Design and Integration of Thermochemical Energy Storage (TCES) into Buildings for Load Shedding/Shifting

Lead Performer: Georgia Tech Research Corp. – Atlanta, GA
Partners:
-- NREL – Golden, CO
-- GTI Energy – Des Plaines, IL
-- Carrier Corp. – Palm Beach Gardens, FL
DOE Total Funding: $2,428,047
Cost Share: $608,233
Project Term: January 1, 2024 – December 31, 2026
Funding Type: Buildings Energy Efficiency Frontiers & Innovation Technologies (BENEFIT) – 2022/23

Project Objective

Thermal energy storage (TES) can facilitate the integration of renewable energy and buildings to the grid with demand-side strategies such as load shedding and shifting. In particular, TES systems using thermochemical materials (TCMs) exhibit higher energy densities and negligible heat loss during storage in both summer and winter months compared to phase-change materials and sensible heat storage, resulting in compact solutions suitable for space-constrained building applications. While the thermochemical energy storage (TCES) literature has largely focused on materials development and open system concepts—which rely on the chemical reaction of TCMs such as salt hydrates with a fluid such as ambient air (water vapor or moist air)—to store and discharge heat, investigations of closed systems as well as building-integrated design and performance evaluation has been lacking. To this end, this project will aim to develop a closed system TCES reactor module integrated with building HVAC (heat pump) to provide both space heating and cooling, which overcomes the challenges of open system TCES that require favorable temperature and moisture conditions for operation. The TES can store off-peak grid electricity or utilize otherwise wasted heat from HVAC to load shift thermal end-uses in buildings at a low levelized cost of storage and boost the overall system Coefficient of Performance (COP). Project goals include:

1. Design of salt hydrate composites with enhanced structural stability that achieve high energy density, reaction kinetics, and hygrothermal stability under charge-discharge cycling.
2. Development of a bench-top TCES packed bed reactor with water vapor in a closed loop that outputs heat during winter and cooling during summer operation with an average heat duty of 1 kW.
3. Demonstration of a proof-of-concept TCES unit integrated with a residential heat pump that delivers at least 40% of the building thermal load using a controls strategy.

Project Impact 

This project will leverage TCES, which has a potential to reduce grid demand by 50% from offsetting at least four hours of the daily space conditioning load for winter heating and summer cooling operation, to provide demand-side strategies for grid flexibility via load shifting and peak shaving. Additionally, this project will establish a new technology baseline that supports electrification of buildings through technoeconomic analysis across a variety of building types and climate zones in the U.S., as well as integration with HVAC equipment that bolsters a lower energy footprint from a 2-4x higher COP when compared to standalone TCES systems. 

Contacts

DOE Technology Manager: Sven Mumme
Lead Performer: Prof. Akanksha K. Menon, Georgia Tech