Lead Performer: University of Massachusetts Lowell – Lowell, MA
-- Insolcorp LLC – Albemarle, NC
-- 3M Company – St. Paul, MN
DOE Total Funding:  $1,391,100
FY20 DOE Funding: $553,265
Total Cost Share: $558,900
Project Term: April 1, 2020 March 31, 2023
Funding Type: Buildings Energy Efficiency Frontiers & Innovation Technologies (BENEFIT) 2019 Funding Opportunity

Project Objective

A phase change material (PCM) is a high latent heat material that can be used to store thermal energy and regulate local temperatures. In buildings, PCMs can be used to mitigate and time-shift thermal load peaks by absorbing heat gain during warmer daytime via melting and releasing the stored thermal energy during cooler nighttime as it solidifies. Numerical simulation and field demonstration studies have shown that application of optimized PCM designs in well-insulated residential buildings can reduce space-conditioning requirements by 5%–35% without accounting for benefits of load shifting and peak load reductions. Today, a great majority of PCM-enhanced building products commercialized in the U.S. market are organic based compounds such as paraffin and biobased fatty acids and esters. However, these products have been unsuccessful in gaining much traction in the building market because of a host of issues, including flammability, low energy density, low thermal conductivity, and high material costs, resulting in high investment payback of >10 years based on energy savings for majority of the U.S. locations.

In contrast, inorganic salt hydrates are nontoxic, nonflammable and significantly less expensive than most organic PCMs. Because of their higher density (~1500–2500 kg/m3), they have a potential to exceed volumetric energy density of 100 kWh/m3 in a cost-effective way.

This project will design, fabricate, and experimentally validate:

  1. Inorganic salt hydrate based PCMs that have high latent enthalpies and are low-cost and durable.
  2. PCM encapsulation (packaging) technology that maximizes PCM concentration and enhances heat transport characteristics in the product and with the external environment/materials.

The proposed technology will encompass multiple salt hydrate PCM formulations that are durable and operate efficiently in the building temperature range (5oC–45oC). The project team is well-aware that salt hydrates have several technical challenges, which will be addressed during the project:

  1. Significant subcooling caused by slow rate of crystallization.
  2. Incongruent melting because of loss of hydration water upon phase cycling.
  3. Phase separation of slat hydrate into a phase with lower water hydration number, which changes the phase transition temperature, compromising the overall efficacy and often energy storage capacity.

The project team has already identified over 30 low-cost and high-performance salt hydrates and salt-based formulations, of phase change enthalpies over 180 J/g. To meet the FOA performance metrics, these compounds and formulations will be examined during the project to develop 6-8 custom PCM formulations (blends) exhibiting an efficient (energy density >100 kWh/m3 and subcooling <2oC) and durable phase transition (>5000 phase change cycles with <10% enthalpy loss).

In addition, the project team will develop three innovative packaging methods utilizing highly thermally conducting and highly impermeable barrier encapsulation. These novel packaging will: 1) maximize the PCM loading, 2) aid in heat exchange within the PCM and to the surrounding space and materials, 3) allow an easy installation/attachment to building structural components, 4) protect hydration water from leaking out, 5) eliminate corrosion potential, and 6) improve the long-term durability.  

All these inexpensive, nonflammable, and easy-to-produce PCMs will enable accelerated commercialization in a wide variety of building applications within 3-5 years.

Project Impact

Using BTO Market Calculator and a conservative estimate of 15%-25% reduction in energy consumption with the proposed PCM in wall and roofing applications, a primary energy-saving technical potential of the PCM technology is estimated to be around 0.7–1.1 quads, when compared to the equivalent energy performance of commercial lightweight thermal insulation for similar applications. Equally important is the fact that the new thermal storage technology will not only improve the overall energy performance of the building envelope without causing any changes to the dimensions of the structural components or sheathing, but will also enable modifications in dynamic energy response of the whole building, allowing effective dynamic integration with the power grid and renewable energy resources. Insolcorp (a manufacturer of inorganic PCM) and 3M are committed to partnering on this effort to ensure a viable pathway to this technology’s commercialization.


DOE Technology Manager: Sven Mumme, sven.mumme@ee.doe.gov 
Lead Performer: Dr. Jan Kośny – University of Massachusetts, Lowell (UML)

Related Publications

Authors: Jan Kosny, William Miller, David Yarbrough, Elisabeth Kossecka, Kaushik Biswas
Title: Application of Phase Change Materials and Conventional Thermal Mass for Control of Roof-Generated Cooling Loads
Journal: Materials; Special issue; Phase Change Materials in Buildings, 2020
Status: Accepted for publication, September 22. 2020