Session: 17-01-01: Research Posters

Paper Number: 150971

150971 - Waste Wood-Derived Composite for Energy-Efficient Thermal Management of Buildings Through Radiative Cooling and Thermal Energy Storage 

Using organic resources for passive thermoregulation technologies promotes carbon neutrality while alleviating the escalating energy demand for thermal comfort due to climate change. Passive daytime radiative cooling (RC) is one of the emerging technologies that achieves cooling by spontaneously rejecting heat through the atmospheric transparency window, demonstrating tremendous benefits in reducing the cooling load on a hot day. Nevertheless, RC alone cannot fully satisfy thermal comfort needs, especially in subtropical climates with large diurnal temperature fluctuations, where continuous RC during the cold night adversely intensifies the heating load. On the other hand, thermal energy storage (TES) that utilizes the latent heat of phase change materials (PCMs) can reduce and shift the peak load, which is advantageous over RC in sustaining continuous thermal comfort. However, efficient TES requires PCM to undergo daily cycles of discharging/recharging through phase transitions, which is not feasible for extremely hot or cold climates where the temperature persists above or below the phase transition temperatures of PCMs.

In this work, we developed a dual-functional composite for synergistic RC and TES, composed of microencapsulated PCMs embedded in a matrix of delignified wood waste fibers, for energy-efficient thermal management of buildings. Attributing to the scattering effect of cellulose fibers and microencapsulated PCMs, the dual-functional composite exhibits 95% solar reflection that minimizes the solar gain, resulting in a slower PCM melting with prolonged effective thermal regulation in the daytime. Meanwhile, the intrinsic thermal emission of the dual-functional composite provides a strong RC effect that facilitates heat dissipation for faster recrystallization of melted PCMs at nighttime – especially in hot climates where the temperature is sustained above the phase transition temperature of PCMs – enabling a complete recharge of PCM for next thermal cycle. Our wood waste-derived encapsulated PCMs composite shows a melting enthalpy of 156 J/g at 24°C due to a high loading ratio of microencapsulated PCMs, robust thermal stability over 500 TES cycles, and excellent shape stability for over 28 days of isothermal testing at 50°C. Benefiting from this synergy of RC and TES, both outdoor testing and COMSOL computational modeling demonstrated that superior thermal regulation performance was achieved by the dual-functional composite in comparison to individual RC and TES, indicating a substantial energy-saving potential. Whole-building simulations by EnergyPlus further showed that the synergistic effect of RC and TES could reduce the annual energy use by heating, ventilation, and air conditioning by 7.2% in a humid subtropical climate (Dallas, TX), equivalent to energy savings of 34.6 kWh/month, which is an increase of 10 kWh/month and 2.4 kWh/month from the solely TES and RC cases, respectively. Additionally, fabricating the composite using abundant wood resources from waste promotes the circular economy and offers a promising avenue for carbon sequestration, further prompting the development of sustainable buildings.

Presenting Author: Bernadette Magalindan The University of Texas at Dallas

Presenting Author Biography: Bernadette is a third-year mechanical engineering PhD student at the University of Texas at Dallas. She is developing green building materials capable of passive thermoregulation via thermal energy storage and radiative cooling to advance the sustainability of the built environment. Bernadette was recently awarded the Innovation in Buildings (IBUILD) Graduate Research Fellowship from the Department of Energy, Building Technologies Office.

Authors:

Bernadette Magalindan The University of Texas at Dallas
Lyu Zhou The University of Texas at Dallas
Zhihao Ma The University of Utah
Sahag Bozoian The University of Houston
Bo Zhao The University of Houston
Jianli Chen The University of Utah
Shuang Cui The University of Texas at Dallas