Estimating Emissions from Electricity Generation Using Electricity Dispatch Models: the Importance of System Operating Constraints

Abstract

The article presents a modeling approach for estimating emissions (e.g., CO2) from electricity generation system mainly consisting of nuclear, coal, natural gas and hydropower generators in reaction to short-term changes to electricity demand. The modeling approach accounts for a set of Operating Constraints (OCs) including scheduled maintenance, forced outage, spinning reserves, fuel switching, seasonal output capacities, and seasonal hydro resource availability. It is found that these OCs are important to achieve reasonable estimates of electricity production by fuel type as well as associated emissions. This conclusion follows from an analysis of electric power generation by networks of power plants in Texas and New York in 2004 and 2005. The inputs to the model with operating constraints (OC Model) developed in this paper include hourly electricity demand, fuel costs, a list of power plants in the network, their basic generation characteristics, and the set of OCs developed in this paper. Given these inputs the OC Model estimates the hourly amount of electricity generation by each power plant in the network, which leads to estimates of marginal resource consumption and emissions. Our central result is that historical annual and monthly generation by fuel type and efficiency are well estimated by the OC Model and that the exclusion of OCs leads to poor estimates.