Social Media Icons DEQ Facebook DEQ Twitter DEQ Instagram DEQ LinkedIn

General Description of Proposed Projects

Virginia, like several other states, is experiencing growth in the number of new power plant permit applications or proposals for planned facilities. Some of the proposed plants will be "peaking units," which means they will operate and produce electricity only during periods of high electricity demand. These peak demand periods generally occur during the extreme hot spells of summer and extreme cold spells, usually in December and January. Other proposed plants will be "baseload units," which means they will generally operate full time. An Excel spreadsheet of basic information regarding power plants currently operating in Virginia and those going through the air permitting process is available for download on this webpage.

To date, the applications received for new power plants are for facilities that will be fueled with natural gas which is less polluting than existing coal-fired units. Most of these facilities will have fuel oil as a backup fuel should the gas supply be interrupted. Peaking units are usually simple cycle turbines and baseload units are usually combined cycle turbines.

Simple Cycle Turbine:

A simple cycle turbine is an internal combustion engine with three major parts; an air compressor, burner(s), and power turbine. In the air compressor, a series of bladed rotors compresses the incoming air from the atmosphere. A portion of this compressed air is then diverted through the burners (also called combustors), where fuel is burned raising the temperature of the compressed air. This very hot gas is mixed with the rest of the compressed air and directed to the power turbine at temperatures up to 2350ºF. In the power turbines, the force of the hot compressed air as it expands pushes another series of blades, rotating a shaft. Greater than 50 percent of the mechanical energy produced by the power turbine is consumed to drive the air compressor. The balanced of the mechanical energy turns a generator and makes electricity. The cycle efficiency, defined as a percentage of useful shaft energy output to fuel energy input, is typically in the 30 to 35 percent range.

Combined Cycle Turbine:

The difference between simple cycle turbines and combined cycle turbines is that in a combined cycle turbine, the hot exhaust gases from the turbine do not directly go to the atmosphere. Instead, the hot exhaust gases from the turbine, which are typically at 1000ºF, are ducted through a waste heat boiler to generate steam. This steam is then used to drive a steam turbine generator to make additional electricity. The recovery of the heat energy in the exhaust of a gas turbine in this manner can increase the cycle efficiency of a combined cycle plant to 50 percent or more. The additional electricity that can be produced by a combined cycle turbine is accompanied by additional capital costs for a waste heat boiler, steam turbine, and cooling system. However, the operating cost per unit of electricity produced is lower compared to that of simple cycle turbines due to the energy recovery.

footer divider
footer divider
footer divider
Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000

Some resources on this website require Adobe Reader and Flash Player, Microsoft Word, PowerPoint or Excel. If you wish to receive this content in an accessible format pursuant to Section 508 of the federal Rehabilitation Act of 1973, as amended (29 U.S.C. ยง 794 (d)), please call 800-592-5482. In addition, this website includes hyperlinks to websites neither controlled nor sponsored by DEQ or the Commonwealth of Virginia. Links may open in a new window. If you wish to receive content from a website which is neither controlled nor sponsored by DEQ or the Commonwealth, please contact the host of that website directly.

Privacy Statement | Terms Of Use | WAI Compliance | Contact Us