Field Testing Results for Residential Gas-Fired Heat Pump Water Heaters Paul Glanville ACEEE Hot Water Forum Monday, February 23 rd , 2015 Nashville, TN
Field Testing Results for Residential Gas-Fired Heat Pump Water Heaters
Paul GlanvilleACEEE Hot Water ForumMonday, February 23rd, 2015Nashville, TN
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>Why Residential Gas HPWHs?>Describing the GHPWH>Field Test Plan>Preliminary Results>What’s Next
Overview
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Why Residential Gas HPWHs?
Residential Water Heating Market has been driven by significant innovation in the past 10 years (well done!).EnergyStar® and past/future changes in Federally allowable minimum efficiencies have resulted in:> A proliferation of “mid-efficiency” gas water heating
products.> A gas tankless market at over 10% of the overall gas WH
market, and growing.> More, lower cost options for condensing-efficiency gas
storage and “hybrid” products.> A recent generation of electric HPWHs that are here to
stay, and also growing in market share.
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Why Residential Gas HPWHs?But…While electric water heating customers have product options with a “step-change” in operating efficiency/cost savings, gas customers can go from 0.59/0.62 EF to:> Non-condensing EnergyStar® water heaters with 0.67-0.70 EF,
with higher equipment/installed cost.> Condensing GSWH/Hybrid, requiring venting/gas piping
upgrade, electrical service, delivering a ~0.80 EF. > Non-condensing or condensing Gas Tankless Water Heater
(GTWH), with an EF 0.82 – 0.95, requiring venting upgrade, electrical service, and often larger gas piping.
Need that “step-change” that retrofits with min. EF gas water heaters, the majority of market.
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Describing the Gas HPWH
GHPWH Units/NotesTechnology Developer Stone Mountain Technologies OEM supportHeat Pump Output 10,000 Btu/hrFiring Rate 6,300 Btu/hrEfficiency 1.3 Energy Factor ProjectedTank Size 75 GallonsBackup Heating Experimenting with backup currently
Emissions (projected) 10 ng NOx/JBased upon GTI laboratory
testingCommercial Introduction 2016 Projected
Installation Indoors or semi‐conditioned space (garage)
Sealed system has NH3 charge < 25% allowed by ASHRAE Standard 15
Venting ½” – 1” PVCGas Piping ½”Estimated Consumer Cost <$1,800
GHPWH System Specifications: Direct-fired NH3-H2O single-effect absorption cycle integrated with storage tank and heat recovery. Intended as fully retrofittable with most common gas storage water heating, without infrastructure upgrade.
Information and graphic courtesy of Stone Mountain Technologies, Inc.
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Describing the Gas HPWH
$0.00
$500.00
$1,000.00
$1,500.00
$2,000.00
$2,500.00
$3,000.00
Tota
l Ins
talle
d C
ost
Equipment Cost Installation Cost
$2,500.00
$3,000.00
$3,500.00
$4,000.00
$4,500.00
$5,000.00
$5,500.00
$6,000.00
10 Y
ear C
ost o
f Ow
ners
hip
California New York > With low firing rate required, GHPWH installation costs are low
> GHPWH has total cost of ownership close to baseline water heaters, cost-engineering will result in the lowest cost of ownership
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How it works - Very similar to EHPWHs, except:
> Compressor is replaced with “thermal compressor”, comprised of several HXs and addition of absorbent.
─ Easier to compress liquid, solution pump requires appx. 1.0% of the compression energy of a standard vapor compression heat pump
> Ammonia is the refrigerant, instead of more common R-134a for EHPWHs, which is:
─ Very efficient thermodynamically, used almost exclusively in industrial refrigeration
─ Has large affinity for water, stable over range of temperature/pressure conditions
─ Non-ozone depleting ─ A natural chemical, with a global warming potential of 0
(R-134a is 1300)─ An irritant and hazardous, requiring special care.
Helpfully, unlike most refrigerants, NH3 is lighter than air.
Describing the Gas HPWH
[Source: MW CHP Center]
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How it works – SMTI System Design:
> Heat pump absorbs heat from the ambient air and recovers heat from the absorption of NH3 to water (in absorber)
─ Heat transfer to potable water is mediated by a closed hydronic loop
> In addition, useful heat from hot flue gases exiting the heat pump is delivered to storage tank by separate HX
> As the GHPWH only partially heats water from the refrigeration cycle, cooling effect at the evaporator is 1/3-1/2 that of equivalently sized EHPWHs
> GHPWH uses Single Effect absorption cycle, more complex cycles were considered by SMTI but were not cost-effective
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Describing the Gas HPWH
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Monitoring Goals1) Pre-commercial GHPWH system reliability and
performance, with monitoring of both the heat pump cycle and the water heating system.
2) Quantifying delivered efficiency versus prior laboratory testing
3) Identifying installation issues and other barriers to market entry, including data concerning the space cooling effect
4) Assessing end-user satisfaction with hot water production and potential nuisances (e.g. system noise)
Field Test Plan
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Building on prior GTI lab testing of early GHPWHs, estimate the:
Field Test Plan
> COP of the heat pump as function of ambient T & RH, inlet water mains, and other installation characteristics.
> Delivered efficiency of hot water as function of usage volumes/patterns, compare to similar high-efficiency systems and extrapolate to annual energy savings.
> Disaggregation of electricity and natural gas inputs, tracking backup heating.
> Space cooling effect on interior space> Robustness of absorption heat pump
startup/shutdowns, as function of operating conditions.
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Measurement Scheme (Continuous)
Field Test Plan
MonitoringPhase
Continuous Measurement
Baseline & GHPWH
• Indoor T &RH• NG Flow• Water Flow• Power Draw (total)• Water inlet/outlet
temperatures
GHPWH Only
• Gas valve on/off• Storage tank
thermostat temperature
HP Temperatures• Evap in/out• Hyd. Loop Rtn/Sup.• Desorber shell• Flue gas exiting
temperature
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Field Test Plan
Initial GHPWH “Controlled” Field Test> First unit installed at SMTI employee home in late 2013, has
been operating ever since. Unit was built by SMTI during initial laboratory prototyping program with GTI/OEM/GIT.
> Second “3rd gen.” unit built specifically for field testing, installed at utility employee home 2014.
> Both sites are in Eastern TN:─ Unit 1 in attached garage, with 2-4 occupants─ Unit 2 in semi-conditioned basement, with 3-4 occupants
> While performing well unattended, both units have been under close watch and improvements have been implemented as a result, including:
─ Control strategy for cold ambient/water startup─ Adjustments to when backup element is operating─ Investigating options for corrosion inhibitors
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Additional Gas HPWH Field Demo Sites:
Field Test Plan
Site #3: Seattle, WA• 3‐4 Occupants• Semi‐conditioned
Site #4: Portland, OR• 5 Occupants• Garage
Site #5: Spokane, WA• 4 Occupants• Garage
Site #6: Boise, ID• 5 Occupants• Garage
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Preliminary Results from Sites #1 & #2Operating conditions and hot water consumption – Weekly Averages
3540455055606570758085
2/5/14 3/27/14 5/16/14 7/5/14 8/24/14 10/13/14 12/2/14 1/21/15 3/12/15
Daily Average
Tem
perature (F)
Site #1 ‐ AmbientSite #1 ‐ Water
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Preliminary Results from Sites #1 & #2Operating conditions and hot water consumption – Weekly Averages
3540455055606570758085
2/5/14 3/27/14 5/16/14 7/5/14 8/24/14 10/13/14 12/2/14 1/21/15 3/12/15
Daily Average
Tem
perature (F)
Site #2 ‐ AmbientSite #2 ‐ Water
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Preliminary Results from Sites #1 & #2Operating conditions and hot water consumption – Weekly Averages
0
20
40
60
80
100
120
0 20 40 60 80
Peak Volum
e (gal) o
r Co
unt
Average Volume (gal) or Count
Daily Draw VolumeDaily Draw Count
Site #20
50
100
150
200
0 20 40 60 80 100 120
Peak Volum
e (gal) o
r Co
unt
Average Volume (gal) or Count
Daily Draw VolumeDaily Draw Count
Site #1
3540455055606570758085
2/5/14 3/27/14 5/16/14 7/5/14 8/24/14 10/13/14 12/2/14 1/21/15 3/12/15
Daily Average
Tem
perature (F)
Site #1 ‐ AmbientSite #1 ‐ WaterSite #2 ‐ AmbientSite #2 ‐ Water
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Preliminary Results from Sites #1 & #2
Heat Pump Performance> Focusing on abs. heat pump
operation, COP is often at high levels observed in prior laboratory testing, 1.4 - 1.8
> Aggregated data over all cycles (~800) show influence of lower ambient temperature on performance
> Site #2 had significant modification, phases 1/2 show pre/post mod.
> COP affected by tank temperature, hot water usage, and other factors 1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
40 45 50 55 60 65 70 75 80
Average Cycle Heat P
ump CO
P
Ambient Temperature (F)
Site #2 ‐ Ph 2Site #2 ‐ Ph 1Site #1
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Some slips in startup early on, issues resolved to maximize COP> A smooth start to the heat pump is critical for high performance, with good
(left) and bad (right) readily apparent from the data.
0.8
1
1.2
1.4
1.6
1.8
2
55
60
65
70
75
80
11:31 12:00 12:28 12:57 13:26 13:55
COP
Tempe
rature (F)
Time of Day
Evaporator Out
Ambient
Evaporator In
COP
0.8
1
1.2
1.4
1.6
1.8
2
50
55
60
65
70
75
80
6:43 7:12 7:40 8:09 8:38 9:07
COP
Tempe
rature (F)
Time of Day
Evaporator Out
Ambient
Evaporator In
COP
Preliminary Results from Sites #1 & #2
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> Aggregating daily input/output data, projected Delivered “EF” is ~ 1.2 and 1.3 respectively for Site #1 and Site #2 units.
> Seeking to reduce impact of standby heat loss to improve results
· ;
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 10000 20000 30000 40000 50000 60000 70000 80000
Daily In
put (Btu)
Daily Output (Btu)
Site #1 Site #2
Preliminary Results from Sites #1 & #2
2020
Preliminary Results from Sites #1 & #2
0
0.5
1
1.5
2
2.5
0 10000 20000 30000 40000 50000 60000 70000 80000
Estim
ated
Delivered
Efficiency (Outpu
t/Inpu
t)
Output (Btu/day)
Comparing GHPWHs to Conventional Gas Water Heaters Non‐condensing Storage Condensing Storage
Non‐condensing Tankless Condensing Tankless
Conventional Gas Water Heater Data from:Kosar, D. et al. “Residential Water Heating Program - Facilitating the Market Transformation to Higher Efficiency Gas-Fired Water Heating - Final Project Report”. CEC Contract CEC-500-2013-060. (2013)
Link: http://www.energy.ca.gov/publications/displayOneReport.php?pubNum=CEC-500-2013-060
2121
Preliminary Results from Sites #1 & #2
0
0.5
1
1.5
2
2.5
0 10000 20000 30000 40000 50000 60000 70000 80000
Estim
ated
Delivered
Efficiency (Outpu
t/Inpu
t)
Output (Btu/day)
Comparing GHPWHs to Conventional Gas Water Heaters Site #1 Non‐condensing Storage
Condensing Storage Non‐condensing Tankless
Condensing Tankless Log. (Site #1)
Conventional Gas Water Heater Data from:Kosar, D. et al. “Residential Water Heating Program - Facilitating the Market Transformation to Higher Efficiency Gas-Fired Water Heating - Final Project Report”. CEC Contract CEC-500-2013-060. (2013)
Link: http://www.energy.ca.gov/publications/displayOneReport.php?pubNum=CEC-500-2013-060
2222
Preliminary Results from Sites #1 & #2
0
0.5
1
1.5
2
2.5
0 10000 20000 30000 40000 50000 60000 70000 80000
Estim
ated
Delivered
Efficiency (Outpu
t/Inpu
t)
Output (Btu/day)
Comparing GHPWHs to Conventional Gas Water Heaters Site #2 ‐ Ph 1 Site #2 ‐ Ph 2Site #1 Non‐condensing StorageCondensing Storage Non‐condensing TanklessCondensing Tankless Log. (Site #2 ‐ Ph 1)Log. (Site #2 ‐ Ph 2) Log. (Site #1)
Conventional Gas Water Heater Data from:Kosar, D. et al. “Residential Water Heating Program - Facilitating the Market Transformation to Higher Efficiency Gas-Fired Water Heating - Final Project Report”. CEC Contract CEC-500-2013-060. (2013)
Link: http://www.energy.ca.gov/publications/displayOneReport.php?pubNum=CEC-500-2013-060
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What’s Next
GHPWH Field Evaluation
> Collect/analyze data from all units, with add’l installations planned for ’15.
> Wrapup in late 2015 monitoring all field units.
> Understand initial challenges/barriers with homeowners, contractors.
> Share findings with stakeholders. > Support rounding out of product
family, size range, “hybrid”, etc.
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Questions & Answers
@gastechnology
http://www.stonemountaintechnologies.com/