Convert CEMS steam load to gross generation

[grgmiller]

A more careful reading of the EPA's Power Sector Emissions Data Guide revealed the following about the reported values for steam_load_klb, which we were previously unsure how to interpret (https://github.com/singularity-energy/open-grid-emissions/issues/103):

Certain EGUs are combined cycle combustion turbines, which generate electricity from a traditional gas turbine as well as a steam turbine that is powered by the heat of the gas turbine. These units are not required to report electrical generation from the steam turbine (although many combined cycle EGUs do include the generation from the steam turbine in their electrical generation data). EGUs that generate steam have the option to report steam load in thousand pounds of steam per hour (1000lb/hr) instead of electrical generation in MWh.

Thus, it seems that we may want to look into converting steam load to gross generation when a unit only reports steam load and no gross generation.

Questions for further research:

• Do any units report both gross generation and steam load for the same hour?
• Is there a standard conversion factor between steam load and gross generation?
• Are there any unit-specific datapoints available about the steam quality/pressure that would result in a more accurate conversion?

[grgmiller]

This may require a refresher on my basic thermodynamic equations. I think if we know the steam flow rate in klb/hr, we need the enthalpy of the steam to convert to MW. I'm not sure if there is data available about the enthalpy of the steam at each plant, but we could assume a typical temperature and pressure.

Resources:

• https://www5.eere.energy.gov/manufacturing/tech_deployment/amo_steam_tool/equipTurbine?random=Outlet
• https://www.govinfo.gov/content/pkg/CFR-2013-title40-vol7/pdf/CFR-2013-title40-vol7-sec60-4350.pdf

[grgmiller]

Also see reporting instructions for more information about steam load data: https://www.epa.gov/system/files/documents/2024-03/ecmps_emissions_reporting_instructions_0.pdf, found at https://www.epa.gov/power-sector/ecmps-reporting-instructions.

It looks like the conversion from klb steam to MWh is approximately 0.3-0.35 MWh per klb, based on https://energystar.my.site.com/PortfolioManager/s/article/How-do-I-enter-District-Steam-that-has-been-billed-in-pounds-1600088536249 and https://www.abraxasenergy.com/energy-resources/toolbox/conversion-calculators/power/