Novel Low-Cost Composite Phase Change Material Poised to Halve Building Energy Peaks

米国エネルギー省 (Department of Energy) USA

Overview

The U.S. Department of Energy (DOE) is spearheading a project to develop a novel low-cost composite phase change material (PCM) designed for building applications, aiming to slash deployment costs to less than $2/kWh, a tenfold reduction from current paraffinic PCMs. This initiative leverages inexpensive salt hydrates, overcoming their low thermal conductivity with the strategic incorporation of compressible expanded natural graphite (CENG). This breakthrough promises to significantly reduce peak load demands in buildings and enhance energy efficiency, with Oak Ridge National Laboratory and Georgia Institute of Technology leading the research.

In Depth

Background

Buildings are major contributors to global energy consumption, with heating and cooling demands placing substantial strain on electrical grids, particularly during peak periods. Phase change materials (PCMs) offer a compelling solution for thermal management in buildings by storing and releasing large amounts of latent heat, thus moderating temperature fluctuations and optimizing HVAC system operation. However, the widespread adoption of conventional paraffin-based PCMs has been hindered by their high deployment costs, typically ranging from $20 to $40 per kilowatt-hour (kWh). Addressing this economic barrier is critical for integrating PCM technology into mainstream building applications and realizing its full energy-saving potential.

Key Findings / Results

To tackle the prohibitive cost of existing PCMs, the U.S. Department of Energy (DOE) has initiated a collaborative research project with Oak Ridge National Laboratory (ORNL) and the Georgia Institute of Technology. The primary objective is to develop a stable, low-cost composite PCM with a target deployment cost of less than $2/kWh, representing a significant order-of-magnitude reduction from current market offerings. The project focuses on a two-pronged innovative approach:

• Inexpensive Salt Hydrate Basis: The core material for the new composite PCM is based on abundant and low-cost inorganic salt hydrates. While salt hydrates possess high latent heat capacities, they are typically plagued by technical challenges such as supercooling, incongruent melting, phase segregation, and inherently low thermal conductivity.
• Incorporation of Compressible Expanded Natural Graphite (CENG): To mitigate the low thermal conductivity of salt hydrates and stabilize their phase transitions, compressible expanded natural graphite (CENG) is integrated into the composite structure. CENG, known for its high thermal conductivity, acts as a heat transfer enhancer, facilitating rapid charging and discharging of thermal energy. Furthermore, the structural framework provided by CENG can help suppress phase segregation and improve the overall stability of the salt hydrate PCM.

The synergy between low-cost salt hydrates and highly conductive CENG is expected to yield a robust and economically viable PCM solution. By addressing the critical technical limitations of salt hydrates through advanced composite formulation, this project aims to create materials that are both high-performing and affordable for widespread building integration.

Technical Significance & Outlook

This development of a low-cost composite PCM holds profound technical and economic significance for the building sector. By drastically lowering the cost barrier, it enables the broader adoption of thermal energy storage in residential and commercial buildings, facilitating the transition to more energy-efficient and sustainable infrastructure. The widespread deployment of these PCMs will help flatten peak electricity demand curves, reduce overall energy consumption, and lower carbon emissions, thereby contributing to grid stability and climate change mitigation efforts. Moreover, this innovation has the potential to stimulate new manufacturing investments and job creation within the advanced materials sector. Future research will concentrate on rigorous validation through large-scale demonstration projects, optimizing material compositions for diverse climate zones, and establishing scalable manufacturing processes to ensure a seamless transition from laboratory breakthrough to market-ready product.