Air Pollution Consequences of Electric Power Generation

Viewed from the perspective of emission rates per unit of power produced in the U.S., Department of Energy figures indicate that coal-fired power plants contribute the lion share of emissions.

Fuel	Sulfur Dioxide SO2	Nitrous Oxide NOx	Carbon Dioxide CO2	VOCs	PM10
Eastern Coal	1.740	2.90	1,000	0.06	0.10
Western Coal	0.810	2.20	1,039	0.09	0.06
Gas	0.003	0.57	640	0.05	0.02
Biomass	0.060	1.25	800	0.61	0.01
Oil	0.510	0.63	840	0.03	0.02

VOCs = volatile organic compounds
PM10 = particulate matter with diameter less than 10 microns
Source: Oak Ridge National Laboratory

Amongst the fossil fuel power plants, natural gas burning plants are the least harmful to the atmosphere since they emit very little sulfur or mercury derivatives and much less nitrogen oxide. Of the natural gas-fueled plants, the combined cycle gas/steam turbine plants achieve the highest thermal efficiencies, and thus emit the least carbon dioxide per kilowatt-hr of electricity.

Since the CEC closed loop cycle design features external combustion, it uses natural gas at line pressure (5 inches of water) and burns at low enough intensity to produce less than 2 parts per million (ppm) of NO_x (nitrous oxides). Of all the conventional gas turbine models, the Capstone Micro Turbine was the first to guarantee less nitrous oxide emission than 9 ppm without the use of catalytic converters. Comparable emission guarantees of other conventional gas turbines are shown in the table below.

Manufacturer	Turbine Model	Power Output(MW)	NOxGuarantee Level (ppm at 15% O2)
General Electric–Frame Series	7FA Plus enhanced	170	9
	7FA Plus	170	15
	7FA	170	25
	7EA	83	9 or 25
	6B	38	9 or 25
GE Aeroderivatives	LM6000	42	25
	LM2500	23	25
Siemens-Westinghouse	V84.3a2	170	15
	V84.3	154	25
	V84.2	106	9 or 25
	501G	250	25
	501F	185	15 or 25
	501D5	115	25
Alstom (formerly ABB)	GT24	166	25
	GT13E2	165	25
	GT10C	30	15

It is important to emphasize that each CEC turbo generator brought into commercial service will likely displace the use of electricity that currently causes atmospheric pollution orders of magnitude higher than CEC units contribute.

Carbon Dioxide Emissions

The oxidation of any hydrocarbon results in the production of carbon dioxide. This is basic and unavoidable. However, the higher the carbon content of the fuel, the more carbon dioxide per unit of heat is generated during combustion. Hence, natural gas, which is mostly methane, creates the least amount of carbon dioxide per unit of heat released of all the hydrocarbon fuels.

The CEC energy system generates electricity more efficiently  and uses the exhaust heat from the turbo generator for space, water and any other direct forms of heating as well as cooling. Therefore, all but a quarter of the heat is captured and used.

Employed in this manner, the CEC energy system creates about half as much carbon dioxide as would normally have been generated.