HVAC Supply Air Phase Change Material

The goal of this project was to conduct a field evaluation of the performance of an Emerging Technology (ET) that could shift electricity load away from the peak energy usage period. The ET used Phase Change Material (PCM) as a thermal battery. This technology consisted of an insulated modular box that housed several plates of PCM in line with the supply airflow, built into the ductwork of a new or existing Rooftop Unit (RTU). Energy and load shift were accomplished by solidifying and charging the PCM earlier in the day, when ambient conditions enabled more efficient RTU operation and allowed compressor operation to be limited during the peak period of 4 p.m. to 6 p.m. The PCM was sized to store enough thermal energy for cooling during the peak period. In this field test, the ET was installed in the ductwork of a four-ton RTU, serving an office space of a building in Climate Zone (CZ) 9. The field test demonstrated the ET reduced the RTU’s energy use and demand during two-hour peak period (4 p.m. – 6 p.m.) by shifting cooling load from the peak to off-peak. When two similar weather days were compared, the technology saved 52% in energy consumed and 51% in average hourly peak demand during the two-hour peak period. When compared to the baseline model, the technology saved 55% in energy and 54% in average hourly peak demand. Based on the significant peak energy and demand reduction attained by the technology during the field test, we recommend adopting the technology as part of a potential Permanent Load Shift (PLS) program, when one becomes available. However, this field testing alone did not provide sufficient information to be directly incorporated into the Demand Response (DR) program, so we recommend subsequent testing, such as scaled field tests and modeling simulations, be conducted to validate the consistency of technology performance with different peak durations, RTU sizes, CZs, and building load types. Refer to the final report for detail information about the project including summary, findings, conclusion and recommendations.