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Research Strategy: Residential Ductless Heat Pumps Research and Evaluation Subcommittee Christian Douglass and Josh Rushton January 8, 2016
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Overview This presentation focuses on a Research Strategy related to residential ductless heat pumps (DHPs) Research would affect multiple RTF measures – Residential Heating/Cooling – DHP for Zonal Heat SF (Proven UES) Residential Heating/Cooling – DHP for Zonal Heat SF – Residential Heating/Cooling – DHP for Zonal Heat MH (Small Saver UES) Residential Heating/Cooling – DHP for Zonal Heat MH – Residential Heating/Cooling – DHP for Forced Air Furnace SF and MH (Planning UES) Residential Heating/Cooling – DHP for Forced Air Furnace SF and MH – Any other measures that may require a DHP to be modeled (e.g., ENERGY STAR home with DHP, weatherization in homes with DHPs) Research needed to support savings for higher-performance DHPs Seeking subcommittee feedback/recommendations: Is the outlined research approach reasonable? – Likely to succeed as advertised? – Does estimated cost range match outlined research? – Recommended modifications or alternative approach? Is more research really needed for Proven category? 2
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Outline Background – Addition of higher DHP efficiency tiers – Existing data and scope of update – Uncertainty in savings for high-performance DHPs Research Strategy – Objectives – Straw-man approach 3
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Background 4 – DHP Background
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Proposed Addition of DHP Efficiency Tiers Current RTF DHP measures assume a single, minimum efficiency level of 9.5 HSPF NEEA interested in offering multiple DHP efficiency “tiers”: – Tier 1: HSPF 9.5 to 11 – Tier 2: HSPF 11 to 12.5 – Tier 3: HSPF >12.5 For Tiers 1 and 2, we already have calibrated, reliable savings estimates based on empirical data from the NEEA DHP pilot project (field study 1 and billing analysis 2 ) We do not have empirical in situ data for Tier 3 5 – DHP Background 1 NEEA, Ductless Heat Pump Impact & Process Evaluation: Field Metering Report, prepared by Ecotope, May 2012.Ductless Heat Pump Impact & Process Evaluation: Field Metering Report 2 NEEA, Ductless Heat Pump Impact & Process Evaluation: Billing Analysis Report, prepared by Ecotope, August 2013.Ductless Heat Pump Impact & Process Evaluation: Billing Analysis Report
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Existing Data and Scope of Update NEEA pilot project was a major effort that collected many pieces of data, most of which do not need to be updated under this research strategy – Site characteristics data – Pre-/post-billing data – Sub-metering of DHP, resistance heat, DHW – Measurement of fraction of heat load met by DHP – Survey of supplemental fuel use – Measurement of in-situ COP, output capacity 6 – DHP Background Only part that would need updating
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Uncertainty in Savings How much uncertainty would we introduce if we estimated Tier 3 savings based on figures published by manufacturers? Published figures suggest 5-7% more energy consumption in first generation Fujistu DHP (top performer in NEEA field study) than third generation Fujitsu (currently available) – Heating COP of first generation unit: 4.39 – Heating COP of third generation unit: 5.33 RTF UES values for DHPs are around 2000 kWh/year for zonal homes and 4000 kWh/year for FAF homes – Published figures therefore suggest about 120 kWh more savings per unit for zonal and 240 kWh for FAF – If we split that uncertainty range in half, uncertainty in savings would be +/60 kWh to 120 kWh per year, per unit (for zonal and FAF, respectively) – 60 kWh/year times 500k potential units plus 120 kWh/year times 225k potential units yields about 7 aMW (range of uncertainty) 7 – DHP Background IMPORTANT: Research strategy states nearly 20%, but we found an error in our math.
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Research Strategy 8 – DHP Research Strategy
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Research Objective Empirically estimate the in-situ COP and output heating capacity of >12.5 HPSF DHPs over a wide range of outdoor temperatures Not objectives of this research strategy: – Fraction of heating load met by the DHP versus other heating sources (know this well enough from NEEA field study) – Effects of wood heat (known well enough from NEEA billing analysis) 9 – DHP Research Strategy
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Straw-man Approach Approach based on detailed metering of small number of units Meter data: Study units equipped with “COP monitoring instruments” same as in NEEA field study, logged at five minute intervals: – DHP power usage, supply air temperature, return air temperature, indoor unit airflow, outside air temperature Analysis: Use interval-level power consumption, heat output, and outdoor temperature to estimate COP as a function of outdoor air temperature – Code this function into SEEM to model >12.5 HSPF DHP systems – UES values then estimated similar to existing DHP for Zonal Heat measures (same baseline and “calibration” factors) 10 – DHP Research Strategy
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Straw-man Approach (continued) Metering period: Minimum of 30 days during the winter to capture a wide range of outdoor temperatures Sample size: Staff proposes sampling 5 units – Small sample because we are only after in situ COPs (not after usage patterns, etc.) Sample disposition: No particular needs called out in research strategy Estimated cost range: $25,000 and $100,000 11 – DHP Research Strategy
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Analyst Recommendation Although estimated range of uncertainty in regional savings potential is not trivial (0-7 aMW), the estimated increment in savings per unit is small and could be difficult to detect Based on this, CAT thinks it is reasonable to: – make a minor extrapolation from the Tier 2 unit consumption to represent Tier 3 unit consumption – propose the Tier 3 DHP measure as Proven 12
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Additional Slides 13 – DHP Additional Slides
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How Data Feeds into Savings Estimates DHP performance characteristics – Data from NEEA field study: Detailed in situ metering data for 95 DHPs (efficiencies ranging from 8 to 12 HSPF) – Used to estimate COP curves and output capacity – Developed SEEM parameters for three DHP options (8, 10, 12 HSPF) Tie SEEM-modelled savings to differences between pre and post billing data – Data from NEEA field study: Site characteristics and pre- and post-DHP billing data for sample of electrically heated homes (screened to eliminate wood heat) – This step accounts for possible comfort take-back and things like systematic error in SEEM’s estimate of the portion of load being met by the DHP – Idea: Relationship between calibrated-SEEM (DHP) and post-DHP billing data must reflect relationship between calibrated-SEEM (ER-zonal) and pre-DHP billing data Account for effect of wood heat in actual program homes – Data from NEEA billing analysis: Square footage, wood heat indicator, and pre- /post-DHP billing data for ~3000 homes – Idea is to quantify this: When DHP is installed, electric heating kWh/ft 2 decreases a lot in homes without wood heat and only a little in homes with wood heat 14 – DHP Additional Slides Part we propose updating
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What is a Research Strategy? Clarifies knowledge gaps in non-Proven measures Focuses on high-priority research objectives – What does the RTF need for the measure to be proven? – Anything researchers should pay special attention to? Outlines a straw-man approach to data collection and analysis – Demonstrates one feasible least-cost research path – Research Sponsors develop final Research Plan Sponsors can work with RTF staff to ensure plan addresses RTF needs RTF reviews final Research Plan later (at Provisional Planning step) Calls out approaches that probably wouldn’t suffice (optional) Provides a rough cost estimate (based on straw-man approach) Research Strategies try to be BRIEF: Critical items shouldn’t get lost in a sea of helpful suggestions 15 – DHP Additional Slides
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