Demand Response Performance of GE Hybrid Heat Pump Water Heater

Abstract

SummaryIncreasing penetration of heat pump water heaters (HPWHs) in the residential sector will offer an important opportunity for energy savings, with a theoretical energy savings of up to 63% per water heater 1 and up to 11% of residential energy use (EIA 2009). However, significant barriers must be overcome before this technology will reach widespread adoption in the Pacific Northwest region and nationwide. One barrier is that the demand response (DR) performance and characteristics of HPWHs is unknown. Previous research has demonstrated the potential of electric resistance water heaters (ERWHs) to provide significant grid stability and control benefits through demand-side management, or DR, strategies (Diao et al. 2012). However, if ERWHs are to be replaced with HPWHs to improve residential energy efficiency, it is important to understand the DR characteristics of HPWHs and how these characteristics will impact DR programs and overall grid stability now and in the future.This project evaluates and documents the DR performance of an HPWH as compared to an ERWH for two primary types of DR events: peak curtailments and balancing reserves. The experiments were conducted with General Electric (GE) second-generation "Brillion™"-enabled GeoSpring™ hybrid water heaters in the Pacific Northwest National Laboratory (PNNL) Lab Homes 2 , with one GE GeoSpring water heater operating in "Standard" electric resistance mode to represent the baseline and one GE GeoSpring water heater operating in "Heat Pump" mode to provide the comparison to heat pump-only DR. Signals were sent simultaneously to the two water heaters in the side-by-side PNNL Lab Homes under highly controlled, simulated occupancy conditions. It is expected that "Hybrid" DR performance, which would engage both the heat pump and electric elements, could be interpolated from these two experimental extremes.Based on the data collected in these DR experiments, both ERWHs and HPWHs are capable of performing peak curtailment and regulation services. However, their characteristics differ, as can be seen in Table 5.1, which shows the average impact on power use during the DR event, energy use during the DR event, and daily energy use for ERWH and HPWH for peak curtailment, 1-2 hour balancing events when generation and load are mismatched either due to higher load than generated power (INC events) or greater power generation than available load (DEC events). In general, the HPWH has much lower power use than the ERWH (587 Watts [W] versus 4,650 W) and provides approximately 38% of the potential to reduce load for peak curtailment or INC balancing events of the ERWH. The ERWH provides more dynamic response with a high magnitude of power increase or decrease per water heater. However, the HPWH has longer and more frequent operating times, which means the HPWH has a higher likelihood of being able to respond when an INC event or peak curtailment is called for. In addition, the inherent efficiency savings of HPWHs (61.7 ± 1.7%, as measured in the PNNL Lab Homes) will resul...

Impact of Ducting on Heat Pump Water Heater Space Conditioning Energy Use and Comfort

“…In addition, this project characterized the DR of this second-generation HPWH to various price signals. The results of the DR experiments are reported separately (Widder et al 2013).…”

“…The occupancy simulation protocol was robustly commissioned and verified daily throughout the baselining and data collection periods. More detailed information on the electrical loads used to simulate occupancy and the relevant schedules is provided in Widder et al (2013).…”

“…To select the hot water draw profile in the Lab Homes for the HPWH experiment, PNNL researched other draw profiles implemented by previous research, available standards, and data on typical field usage. The draw profile PNNL selected is described in this section and the full results of PNNL's analysis are presented in Widder et al (2013).…”

Experimental Characterization and Modelling of a Heat Pump Water Heater

“…Widder et al [16] conducted a field study on a commercially available HPWH at the Pacific Northwest National Laboratory to examine the interaction between the HPWH and the heating and cooling systems of the tested space for three exhaust set-ups: full ducting, exhaust ducting and no ducting. It was concluded that the HPWH performance enhancement in a conditioned space is compromised by the increased demands for the heating system of the residence.…”

“…tank,i T tank,N-1 T tank,N Outlet Outlet Inlet Schematic for a storage tank model and energy balance on a node (adopted from [54])The HPWH Type will calculate the COP of the unit based on the total heat delivery value obtained from the performance map and the compressor power, plus any other added power consumption, such as the power consumed by the unit's controller and the fan. The COP equation is shown in Equation(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). total is the total heat delivery to the storage tank in kJ/h, fan , P compressor , and controls are the fan, compressor and controls power consumption, respectively.…”