Lorenzo Castelli, a fourth-year doctoral student in mechanical engineering (MECH) at Rice, is the lead researcher on a paper describing a new mode of insulation that could reduce energy consumption for heating and cooling buildings and operate without power.
“Multi-season passive variable insulation for buildings using magnetic thermal diodes” is published in Cell Reports Physical Science.
Castelli graduated with a B.S. in MECH from the University of Texas at Austin in 2021, and now works in the Nanoscale Heat Transfer Lab of Geoff Wehmeyer, assistant professor of MECH. Wehmeyer and Monisha Vijay Kumar, a third-year doctoral student in applied physics at Rice, are Castelli’s co-authors.
“The idea of passive variable insulation (PVI) is that the inside of the building could naturally cool during a cold summer night or naturally heat during a sunny winter day by exchanging heat with the exterior. This would reduce the energy you need to run your heating or air conditioning system, and would not require any electricity,” Castelli said.
Existing PVI systems are limited to single-season operation. Castelli’s work demonstrates that a multi-season PVI consisting of two oscillating thermomagnetic diodes can enable both the passive heating during a warm winter day and the passive cooling during a cold summer night.
“Our centimeter-scale prototype experiments show that the multi-season PVI has an ideal passive temperature regulation band, works in all gravitational orientations, and has a factor-of-three thermal switch ratio in air,” Castelli said. “We performed thermal modeling for different U.S. climate zones and found that this multi-season PVI is particularly useful in the South and Southwest where you need both passive heating and passive cooling capabilities.”
Last year, Castelli was named an IBUILD (Innovation in Buildings) Fellow by the Buildings Technology Office of the U.S. Department of Energy, which provided funding for his current research on passive thermal management devices, including thermal transistors, thermal diodes and thermal regulators.
“Lorenzo’s research has shown that we can use these magnetic thermal diodes in both aerospace and terrestrial applications,” Wehmeyer said. “His work opens the door for innovative designs to improve the energy efficiency of buildings using passive, low-power thermal solutions.”