Electricity demand has continued to increase over the past four decades. Demand has grown largely due to the emergence of new technologies as well as the urbanization and modernization of populations in emerging economies.
Why Coal Use is Growing
Global coal use has soared 335 percent since 1970; this rapid rise is closely correlated with growth in gross domestic product and higher standards of living.
The world’s strongest economies continue to turn to coal as the only sustainable fuel, at scale, that can meet growing energy needs. One new, 500 megawatt coal-fueled power plant is expected to start up somewhere in the world every three days for the next five years. And in five years, 20 percent more steel will be required to build the world’s rising megacities, requiring an additional 200 million tons of metallurgical coal.
Coal makes up 55 percent of global energy resources. It is widely dispersed, broadly available, easily transported, energy-dense and accessible.
Where Coal Comes From
Coal deposits can be traced to many eras, but the most abundant come from lush forests in the warm, swampy river deltas some 320 million years ago. Coal was created through a series of powerful geological events over millions of years. When plants died, they formed a thick layer that was buried under prehistoric forests and seas. Eventually, the plant matter changed into a substance called peat. Massive layers of sand and sediments covered the peat, and as they became more compact, the ever-increasing pressure and heat transformed peat into coal.
How Coal is Transformed into Electricity
Electricity lights, heats and cools our lives, and serves as the backbone of our transportation, communication, healthcare, manufacturing and technology systems.
Converting coal into electricity is a multi-step process:
- Coal is pulverized into a fine powder, and mixed with hot air.
- The combination is transferred to a furnace, and heats a boiler containing water to create steam. Steam turns a turbine engine, transforming heat energy from burning coal into mechanical energy.
- The spinning turbine powers a generator, which transforms the mechanical energy into electric energy.
- A condenser cools the steam, turning it back into water that returns to the boiler.
A transformer transmits electricity from the power plant, along transmission lines to substation transformers, and then to distribution lines, which can be either above or below ground. These distribution lines deliver electricity into our homes and businesses.
How Clean Coal Becomes Green Coal
Coal also has a strong and improving environmental track record. Since the first Clean Air Act became law in 1970 in the United States, emissions from U.S. coal-fueled plants have decreased nearly 90 percent per megawatt hour as coal used for electricity has tripled. The next generation of supercritical, gasification and carbon capture and storage -- or green coal technologies -- builds on this progress.
New efficient coal plants have significantly lower emissions than the existing fleet and a dramatically reduced carbon dioxide footprint. Continual technological improvement will lead to the ultimate goal of near-zero emissions coal-fueled energy. Studies suggest that coal with carbon capture and storage (CCS) may be the low-cost, low-carbon solution, 15 to 50 percent less expensive than alternatives such as nuclear, wind or natural gas with CCS.
The Prairie State Energy Campus includes a 1,600 MW (net) coal-fired, steam-electric generating station that was commissioned in 2012 in Southern Illinois. The station uses state-of-the-art pulverized coal supercritical boiler technology.
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