By Jim Staudt, presented to the EPRI CEMS meeting, 2018
ABSTRACT – Lowering heat rate from electric utility boilers has the economic benefit of reducing fuel consumption and the environmental benefit of reducing pollutant emissions. There have been various estimates of the potential heat rate improvements possible from the existing fleet of electric utility boilers – some estimates from engineering studies and others from statistical studies of available publicly available data.
While power plants measure megawatt-hours (the denominator of heat rate) accurately, for coal plants heat input to the boiler (the numerator) is inferred from measured stack parameters (as used in EPA’s Air Markets Program Data) or fuel consumption and fuel characteristics (EIA Form 923 data). Estimates of heat rates are also shown in US EPA’s National Electric Energy Database System (NEEDS). Plants may also perform a heat balance, but this method is not used for the publicly available data.
To estimate the potential heat rate improvements for the existing coal fleet, EPA used a statistical analysis of estimated gross heat rate using Air Markets Program Data (AMPD). Heat input as reported in AMPD is determined from the relationship that exists between exhaust flowrate and heat input that is commonly referred to as “F factor”. Another public data source for estimating boiler heat input is plant fuel use data as found in EIA form 923. In this study these two sources of data were compared for several coal fired power plants.
In addition, potential sources of variability in these methods are explored, including variability in the relationship between fuel heating value and exhaust gas flowrate, or F factor, and the degree to which it may impact variability in estimated gross heat rate using AMPD. Data from NEEDS was also examined to evaluate trends based upon facility type – as well as anomalies that may be from “noise” in the data. Finally, areas for improving the usefulness of this data will be offered.