The steam turbine continues to be a major factor in electric power generation throughout the world. Even nuclear power plants use the heat from a controlled nuclear chain reaction to produce needed steam. In the United States, more than 88 percent of all electricity is produced by steam turbines [source: Popular Mechanics].
As mentioned earlier, there are basically three stages of matter: Solid, liquid and gas. Each stage is held together by a different level of molecular force. With water, gaseous steam takes up space due to its molecules being furthest apart. However, when enough pressure is applied to steam, an amazing thing happens. The molecules are forced together to the point that the water becomes more like a liquid again, while retaining the properties of a gas. It is at this point that it becomes a supercritical fluid.
Many of today's power plants use supercritical steam, with pressure and temperature at the critical point. This means supercritical steam power plants operate at much higher temperatures and pressures than plants using subcritical steam. Water is actually heated to such a high pressure that boiling does not even occur.
The resulting high-pressure fluid of supercritical steam provides excellent energy efficiency. With the aid of high pressure, supercritical steam turbines can be driven to much higher speeds for the same amount of heat energy as traditional steam power. They also release less CO2 exhaust into the atmosphere. Additionally, new high-pressure boilers built with rocket technology are being developed to further control the levels of CO2 emitted. Some boilers will even cool the steam back into a liquid and channel it into the ground to capture emissions.
The future is bright for steam on other fronts as well. In the search for alternative automobile fuel systems, some scientists continue to pursue the 15th century dream of a car driven on steam power.
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