NREL Field Validation of Air-Source Heat Pumps for Cold Climates 2021-2023
This dataset includes the findings from U.S. Department of Energy (DOE) funded field study conducted by National Renewable Energy Laboratory (NREL) monitoring 12 centrally ducted, variable-speed air-source heat pumps (ASHPs) installed in single-family homes located in cold climate for an entire winter season in 2021–2022. Given the interest in cold temperature heat pump performance, 6 of 12 instrumented heat pumps were monitored for one additional winter during 2022-2023 to collect more data at cold temperatures. The study focused on evaluating heat pump performance at cold temperatures by measuring the in-field performance of centrally ducted, variable-capacity ASHPs and analyzed energy consumption at different operating modes.
The sites identified for the study were primarily located in the Northwest United States (Washington and Montana) and one site was near NREL outside Denver, Colorado. All the sites in Washington and Colorado were in International Energy Conservation Code (IECC) Climate Zone 5 and the one in Montana was in IECC Climate Zone 6. Every site had a high-efficiency, fully electric, variable-capacity central heat pump system already installed even prior to the study. The only variable-speed dual fuel heat pump in the study was located at the site in Colorado, and it was equipped with a natural gas furnace for backup heating. Sites 1 to 13 except Site 9 were monitored over the course of 2021–2022 winter season. Site 9 dataset is not included here due to data logging issues. Six of the twelve instrumented heat pumps (Sites 2, 3, 5, 6, 8 and 10) were monitored for an extra winter during 2022-2023 aiming to gather more data specifically at colder temperatures.
At each site location, two independent, standalone data loggers were employed, one positioned near the indoor unit (IDU) and the other near the heat pump outdoor unit (ODU). A weather station was integrated into the ODU data logger to record the outdoor air dry-bulb temperature and relative humidity. Airside and power measurements were collected at five-second intervals to assess the heat pump performance including heat pump capacity, coefficient of performance (COP), and auxiliary heater energy consumption. We developed algorithms to automatically identify the heat pump operating modes including defrost and auxiliary heating operation. An air handler flow plate or Duct Blaster® was installed to measure the indoor airflow at various blower speeds during the initial site visit to establish a correlation between the IDU airflow rate and the blower power consumption. Throughout the duration of the study, blower power was continuously monitored to estimate the indoor airflow rate. Winkler and Ramaraj (2023) documented site information, house characteristics, heat pump and auxiliary heat specification for 12 monitored heat pumps, field monitoring and data analysis methodologies, and measured heating and cooling field performance for winter 2021–2022. The site numbers used throughout this dataset are consistent with the site numbers used by Winkler and Ramaraj (2023). The attached raw data file for each site consists of 5-second timeseries data resampled to 30-second interval and includes the following data:
Indoor and outdoor logger data that includes airside temperature and humidity measurements, and power measurements.
Moist air properties calculated using measured supply and return dry-bulb temperatures and relative humidities.
Seven different heat pump operating modes (system off, fan-only, compressor heating, auxiliary heating, compressor + auxiliary heating, defrost, and cooling) detected by comparing temperature and power measurements with the tolerances.
Periods of steady state operation and heat pump start-up periods.
Heat pump indoor mass flow rate, capacity, and COP calculated for heating and cooling modes.
References:
Winkler, Jon, and Sugi Ramaraj. 2023. Field Validation of Air-Source Heat Pumps for Cold Climates. No. NREL/TP-5500-84745. National Renewable Energy Laboratory (NREL), Golden, CO (United States).