Abstract
This paper proposes and validates a dual-season thermal energy storage-integrated heat pump (TES-HP) system that shifts building electric load in both cooling and heating modes using a single phase-change TES. The design uses the TES as a heat sink for the condenser in summer and a heat source for the evaporator in winter, thereby reducing on-peak electric demand while ensuring compatible with existing air-distribution systems. A 14-kW TES-HP prototype with six operating modes and novel refrigerant charge management strategies was experimentally tested under varied conditions. Subsequently, data-driven polynomial performance curves were developed and validated against experiments, then coupled with a phase change material (PCM) model and a calibrated building model within a rule-based controller. Single-day case studies demonstrated effective on-peak demand reduction while maintaining thermal comfort. During cooling, hourly power was lowered by up to 1.5 kW; in heating, average hourly power decreased from over 3.5 kW to 1.8 kW, compared to an HP-only system, achieving 64.5 % load shifting, and the need for resistance heating was eliminated. Seasonal simulations showed typical on-peak electricity savings of 25–35 % in cooling and 40–65 % in heating, with the largest benefits on the hottest and coldest days. Extended response-surface analysis and nationwide mapping quantified load shifting as functions of ambient and TES temperatures, revealing a seasonal trade-off in TES phase-change temperature. These results demonstrate the TES-HP system as a practical and scalable solution for grid-interactive buildings that reduces on-peak demand and electricity use while maintaining thermal comfort and enhancing grid flexibility and reliability.
| Original language | English |
|---|---|
| Article number | 139849 |
| Journal | Energy |
| Volume | 344 |
| DOIs | |
| State | Published - Feb 1 2026 |
Funding
This work is supported by Stor 4Build , a multi-lab consortium funded by the U.S. Department of Energy (DOE) Building Technologies Office (Awarded Under Lab Call L095 ). The consortium is co-led by Lawrence Berkeley National Laboratory (LBNL), the National Renewable Energy Laboratory (NREL), and Oak Ridge National Laboratory (ORNL). LBNL is managed by the University of California for DOE under Contract No. DE-AC02-05CH11231; NREL is operated for DOE under Contract No. DE-AC36-08GO28308; and ORNL is managed by UT-Battelle LLC for DOE under contract No. DE-AC05-00OR22725. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- Grid-interactive buildings
- Heat pump
- Load-shifting
- Space heating and cooling
- Thermal energy storage