The National Academies: What You Need To Know About Energy

The National Academies

What You Need To Know About Energy

Advanced Coal Technologies

In the endeavor to reduce the emission of carbon dioxide (CO2) when fossil fuels are burned, coal is a prime target: It accounts for more than one-third of the nation’s CO2 emissions. New technologies focus on increasing the efficiency of the electricity generating process and separating, capturing, and safely storing the CO2 before it is discharged from the smokestack. Several approaches are possible. The latest generation of pulverized coal (PC) plants, incorporating “ultrasupercritical” boilers capable of operating at extremely high temperatures and pressures, can achieve efficiencies—before CO2 is captured and stored—of up to 45% (meaning that 45% of the energy stored in the coal is converted to electrical energy). However, when a portion of the energy from burned coal is diverted from making electricity to capturing and storing carbon, efficiency is projected to drop to about 30%.

Another advanced coal technology is coal gasification, a process in which coal is converted to a gas (called syngas) before it is burned, making it easier to separate the CO2 as a relatively pure gas before power is generated. Such Integrated Gasification Combined Cycle, or IGCC, plants may achieve even higher efficiencies.

New technologies focus on increasing the efficiency of the electricity generating process and on separating, capturing, and safely storing the CO2 before it is discharged from the smokestack.

Another option is to burn coal in oxygen instead of air (as is currently done), to reduce the amount of flue gas—essentially exhaust—that must be processed to isolate CO2. These techniques show promise but require more research and development. They also substantially increase the cost of the electricity produced.

Once CO2 has been captured, it must be sequestered, or permanently stored. Current options focus on such geological formations as oil and gas reservoirs, unmineable coal seams, and deep saline aquifers, all of which are geologically sealed and unlikely to allow injected CO2 to escape. While these technologies are very promising, it still must be proven that large quantities of CO2 can be stored effectively underground and monitored for long periods of time. The methods also must be acceptable to the public and regulatory agencies. Large-scale field trials of prototypes of coal-fueled, near-zero-emissions power plants are needed to test the viability of several of these new “clean coal” technologies.

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Energy Hands-on

What do you know about energy?

Most of the world's energy originates from which two primary sources:

  • Correct!

    The energy we capture for use on Earth comes largely from the sun or from nuclear forces local to our own planet.

  • Sorry, that’s incorrect.

    The energy we capture for use on Earth comes largely from the sun or from nuclear forces local to our own planet.

  • Sorry, that’s incorrect.

    The energy we capture for use on Earth comes largely from the sun or from nuclear forces local to our own planet.

Energy Defined

Energy

The capacity for doing work; usable power (as heat or electricity); the resources for producing such power.

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