Using a phase change composite material, researchers at the University of Illinois at Chicago have developed a novel thermal energy storage system that has the potential to downsize conventional air-conditioner compressors by 50 percent and double compressor efficiency during off- and mid-peak hours.
The research is described in a paper titled “Design and optimization of a hybrid air conditioning system with thermal energy storage using phase change composite,” recently accepted for publication in Energy Conversion and Management. One of the authors, Said Al-Hallaj, a research professor of chemical engineering at UI-Chicago and CEO of AllCell Technologies LLC, answered a few questions by e-mail.
Q: Who led the research team, and how long did the project take?
A: “It is an ongoing project since 2015 at the University of Illinois at Chicago, where I work as a Research Professor of Chemical Engineering, and part of the PhD thesis for my graduate student Ahmed Aljehani.”
Q: Who funded the project?
A: “Ahmed has a scholarship from his government in Saudi Arabia and we get technical support from our industry partners NETenergy and AllCell Technologies LLC.”
Q: Who supplied the PCM?
A: “I believe it is n-tetradecane (C14H30) PCM that we bought from a distributor and not sure about actual source.”
Q: What is its peak melting point?
A: “4-6 degrees Celsius.”
Q: What is its thermal storage capacity?
A: “180 kJ/kg (78% PCM, 22% graphite).”
Q: Describe the benchtop PCC/TES system size, components and functionality.
A: “The actual 4 kWh PCC-TES structure is made of 28 slabs of PCC [right]. The whole PCC-TES structure is thermally insulated with building insulation materials. Each slab represents a graphite structure that has been soaked into n-tetradecane for at least 24 h until impregnated with n-tetradecane. The slabs are numbered from top to bottom; top being number 1. The second component is the copper tubes or the copper coils, which pass back and forth in between the 28 slabs. The copper tubes enter the PCC-TES structure from the top and exits from the bottom of the structure.”
Q: Is the concept intended mainly for commercial AC systems, or could it be adapted for residential use?
A: “It should work for both, but commercial AC applications are more economically beneficial due to rate structure and peak demand requirements.”
Q: What are the next steps in developing this concept?
A: “NETenergy, our technology commercialization partner, is partnering with National Renewable Energy Laboratory and a major OEM to build and test a full-scale prototype at NREL facilities in the next year or so.”