oasis heat presentation v3

The  Curious  Economics  of  Home  Heat  

Todd  Hixon  

Oasis  October  26,  2010  

$5,000  Heat  Bill  

•  3,800  B2  house  •  InsulaDon  not  great  

•  Forced  hot  air:    oil  heat  +  AC  

•  Two  systems:    first  &  second  floors  

•  Concord,  MA  

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2007-­‐2009  Energy  Use  

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50  

60  

70  

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Nov   Dec   Jan   Feb   Mar   Apr   May-­‐Oct  

Oil  Gal/d  

kWh/d  

HDD  index  

Summer  AC  Cost  is  a  small  %  of  total  

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Energy  Units  

•  BTU  (BriDsh  Thermal  Unit)  is  a  measure  of  energy  in  the  form  of  heat    – Heat  to  raise  temp  of  1  lb  of  water  by  1°  F  – Analogous  to  1  calorie  =  heat  1  gm  of  water  by  1°  C  

•  KiloWae-­‐hour  (kWh)  =  unit  of  electrical  energy  –  Can  be  converted  to  heat:    1  kWh  delivered  to  a  resisDve  load  releases  3,412  BTUs  of  heat  

•  Thermal  efficiency  =  heat  delivered  to  house  ÷  heat  released  when  fuel  is  consumed  

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Cost  of  Heat  By  Fuel  Natural  Gas  Is  The  Obvious  Choice  

Wholesale  Cost/unit  

Retail  Cost/unit  

Units/  MMBTU  

Thermal  Efficiency  

Cost/Usable  MMBTU  

Lb  CO2/Usable  MMBTU  

Oil  (gallon)  

$2.284   $3.023   7.41   82.5%   $27.11   1995  

N  Gas  (therm)  

$0.372   $1.493   10.00   87.5%   $17.00   1345  

Electricity  (kWh)  

$0.0431   $0.13   293.1   100%   $38.10   1626  

1)  ISO  New  England  2)  U.S.  EIA:  hep://www.eia.gov/pub/oil_gas/natural_gas/feature_arDcles/2010/ngyir2009/ngyir2009.html#markets  3)  U.  S  EIA,  June  2010:  hep://www.eia.doe.gov  4)  New  York  harbor  spot  price,  10/13/10    5)  Naturalgas.org:  hep://www.naturalgas.org/environment/naturalgas.asp#greenhouse/  6)  81  lbs/MMBTU  for  New  England  electric  system  fuel  mix  ÷  50%  transmission  loss  factor.  

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Natural  Gas  /  Oil  Price  RaDo  Is  VolaDle  

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40  

60  

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120  

07/08   08/09   Current  

Retail  N  Gas  $/M

MBT

U  As  %  of  O

il  

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Electricity  and  Heat  Are  Not  Equivalent  

•  Electricity  is  a  more  useful  form  of  energy  – Converts  efficiently  to  mechanical  energy  

•  Electricity  is  a  service  –  difficult  and  expensive  to  store  – Value  different  at  different  Dmes  

This  makes  a  simple  comparison  of  oil  and  electricity  misleading  

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Heat  Pump  Physics  

•  Pumps  heat  into  house  –  “recycles”  lost  heat  

•  Powered  by  electric  motor  

•  Delivers  ~3  heat  units  to  house  per  unit  of  electrical  energy  

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Heat  Pump  Economics  

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0.5  

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1.5  

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2.5  

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3.5  

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17   20   30   35   40   45   47  

Outside  Temperature  (deg  F)  

Delivered  Heat  /  Energy  Used  •  3x+  leverage  •  Called  “Coefficient  of  

Performance”  (COP)  •  LimitaDons:  

–  Throughput  declines  with  outside  temperature  

–  Delivers  heat  at  ~95°F  •  Cheap  supplemental  heat    

–  Not  enough  to  heat  house  in  mid-­‐winter  

Source:    Carrier  25HPA5H  Spec  Sheet  

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Electricity  Is  Cheap  At  Night  

Marginal  Cost  ($/MWh)  

Source:    ISO  New  England,  Weekly  Market  Summary,  9/27/10  10  

Electricity  Is  Green  At  Night,  Too  

0%  

10%  

20%  

30%  

40%  

50%  

60%  

70%  

80%  

90%  

100%  

NE  Electric  Capacity  Ordered  By  Variable  Cost/MWh  

Nuclear  

Hydro,  Wind,  etc.  

NGas  -­‐  CoGen  

Coal  

NGas  -­‐  Conv  

Oil  

3am  Load  

Average  Daily  Peak  

Annual  Peak  

Source:    NE  ISO,  Concord  Municipal  Light  

Electricity  costs  in  NE  are  Ded  to  N.  Gas  –the  marginal  supply  most  of  the  year  

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Concord  Off-­‐Peak  Tariff  

Cents/kWh  

Peak  Hours   13.4  

Off-­‐Peak  Hours*   5.5  

•  Off-­‐Peak  =  11p-­‐6a,  1p-­‐3p,  for  residenDal  heaDng  &  hot  water  

•  Implemented  via  a  2nd  meter  +  load  controller  that  responds  to  a  power-­‐line  carrier  signal  indicaDng  peak/off-­‐peak  

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Cost  of  Heat  By  Fuel  

Wholesale  Cost/unit  

Retail  Cost/unit  

Units/  MMBTU  

Thermal  Efficiency  

Cost/Usable  MMBTU  

Lb  CO2/Usable  MMBTU  

Oil  (gal)   $2.284   $3.023   7.41   82.5%   $27.11   1995  

Gas  (therm)   $0.372   $1.493   10.00   87.5%   $17.00   1345  

Electric  (kWh)  

•   Peak   $0.0501   $0.130   293.1   100%   $38.10   1626  

•   Off-­‐Peak   $0.0278   $0.055   293.1   100%   $15.63   1127  

•   Heat  Pump   $0.0501   $0.130   293.1   300%   $12.70   546  

•   RegulaDon   $0.0109   $0.035   293.1   100%   $9.95   1127  

1)  EsDmated  from  ISO  New  England  data  2)  U.S.  EIA:  hep://www.eia.gov/pub/oil_gas/natural_gas/feature_arDcles/2010/ngyir2009/ngyir2009.html#markets  3)  U.  S  EIA,  June  2010:  hep://www.eia.doe.gov  4)  New  York  harbor  spot  price,  10/13/10    5)  Naturalgas.org:  hep://www.naturalgas.org/environment/naturalgas.asp#greenhouse/  6)  81  lbs/MMBTU  for  New  England  electric  system  fuel  mix  ÷  50%  transmission  loss  factor.  7)  56  lbs/MMBTU  for  New  England  electric  system  off-­‐peak  fuel  mix  ÷  50%  transmission  loss  factor.  8)  EsDmated  from  ISO  New  England  data                    9)  VCharge  CorporaDon  

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Heat  Pump  &  Off-­‐Peak  Can  Be  Combined  

Heat  provided  by  each  system  proporDonal  to  temperature  liB  

Heat  Pump  heats  air    to  95°  F  

Electric  Thermal  Storage  (ETS)  Tops  Off  Heat  

Return  Air  @  65° F  

Supply  Air  @  110° F  

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New  System  for  Upstairs  Heat  Pump  

(on  right)  

Electric  Thermal  Storage    (ETS)  Unit  

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Return  air  

Heat  Pump  Condenser  

Brick  Stack  Air  Handler  Supply  Air  

Cost  Model  for  Upstairs  

•  51%  cost  savings  •  63%  of  heat  from  Heat  Pump  

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Results  Measurement  

•  Oil  deliveries  •  Separate  meter  for  off-­‐peak  electricity  

•  Installed  power  meter  on  Heat  Pump  supply  circuit  

Current  Sensors  Power  line  communicaDons  node  

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Results  Measurement  

•  Power  sensor  on  Heat  Pump  shows  power  usage  

•  Maintains  hourly  log  file  

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QuanDtaDve  Results  

•  Cost  savings  =  54%  ($1,300)  –  Invested  ~$3,000  over  replacement  cost  of  old  system  

•  Saved  850  gal  oil  &  4.75  tons  CO2  

•  Heat  pump  carries  less  of  heat  load  than  expected  

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Comfort  Factor  

•  Electric  heat  is  inherently  cleaner  and  more  reliable  

•  The  heat  pump  is  an  awesome  air  condiDoner  – Made  light  work  of  the  2010  heat  

•  It  feels  good  to  be  green  – Especially  if  you  save  money  

•  My  wife  gave  the  new  system  thumbs-­‐up  – More  powerful  air  handler  eliminated  cold  spots  

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