Water  Implica-ons  of  CO2  Emission  Performance  Standards  for  Fossil  Fuel-­‐Fired  Power  Plants    

Shuchi  Tala-,  Haibo  Zhai,  and  Granger  Morgan    

Department  of  Engineering  and  Public  Policy,  Carnegie  Mellon  University,  Pi<sburgh  PA  

BACKGROUND    Understanding   water   demand   in   the   context   of   carbon  regula6on   policies   and   the   mandate   to   begin   using   carbon  capture   systems   is   essen6al   to   future   energy   genera6on  planning.  The  impacts  of  emission  performance  standards  (EPS)  recently  proposed  by  U.S.  Environmental  Protec6on  Agency  (US  EPA)  to  regulate  CO2  emissions  from  coal  and  natural  gas  plants  have   not   been   quan6fied.   Currently,   it   is   known   that   the  addi6on   of   90%   carbon   capture   systems  will   lead   to   a   nearly  doubling  of  water  use,  however  specific  changes  in  water  use  to  adhere  to  the  proposed  regula6on  are  not  known.      Research  Objec-ves  1)  Inves6gate   plant   level   changes   in  water   use   for   fossil   fuel-­‐

fired   power   genera6on   systems   with   adherence   to   the  proposed  emissions  performance  standard  

2)  Explore   changes   in   water   use   from   the   impact   of   plant  design  as  well  as  policy  choices    

3)  Evaluate  the  uncertainty  in  water  use  from  the  EPS  4)  Understand  the  water  management  policy  implica6ons.    The  proposed  EPS  is  as  following  [2]:    •  New  Coal  Units  (PC  &  IGCC):  1,100  lb  CO2/MWh  gross  over  a  

12-­‐opera6ng   month   period,   or   1,000-­‐1,050   lb   CO2/MWh  gross  over  a  7-­‐year  period  

•  NGCC   units:   1,000   lb   CO2/MWh   gross   for   larger   units   or  1,100  lb  CO2/MWh  gross  for  smaller  units    

   METHODS      The  Integrated  Environmental  Control  Model,  developed  by  Carnegie  Mellon  University  and  the  Na6onal  Energy  Technology  Lab,  was  the  main  tool  u6lized  to  conduct  this  analysis  [3].      We  first  established  base  case  PC  and  NGCC  power  plants  without  carbon  capture,  and  a  PC  plant  in  compliance  with  the  proposed  EPS.  We  then  conducted  a  large  scale  sensi6vity  analysis  to  look  at  a  range  of  factors  affec6ng  water  use  in  fossil  fuel  power  plants  with  an  EPS  measure  in  place.  We  then  assessed  uncertainty  through  the  use  of  IECM’s  uncertainty  func6onality.                                  

[1]  Freshwater  Use  by  U.S.  Power  Plants:  Electricity’s  Thirst  for  a  Precious  Resource,  UCS  (2011)    hbp://www.ucsusa.org/assets/documents/clean_energy/ew3/ew3-­‐freshwater-­‐use-­‐by-­‐us-­‐power-­‐plants.pdf    [2]  US  EPA:  hbp://www2.epa.gov/carbon-­‐pollu6on-­‐standards/2013-­‐proposed-­‐carbon-­‐pollu6on-­‐standard-­‐new-­‐power-­‐plants  [3]  IECM:  hbp://www.cmu.edu/epp/iecm/    

RESULTS    Base  cases  Three   power   plant   base   cases   were   analyzed:   supercri6cal   pulverized   coal  (PC),  supercri6cal  PC  with  CCS  to  meet  the  EPS,  and  an  NGCC  plant.                              Plant  Design  Sensi-vity  PC  plant  type,  coal  type,  and  cooling  system  type  all  significantly  contribute  to  determining  carbon  removal  efficiency  and  overall  water  use.  An  example  of  such   sensi6vity   is   below,   illustra6ng   the   varia6ons   that   occur   based   on  changes   in   plant   type.   Cooling   system   type   has   the   largest   effect   on   overall  water   use,   however     plant   type   and   coal   type   have   larger   effects   on   the  carbon  removal  efficiencies  and  water  use  from  the  carbon  capture  system.        

 Compliance  Timing  Sensi-vity    The  EPS  allows  for  choice  between  a  12  and  84-­‐month  opera6ng  period,  with  6ghter  regula6ons  for  the  laber.  An  analysis  was  conducted  to  determine  if  1)  there  would  be  a  significant  difference  in  water  2)  how  long  a  plant  would  be  able   to  wait   before   installing   and   u6lizing   90%   carbon   capture   to  meet   the  standard  and  3)  if  this  would  cause  significant  differences  in  water  use.    

 

  We  thank  the  Center  for  Climate  and  Energy  Decision  Making  and  the  Department  of  Engineering  and  Public  Policy  at  Carnegie  Mellon  University,  for  their  support  of  this  work.    

Sensi-vity  to  Policy  Choices    NGCC   plants   fall   within   compliance   of   the   EPS.   Only   if   more  stringent  measures  were  put   in   place  would  NGCC  plants   need   to  install   CCS.   Subsequent   NGCC   and   PC   consump6on   intensi6es   are  shown  below.  

The   net   vs.   gross   dis6nc6on   in   the   policy   is   an   important   one.  Requiring   capture   on   a   net   basis,   leads   to   a   10%   increase   in   the  carbon  removal  efficiency  and  subsequent  higher  water  use.      Uncertainty  Uncertainty  of  the  water  use  was  assessed  by  looking  at  cumula6ve  probability  distribu6ons  of  plant  water  use  for  a  500  MW  net  Super  PC  plant  with  and  without  CCS  to  meet  the  EPS  (a).  We  then  looked  at   the   cumula6ve   distribu6on   of   added  water   use   based   by   using  the   no-­‐CCS   plant   output   as   the   input   distribu6ons   (b).  We   found  that   95%   ranges   from   238-­‐258   tonnes/hour   –   an   increase   of  approximately  30.4%.                          DISCUSSION    Water  use  from  carbon  regula6on  policies  will  have  large  effects  on  water  use,  however  it  can  be  decreased  through  the  use  of  adap6ve  strategies  to  limit  it  as  much  as  possible.  As  standards  become  more  and  more   stringent,  more  water  will   be   required   to   generate   the  same  amount  of  power  from  fossil  fuel  powered  genera6on.    

Source:  UCS  [1]  

0%  

10%  

20%  

30%  

40%  

50%  

Sub  Cri6cal   Super  Cri6cal  Ultra  Cri6cal  CO2  Re

moval  Efficien

cy  (%

)  

Plant  Type  

0  0.5  1  

1.5  2  

2.5  3  

3.5  

Sub  Cri6cal   Super  Cri6cal   Ultra  Cri6cal  

Water  Use  In

tensity

 (m^3/

MWh)  

Plant  Type  

Consump6on    Withdrawal  

0  200  400  600  800  1000  1200  1400  1600  1800  

1   2   3   4   5   6   7   8   9   10  11  12  

CO2  Em

ission

 Rate  (lb

/MWh-­‐

gross)  

Deployment  Time  of  CCS  (nth  month)  

No/90%  Capture  40%  Capture  

0  

0.25  

0.5  

0.75  

1  

230   240   250   260   270  

Cumula-

ve  Proba

bility  

Added  Water  Consump-on  from  CCS  (tonnes/hr)  

(b)  

0  

0.25  

0.5  

0.75  

1  

750   900   1050   1200   1350  

Cumula-

ve  Proba

bility  

Plant  Water  Consump-on  (tonnes/hr)  

(a)  

CCS  (40%  Capture)  

No  CCS  

Variable   Results  

Plant  Type   Super  PC   Super  PC   NGCC  

EPS  (1100  lb/MWh-­‐g)   No     Yes   No  

Gross  output  (MW)   536   578   557  

Net  output  (MW)   500   500   542  

Net  plant  efficiency   38.2%   32.8%   50.1%  

CO2  removal  efficiency   -­‐   40%   -­‐  

Emissions  rate  (lb/MWh-­‐g)   1687   1097   782  

Consump6on  Intensity  (m3/MWh)   1.63   2.13   .67  

Withdrawal  Intensity  (m3/MWh)   2.33   3.06   .89  

Type   90%  Capture  (months)  

Consum  Intensity  

Withdr  Intensity  

Avg  Annual  Consump  

Avg  Annual  Withdr    

12  months   4.75   2.10   3.00   6.9  E6   9.8  E6  

84  months   36.1   2.14   3.05   7.0  E6   10  E6  

Consistent   0   2.13   2.64   7.0  E6   8.7  E6  

0  

0.5  

1  

1.5  

2  

2.5  

3  

1500   1100   800   500   300  

Water  Con

sump-

on  In

tensity

 (m^3/

MWh)  

Emissions  Performance  Standard  (lb-­‐MWh-­‐gross)  

PC  

NGCC