Potentially available natural gas combined cycle capacity : opportunities for substantial CO₂ emissions reductions

Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.This thesis analyzes the potential for existing natural gas combined cycle (NGCC) power generation to displace coal generation thereby reducing emissions of CO₂ and criteria pollutants regulated under the Clean Air Act. It also examines the potential for unused NGCC capacity to eliminate transmission congestion while simultaneously reducing CO₂ and other criteria pollutant emissions. The average capacity factor of the entire natural gas fleet in year 2008 was 26%. The average capacity factor of NGCC units, a subset of the gas fleet, is 41%. NGCC units, however, are designed to operate at capacity factors as high as 85%. The delta of these two numbers has generated significant policy interest as a means for reducing C02 emissions through some type of environmental dispatch that would favor NGCC over coal generation without the need for additional capital investment. The maximum potential of natural gas power generation to displace inefficient coal generation was determined. This upper limit can provide regulators and policy makers with guideposts for further review. Various operational constraints including transmission limitations were then modeled to determine the extent to which these constraints limit fuel switching opportunities. An analysis was conducted to estimate the effects of fuel switching on transmission congestion. The conclusion of this analysis was that generation from potentially available NGCC capacity located in regions with high load centers can help alleviate the transmission congestion problem with minimal or zero capital investment for building new generation capacity. Next, an hourly dispatch model was developed that incorporates many of the complexities of the power system. This model dispatches generation from various power plants under two scenarios: a carbon unconstrained scenario (base case); and a carbon constrained scenario. Under the carbon constrained scenario, dispatch preference is give to NGCC generation over coal generation. Two regions were modeled: the Electric Reliability Council of Texas (ERCOT), which is primarily Texas; and the Florida Reliability Coordinating Council (FRCC), which is primarily Florida. Results from the two cases indicate that, without compromising system reliability: In the ERCOT region, displacing some coal generation with existing and available NGCC generation would lower CO₂ emissions by nearly 22%, SO2 by 70% and NOx by 49%, compared to the base case. * In the FRCC region, displacing some coal generation with existing and available NGCC generation would lower CO₂ emissions by nearly 10%, 502 by 38% and NOx by 25%, compared to the base case. The model results also indicate that for both ERCOT and FRCC, these emissions savings can be achieved with a 10% increase in electricity prices. This translates into a cost of emissions reductions of $20/ton of CO₂ in ERCOT and$40/ton of CO₂ in FRCC. This compares to the cost of emissions reductions from corn ethanol, which is about $750/ton of CO₂, as reported by Congressional Budget Office'. Finally, a comparison was made between the results of the hourly dispatch model and the ReEDS model, a more complex model developed by Department of Energy's (DOE) National Renewable Energy Laboratory (NREL).by Anil Rachakonda.S.M.in Engineering and Managemen