The article does not specify a calendar period when the laboratory experiments were conducted. It records that the manuscript was received on July 27, revised on August 25, and accepted on September 23, 2026.
Growing Demand for Building Cooling
Cooling buildings is an important energy challenge, particularly in hot and humid regions. Higher outdoor temperatures and increasing demand for indoor comfort can increase reliance on mechanical cooling systems, which contributes to building energy consumption.
The researchers examined PCM technology as a passive approach to managing heat. PCM can absorb heat when it changes from a solid to a liquid state and release the stored heat when it returns to a solid state. When integrated into building components, such as walls, roofs, ceilings, or floors, PCM can absorb part of the incoming heat and delay its transfer into indoor spaces.
However, PCM generally has relatively low thermal conductivity, meaning heat may not move through the material quickly enough for some building applications. The Udayana University researchers therefore tested formulations containing different concentrations of a thermal-conductivity-enhancing additive.
Four PCM Formulations Tested
The researchers prepared four PCM formulations: one baseline formulation and three modified formulations containing low, medium, and high concentrations of the additive. Each formulation was independently prepared three times, producing 12 experimental samples.
The samples were evaluated for thermal conductivity, latent heat storage capacity, phase transition temperature, and thermal stability. Laboratory measurements were then incorporated into a building thermal model using EnergyPlus version 23.2.
Five building scenarios were simulated: a reference building without PCM and four buildings incorporating the different PCM formulations. Building geometry, envelope configuration, ventilation, internal heat gains, cooling settings, operating schedules, and weather conditions were kept constant for comparison.
Medium-Additive Formulation Shows the Best Balance
The results showed that adding more conductive material generally increased thermal conductivity. The baseline PCM had an average thermal conductivity of 0.210 W/m·K. This increased to 0.241 W/m·K with the low-additive formulation, 0.281 W/m·K with the medium-additive formulation, and 0.310 W/m·K with the high-additive formulation.
Statistical analysis also found significant differences among the formulations for both thermal conductivity and latent heat capacity. The formulation factor accounted for 95.8% of the observed variation in thermal conductivity and 95.0% of the variation in latent heat capacity.
Simulation Shows Lower Indoor Temperature and Energy Demand
The building simulation showed improvements across all PCM scenarios compared with the reference building without PCM.
The F2 formulation produced the largest overall reductions:
- Maximum indoor temperature: reduced from 33.8°C to 31.4°C, a decrease of 2.4°C.
- Indoor temperature fluctuation: reduced by 32.1%.
- Peak cooling load: reduced by 17.2%.
- Cumulative cooling demand: reduced by 13.8%.
- Energy consumption: reduced by 14.3%.
According to I Made Astika and colleagues at Udayana University, these findings indicate that PCM optimization cannot rely on thermal conductivity alone. The researchers' analysis shows that thermal conductivity, latent heat capacity, phase transition temperature, and thermal stability need to be considered together when developing PCM for buildings.
Potential Applications in Energy-Efficient Buildings
The findings could support the development of passive thermal-management materials for building envelopes. The researchers identify walls, roofs, and ceilings as potential locations for PCM integration, particularly in buildings where cooling demand is high.
Reducing cooling demand could potentially lower electricity use associated with air-conditioning systems. However, the researchers caution that the reported energy savings are specific to the simulation conditions. Building geometry, weather, envelope configuration, cooling settings, occupancy, and internal heat gains can influence actual performance.
The study is therefore an initial basis for further development rather than evidence that the material is ready for large-scale construction use. The researchers recommend physical building tests and further assessments of fire safety, mechanical compatibility, leakage resistance, durability, environmental performance, toxicity, and production cost before wider implementation.
Future research should also examine the material under different climates and building configurations and conduct hundreds to thousands of thermal cycles. Physical validation using instrumented building cells would help determine whether the simulated energy reductions can be reproduced under real operating conditions.
Author Profiles
I Made Astika — Department of Mechanical Engineering, Faculty of Engineering, Udayana University, Bali, Indonesia. The article identifies Astika as the corresponding author but does not state an academic degree or specific field of expertise beyond the department affiliation.
I Ketut Suarsana — Department of Mechanical Engineering, Faculty of Engineering, Udayana University, Bali, Indonesia. The article does not provide an academic degree or specific field of expertise.
I Nyoman Budiarsa — Department of Mechanical Engineering, Faculty of Engineering, Udayana University, Bali, Indonesia. The article does not provide an academic degree or specific field of expertise.
Dewa Ngakan Ketut Putra Negara — Department of Mechanical Engineering, Faculty of Engineering, Udayana University, Bali, Indonesia. The article does not provide an academic degree or specific field of expertise.
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