SBIR Phase I: Dispatchable Thermal Energy Storage with Foundation-Integrated Phase Change Materials

The broader/commercial impact of this Small Business Innovation Research (SBIR) Phase I project will be in helping homes and community facilities use locally available heat sources to improve resilience during extreme weather and increase dispatchable energy. The project will investigate a practical way to store heat under a building foundation and use it later to reduce heating costs and peak energy demand in cold climates. Thermal energy storage is often too expensive or too uncertain in real-world conditions to be widely adopted. This project will test whether a foundation-integrated heat storage approach can be built using common construction practices while remaining safe, durable, and measurable. The work will focus on key public concerns: whether storage materials remain contained under severe moisture exposure, whether performance stays stable after repeated heating and cooling, and whether net energy benefit remains after accounting for the electricity used by pumps and controls. This project advances practical, measurable dispatchable energy innovation aligned with the current national energy priorities. This project will investigate a high-risk innovation: increasing usable under-building thermal energy storage by integrating a phase change material, specifically sodium acetate trihydrate (SAT), into a controlled low-strength cementitious matrix while maintaining containment, durability under thermal cycling, and verified net energy performance. The Phase I scope will reduce uncertainty in three areas: (1) the effect of SAT on fresh and hardened cementitious properties relevant to buildability, including placement stability, density, and compressive strength targets for sub-slab support; (2) durability under repeated heating and cooling, including dimensional stability and strength retention; and (3) containment integrity under severe moisture exposure, including transport-pathway control at seams, edges, and penetrations. Laboratory and pilot-scale specimens will be subjected to controlled thermal cycling and moisture challenges, with pre- and post-conditioning measurements of mechanical properties and indicators of leakage risk. An instrumented test configuration will quantify thermal energy stored and recovered together with auxiliary electrical energy consumed by pumps and controls, enabling net performance comparisons across configurations. A key hypothesis is that higher energy density storage can increase usable capacity within a fixed footprint and improve delivered-heat effectiveness by reducing the storage volume or surface area required for a target heat delivery; Phase I will quantify these effects using normalized performance metrics. Results will define acceptance criteria, jobsite quality-control metrics, and performance reporting methods that enable Phase II scale-up, including evaluation of higher-temperature dispatch for future applications such as dehumidification where feasible. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.