### MEMORANDUM

TO: Rulemaking docket, "State Implemen tation Plans: Response to Petition for Rulemaking; Findings of Substantial Inadequacy; and SIP Calls to Amend Provisions Applying to Excess Emissions During Periods of Startup, Shutdown,
and Malfunction," ID No. EPA-HQ-OAR-2012-0322

FROM: Lisa Sutton, Air Quality Policy Divi sion, Office of Air Quality Planning and
Standards, Office of Air and Radiation, U.S. Environmental Protection Agency

DATE: May 13, 2013

SUBJECT: Report of in-person meeting with re presentatives of the National Environmental Development Association's Clean Air Project

On April 17, 2013, members of the Air Quality Po licy Division, Office of Air Quality Planning
and Standards, Office of Air and Radiation, U.S. Environmental Protection Agency, met in person and by conference call with memb ers of the National Environmen tal Development Association’s Clean Air Project (NEDA/CAP). A meeting sign-in sheet is include d as an attachment to this memorandum. At this meeting, members of NEDA /CAP discussed their concerns with EPA’s proposed response to the Sierra Club petition on startup, shutdow n, and malfunction provisions in state implementation plans. EPA staff encouraged NEDA/CAP to fully restate these concerns in

their written comments to the docket.

Following the meeting, Anna Wood of EPA receive d a related email (including an attachment)
from Barbara Bankoff, a consultant on environmen tal and regulatory policy. That email is also

included as an attachment to this memorandum.

LS

AttachmentsFrom: barbara bankoff

To: Wood, Anna

Cc: Leslie H. Witherspoon ; Rising, Bruce W (E ST MOP 3) ; Leslie Ritts

Subject: Fwd: SSM and gas turbine nsps

Date: Friday, April 19, 2013 6:12:40 PM

Attachments: Final GTA Comments 6_25_12 (3).pdf



### Anna - You had shown some interest in the SSM exemption for gas turbines when we met on Wednesday. I asked Bruce Rising of Siemens about concerns regarding removing the current SSM exemption. I am forwarding his recent comments. I have also attached the Gas Turbine Association comments on the GHG NSPS, which includes a paragraph about the need for an SSM exemption.

Thank you for the time you and your staff spent with us the other day. Regards,

Barbara

---------- Forwarded message ----------

From: Rising, Bruce W (NAM RC-US E P-S) < bruce.rising@siemens.com > Date: Wed, Apr 17, 2013 at 3:23 PM Subject: RE: SSM and gas turbine nsps

Non-compliance is an issue. Emission controls don’t operate

uniformly at all operating points, especially during the start and

shutdown cycles.

The more starts and stops required by the system, the more time a

specific piece of equipment will be operating without its emission

controls in an optimal range.

The problem is much worse for post combustion emission controls
(like SCR or and FGD on a coal plant) because

those devices have to wait until the base unit reaches a previously

established operating range before “turning on”.

An SCR won’t reduce NOx at temperatures much below 600F, nor above

950F. So the ammonia injection system won’t kick in during those
periods (and hence the catalyst won’t reduce NOx). Likewise CO.

Most CO catalysts work well at low temperatures, and better at high

### temperatures. But during the cycling process, the CO catalyst may

not be able to oxidize either CO or unburned hydrocarbons. Those

emissions are highest at the lowest loads. So during the start
cycle (and shutdown), even the CO catalyst, which is pretty

forgiving, will likely have a tough time holding the line.

Then you have the problem of determining the non-compliant level.

It takes 20-30 seconds for combustion gases to leave the gas

turbine, pass through the boiler, then reach the stack. The

sampling system will pump gases back down to the instruments, each

will have a different response time. The data collection system

will sample the data for anywhere from 5 to 15 minutes, then try

and average the data. Now with the emissions going up and down,

it’s not quite clear if the averaging will have any real meaning.

So reported data could be rather misleading.June 25, 2012

RE: Environmental Protection Agency
Docket number EPA-HQ-OAR-2011-0660 Proposed Rules for GHG Emissions for Electric Util ity Generating Units

Submitted By: Gas Turbine Association Dr. William H. Day, Managing Director

billday3@comcast.net

The Gas Turbine Association (GTA) appreciates the o pportunity to comment on EPA’s proposed rulemaking to regulate greenhouse gas (GHG ) emissions from electric utility generating units (EGUs) under the Clean Air Act’s n ew source performance standards (NSPS)

program. See

77 Fed. Reg. 22,392 (April 13, 2012). GTA’s comme nts will be focused on emissions from gas turbines, which are highly effic ient energy conversion devices with low CO 2 emissions normalized to energy production. The suc cess of gas turbines can be measured by their market presence. The current installed capac ity of combined and simple cycle gas turbines represents over 350,000 MW, producing over 20% of the total United States generation. Nearly all of the energy production is achieved using natural gas fuel.



### Summary of GTA Recommendations

• Continue to exclude simple cycle gas turbines

• Include language that specifically prohibits the NS PS CO 2 limit from being adopted as
the presumptive CO 2 BACT level for simple cycle turbines

• For units other than simple cycle, raise the CO 2 level to at least 1,100 lb/MWh to account
for typical operating scenarios including part-load , rapid ramping and cycling,
performance degradation and differences in site and atmospheric conditions

• Include exemption for startup/shutdown and part loa d operation

• Allow an alternate method to CEMs for compliance me asurement, specifically fuel
consumption

• Modify method for computing the 12-month rolling av erage

• Exempt combined heat and power units since their ex haust energy is very efficiently

utilized

• Allow 500 hours of operation on backup fuel without inclusion in the emission average2 | Gas Turbine Association



### Exemption for Simple Cycle Gas Turbines

The proposed rulemaking recommends that simple cycl e gas turbines be excluded from the proposed CO 2 NSPS in the amended 40 C.F.R. Part 60. See 77 Fed. Reg. at 22,411, 22,431- 32. The rationale laid out in the proposed rulemak ing is that simple cycle gas turbines (which generally cannot meet the 1,000 lb/MWh rule on any fuel) are primarily used for peak shaving duty which is generally viewed to include less than 2,500 hours per year of operation. The proposed rulemaking excludes all gas turbines with the justification that most simple cycle gas turbines operate less than 2,900 hours per year (le ss than 1/3 of the total generation capacity).

The GTA agrees that simple cycle gas turbines shoul d remain completely excluded from the rulemaking. GTA strongly supports the exclusion fo r the reasons EPA identifies, but even beyond the rationale EPA identifies, there are at l east two additional reasons to exclude simple cycle gas turbines.

First, including simple cycle gas turbines in the N SPS will amount to an effective ban on simple cycle in other contexts (e.g. the NSPS level of 1,0 00 lb/MWh might be used as an upper limit for Best Available Control Technology (BACT) calculatio ns if simple cycle gas turbines are included). The current Prevention of Significant D eterioration (PSD) GHG rule has a very low tons-per-year threshold, which means that PSD could be invoked for a large portion of newly installed simple cycle gas turbines in electric pow er generation that would not otherwise be subject to PSD. The Gas Turbine Association is alr eady aware of one state environmental protection department that has given such guidance to a customer’s permitting consultant for a simple cycle installation.

The GTA also wishes to emphasize that there is a st rong likelihood that, even if simple cycle gas turbines are excluded from the proposed rulemak ing, the 1,000 lb/MWh limit could be considered as a ceiling for BACT for all gas turbines regardless of cycle. If the 1,000 lb /MWh level is interpreted as a presumptive BACT for all turbines, such interpretation would effectively ban simple cycle gas turbines. Similarly, the propo sed rule should not be allowed to be used in some way to establish lowest achievable emission ra te (LAER). Thus, we request EPA include specific language in 40 CFR Part 60 amendment to ex plicitly prevent the unintended adverse impact on simple cycle gas turbines.

The GTA suggests that 40 CFR § 60.5520 (d) of the p roposed rule be amended to add the following:

“Simple cycle combustion turbines are not subject t o the requirements of this subpart. Further, this subpart and any emi ssions limits

included herein is not intended to and shall not be used as a basis for establishing for simple cycle combustion turbines e ither best available control technology (BACT) or lowest achievable emis sion rate (LAER).

Secondly, an effective ban on simple cycle gas turb ines could risk the stability of the nation’s power grid and hinder the Administration’s goals to advance renewable energy. Increasingly, renewable generation resources are being added to t he mix of generation assets and are forming a much greater percentage of the nation’s e lectric power generation. The effect of increasing renewable generation share is a signific ant increase in power generation variability and thus significantly increased grid instability. The most effective means to mitigate the destabilizing effects of renewable additions is the installation of simple cycle gas turbines.3 | Gas Turbine Association

Simple cycle gas turbines can accommodate the very quick start times and rapid ramp rate load-following required to stabilize the grid in th e presence of significant renewable generation. Grid instability may require a significant share of simple cycle gas turbines to run more than 2,900 hours per year. An effective ban on simple c ycle gas turbines would eliminate a crucial tool for maintaining grid stability.

Further, the final rule should clearly state the si mple cycle exemption does not impose a restriction on simple cycle turbine annual hours of operation. While a majority of current, and anticipated future simple cycle turbine installatio ns, operate less than 2900 hours, many installations are operate in excess of these number of hours to support grid requirements. The facility will be required to operate the number of hours required by electric demand. Limiting hours of operation again would restrict the operati onal flexibility of this fleet of turbines necessary ensure reliable and stable electricity su pply.

Finally, the exclusion of simple cycle gas turbines from the NSPS rulemaking would not inappropriately favor them over combined cycle gas turbines in the marketplace, nor have the unintended effect of delaying the upgrade of simple cycle installations to combined cycle. Cf. 77 Fed. Reg. at 22,432. The economics of the applicat ion always govern the choice between simple and combined cycle with capital costs and ef ficiencies being significantly different between the two. Thus anticipated run times (peaki ng, daily start-stop, or base load), the price of fuel, and capital cost of the power plant are th e controlling drivers in decision making. Because most combined cycle units will have less tr ouble meeting the proposed regulation, at least at high loads, we believe that the proposed r egulation will have little effect on the timing of upgrade decisions.



### Proposed CO 2 

### Limit

EPA has proposed a standard of 1,000 lb/MWh for CO 2 emissions, but has requested comments on a range of 950 to 1,100 lb/MWh. See 77 Fed. Reg. at 22,406. In addition to excluding simple cycle turbines entirely, GTA belie ves the limit should be raised to 1,100

lb/MWh for other units.

While the GTA recognizes the 1,000 lb/MWh level may be achievable under certain limited conditions – particularly when units are newly inst alled, clean, with no degradation due to thousands of hours of operation, at sea level, unde r standard day conditions, and running at base load – the standard is unlikely sustainable un der real world conditions. During real life operating scenarios, combined cycle gas turbines (C CGTs) operate in a wide variety of ambient conditions (high altitudes, hot weather) with frequ ent starts and stops and operate across a wide load range. Also, gas turbine equipment will exper ience varying amounts of performance degradation due to service.

An critical attribute of CCGT facilities is the gen eration flexibility that is essential to ensuring a stable, secure, reliably energy supply while enabli ng the deployment of variable renewable energy generation. The proposed limit is attainabl e by most new CCGT facilities, when operating at base load, however during variable ope ration, including frequent starts/stop cycles and significant part load operation, many facilitie s are not able to maintain these emission levels. As a result, a more restrictive limit woul d not result in a lower emitting facility, but woul d result in a constraint in the necessary flexible op eration of the CCGT. To ensure and enable flexible plant operation, which is essential to the mission of CCGT operation, the GTA recommends an emission limit no lower than 1,100 lb s CO2/MW-hr.4 | Gas Turbine Association

Also, various design features and site requirements must also be considered. As example, air cooled condenser equipment is often required in ari d climates. Air cooled condensers have the advantage of reduced water consumption. This benef it comes at a performance penalty. This penalty can range from a 1 to 4% percent loss in pl ant efficiency dependent on site climates and design basis. The variable operating conditions an d range of design requirements result in actual performance below the reference case.

A recent report by the University of California Cen ter for Energy and Environmental Economics reported similar findings regarding only base loade d CCGTs: “ The EPA reports that 95 percent of these units first operating between 2006 and 201 0 would meet the target, and we find a similar percentage when looking at predicted emissi ons based on power plant heat rates. Yet we find a lower number at 84 percent based on actua l emissions and self-reported generation.” 1
The study captures only a small amount of real worl d variability. Analysis for daily start and stop, intermediate duty, and power plants operating for a significant period of time at part load are not included. Inclusion of such plants would h ave further reduced the percentage of complying power plants. It is, in fact, critical t o the management and stability of the electric grids in the United States that dispatching authori ties have the flexibility to dispatch CCGTs at loads from 50% to 100%. Dispatch flexibility is op erational flexibility. A limit of 1,000 lb/MWh will greatly impede real world operational flexibil ity and the stability of grids in the United States

will suffer.

The GTA recommends the emission limit be set at 1,1 00 lbs CO2/MW-hr. The 1,100 lbs

CO2/MW-hr level is consistent with levels set in Ca lifornia, Oregon, and Washington.



### Exemption for Startup/Shutdown and Part Load Operat ion

GTA’s analysis of the operating fleet reveals that part load operation is a very likely operating scenario going forward due in significant part to t he need for rapid response in support of nondispatchable generation ( i.e. , wind and solar). Reduced load operations (as wel l as starts and shutdown) can result in a level of CO 2 emissions above the proposed level because gas tur bine efficiency declines significantly at off-design ope rating loads. CO 2 emissions above the proposed 1,000 lb/MWh level is expected to also occ ur with new advanced gas turbines entering operation due to the basic physics of turb omachinery.

Because of the severe penalty encountered with part load operation, GTA recommends that

CO 2 emissions during operations below 50% of maximum c ontinuous rating (of the gas turbine) be excluded from the averaging and reporting.



### Continuous Monitoring

EPA proposes to require compliance monitoring with the NSPS via a CO 2 mass rate continuous emissions monitoring system (CEMS). 77 Fed. Reg. a t 22,409. The GTA believes that fuel consumption monitoring should be available as an ac ceptable alternative to CEMS.

CO 2 mass rate CEMS and associated automatic data acqui sition and handling are but one technical approach to determine compliance. A CEMs system measures CO 2 species

concentration in the stack as well as stack total a nd static pressures in the stack. From the data

1 Kotchen and Mansur, How Stringent is the EPA’s Proposed Carbon Pollutio n Standard for New Power Plants?, University of California Center for Energy and Environmental Econ omics, April 2012.5 | Gas Turbine Association

the total stack mass flow rate and mass flow rate o f CO 2 are calculated and then integrated over time and normalized, by the electric output in MWh, to determine CO 2 lb/MWh over a timeframe.

While the CEMS method is necessary for criteria pol lutants, such as NO

x and CO which vary widely in emissions characteristics from one engine model and operating condition to another, a much simpler and more accurate method is available for CO 2 . By accurately measuring fuel flow over time and assuming that all the carbon in the fuel is oxidized to CO 2 (a very accurate assumption) the total emission of CO 2 may be determined very easily and accurately. EPA has relied heavily on fuel consumption monitoring as an alternative to CEMS for its Mandatory Reporting of Greenhouse Gases Rule, with three of t he four methodological tiers for calculating CO2 emissions under that rule relying on fuel consu mption data, rather than on CEMS. See

e.g. , 74 Fed. Reg. 56290. EPA should allow fuel consum ption monitoring here as well. Using fuel consumption monitoring instead of CEMS i s far more accurate and avoids the challenging problem of measuring emissions during t ransient periods when stack flow rate measurements are inaccurate. During transient oper ation stack flow conditions may be changing rapidly, the kind of conditions that would be difficult for a CEMS to produce accurate results. Many combined cycle units that were expec ted to operate at base load in the United States are now found to be operating over a much wi der range of loads, with many more starts and stops, thus relegating a fuel consumption monit oring method appropriate

EPA may already have envisioned a fuel consumption monitoring alternative, but an apparent drafting error makes that ambiguous. Proposed regu lations 40 C.F.R. §§ 60.5535(c) and 60.5560(c) refer to fuel combustion monitoring. See 77 Fed. Reg. at 22,437, 22,438. Criteria for using fuel combustion monitoring method, howeve r, are cross-referenced to a proposed provision, § 60.5525(c)(2), which does not exist. GTA urges EPA to correct the oversight and make fuel consumption monitoring a widely-available alternative to CEMS.



### Method for Computing the 12-Month Rolling Average

GTA believes the specified method of averaging will lead to an inaccurate measure of CO 2 emissions. Monthly operation of gas turbines can v ary widely from a very small capacity factor to 100% capacity factor depending on a wide variati on in parameters affecting unit dispatch such as load demand, periods of overhaul and refurb ishment, fuel availability, and amount of time spent starting and stopping. Therefore, all m onths should not be weighted equally, a feature of the current methodology specified in § 6 0.5540. We note further that there is no public health reason to compel compliance on a mont hly basis. It would be far more accurate, at the end of each month, to compute a new rolling average by summing all CO 2 emitted in the past 12 months and dividing by the total MWh’s gene rated in the past 12 months.



### Combined Heat and Power (Cogeneration)

GTA recommends that EPA develop a specific exclusio n for Combined Heat and Power (CHP) applications. CHP plants operate in a similar mann er to the CCGTs that are covered by the proposed rule. The thermal energy from CHP plants can be diverted to either energy production (kWh) or to thermal loads (heating and cooling). T he regulatory challenge of quantifying the equivalence of the thermal energy used in terms of kWh to determine compliance with the proposed NSPS would be immense and impractical. Be cause of that complexity, we propose that CHP and cogeneration facilities be specificall y exempted from the rulemaking.6 | Gas Turbine Association



### Backup/Multi-Fuel Operation

Because of the stringency of the proposed complianc e level, GTA requests EPA clarify that the NSPS rule only apply during periods of natural gas operation with an exemption for 500 hours of operation on backup fuel. During periods of extrem e weather events (typically cold winter days), plants operating with interruptible gas supp lies may be forced to use an alternative or backup fuel. Most commonly the backup fuel is numb er 2 distillate (or similar fuels); which have a significantly higher CO 2 emission profile. 2 As Figure 1 shows, there is a large difference between emission levels based on natural gas and ot her fuels. An exemption to operate on a backup fuel for a period of up to 500 hours per yea r would accommodate the potential need to use a back up fuel.

Figure 1. CO 2 emissions as a function of fuel choice and cycle e fficiency (based on Higher Heating Value)

GTA Member Companies

Alstom Power GE Energy Florida Turbine Technologies Pratt & Whitney Power Systems

Rolls-Royce Siemens Energy Solar Turbines Incorporated Meggitt Sensing Systems

2 Other liquid backup fuels include diesel, ultra-lo w sulfur diesel, Jet A, K-1, GT No. 1, No. 2 distil late, and some bio-based fuels

such as bio-diesel.