Field Testing Results for Residential Gas-Fired Heat Pump Water Heaters Paul Glanville ACEEE Hot Water Forum Monday, February 23 rd, 2015 Nashville, TN
Overview >Why Residential Gas HPWHs? >Describing the GHPWH >Field Test Plan >Preliminary Results >What s Next 2
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. 3
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. 4
Describing the Gas HPWH GHPWH System Specifications: Direct-fired NH3-H2O singleeffect absorption cycle integrated with storage tank and heat recovery. Intended as fully retrofittable with most common gas storage water heating, without infrastructure upgrade. GHPWH Units/Notes Technology Developer Stone Mountain Technologies OEM support Heat Pump Output 10,000 Btu/hr Firing Rate 6,300 Btu/hr Efficiency 1.3 Energy Factor Projected Tank Size 75 Gallons Backup Heating Experimenting with backup currently Emissions (projected) 10 ng NO x /J Based upon GTI laboratory testing Commercial Introduction 2016 Projected Installation Sealed system has NH3 Indoors or semi conditioned charge < 25% allowed by space (garage) ASHRAE Standard 15 Venting ½ 1 PVC Gas Piping ½ Estimated Consumer Cost <$1,800 Information and graphic courtesy of Stone Mountain Technologies, Inc. 5
Describing the Gas HPWH Total Installed Cost $3,000.00 $2,500.00 $2,000.00 $1,500.00 $1,000.00 $500.00 Equipment Cost Installation Cost 10 Year Cost of Ownership $6,000.00 $5,500.00 $5,000.00 $4,500.00 $4,000.00 $3,500.00 $3,000.00 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 $0.00 $2,500.00 6
Describing the Gas HPWH 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. [Source: MW CHP Center] 7
This image cannot currently be displayed. Describing the Gas HPWH 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 costeffective 8
Field Test Plan Monitoring Goals 1) 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) 9
This image cannot currently be displayed. Field Test Plan Building on prior GTI lab testing of early GHPWHs, estimate the: > 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. 10
Field Test Plan Measurement Scheme (Continuous) Monitoring Phase Baseline & GHPWH GHPWH Only Continuous Measurement Indoor T &RH NG Flow Water Flow Power Draw (total) Water inlet/outlet temperatures Gas valve on/off Storage tank thermostat temperature HP Temperatures Evap in/out Hyd. Loop Rtn/Sup. Desorber shell Flue gas exiting temperature 11
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 3 rd 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 12
Field Test Plan Additional Gas HPWH Field Demo Sites: Site #5: Spokane, WA 4 Occupants Garage Site #3: Seattle, WA 3 4 Occupants Semi conditioned Site #4: Portland, OR 5 Occupants Garage Site #6: Boise, ID 5 Occupants Garage 13
Daily Average Temperature (F) Preliminary Results from Sites #1 & #2 85 80 75 70 65 60 55 50 45 40 Operating conditions and hot water consumption Weekly Averages Site #1 Ambient Site #1 Water 35 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 14
Daily Average Temperature (F) Preliminary Results from Sites #1 & #2 85 80 75 70 65 60 55 50 45 40 Operating conditions and hot water consumption Weekly Averages Site #2 Ambient Site #2 Water 35 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 15
Daily Average Temperature (F) Preliminary Results from Sites #1 & #2 85 80 75 70 65 60 55 50 45 40 Operating conditions and hot water consumption Weekly Averages Site #1 Ambient Site #1 Water Site #2 Ambient Site #2 Water 35 2/5/14 3/27/14 5/16/14 7/5/14 8/24/14 10/13/14 12/2/14 1/21/15 3/12/15 200 120 Peak Volume (gal) or Count 150 100 50 0 Daily Draw Volume Daily Draw Count Site #1 0 20 40 60 80 100 120 Average Volume (gal) or Count Peak Volume (gal) or Count 100 80 60 40 20 0 Daily Draw Volume Daily Draw Count Site #2 0 20 40 60 80 Average Volume (gal) or Count 16
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 Average Cycle Heat Pump COP 1.8 1.7 1.6 1.5 1.4 1.3 Site #2 Ph 2 Site #2 Ph 1 Site #1 > Site #2 had significant modification, 1.2 phases 1/2 show pre/post mod. 1.1 > COP affected by tank temperature, hot water usage, and other factors 1 40 45 50 55 60 65 70 75 80 Ambient Temperature (F) 17
Preliminary Results from Sites #1 & #2 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. Temperature (F) 80 75 70 65 Evaporator Out Ambient Evaporator In COP 2 1.8 1.6 1.4 1.2 COP Temperature (F) 80 75 70 65 60 Evaporator Out Ambient Evaporator In COP 2 1.8 1.6 1.4 1.2 COP 60 1 55 1 55 0.8 11:31 12:00 12:28 12:57 13:26 13:55 Time of Day 50 6:43 7:12 7:40 8:09 8:38 9:07 Time of Day 0.8 18
Preliminary Results from Sites #1 & #2 > 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 90000 80000 70000 Daily Input (Btu) 60000 50000 40000 30000 20000 10000 0 0 10000 20000 30000 40000 50000 60000 70000 80000 Daily Output (Btu) Site #1 Site #2 ; 19
Preliminary Results from Sites #1 & #2 2.5 Comparing GHPWHs to Conventional Gas Water Heaters Non condensing Storage Condensing Storage Estimated Delivered Efficiency (Output/Input) 2 1.5 1 0.5 Non condensing Tankless Condensing Tankless 0 0 10000 20000 30000 40000 50000 60000 70000 80000 Output (Btu/day) 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 20
Preliminary Results from Sites #1 & #2 Estimated Delivered Efficiency (Output/Input) 2.5 2 1.5 1 0.5 Comparing GHPWHs to Conventional Gas Water Heaters Site #1 Non condensing Storage Condensing Storage Non condensing Tankless Condensing Tankless Log. (Site #1) 0 0 10000 20000 30000 40000 50000 60000 70000 80000 Output (Btu/day) 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 21
Preliminary Results from Sites #1 & #2 Estimated Delivered Efficiency (Output/Input) 2.5 2 1.5 1 0.5 Comparing GHPWHs to Conventional Gas Water Heaters Site #2 Ph 1 Site #2 Ph 2 Site #1 Non condensing Storage Condensing Storage Non condensing Tankless Condensing Tankless Log. (Site #2 Ph 1) Log. (Site #2 Ph 2) Log. (Site #1) 0 0 10000 20000 30000 40000 50000 60000 70000 80000 Output (Btu/day) 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 22
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. 23
Questions & Answers @gastechnology http://www.stonemountaintechnologies.com/ 24