الملخص الإنجليزي
Residential buildings consume a significant amount of Oman's electrical
energy, and the air conditioning systems are the highest energy consumers in these
buildings. Phase Change Material (PCM) is a new technology that stabilizes the indoor
temperature and reduces energy consumption. The overall aim of this study is to
evaluate the techno-economic feasibility of PCMs-embedded wall systems in
residential buildings under four climates in Oman: hot-humid climate, moderate
climate, hot-dry climate, and cold climate. A typical Omani villa was selected, and a
simulation model was generated in DesignBuilder software and subsequently
calibrated using actual electricity consumption readings. More than 160 variations of
the thermophysical properties of the PCMs were explored for each climate. The
thermophysical properties include melting temperature, latent heat, PCM's location,
melting temperature range, density, heat capacity, and PCM's thickness. Enhancement
techniques such as adding high conductive materials to the PCM, which include
Ferrochrome slag, adding a layer of thermal insulation material, or using natural
ventilation, were also explored to improve PCM's thermal and energy performance.
The results showed that the optimal melting temperatures were 1 ºC above the
thermostat setpoint for Muscat and Salalah and 2 ºC above the thermostat setpoint for
Nizwa. Al Jabal Al Akhdar's optimal melting temperature is always 19 ºC. The optimal
latent heat is 250 kJ/kg in Muscat and Salalah, 200 kJ/kg in Nizwa, and 400 kJ/kg in
Al Jabal Al Akhdar. The best location for the PCM layer in hot climates was found on
the inner side of the wall and the outer side for the cold climate. The study also found
that the PCM's melting range, density, and heat capacity have no significant impact
on reducing energy consumption in all climates. The optimal PCM layer thickness for
all climates was 25 mm, which has doubled the annual energy consumption reduction
compared to the 10 mm thick cases. After analyzing the PCM-Ferrochrome Slag Cement mixture plaster cases, it was found that all cases resulted in a lower reduction
in energy consumption than the pure PCM, and the reduction of energy consumption
negatively correlates with thermal conductivity. After that, the optimal properties
found in this study were combined in one case for each climate. These cases have
achieved a reduction in annual energy consumption of 3.28% for Muscat, 2% for
Salalah, 3.65% for Nizwa, and 3.93% for Al Jabal Al Akhdar compared to the base
case. The thermal performance analysis indicated that the PCM layer positively
impacts the thermal performance between 1 pm and 1 am and negatively between 9
am and 11 pm for all climates. An economic analysis of the PCMs-embedded walls
with the optimized properties was conducted, and it was found that they are
economically infeasible. The study also found that the controlled natural ventilation
slightly impacted energy performance and enhanced the PCM performance in the
winter months only. Finally, a set of design guidelines for the PCMs-embedded wall
systems for Oman were developed.