Making Coal-Fired Electricity Cheap and Clean

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Making Coal-Fired Electricity Cheap and Clean

For the past several years, clean-burning natural gas has been getting the headlines as the energy source that is abundant and cheap, thanks to breakthroughs in technology.  New fourth-generation nuclear plants are emerging as an increasingly safe and cost-efficient alternative.  But now, coal is beginning to get a second look as an option that will meet our long-term energy needs and goals.

Coal has always had two key characteristics that have made its use attractive:

  • It is readily available.
  • It is low in cost.

The downside is that burning coal produces high levels of carbon dioxide emissions,  as well as pollutants like mercury and sulfur dioxide. 

Of the 30 billion tons of carbon dioxide that human activity causes to be released into the atmosphere each year, the burning of coal ranks second, behind only petroleum-fueled vehicles.

However, there has recently been a renewed interest in building more coal-fired electrical plants due to the engineering of new technologies that:

  • Dramatically reduce carbon dioxide emissions.
  • Reduce emissions of other pollutants.
  • Radically increase fuel efficiencies.
  • Create by-products that can actually help pay for the new technology.

Specifically, two new coal-burning technologies are now at an advanced pre-commercial stage of development, and both utilize pure oxygen in the burning of coal.  The benefits of a pure oxygen combustion cycle have long been appreciated. 

But the cost of separating oxygen and nitrogen has, until recently, presented a major barrier to commercialization.  However, the increased efficiencies of these new technologies, coupled with reduced capital costs in other areas of the plant, have finally made this solution attractive.

The first promising approach is being developed by a consortium consisting of NET Power, Exelon, Toshiba, and The Shaw Group.  Designed to run on “gasified coal,” this system improves on today’s most efficient power plants, which use a gas turbine plus a steam turbine that runs off the gas turbine’s exhaust heat.1  The NET Power technology eliminates the steam turbine by directing part of the carbon dioxide in the exhaust stream back into the gas turbine. 

The result is a coal plant that runs at more than 50 percent efficiency, compared to an efficiency of only 30 percent for a traditional gas turbine system.  This increased efficiency more than pays for the added cost of the oxygen separation equipment.

This approach is called a “high-pressure, super-critical carbon dioxide, oxyfuel power cycle...

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