This research is focused on analyzing building envelopes that had been enhanced with phase change materials (PCMs), which can simultaneously reduce total cooling loads and shift peak-hour loads in residential and commercial buildings.
Traditionally, the thermal design of building envelope assemblies is based on steady-state energy flows. In practice, however, building envelopes are subject to varying environmental conditions. Design work to support the development of very low-energy homes shows that conventional insulation may not always be the most cost-effective energy solution.
Fraunhofer CSE's Building Enclosures team performs both detailed material search/testing, as well as economic analysis to evaluate thermal performance and cost effectiveness of organic and inorganic latent heat storage materials and their packaging method. In addition, we perform lab-scale and field testing focused on durability of the PCM products. Our goal is to identify the cost levels at which PCMs can be durable and at the same time cost competitive.
In the past, the only existing readily available methods of thermal evaluation utilized DSC testing, or sometimes T-history method measurements for limited number of materials. Unfortunately, the DSC method required small, relatively uniform test specimens. This requirement is unrealistic in the case of many PCM-enhanced building envelope products. That is why a new lab-scale testing procedure enabling testing of significantly larger specimens was introduced by Fraunhofer CSE, ORNL, R&D Services and LaserComp, for the analysis of dynamic thermal characteristics of PCM-enhanced materials. It is using the conventional Heat Flow Meter Apparatus (HFMA), which has been already widely used for steady-state thermal conductivity measurements. Based on this work a new testing standard was developed in 2013 - ASTM C1784 – 13, “Standard Test Method for Using a Heat Flow Meter Apparatus for Measuring Thermal Storage Properties of Phase Change Materials and Products.”
As a part of the U.S. DOE- funded project, Fraunhofer CSE's Building Enclosures team performed an economic analysis to evaluate the cost effectiveness of simple PCM-enhanced building envelopes and find cost levels at which PCMs can be cost competitive with conventional thermal insulation.
The study team selected two basic PCM applications for analysis: dispersed PCM applications and simple building board products using concentrated PCMs. The team then used these results as performance benchmarks for different PCM configurations that were tested in the United States for different building applications. In addition, several potential methods for future cost reductions were analyzed, for North American PCM-enhanced building applications – ref: www.nrel.gov/docs/fy13osti/55553.pdf.