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Photochemical Modeling of June 2012 for the HOTCOG Area

Sue Kemball-Cook, Jeremiah Johnson, John Grant and Greg Yarwood

November 20, 2015

Presentation to the HOTCOG Air Quality Advisory Committee

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PREPARED UNDER A GRANT FROM THETEXAS COMMISSION ON ENVIRONMENTAL QUALITY

The preparation of this presentation was financed through grants from the State of Texas through the Texas Commission on Environmental Quality. The content, findings, opinions and conclusions are the work of the author(s) and do not necessarily represent findings, opinions or conclusions of the TCEQ.

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Waco Monitor Ozone Attainment Status

• Waco ozone monitor (CAMS 1037) design value is 67 ppb– In October 2015, EPA

lowered NAAQS from 75 ppb to 70 ppb

– Waco monitor attains 70 ppb NAAQS

• EPA will make attainment designations based on 2014-2016 data

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Waco Monitor Ozone Trends

June 26, 2012 Hourly Ozone at Waco CAMS 1037

2012 4 Highest Daily Maximum 8-hour Average (MDA8) Ozone Values at Waco CAMS 1037

MDA8 for June 26, 2012

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Ozone Model

AWMA Environmental Manager magazine July 2012 issue on AQMEIIDouw Steyn, Peter Builtjes , Martijn Schaap and Greg Yarwood

Monitor

How do ozone, NOx, VOC, etc.change with time?

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June 2012 Ozone Model

• TCEQ has developed a June 2012 ozone model for the Texas Rider 7 Areas– Recent episode with emissions

closer to current levels than previous June 2006 episode

– Effects of recent emissions controls

– TCEQ plans to expand episode to include entire 2012 ozone season

• HOTCOG uses the 2012 model to understand ozone in the 6-county area and model emission control strategies

TCEQ Figure

CAMx and WRF Modeling Domains

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Ozone Modeling Overview

• Base case model– Model historical periods (episodes)– Develop and evaluate input data– Model performance evaluation

How well does model reproduce observed air quality? Probing tools (source apportionment, emission sensitivity

tests)

• Baseline year model• Future year model• Control strategies

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Ozone Evaluation at CAMS 1037

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June 27, 2012 at 11 am

• Errors in WRF modeled wind direction affect ozone at Waco monitor• Modeled winds too southerly, obs are more easterly

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Texas Border/Coastal Sites

• High bias at Texas border/coastal sites• Effect of transport may be overstated

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WRF 4 km Grid Cloud-Radiation Simulation

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WRF 12 km Grid Cloud-Radiation Simulation

• Clouds underestimated on 12 km grid

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Ozone Source Apportionment Results• For a certain receptor

and time, how much ozone is contributed by each source category and/or source region?– Relative importance

of transport and local emissions

• Would ozone at that time and location more likely respond to upwind NOx or VOC controls?

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Contribution of Local NOx and VOC Emissions to Waco Monitor Ozone: 2006 and 2012

• HOTCOG area remains NOx-limited in 2012• Local emissions controls should continue to focus on NOx

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Relative Contributions of 6-County Area Emissions and Transport to Waco Ozone

• Transport contribution far larger than local contribution, both decrease from 2006 to 2012• The local HOTCOG contribution varied from day to day depending on the wind direction, but

reached a maximum of 12 ppb. • Local emissions control measures can be effective in reducing ozone in the HOTCOG area

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Breakdown of Transported Contribution

• IC+BC (initial conditions+boundary conditions) is contribution from outside U.S. and from the stratosphere

Transport

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Episode Maximum Contribution to Waco Mazanec Ozone from HOTCOG Emissions

• In 2012, power plant NOx emissions contribute the most to ozone at the Waco monitor, followed by on-road mobile, non-road and oil and gas sources

• Decreases in ozone contribution for all source categories going from 2006 to 2012

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June 2012 Modeling: Summary

• Improve CAMx performance at Waco monitor• Reduce overall model high bias

– Use updated biogenic VOC emissions (isoprene)– Ozone removal processes (deposition)

• Improve WRF model performance in simulating winds and clouds/radiation– New WRF cumulus cloud parameterization has

become available since TCEQ’s original WRF run WRF run is available, test in CAMx

– Alternate methods of WRF nudging to observations

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Update to Tradinghouse/Lake Creek EGU Ozone Impact Analysis

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13 km (8 miles)

22 km (14 miles)

Proposed EGUs in McLennan County

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Lake Creek Process Flow Diagram

• Simple cycle• No waste heat recovery• ~30% efficiency• Rapid startup

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Tradinghouse Process Flow Diagram

• Combined cycle• Waste heat recovery• ~60% efficiency• Lower NOx emissions• Longer startup• More expensive

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Update to Tradinghouse/Lake Creek EGU Analysis

• Draft report on initial study completed August, 2015– Ozone impacts for scenario with maximum permitted hourly NOx

emissions rate 24 hrs/day• HOTCOG AQAC reviewed the draft report

– Luminant provided comments on the draft Maximum utilization scenario would not occur because CTG would not be

operated in ramping/peaking mode for 24 hrs/day– Luminant provided two emissions scenarios: Realistic and Permitted– We estimated ozone impacts for these scenarios

• Draft report on PGA Photochemical Modeling task includes updated EGU analysis – TCEQ has provided comments on the draft

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Tradinghouse Simple Cycle Scenarios

• Simple Cycle “Permitted” Option – 4 CTGs operate 12 hrs/day, with 10 hours at the max hourly emission rate for normal operations, and 2 hours at the fast

ramping/peaking emission rate– 1 start-up event and 1 shut-down event

• Simple Cycle “Realistic” Option – 4 CTGs operate simultaneously for 8 hrs/day, with 7 hours at the maximum hourly emission rate for normal operations and 1

hour at the fast ramping/peaking emission rate– 1 start-up event and 1 shut-down event

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Tradinghouse Combined Cycle Scenarios

• Combined Cycle “Permitted” Option – 4 CTGs operate 24 hrs/day with maximum duct firing (max hourly emission rate for normal operations)– No startups or shutdowns.

• Combined Cycle “Realistic” Option – 4 CTGs operate for 24 hrs/day, – 14 hours at base load without duct firing, 5 hours at base load with maximum duct firing (max hourly emission

rate for normal operations), and 5 hours at low-load operation (50% load).

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Lake Creek Scenarios

• Simple Cycle “Permitted” Option – 2 CTGs operate for 12 hrs/day, with 10 hours at the maxihourly emission rate for normal operations, and

2 hours at the fast ramping/peaking emission rate, with 1 start-up event and 1 shut-down event.• Simple Cycle “Realistic” Option

– 2 CTGs operate for 8 hrs/day, with 7 hours at the maximum hourly emission rate for normal operations, and 1 hour at the fast ramping/peaking emission rate, with 1 start-up event and 1 shut-down event.

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NOx Emissions and Ozone Impacts Summary

• Ozone impacts lower in Luminant scenarios than max utilization scenario for SC, comparable for CC

Conclusions

• NOx emissions from the permitted/proposed EGUs are predicted to increase ozone in McLennan County– Estimates of max MDA8 ozone impacts for Lake Creek and

Tradinghouse at Waco monitor ranged from 0.27-1.1 ppb for SC case, 0.15-0.19 ppb for CC case

– With both facilities operating, max MDA8 ozone impacts ranged from 0.50-2.0 ppb

– Impacts are lower when Tradinghouse is run in combined cycle mode

• Waco Mazanec (CAMS 1037) monitor ozone impacts for a different time period could be higher or lower depending on winds

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Avenues for Further Analysis

• The DDM procedures provided flexibility to consider multiple emission scenarios without re-running CAMx – Limited by not accounting for changes in the temporal profile of

emissions. – Method could be improved by computing ozone sensitivity to

emissions from several time blocks within the day (e.g., eight blocks of 3 hours)

• Once the emission scenarios are finalized, their ozone impacts could be evaluated using a brute-force sensitivity test – Add new EGU emissions to the TCEQ June 2012 base emissions and

measuring the ozone response by re-running CAMx – Brute-force approach may suffer from numerical noise if the added

emissions are small and produce ozone changes of tenths of a ppb or less

END

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Proposed EGUs in McLennan County: Lake Creek

• The TCEQ granted Lake Creek NSR Permit 117857 in 2014– Two new natural gas-fired, simple-cycle combustion

turbine generating units at the Lake Creek facility near Riesel

– New units replace two lower efficiency, natural gas-fired electric generation boilers

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Proposed EGUs in McLennan County: Tradinghouse

• TCEQ granted Tradinghouse NSR Permit 110357 in 2014– Two new natural gas-fired, simple-cycle (SC) combustion

turbine generating units (CTs; Units 1 and 2) at Tradinghouse facility near Hallsburg

– Units 1 and 2 replace two lower-efficiency, natural gas-fired electric generation boilers

• Amendment to Tradinghouse Permit 110357 filed in 2015– Add year-round combined cycle (CC) capability to its

permitted SC CT units 1 and 2 – Add an additional set of CTs, Units 3 and 4, which may also

be used in SC or CC mode

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EGU Emissions Modeling

• Emissions (in tons) from EGU permits/applications

• Temporal allocation based on 2012 DFW area typical ozone season day activity data for CT facilities

• Stack parameters from permits/applications

• Default speciation for NOx– 90% NO, 10% NO2

Tradinghouse

Lake Creek

Ozone Impact Analysis• Examine max utilization scenario running 24 hrs/day

– Tradinghouse: 2 scenarios 4 CTs running in SC mode 4 CTs running in CC mode

– Lake Creek: 1 scenario, 2 CTs running in SC mode• Examine ozone impacts of the two facilities singly and in

combination• NOx emissions:

– Lake Creek SC: NOx emissions = 2.88 tpd– Tradinghouse SC NOx emissions = 5.78 tpd– Tradinghouse CC NOx emissions = 0.98 tpd– Lake Creek SC + Tradinghouse SC– Lake Creek SC + Tradinghouse CC

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Maximum Ozone Impacts of Tradinghouse Emissions

• Largest impacts in vicinity of Tradinghouse• Ozone impacts at Waco monitor lower by 0.88 ppb when

Tradinghouse CTs run in CC mode compared to SC mode35

Max at Waco Monitor: 0.18 ppb Max at Waco Monitor: 1.06 ppb

CC SC

Maximum Ozone Impacts of Tradinghouse and Lake Creek Emissions when Both are Operating

• Impacts in vicinity of City of Waco range from 1-4 ppb • Ozone impacts lower when Tradinghouse CTs run in CC mode compared

to SC mode36

Max at Waco Monitor: 1.21 ppb Max at Waco Monitor: 2.04 ppb

SC+CC SC+SC

Maximum Ozone Impacts of Tradinghouse and Lake Creek Emissions: Expanded View

• Impacts > 1 ppb extend northward into DFW nonattainment area for both cases– Impacts > 2 ppb in vicinity of Cleburne monitor in SC case

• Impacts > 3 ppb extend southward into Bell County in vicinity of Temple Georgia monitor

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Max at Waco Monitor: 1.21 ppb Max at Waco Monitor: 2.04 ppb

SC+CC SC+SC