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Gas-Fired Absorption Heat Pumps for Residential Heating Applications
Stone Mountain Technologies, Inc.Michael Garrabrant, President
ACEEE Hot Water ForumAtlanta, GA
Nov 5, 2013
Topics of Discussion
Technology Background and Potential
Residential Water Heating Development
Space-Pool Heating Development
Vapor-Compression Heat Pump Cycle
COPh = Qout/Ein = 2.0-4.0
Qheating = Qcond ̴̴ Qevap
Simplified Absorption CycleRefrigerant – Absorbent Pair
COPh = (Qcond + Qabs)/Qin = 1.5-2.5
Qheating = (Qcond + Qabs) ̴̴ 2.5(Qevap)
Excellent Heating Efficiencies
1.2
1.3
1.4
1.5
1.6
1.7
1.8
-20 -10 0 10 20 30 40 50 60 70 80
Cycle
CO
P
Ambient Temperature [deg F]
"Typical" Cycle COP vs AmbientSingle-Effect NH3-H2O Heat Pump
Producing 120 oF Water
Non-Condensing ~82%
Condensing ~95%
Gas Heat Pump ~1.5 COP
Can Provide……….
Space Heating Domestic Hot Water Process Heating Space Cooling Refrigeration Heating and Cooling Simultaneously
Can Be Powered By……….
Combustion of Natural Gas/Propane Combustion of BioFuels Waste Heat Sources Over 220 oF Solar Heat Over 220 oF
NH3-H2O Absorption Heat Pumps
Applications With Good Economics
Domestic Hot Water Heating
Building Space Heating Heating Dominated Climate Zones
Pool Heating
Waste Heat Driven Cooling/Refrigeration 0.5 – 15 RT Capacities
Solar Driven Cooling 0.5 – 5 RT Capacities
Gas-Fired Residential Heat Pump Water Heater
Proof-of-Concept R&D Complete 3 “Beta” Prototypes Tested
Beginning Field Test Program and DFM
EF: 1.3 Input: 6,300 Btu/hr Heating Output: 9,500 Btu/hr (2.8 kW)* Storage: 60 – 80 gallon Ambient: 35 – 120 F Condensing DV ½ - 1” PVC Venting Emissions: SCAQMD Compliant GWP = Zero
Patent Pending
Cycle COP vs Supplied Water Temperature @ 68 oFBeta GHPWH Prototypes
1.20
1.30
1.40
1.50
1.60
1.70
1.80
1.90
80 90 100 110 120 130 140 150
Cyc
le C
OP
Supplied Water Temperature (deg F)
GHPWH Prototype Steady State PerformanceNominal 68oF Ambient
Beta1 Beta 2 Beta3
COPHHV vs Supplied Water Temperature @ 68 oFBeta GHPWH Prototypes
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
80 90 100 110 120 130 140 150
Ove
rall
Syst
em
CO
P_
hh
v
Supplied Water Temperature (deg F)
GHPWH Prototype Steady State PerformanceNominal 68oF Ambient
Beta2 HHV Beta1 HHV Beta3
Beta 3 Field Test InstallationData Acquisition/Monitoring By GTI
Attached Drive-Under Garage
2 Adults, 2 Teenagers (one college) 68 Gallon Tank Capacity Replacing 50 gal / 40 kBth PDV ¾” PVC Vent
Water Flow Gas Flow (propane) Electrical Power Cold Water In Hot Water Out Ambient Temperature + Humidity A Few Key HP Cycle Temperatures
Start: November 2013
Relative Cost To Heat 100 Gallons, 77o Rise
Fuel Heater Type EF $ Savings %
Natural Gas Gas Heat Pump 1.30 $0.59
Natural Gas Condensing Tankless 0.90 $0.86 $0.26 44%
Natural Gas Tankless 0.82 $0.94 $0.35 59%
Natural Gas Gas Storage 0.70 $1.10 $0.51 86%
Electric Electric Heat Pump 2.00 $1.13 $0.54 91%
Natural Gas Gas Storage 0.60 $1.28 $0.69 117%
Electric Electric Resistance 0.95 $2.37 $1.78 301%
Approximate Cost To Heat 100 Gallons of Water
Natural Gas: $1.20 per Therm
Electricity: $0.12 per kW-hr
Ambient: 68 oF
Gas-Fired Heat Pump For Space-Pool HeatingPrototype R&D Stage
COPHHV = 1.4 at 47oF
80,000 Bth at 47oF Ambient: 100/120oF Hydronic Condensing 3:1 Modulation
Heating Dominated Climate Zones Long Heating Season For Payback Can Also Provide DHW
SMTI GAHP Target PerformanceHydronic Return = 100F ; Supply = 120F at 47F Ambient
EHP COP is “Primary Fuel Based” in which incoming electric power is 32.5% efficient
EHP = 13 SEER, 8 HSPF
GAHP vs EHP Performance
Gas Heat Pumps are better suited for Heating Dominated climate zones.
Electric Heat Pumps are better suited for Cooling Dominated climate zones.
EHP more cost effective than non-condensing gas at ambients above ~20F (ignoring aux input)
EHP more cost effective than condensing gas at ambients above 30F (ignoring aux input)
EHP never more cost effective than GAHP
Results dependent on assumed cost of electric and gas
Heating Cost Per Delivered Therm ComparisonEHP: 13 SEER, 8 HSPF, 70F Indoor Temp
GAHP: 100F Return, 120F Supply (at 47F)
$0.50
$1.00
$1.50
$2.00
$2.50
$3.00
$3.50
$4.00
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
Ambient [deg F]
Cost Per Therm Heating DeliveredElectric: 12 cents/kW-hr ; Gas: $1.20/therm
Elec HP Gas HP Cond Gas NC Gas Elec HP
Simple Payback
Non-Condensing Condensing
Northeast 3 - 3.5 4 - 5
Mid-West 3 - 4 5 - 6
Northwest 4 - 5 6 - 7
Mountain 4 - 5 6 - 7
Central 5 - 6 7 - 8
Northeast 3 - 3.5 3 - 3.5
Upper Mid-West 3 - 4 3 - 4
Northwest 4.5 - 5.5 4.5 - 5.5
Mountain 4 - 5 4.5 - 5.5
Central 5 - 6 5 -6
Residential Furnace
Light Commercial Boiler
Simple Payback - Years
U.S. Department of Energy
DE-EE0003985
DE-EE0006116
Gas Technology Institute
Acknowledgements
