NYISO SCUC Largely Decides Carbon Emissions

In the day-ahead energy market, NYISO decides how many and which Brooklyn/Queens baseload generating plants are selected for operation the next day – through a process called security-constrained unit commitment (“SCUC”).  At this point, carbon emissions for NYC for the next day are largely decided.

 

Hourly marginal carbon emission rates that reflect SCUC would tell the building industry how to best invest in and operate buildings for greatest carbon reduction.  “Hourly” distinguishes which hours are important to SCUC each week … and the many hours that are not important.  Moreover, hourly marginal emission rates that reflect SCUC are large and variable.  This means that, concerning emissions, when you use electricity is just as important as how much.

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By contrast, the “average” emission rates calculated by the U.S. Environmental Protection Agency and broadly used in the energy industry – whether for carbon, SO2, NOx or PM – are second best in two respects.  The first and fatal flaw is that such rates reflect only the much smaller emissions reduction opportunities left over once the baseload generating plants have already been selected by SCUC and turned on.  The second flaw is that average emission rates cannot time-differentiate – by season, day-of-week, or hour.  Again, concerning emissions, when you use electricity is just as important as how much.

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Corollary:  energy efficiency programs and technologies that affect SCUC have (much) greater carbon reduction value than do programs and technologies that only move the needle, that is, that only affect the incremental dispatch of already selected and operating baseload generating plants.

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Energy efficiency, storage, and local distributed PV reduce SCUC

EMeister MPC is one of many examples of an efficiency measure that affects SCUC day-ahead and therefore can make good use of marginal hourly CO2e emission rates that reflect SCUC.  (See examples on this website.)  NYC buildings can reduce SCUC every week of the year through capital and operating improvements focused on:

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• reducing weekly peak hours electric use (energy efficiency).

• shifting use out of weekly peak hours (storage).

• providing operating reserves during weekly peak hours (storage or demand response).​

• taking advantage of local distributed PV and its coincidence with weekly peak hours.​

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​​EMeister MPC does all four as a byproduct of reducing building energy expense.

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“Using eGrid for Environmental Footprinting of Electricity Purchases”*

This U.S. EPA publication excellently documents a method for using average regional emission rates for footprinting.  For example, for NYC for 2020, EPA recommends use of an average CO2e emission rate of 636.0 lbs/MWh or 0.32 tons/MWh for footprinting.  For evaluating the effect of efficiency measures at the margin, this same method recommends use of an average fossil fuel CO2e emission rate of 971.4 lbs/MWh or 0.49 tons/MWh.  This rate is “marginal” in that it properly reflects that efficiency measures reduce fossil plant operation, that is, do not reduce nuclear or renewable plant operation.  However, this rate implicitly reflects the real-time market, and not the opportunity provided by SCUC in the day-ahead market.  This EPA rate also does not reflect time-of-use.  The EPA does not have the local expert ISO knowledge needed to capture time-of-use or SCUC for marginal emission rates.