Cold Climate Air Source Heat Pumps: Study Update

Ben Schoenbauer, Senior Research Engineer

Better Buildings: Better Business ConferenceMarch 2, 2017

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What We Do

• Energy Program Design & Delivery• Engineering Services• Lending Center• Public Policy• Research• Education and Outreach

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Acknowledgements

• These projects are supported in part by grants from the Minnesota Department of Commerce, Division of Energy Resources through a Conservation Applied Research and Development (CARD) program

• The heat pump project was also supported by Great River Energy and the Electric Power Research Institute

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Learn about…

• The energy savings potential for ASHPs, as well as the potential for offsetting the reliance on delivered fuels in areas where natural gas is unavailable

• The differences in ASHP installed performance compared to the manufacturer specified performance

• The applicability of both technologies to Minnesota’s housing stock and the process that can be used to determine where the best potential exists for each technology

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www.mncee.org

Cold Climate Air Source Heat Pump Field Assessment

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Agenda

• Cold Climate Air Source Heat Pump• What is different?• Opportunity• Installation and operation• Preliminary results• Conclusions

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Cold Climate Air-Source Heat Pump?

• An ASHP uses a refrigerant system involving a compressor, condenser, and evaporator to absorb heat at one place and release it at another.

• Delivery of both heating and cooling via forced air distribution

• New generation systems can operate as low as -13 °F

• ASHPs have the potential to deliver energy and peak saving as well as reduce reliance on delivered fuels.

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Opportunity

• Winter of 2013/2014 saw delivered fuel shortages in MN• Delivered fuel expensive or unavailable • Compensation with electric resistance space heaters

• Market:• Delivered fuel are the primary space heating fuel for more than 40%

of homes in MN, IA, SD, ND (RECS, 2009)• Over 25% of Midwest homes rely on fuels other than natural gas for

space heating (RECS, 2009)• Over 47% of homes in the US rely on fuels other than natural gas for

space heating (RECS, 2009)

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• Primary Heating with LP1

• Metro, < 4%• Outstate, up to 40%

• Primary Heat Sources2

• Utility gas, 67%• Electricity, 16%• LP, 10%• Fuel Oil, 3%• Wood, 3%

Source: Levenson-Faulk, Annie. 2015. “Propane Conversion Strategies: Energy Alternatives for Minnesota Users of Propane Gas.” St. Paul, MN: Legislative Energy Commission

1 U.S. Census Bureau. American Community Survey 5-Year Estimates - 2009-20132 U.S. Census Bureau. American Community Survey 5-Year Estimates - 2010-2014

Opportunity - Minnesota

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Utilities and Rebates

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Study Overview• Field Study

• 6 ccASHP in a variety of MN residences• 3 installed for the 2015-2016 heating

season • Monitor installed field performance of

ASHP and backup

• Incorporate into Conservation Improvement Program (CIP)

• Climate zones 6 & 7

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Instrumentation

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Power Measurements:1) Outdoor unit2) Indoor unit3) Indoor fan 4) Reversing valve

Temperatures:5) Supply Air6) Return Air7) Mechanical area ambient8) Conditioned space

Additional:9) Back up fuel consumption10) Delivered air flow11) NOAA data

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Installation

• Important Issues:• Equipment• Sizing• Operation• Integration with back-up systems

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Site Equipment

Site Number ASHP System ASHP Size ASHP Type Backup

1*Carrier Infinity with Greenspeed [25VNA048A003] 4 ton Ducted LP Cond. Furnace

2*Bryant Extreme Heat Pump [280ANV048] 4 ton Ducted LP Cond. Furnace

3*Carrier Infinity with Greenspeed [25VNA036A003] 3 ton Ducted LP 80% Furnace

4Trane XV20i [4TWV0036A] 3 ton Ducted LP Cond. Furnace

5Mitsibishi Ductless Hyper Heat [MUZ-FH18NAH] 1.5 ton Ductless Electric Resistance

6Mitsibishi Ductless Hyper Heat [MSZ-FH12NA]

1 ton (2 units) Ductless Electric Resistance

* Installed during 2015-2016 heating season

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Manufacturer Specified Performance

NEEP | Cold Climate Heat Pump Specification

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Cold Climate Specification

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System Design: Sizing

The OAT for the systems to switch to back up: 4 ton ~3 F3 ton ~10 F 2 ton ~19F

Percentage of heating load meet by ASHP:4 ton ~ 86%, 3 ton ~ 77% 2 ton ~ 60%

3 °F

10 °F

19 °F

3 ton

4 ton

2 ton

House heating load

Targeted a maximum change-over temp of 10 F

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Operation

• Switchover set point:• Ducted Systems: 10 degrees F• Ductless Systems: -13 degrees F

• Controls:• Ducted Systems: automated controls to bring up backup• Ductless Systems: manual action by homeowner

• Interaction with back-up systems• Ducted Systems: Integrated installs with shared controls• Ductless Systems: Separate systems

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Furnace Integration – Keep or Replace?

• Issues:• Air handler requires a multi-stage fan to achieve the full capability of

the ccASHPs• Furnace and heat pump require integrated controls

• Proposed Solutions:• New condensing furnace with control integration• New 80% AFUE with multi-stage fan with control integration• Retrofit existing system (future?)• Plenum electric resistance heater

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Ductless

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Ductless: Install Location

Performance: Ducted Systems

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System Operation

• Heating system has 3 modes of operation• ASHP heating• Furnace heating• Defrost

Outdoor Fan OFF

Refrigerant in reverse

Furnace ONDefrost

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ASHP and Furnace Cycle Efficiency, Site 2

• Without propane:• COPs 1.5 to 3.5

• Furnace SS Efficiency• 90% +

• Defrost reduces COP to < 0.5

• ASHP lockout at 10 F

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System COP vs OAT

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System COP vs Furnace runtime

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ASHP Performance

• Rated COPs of 3.0-3.5 at 47 F

• COP observed• 1.5-3.5 (site 1 &

2)• 1-3.5 (site 3)

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Example: Capacity on a 17 ⁰F day

At 18:45OAT = 15 FHouse load = 15,300 Btu/hrASHP Output = 16,700 Btu/hrASHP Sup Temp = 89 FAirflow = 734 CFM

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Meeting the Load

Performance: Ductless Systems

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Daily Performance

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Ductless with Backup

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Ducted v Ductless

• Heat pump only events have comparable COPs

• Ducted systems • have larger capacities than single head ductless• have larger airflows

• Ductless systems• provided a smaller fraction of the homes energy (by design)• operated at lower outdoor temperatures

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System Airflow

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Air Temperatures

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Energy Use Vs OAT Models

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Preliminary Results

• Compared to LP furnaces the ccASHPs• Reduced between 40% and 65% of site energy consumption• Reduced total heating costs 19% to 35%• On average ccASHP met 84% of the homes heating loads• Reduced propane consumption by around 60%, up to 89% at one

site

• Compared to Electric Resistance Heat• Provided more efficient space heating (COP of 1.6, compared to 1.0)• Savings are largely dependent on usage and install location

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Conclusions

• Systems should sized for heating, typically results in 1-ton larger system that if sized for cooling

• With proper sizing ccASHPs are capable of meeting the loads in typical MN homes at or below 10 ⁰F outdoor temps.

• Preliminary results show ccASHP COPs of 1.5-3.5 and annual system COPs between 1.4 and 1.8.

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Conclusions: LP

• ccASHPs will reduce delivered fuel consumption enough to avoid costly winter refueling in most MN homes.

• 60% to 89% reduction

• Estimate annual usage of for a most homes should be under 375 gal

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Future Needs

• There is still room for improvement:• Reduce unnecessary back-up heating

• Defrost?• Lower change over point?

• Reduce upfront installation costs • Systems with new furnaces cost $15,000

• New LP furnaces with modulating fans ~$5,500• NREL database ccASHP only ~$7,000

• Costs are much higher than incremental equipment costs compared to AC systems

Ben Schoenbauer: bschoenbauer@mncee.org

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Policy Work

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Policy Analysis – Minnesota context

• Lack of structure for achieving delivered fuel savings from ccASHPs for electric utilities

• The fuel switching concern – should not apply in these scenarios

• Precedents: low income CIP• New program suggestions

• Net BTU analysis• Target homes that do not use utility natural gas

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Policy Analysis – Minnesota context

• Kushler, Marty. (2016). Analysis of the Policy Context and Potential for an Air Source Heat Pump Pilot Program to be Incorporated into Minnesota’s Energy Conservation Program Structure for Cooperative Electric Utilities.

• mncee.org/heat_pumps

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ASHP Event w. Defrost

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Annual Energy Use and Costs

Baseline ccASHP Savings per Year

LP Use (Gal) LP Cost

LP Use (Gal) LP Cost

Elec. Use (kWh)

Elec. Cost Total Cost Cost [%]

Energy (KBtu) Energy % Propane %

Site 1 1022 $1,320 372 $480 5,406 $649 $1,129$191

[14%]

41,130 44% 64%

Site 2 928 $1,199 102 $131 5,978 $718 $849$350

[29%]

55,338 65% 89%

Site 3 1123 $1,450 539 $696 4,051 $487 $1,183$267

[18%]

39,606 39% 52%

• Payback? TBD! Still gathering data on the incremental cost of replacement• Assumed costs: LP $1.29/gal, Electric $0.12/kWh