Phase Change Material in New Construction Training Center

The purpose of this Emerging Technology (ET) Field Assessment is to study the impacts of installing phase change material (PCM) in a new construction commercial building and recommend how appropriate modelling strategies may be used for a Savings by Design (SBD) or residential new construction program.

PCM is a thermal energy storage product and has evolved over the years. Early PCM versions were either toxic or flammable and posed potentially unsafe conditions and possible health risks in buildings. However, some newer PCM materials incorporate non-toxic microencapsulation bio-based organic materials and propose to save energy by absorbing and releasing heat within pre-defined temperature ranges in order to maintain a targeted air temperature within a space.

Despite decades of prior research, the effect of PCM on energy consumption within various commercial buildings is still not well understood. Consequently, several field assessments have been recently conducted to determine the PCM’s potential energy savings in different commercial buildings.

The bio-based PCM material, assessed in this ET field study, is encapsulated in flame retardant, super-engineered polyfilm. The manufacturer indicates that the material is engineered around a fundamental property of nature where materials transfer heat more effectively during a phase change. Materials absorb heat when they melt (phase change from solid to liquid) and release heat when they solidify (phase change from liquid to solid). This field assessment was conducted at a new construction training center located in Chula Vista, California. The Training Center was built with the intent to meet the highest possible standards of LEED Certification, sustainability, and energy efficient design and was originally designed and built with PCM in the walls and roof.

Because the newly constructed training center already installed PCM, the International Performance Measurement and Verification (IPMVP) Option D was used to estimate potential savings due to the PCM. IPMVP Option D involves the use of computer simulation software to predict baseline facility energy use. Thereafter, a post simulation model must be "calibrated" so that it predicts an energy pattern that approximately matches the actual metered energy data from the facility. Annual energy savings estimates were arrived at by taking the difference between the baseline predicted model and the post calibrated model.

Relying on the EnergyPlus Simergy Interface, the autosized baseline and post calibrated model runs showed annual energy savings at the heat pumps of 19,746 kWh with peak demand savings of 14.98 kW due to the installation of the PCM. An additional 124,148 kWh of annual energy savings were shown at the fans in the facility. However, these results are questionable because the software produced a large number of simulation warnings and errors related to the simulation of the fans. It is not entirely clear what caused these warnings and errors. However, it can be reasonably inferred that the complexity of the building design and the newness of the mechanical HVAC VRF system models caused the issues within the EnergyPlus software. Despite potential energy savings, the savings in new construction applications are inconclusive and not easily quantifiable using the software tools available. Therefore, if energy and peak demand savings estimates are claimed, it should be limited to the heat pumps only until the EnergyPlus software warnings and errors are resolved