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

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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”

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“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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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

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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

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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?

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Thank You !

Michael Garrabrantmgarrabrant@stonemtntechnologies.com