Stone Mountain Technologies, Inc.
Michael Garrabrant, President
Johnson City, Tennessee, USA
www.StoneMountainTechnologies.com
Gas Heating with Absorption Heat
Pumps – How, Where and WhyJune 04, 2019
Confidential 1
The World Gas Engineers Now Live In
“The world is going to end in 12 years”
“We need to stop using all carbon fuels, immediately”
Confidential 2
“We will ban all gas by 2050”
“The world is going to end in 10 years”
The world has already ended....Global Warming!Climate Change!
Rising Oceans!
MeIting Icecaps!
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Agenda
➢ Types of gas heat pumps
➢ How does an absorption heat
pump work?
➢ History of absorption heat pumps
➢ Best applications of absorption
heat pumps
➢ Why do absorption heat pumps
matter?
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Types of Gas Heat Pumps
➢Gas-Engine Heat Pumps
➢Heat Engines (Stirling/Vuilleumier)
➢Adsorption
➢Absorption
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Gas Engine Heat Pumps
Photo Courtesy Illios
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Photo Courtesy Intellichoice
Gas Engine Heat Pumps
• COP Water Heating at 75F Ambient ~2.0
• COP Space Heating at 47F Ambient ~1.3
• Commercial Sizes Only (100 to 500 kbtu/h)
• Hydronic or Direct Refrigerant Delivery
• Very High Capital Cost
• Engine Maintenance/Cost
• COP Decreases Sharply as Ambient Decreases (vapor compression cycle)
• Areas with High Electric Rates/Demand Charges
• Most Popular in Japan
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Heat Engines
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Direct Compression Vapor Compression Cycle
Figures Courtesy BoostHeat
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Heat Engines
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• COP Space Heating at 47F Ambient ~1.4 to 2.0
• Hydronic Delivery
• Hot end 1000+ oF and psig
• Helium or CO2 working fluid (gas)
• Very High Capital Cost
• System available in Europe at $250/kbtu/h
• typical condensing furnace ~$25/kbtu/h
• Direct-compression system requires boiler for low ambients
Adsorption Heat Pumps
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Solar-Thermal Adsorption ChillerPhoto Courtesy Climatewell
Absorbent is a Solid
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• Water – Salt or Water – SilicaGel (cannot be used for heating)
• Ammonia – Carbon or Ammonia – Salt
• Other exotic combinations......
• Hydronic Delivery
• COP Space Heating at 47F Ambient ~ 1.2
• Large Size, Heavy, High Capital Cost
• Low heat/mass transfer coefficients, poor internal heat recovery
• Normally used for cooling using low-temperature waste/solar energy
Adsorption Heat Pumps
Absorption Heat Pumps
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Absorbent is a Liquid
Figure Courtesy Robur
How do Absorption Heat Pumps Work?
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How Does It Work?
COPh = (Qcond + Qabs)/Qin = 1.4-2.0
Qheat = (Qcond + Qabs) ~ 2.5 times Qevap
COPh = Qcond/Ein = 3.0-4.0
Qheat = ~1.1 x Qcooling
Capacity & COP Remain High at Low Ambient Temperatures
Vapor Compression Heat Pump Gas-fired Absorption Heat Pump
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What happens when it gets cold outside?
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COP (Coefficient of Performance): Useful Energy Produced ÷ Energy Input• Cycle• Gas-Fired or HHV (includes combustion loses)• Electrical Parasitic Included?
Beware• HHV or LHV• Ambient Temperature
• wet or dry ambient sink• Chilled/Hot Water Delivery Temperature• With or Without Electrical Parasitic Power• Energy Source: Site or Primary Basis
Pause For A Few Definitions
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Confidential 18
NH3-H2O Absorption
❖ Cooling COP(SE) = 0.65 Cycle / 0.5 Gas
❖ Cooling COP(GAX) = 0.83 Cycle / 0.7 Gas
❖ Refrigeration COP(SE) = 0.5 Cycle / 0.4 Gas
❖ Heating COP(SE) =1.7 Cycle / 1.5 Gas
❖ Heating COP(GAX)* = 2.1 Cycle / 1.8 Gas
❖ Gas-Fired Heating
❖ Small Waste/Solar Cooling
❖ Residential/Light Commercial
* GAX advantage = minimal below 30 oF
LiBr-H2O Absorption*
❖ Cooling COP(SE) = 0.7 / 0.55
❖ Cooling COP(DE) = 1.2 / 1.0
❖ Cooling COP(TE) = 1.55 / 1.3
❖ Large Gas-Fired Cooling (100+ RT)
❖ Large Waste/Solar Cooling
❖ Commercial/Industrial
* All applications require wet cooling tower
Two Commonly Used Absorption Cycles
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NH3-H2O Absorption
❖ Reversible (heat or cool)
❖ Direct Air-Cooled
❖ Can do Refrigeration
❖ Small Footprint
❖ Lower Cost/RT in Smaller Systems
❖ SE (220oF) or GAX (400oF)
LiBr-H2O Absorption
❖ Non-Reversible (cooling only)
❖ Requires Wet Cooling Tower
❖ Cannot do Refrigeration
❖ Large Footprint
❖ Higher Cost/RT in Smaller Systems
❖ SE (180oF), DE (350oF) or TE(>500oF)
Two Commonly Used Absorption Cycles
Figure Courtesy Robur Figure Courtesy York
For Remainder of Presentation
Focus on Heating Using NH3-H2O Cycle
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NH3-H2O Cycles
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Single Effect (SE)
GAX
Double
Effect
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Single Effect Heating Cycle
w/Condensing Heat Exchanger
Hydronically-Coupled to
Building or Storage Water Tank
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Vapor To Condenser , 99.9%, ~155 oF
Strong Solution from Solution Pump
50% NH3, ~ 110 oF
Weak Solution
15% NH3, ~270 oF
To Absorber
~135 oF
Solution Heat Exchanger
(SHX)
Rectifier
Desorber
~ 215 oF
~ 220 oF
97% NH3
High Pressure Side
High Side Pressure
200 – 370 psig
Depending on Hydronic Return Temperature
Hydronic Fluid
Being Heated
~ 100 oF
~ 120 oF
To Sub-Cooler
~117 oF
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NH3 Vapor
~43 oFWeak Solution
15% NH3, ~135 oF
Strong Solution To Rectifier Coil
~ 110 oF, 50% NH3
Refrigerant Heat Exchanger (Sub-Cooler)
(RHX)
Solution Pump
Absorber
~ 105 oF
Low Pressure Side
NH3 LP Liquid
~37 oF
NH3 HP Liquid from Condenser
~115 oF
Hydronic Fluid
Being Heated
~ 100 oF
~ 120 oF
Low Side Pressure
0 - 120 psig
Dependent on Ambient Temperature
EEV
~ 48 oF
Evaporator
Air
Very Difficult Pump Application• Solution at or near saturation (can flash in pump)• Often required to pump 2-phase vapor/liquid • Inlet pressure can be at a slight vacuum• Outlet pressure up to 390 psig
• Viscosity very low, less than water• Very poor liquid lubricity• Cannot leak
• Oil-driven diaphragm or piston pumps normally used
Solution Pump
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Evaporator Boiling Temperature Profile
• 2-Component Mixture
• EEV Controls a Glide, Not
Superheat
• Proper Glide Very Critical for
Maximizing Performance at
all Operating Conditions
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Single-Effect Cycle Performance vs Operating Condition
Brief History of NH3-H2O Absorption
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First Absorption Refrigerator - 1859
Ferdinand Carré
• H20 / NH3 refrigerant pair
• Heat – driven
• Produced “artificial ice” in large
commercial quantities
• Patented France (1859)
US (1860)
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Bryant, 1962-1970 (COP 0.28 – 0.42) Arkla-Servel, 1965 (COP – 0.33)
First Residential Gas-Fired Air-Conditioners
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Whirlpool, 1965 – 197x (COP - 0.50)
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Arkla-Servel, 1968 (COP – 0.48)
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Columbia Gas of Ohio, 1972 (COP - 0.40)
Never Commercialized
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2004 – GAX Heat Pump0.60/1.26 COP
Robur, 1991 to Present
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Energy Concepts
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DOE and Gas Utilities Launch Series of R&D Programs to Develop Gas-Fired Residential Heat Pump
“Search for the Holy Grail”
Gas-Fired COP Goal: 0.7+/1.2+
Cooling Focus – Heating an Afterthought
Gas Utilities Want To Sell More Gas In Summer
Peak Load ReductionTypical EHP SEER ~5-7
1980 – Almost 40 Years Ago..........
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Columbia Gas of Ohio, 1988 (COP - 0.80/1.55)
NH3-H2O Double Effect• High Side Pressure >1500 psig !!!• Abandoned, not cost effective
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Battelle/GRI Dual-Cycle (1983 – 1990)
SE NH3-H2O Cycle + SE LiBr-H2O Cycle Operating in Series
Never Commercialized, Too Expensive/Complicated
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Phillips Engineering, 1981 to 2000
❖3 RT GAX Heat Pump❖Target 0.8/1.8 COP❖Proprietary Cycle❖Proprietary HXs❖Magnetic Piston Pump❖DOE Supported
Never Commercialized, Too Expensive/Complicated
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Cooling Technologies Inc., 1997 to 2003
❖5 RT GAX Chiller, Target 0.7 COP❖Proprietary HXs❖GRI Supported
Field Tested, UL Approval, Not Commercialized: Not competitive vs electric air-conditioners
❖ 5RT GAX Heat Pump❖ Attempt to Salvage Phillips Intellectual Property
❖ DOE/Gas Utility Supported
Ambian, 1999 to 2004 (COP – 0.70/1.40)
Never Commercialized, Too Expensive/Complicated
SMTI GAHP (2010 – Present)
10 kBth 20 kBth 80 kBth 140 kBth
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Single Effect NH3-H2O Cycle
Focus on Heating only, Reducing First Cost
Confidential
Best Applications for
Gas-Fired Absorption Heat Pumps
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Space-Water-Pool Heating• COP ~ 1.4+ compared to <1.0 for condensing
• Cool-Cold Climate Space Heating
• All-climate Water Heating
• All-climate Pool Heating
Cooling not a Great Option, except• “Free Cooling” while Water Heating
• Using Waste Heat as Energy source
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GAHP Applications
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Residential Forced-Air Space Heating
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Residential Hydronic Space Heating
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Residential Water Heating
❖ Fuel Sources: Natural Gas, Propane❖ COP: 1.40 average recovery at 68oF❖ Expected UEF: 1.20❖ First Hour (tank) Capacity: 60-80 gallons❖ Heating Output: ~10,000 Btu/hr (3 kW)❖ NOx Emissions: < 10 ng/J❖ Refrigerant GWP: None
❖ Location: Conditioned or semi-conditioned space ok❖ Venting (condensing operation): 3/4 - 1” PVC pipe❖ Condensate management: As per local code❖ Electrical requirement: 115 VAC / ~1 amp❖ Supplemental heating capacity: Available for high loads (1.2 kW element)
© SMTI 2015
Commercial Water Heating
Strategies:
➢ Baseload / Peak load
➢ Extend life of existing tanks
Food Service, Hospitality, Laundry, etc…)
With Cooling, COP =2.0
Multi-Family, Medical, Office, etc
Strategies:
➢ Baseload / Peak load
➢ Extend life of existing boilers
Commercial Space Heating (with or without DHW)
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Why do Gas Absorption Heat Pumps Matter?matter?
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Space & Water Heating Require a lot of Energy
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eGrid 2016US Avg Calif.
Nat. Gas(lbs / therm) 11.69 11.69
Elec. - All output(lbs / kWh) 0.99 0.53
Elec. - Non-Baseload(lbs / kWh) 1.50 0.94
CO2e Emissions
Baseload vs Non-Baseload Grid
Emissions is CRITICAL
Use Non-Baseload When• Fuel-Switching
• Adding/Subtracting Load from Grid
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Courtesy California Energy Commission
Seasonality & Time of Day Matter.....A Lot
California Grid
Emissions vs
Natural Gas
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Residential Water Heating CO2 Emissions
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Utility Costs US
AvgCalif.
Nat. Gas ($ /
therm)$1.25 $1.19
Electricity ($ /
kWh)$0.12 $0.19
$4,000
$4,500
$5,000
$5,500
$6,000
GHPWH EHPWH Std GasStorage Tank
Non-CondTankless
Cond Tankless
Lifecycle Cost (12 yr) by Technology & Region
US Average
California
Residential Water Heating Economics
Space Heating
CC-EHP = Cold-Climate Electric Heat Pump. EHP = Standard 8 HSPF Electric Heat Pump
56Confidential
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Method and Assumptions
• 2,700 sqft home
• 4 occupants
• Space-heating load only
• EIA 2018 energy prices by state
• Energy Planning Analysis Tool (GTI –
based on EnergyPlus)
• Performance: mfr data except GAHP
(prototype test data)
http://epat.gastechnology.org/
Space Heating Example: Operating Costs
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Compared to Cold-Climate Electric Heat Pump
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Space Heating Example: CO2 Emissions
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Compared to Cold-Climate Electric Heat Pump
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-
5
10
15
20
25
30
35A
nn
ual
Lb
s
NOx Emissions by Technology and Geography Furnace 80%
Furnace 96%
EHP HSPF 9.0
GAHP 140%
Space Heating Example: CO2 Emissions
Space Heating Example: NOx Emissions
GAHPs Leverage Future Renewable Gas
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% Renewable in Delivered Heat
GAHP vs. Condensing Furnace/Boiler
A more economically viable path to decarbonization?
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Is this a discussion about electricity vs. thermal fuels?
Or is it one about the fastest and lowest cost method to
decarbonize heating?