Field Experience with Ground-Source Heat Pumps in Affordable Low Energy Housing

Daniel EllisPresident

ClimateMaster, Inc.Oklahoma City, U.S.A.

dellis@climatemaster.comwww.climatemaster.com

Non-profit Christian housing ministryFounded in 1976

Has built 250,000 homes world-wideProviding over 1 million people with safe, decent, affordable shelter

3rd largest private homebuilder in USA5,000 homes per year in USA

Plus 20,000 homes per year in other countries

Not a give-away programVolunteer labor and donations reduce costs

Homeowners provide down-payment, interest-free mortgage payments, and sweat equity

COHFH Builder’s “Blitz” Week (June 2006)(1/3)

Monday 08:00 slab with GHX Friday 16:00 owner move-in

10 professional home builders each sponsored a separate house and constructed it from start to finish in 5 days!

SO HOW DID THEY DO IT?SO HOW DID THEY DO IT?

COHFH Builder’s “Blitz” Week (June 2006)(2/3)

Brute Force!Brute Force!

COHFH Builder’s “Blitz” Week (June 2006)(3/3)

Ongoing Partnership Formed in 2007

COHFH, GHP manufacturer, and local electric utility partner to make all COHFH homes low energy

Higher initial costs could not be passed on to homeowners due to COHFH cash flow considerations

COHFH is the mortgage lender

GHP manufacturer and electric utility agree to share initial cost difference over standard construction

Act of corporate stewardship

Gift of reducing energy consumption provides long-term benefits to the homeowners and to our environment

Provides valuable experience in unexplored segment of housing market

Partnership Goals

Install GHP systems in all COHFH homes

Reduce total energy demand of these homes to maximum reasonable extent

Using cost-effective and generally available measures

Track the energy consumption of the homesCollect monthly utility meter data to establish a baseline of actual performanceInstall a proportion of “smart” recording meters to collect detailed data on electric demand profiles

Demonstrate potential for zero energy homesBy integrating grid-tied solar PV systemInitial goal of zero peak demand and zero net GHP energylater goal of zero net total energy

Utilize project as a market transformation toolLarge-scale demonstration of affordable, low-energy housingRaise public and construction trade awareness, generate spin-off projects with other HFH affiliates, and attract additional COHFH funding

Exhaust Ai r

Supply Ai r Return Ai r

VentedUncondi tioned

Attic

GasFurnace

Attic Venti la tion

Attic Venti la tion

Outside Ai r

Exhaust Ai r

Supply Ai r Return Ai r

SealedAttic

Ground-Source

HeatPump

Dual Pane Clear

Dual Pane Low-ELow SHGC

400 ft. BoreUnder Slab

Internal Pump

A/CCoil

Flue

CombustionAi r

Condensing Uni t

So lar PV Array

IncandescentLighting

FlourescentLighting

Evolution of COHFH Homes

Standard Gas House

Energy Use: 252 kWh/(m2· yr)Energy Cost: $1,739 CO2 Emissions: 105 kg/(m2· yr)

Low Energy GHP + PV House

Energy Use: 52 kWh/(m2· yr)Energy Cost: $522 CO2 Emissions: 41 kg/(m2· yr)

COHFH Housing Characteristics (1/2)

Standard Standard Low Energy Low EnergyGas GHP GHP GHP + PV

Heating Gas GHP GHP GHPCooling Split A/C GHP GHP GHPHot Water Gas Storage Elec Storage1 Elec Storage1 Elec Storage1

Lighting Incandescent Incandescent Flourescent FlourescentAppliances Standard Standard Energy Star2 Energy Star2

Solar PV Array DC kW 2.3

Construction Wood Frame Wood Frame Wood Frame Wood FrameFloor Slab on Grade Slab on Grade Slab on Grade Slab on GradeAttic Vented Vented Sealed SealedInsulation Type Fiberglass Fiberglass Spray Foam Spray FoamAir Duct Location Attic Attic Attic AtticVentilation Spot Exhaust Spot Exhaust Central Supply Central Supply

1. GHP desuperheater assist

2. Energy Star appliances meet strict efficiency guidelines

House Type

COHFH Housing Characteristics (2/2)

Standard Standard Low Energy Low EnergyGas GHP GHP GHP + PV

Average Floor Area m2 110 110 110 110

U-value - Total Envelope W/(m2· K) 1.66 1.66 1.25 1.25U-value - Slab Perimeter W/(m2· K) 1.10 1.10 1.10 1.10U-value - Wall W/(m2· K) 0.35 0.35 0.35 0.35U-value - Flat Ceiling W/(m2· K) 0.19 0.19U-value - Sloped Roof W/(m2· K) 0.26 0.26U-value - Air Duct W/(m2· K) 0.95 0.95 0.71 0.71U-value - Window W/(m2· K) 2.84 2.84 1.99 1.99SHGC - Window 0.62 0.62 0.40 0.40Natural Air Change Rate - Htg 1/h 0.78 0.78 0.30 0.30Natural Air Change Rate - Clg 1/h 0.56 0.56 0.22 0.22Envelope Air Leakage Rate Untested Untested Tested TestedAir Duct Leakage Rate Untested Untested Tested Tested

Heating Load (-11°C, 21°C) kW 8.2 8.2 5.3 5.3Cooling Load (36°C, 24°C) kW 6.1 6.1 4.7 4.7Hot Water Load (55°C) kWh/yr 3200 3200 3200 3200Lighting Load kWh/yr 1753 1753 701 701Appliance Load kWh/yr 4667 4397 3518 3518

House Type

COHFH Hope Crossing Project(1/4)

COHFH Hope Crossing Project(2/4)

COHFH Hope Crossing Project(3/4)

COHFH Hope Crossing Project(4/4)

Average Metered Energy Consumption

0

10

20

30

40

50

Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Nov-07 Dec-07 Annual

kW

h/(

m2 ·

mo

)

0

50

100

150

200

250

kW

h/(

m2 ·

yr)

Standard Gas Homes - Electricity Use

Standard Gas Homes - Gas Use

Standard GHP Homes - Electricity Use

234

116

50% Reduction

Derivation of Htg & Clg Energy Consumption

0

5

10

15

20

25

-600 -500 -400 -300 -200 -100 0 100 200 300 400

Monthly Degree Days ( Basis 18°C, - DDH, + DDC)

No

rmal

ized

kW

h/(

m2 ·

mo

)

Std Home - GasEH = -0.0397· DDH

R2 = 0.895

Std Home - GHPEH = -0.0134· DDH

R2 = 0.781

Std Home - A/CEC = 0.0284· DDC

R2 = 0.890

Std Home - GHPEC = 0.0145· DDC

R2 = 0.886

49% Reduction

66% Reduction

Average Metered Energy Costs

$0

$100

$200

$300

$400

Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Nov-07 Dec-07 Annual

Mo

nth

ly C

ost

$-

$500

$1,000

$1,500

$2,000

An

nu

al C

ost

Standard Gas Homes - Electricity Cost at $0.088/kWh

Standard Gas Homes - Gas Cost at $0.045/kWh

Standard GHP Homes - Electricity Cost at $0.080/kWh $1,606

$1,023

36% Reduction

Energy Consumption Estimates

Benchmark hot water, lighting, and appliance loads for standard houses estimated using NREL methodology (Hendron, et al. 2004)

CFL lighting and Energy Star appliance adjustments made for low energy houses

Heating and cooling energy estimated using GeoDesigner software from ClimateMaster

Solar PV contribution estimated using PVWATTs software from NREL

Estimated Site Energy Consumption by End Use

252

119

27

48

16

42

0

112

2316 17 16

40

0

82

13 1021

6

32

0

52

13 1021

6

32

-30-50

0

50

100

150

200

250

300

Total Heating Cooling Hot Water Lighting Appliance Solar PV

kW

h/(

m2 ·

yr)

Std Home - GAS Std Home - GHP

LE Home - GHP LE Home - GHP + PV

Validation of Energy Consumption Estimates

252

112

233

106

234

116

0

100

200

300

Std Home - GAS Std Home - GHP

kW

h/(

m2 ·

yr)

Average Weather Year Estimate

Degree Day Adjusted Estimate

Actual Metered Consumption

Source Energy and C02 Emission Estimates

US national average factors for electricity and natural gas obtained from NREL (Deru and Torcellini 2006)

Includes power plant conversion, transmission, and distribution losses for electricity

Includes pre-combustion effects associated with extracting, processing, and delivering primary fuels to point of conversion in power plant

For natural gas includes both pre-combustion effects and on-site combustion emissions

Estimated Total Energy Consumption and Emissions

252

112

82

52

465

373

271

171

105

88

64

41

0

100

200

300

400

500

Std Home - GAS Std Home - GHP LE Home - GHP LE Home - GHP + PV

kW

h/(

m2 ·

yr)

0

25

50

75

100

125

CO

2 eq k

g/(

m2 ·

yr)

Site Energy

Source Energy

GWP Emissions

Planned Future Improvements

Advanced GHP with variable capacity and integrated full-condensing hot water modes

Zero-energy home using larger grid-connected PV array

Estimated Site Energy Consumption by End Use

82

13 10

21

6

32

0

67

118 10

6

32

0

37

118 10

6

32

-30

0

118 10

6

32

-67

-80

-60

-40

-20

0

20

40

60

80

100

Total Heating Cooling Hot Water Lighting Appliance Solar PV

kW

h/(

m2 ·

yr)

LE Home - GHP LE Home - Adv GHPLE Home - Adv GHP + 2.3 kW PV ZE Home - Adv GHP + 5.3 kW PV

Additional Investment and Annual Energy Cost Savings

Standard Standard Low Energy Low Energy Low Energy Low Energy Zero EnergyGas GHP GHP Adv GHP GHP Adv GHP Adv GHP

2.3 kW PV 2.3 kW PV 5.2 kW PV

Additional Investment3:

Heating and Cooling -$ 4,500$ 4,500$ 6,000$ 4,500$ 6,000$ 6,000$ Solar Photovoltaic -$ -$ -$ 15,000$ 15,000$ 30,000$ Insulation, Lighting, Appliance -$ -$ 2,500$ 2,500$ 2,500$ 2,500$ 2,500$

Total -$ 4,500$ 7,000$ 8,500$ 22,000$ 23,500$ 38,500$

Annual Energy Cost1,2:

Heating 596$ 127$ 69$ 60$ 69$ 60$ 60$ Cooling 270$ 155$ 101$ 76$ 101$ 76$ 76$ Hot Water 275$ 132$ 158$ 78$ 158$ 78$ 78$ Lighting 175$ 175$ 70$ 70$ 70$ 70$ 70$ Appliance 423$ 440$ 352$ 352$ 352$ 352$ 352$ Solar PV Contribution -$ -$ -$ -$ (228)$ (228)$ (636)$

Total 1,739$ 1,029$ 750$ 636$ 522$ 408$ -$

Annual Energy Cost Saving3 -$ 710$ 989$ 1,103$ 1,217$ 1,331$ 1,739$

1. based on electricity at $0.100/kWh for first 600 kWh/month, then $0.050/kWh winter and $0.090/kWh summer for all kWh/month over 600

2. based on natural gas at $0.045/kWh equivalent

3. Relative to Standard Gas Home

House Type:

Return on Investment vs. Standard Gas Home

$8,500$7,000

$23,500

$38,500

$4,500

$22,000

0

10,000

20,000

30,000

40,000

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

Annual Energy Cost Savings ($)

Ad

dit

ion

al

Inv

es

tme

nt

($)

LE Home - Adv GHP

LE Home - GHP + 2.3 kW PV

LE Home - Adv GHP + 2.3 kW PV

ZE Home - Adv GHP + 5.2 kW PV

ROI = 20%

ROI = 15%

ROI = 10%

ROI = 5%

ROI = 0%

Std Home - GHP

LE Home - GHP

Annual Fuel Escalation Rate 2%

Conclusions

Total site energy consumption reduction of 50-75%Using GHPs and low-energy construction techniques

50% reduction in metered energy was achieved using GHPs alone

1,100 tons of annual CO2 emissions avoidedCollective contribution of 240 low energy GHP homes in Hope Crossing as compared to standard gas homes

Not including the contribution of solar PV systems

Low energy GHP homes are cost-effectiveEven at standard builder pricing, the ROI is over 15% after tax

Concepts employed are generally available

Low energy demand makes solar PV more viableSmall array on first two PV homes will reduce peak demand to near zero on hot summer afternoons and produce enough annual power to completely operate the GHP system

Zero net energy is feasible, but not yet cost-effective

Thank You!