Dustin Schafer, senior vice president and director of engineering at Henderson Engineers of Lenexa, Kansas, first became familiar with phase change material when he read an ASHRAE article about conference room air conditioning.
The method struck him as a small-scale version of a stadium or arena. "From there," he says, "I began I began devising a plan for us to implement this into our large-scale venues we design."
Schafer developed the idea of using PCM inside the hollow portions of seats and seating structures to keep open-air stadiums cooler on hot days. The concept underwent testing at Kansas State University and was awarded a U.S. patent, "Stadium Ambient Temperature Control System," in 2017. He is giving a presentation on the concept June 12 at an event sponsored by AIA Kansas City at the Center for Architecture & Design in Kansas City, Mo. In an email interview, he discussed the development process.
Q: How long have you worked at your company?
A: "I joined Henderson in 2008 and have nearly 20 years of industry experience."
Q: Can you briefly describe the process of testing the concept?
A: "In looking to develop an innovative, cost effective, and energy efficient option, we began conducting research on the potential implementation of PCM on venue seats to increase the thermal mass in the space and extend the length of time occupants are comfortable. Essentially, the material could be frozen (the material we used has a freezing point of 70° F) prior to the event, then as the PCM reaches its melting point, it would absorb some of the heat brought on by the human and/or solar load, prolonging the time the space is comfortable for attendees.
"I led a team in conducting a variety of tests to determine the efficacy of this idea. We worked with Kansas State University and utilized their Institute for Environmental Research to complete our testing. We set up a lab that included actual stadium seats arranged in a layout consistent with typical venues. Each seat in the testing area had 10 pounds of PCM attached to the back and a dummy in the seat equipped with electric resistance heaters that produced an amount of heat equivalent to that of a human being. The layout also included suspended wires with thermocouples to create the temperature sensor array around the dummy occupant.
"We conducted two tests to evaluate the impact this technology could have, each with two test value temperatures, 90° F and 100° F. In both tests we took measurements in an environmental chamber that simulated different ambient conditions during an event and compared both a control chamber and a chamber with PCM attached to the chairs. The tests ran until the effect of PCM was no longer noticeable."
Q: Can you provide a summary of the test results?
A: "In our research, we determined that PCM could be an impactful option for open stadiums situated in mild climates where the night temperatures drop low enough to freeze the material. To have an even greater impact, application of PCM should be seriously considered in enclosed arenas. Because the HVAC system could be used to pre-charge the bowl and freeze the material, this application could be even more significant. Additionally, the cooling result could materially affect the peak load needs for the HVAC systems in these spaces, saving the owner on energy costs.
"We also identified areas where PCM would not make sense a part of the temperature control solution, such as in climates with high winds that would simply blow away the cooled air, areas where the temperature does not drop below 70° F and thus doesn’t allow the PCM to freeze, or areas where the temperature rises too far above the melting point prior to the event meaning the cooling effect is lost before it is needed. Finally, we’ve found it necessary to note that this process only impacts spaces that need to be cooled – it cannot be used in heating conditions.
"We determined that phase change material does have a significant and sustained impact on occupant comfort. While it is not the whole solution, it can be a meaningful portion of the overall answer."
Q: Can you provide information on the PCM used in testing?
A: "We used InsolCorp’s Infinite-R phase change material."
Q: Is Henderson now working on any projects that include the use of PCMs in this manner?
A: "We are not working on any projects that include the use of PCM."
Q: What interests you most about the use of PCM in building and construction?
A: "It’s a sustainable solution that is relatively low cost. It’s not the end all, be all, but it’s a small step that can have a nice impact. Professional sports teams focus heavily on the fan experience and this is a difference maker when it comes to their in-venue comfort."