Only anthracite coal is harder than bituminious. (Courtesy: World Coal Institute)

Coal is an organic, sedimentary (produced from sediments) rock composed primarily of carbon, hydrogen and oxygen.

Coal was formed from pre-historic vegetation that has been under the heat and pressure within the earth. After going through physical and chemical changes over millions of years, the vegetation was converted into coal. Such processes did not begin until land plants evolved some 400 million years ago.

Peat was the first stage of coal to form, which was eventually converted into lignite or brown coal. After millions of more years of heat and pressure from within the earth's surface, bituminous or hard coal evolved. Ultimately, the bituminous coal transforms into an even harder form called anthracite coal. Anthracite has a higher carbon and energy content and a lower level of moisture than bituminous coal, and is used for domestic and industrial purposes, including smokeless fuel. Bituminous coal is primarily used for power generation, and the production of cement, iron and steel.

- Eric McLamb

Did you know....?

The largest environmental threat from coal is not in its use, but in mining it. Strip mines, such as the technique that had been heavily used in West Virginia, essentially strips the top layers of earth away to expose the coal reserves underneath. This has resulted in devastation to natural habitats, natural growth and water supplies on the surface. Over time, however, coal mining companies have worked diligently to reduce the environmental impact of strip mines by reclaiming the land with original matter and re-seeding the mined surface. This is still a highly controversial practice and strip mining bans are placed or sought in many regions, including such Federal restrictions in the Appalachian Mountains (see Strip Mining on Black Mountain).

Also...

The commercial airline industry should be able to use coal-based fuels to power current commercial aircraft in the not too distant future. Not only would this technological enhancement provide deeper and more stable reserves than petroleum-based fuels, but it would provide less atmospheric pollution. The aircraft would not fly faster, but they would fly cleaner.