Field rial of Residential Ammonia-Water Absorption Heat Pump Water Heaters Paul Glanville, P.E. Gas echnology Institute @gastechnology
Motivation for a Gas HPWH: Despite low natural gas prices, Gas HPWH has potential to leapfrog» Energy/Operating Cost Savings, Fewer Infrastructure Needs, Recent Regulatory Drivers Baseline: ~90% of Gas WHs sold. At risk with advancing efficiency, combustion safety requirements Mid-Effiency: UEF approx. 0.67 0.72, 50-100% greater equipment costs, simple paybacks beyond life of product. Condensing Storage: UEF approx. 0.74 0.82, ~ 20% therm savings with 4-5X equipment cost and retrofit installation costs of $1000 or more. ankless and Hybrids: UEF approx. 0.82 0.95, ~ 33% therm savings with 2-3X equipment cost and similar infrastructure req s as condensing storage. Gas HPWH: UEF approx. 1.3, > 50% therm savings with comparable installed cost to tankless. echnology Leapfrog through Direct Retrofit HPWH = Heat Pump Water Heater; UEF = Uniform Energy Factor
Describing the Gas HPWH - Specification 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. GHPWH Units/Notes echnology Developer Stone Mountain echnologies OEM/GI support Heat Pump Output 2.9 kw Firing Rate 1.8 kw Efficiency 1.3 UEF Projected ank Size 230/300 Liters Backup Heating Experimenting with backup currently Emissions (projected) 10 ng NO x /J Based upon GI laboratory testing Commercial Introduction ~2 years Projected Installation Indoors or semi-conditioned space (garage) Sealed system has a 0.6 kg NH3 Charge Combustion Venting ½ 1 PVC Gas Piping ½ Estimated Consumer Cost <$1,800
Describing the Gas HPWH How It Works Sealed NH3/H2O absorption cycle delivers heat to the storage tank via two heat exchangers: 1) A closed, pumped hydronic loop extracting heat from the Absorber and Condenser to a submerged hydronic coil. 2) A flue gas coil, extracting remaining waste heat leaving the desorber flue outlet Simplified Single-Effect Absorption Cycle
Describing the Gas HPWH Challenge in Scaling Down Custom combustion system designed to meet the requirements of the Gas HPWH using a very compact premix burner, fuel/air mixer, and gas train. Small burner requires small gas piping, venting, easing installation. For material compatibility and for the very low charge system, 0.6 kg NH3, heat exchangers within the sealed system were primarily custom design. Several iterations were evaluated by SMI during breadboard testing and within early prototypes prior to field evaluations. A HPWH requires a wide operating range, firing in a cold garage with a hot storage tank for example, require a robust expansion valve. Off-the-shelf options, oversized for this application, had challenges during field testing and were the subject of review and redesign.
Average Daily Draw Volume (Gal.) Hot water out F Cold water in Field Site Characteristics Compared to typical Pac. NW homes, Ambient & RH Evaporator GHPWH sites have higher than Mechanical P average occupancy (> 2.5) and hot water usage. F Natural Gas Power meter GHPWH Detail 90.0 Existing WH Seattle Spokane Portland Boise 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 GHPWH Study EHPWH Validation Study 2 3 4 5 6 No. of Occupants GHPWH Location Conditioned Basement Garage Garage Garage Occupants 3-4, wo adults with one teenager permanently and one college-aged child periodically 4, wo adults and two children under 3 years old 5, wo adults and three children under 6 years old 5, wo adults and three children ank Size (Gal.) 40 34 50 40 Firing Rate (Btu/hr) 36,000 100,000 40,000 40,000 Age 14+ Years 18 Years 0 years 13 years Rated / Avg. Delivered EF/E 0.59 / 0.56 96% / 0.91 0.62 / 0.47 0.59 / 0.45 Average Inlet ( F) 53.3 61.2 54.8 58.7 Average Outlet ( F) 123.8 122.8 115.2 138.0 EHPWH Validation: Heat Pump Water Heater Model Validation Study, Prepared by Ecotope for NEEA, Report #E15-306 (2015)
Percentage of Cycles 45% Portland 40% Boise 35% Seattle 30% Spokane Heat Pump Performance 25% > COP HP at lab test targets (1.4-20% 1.8), near theoretical limits. 15% > Generally, low COPs from EEV > With reliable heat recovery, steady power consumption (~150W), and minimal backup heating COP SYS /COP HP has correlation coeff. of 0.83. > For all cycles: 10% 5% 0% Heat Pump COP Bins 75% COP HP > 1.4 Q Evap Q HW 45% COP HP > 1.6 GHPWH 68% COP SYS > 1.3 42% COP SYS > 1.4 Rest of Heat Pump Q HP Des Q HP ank Q FG Out Q NG otal Desorber Q FG Des
Heat Pump COP and Output (kw) 4 3.75 3.5 Heat Pump Performance 3.25 COP less affected by ambient > Known from prior lab testing, GHPWH efficiency is affected more by storage tank temperature than ambient air. Over one cycle, COP and heat pump output drop as tank warms Over range of ambient air temperatures observed, COP nearly flat for GHPWHs Evaporator cooling effect is small > Function of cycle COP, higher efficiency greater cooling effect (same as EHPWHs). > Observed range from 0.7-1.2 kw 3 2.75 2.5 2.25 2 1.75 1.5 1.25 1 COP Output 70 75 80 85 90 95 100 105 110 115 120 125 Hydronic Return emperature (F)
Delivered Efficiency Factor 2.0 1.5 Measured Energy Savings > Charting daily input/output creates linear input/output relationship, for gas input only. > In comparison to baseline, all sites showed greater than 50% savings except for Spokane with higher eff. baseline. > Sites had large range of daily hot water usage, average from 155 364 L/day. Output Low Usage (Seattle) High Usage (Portland) Daily DHW Draw (L) 155 364 Baseline DEF GHPWH DEF 242 L/day 0.59 0.48 318 L/day 0.60 0.50 242 L/day 1.21 1.15 318 L/day 1.25 1.18 1.0 0.5 0.0 Portland Seattle Spokane Spokane wo Feb. Boise 0 5 10 15 20 25 30 Output (kwh/day) Input = m Output + b; Output Input = DEF = m + b Output 1
GHPWH Savings for 10 Year Cost of Ownership $10,000.00 $9,000.00 Projected GHPWH Economics For DOE High Usage category, GHPWHs have projected 1.2 < DEF < 1.3, > 50% savings versus baseline (except Spokane), can be competitive for moderate/high usage homes despite low NG prices. With new min. eff. guidelines GHPWH leapfrogs condensing storage. 10 Year Cost of Ownership $8,000.00 $7,000.00 $6,000.00 $5,000.00 $4,000.00 $3,000.00 $2,000.00 $2,000.00 $1,500.00 Storage Non-condensing Storage Condensing ankless Non-condensing ankless Condensing GHPWH - Conditioned GHPWH - Semi/Unconditioned Baseline GWH - High DEF Baseline GWH - Low DEF 50 150 250 350 450 550 650 750 Average Hot Water Draw (L/Day) $1,000.00 $500.00 $- 50 150 250 350 450 550 650 750 $(500.00) $(1,000.00) Average Hot Water Draw (L/Day) Utility Costs: Assumes OR averages of 11.72 /kwh, $1.11/therm with 1.9% and 1.2% utility escalation rates per EIA 2015 Annual Energy Outlook through 2027. Conventional Gas Water Heater Data from: Kosar, D. et al. Residential Water Heating Program - Facilitating the Market ransformation 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
GHPWH - Next Steps > Continued laboratory-based reliability testing and field trials of next generation design in different climate zones and housing types. > Improvement of components based on lab/field findings. > Evaluation of technology by interested OEMs. > Parallel program evaluating larger gas absorption heat pump for combination space/water heating applications and commercial water heating.
Further information: Paul.glanville@gastechnology.org Published Materials: Garrabrant, M., Stout R., Glanville, P., Fitzgerald, J., and Keinath, C., (2013), Development and Validation of a Gas-Fired Residential Heat Pump Water Heater - Final Report, Report DOE/EE0003985-1, prepared under contract EE0003985, link: http://www.osti.gov/scitech/biblio/1060285-development-validation-gas-fired-residential-heatpump-water-heater-final-report Garrabrant, M., Stout, R., Glanville, P., Keinath, C., and Garimella, S. (2013), Development of Ammonia-Water Absorption Heat Pump Water Heater for Residential and Commercial Applications, Proceedings of the 7 th Int l Conference on Energy Sustainability, Minneapolis, MN. Garrabrant, M., Stout, R., Glanville, P., and Fitzgerald, J. (2014), Residential Gas Absorption Heat Pump Water Heater Prototype Performance Results, Proceedings of the Int l Sorption Heat Pump Conference, Washington, DC. Glanville, P., Vadnal, H., and Garrabrant, M. (2016), Field testing of a prototype residential gasfired heat pump water heater, Proceedings of the 2016 ASHRAE Winter Conference, Orlando, FL. http://www.stonemountaintechnologies.com/