4- Model Set-Up
4.4 The validation of the first case study
4.4.1 Set-up the model in the software
70
71
The study concentrates on the investigation of energy performance and thermal comfort of the villas before and after the modification; therefore, the climate conditions of the selected case study play a significant role in achieving reliable and accurate outcomes. Dubai city location and initial weather data are included in the IES-VE database, so the author defined it directly, as shown in Fig (4.11), followed by addressing the nearest climate data file where the list of surrounding cities was presented, to choose the nearest one. In this case study, Abu Dhabi weather file is the closet of Dubai. The obtained data involve latitude, longitude, temperature ranges, wind velocity and solar radiation.
Figure 4.10: Perspective view of the case study with the adjust building source: IES-VE software, 2019
Figure 4.11: Location and weather data of the case study setup source: IES-VE software, 2019
72
The construction materials of the villa, including block works, concrete works and finishes works, considering their thermal properties, were assigned in the software as shown in Table 4.3.
The inside heat must be extracted from the villa by the air conditioning system created from various resources, externals and internals—external heat gains produced from solar radiation, outdoor air and ambient temperature, where air enters the villa by infiltration and ventilation.
While, internal heat gains generate due to the usual internal activities of the household and electrical devices.
Evolving the internal gains in the analysis will add more accuracy to the study. The three most effective sources of the heat gain defined in the project are the lighting, electrical devices, and housing occupants' presence. The below table presents the summary of the heat
Figure 4.12: External wall (AAC Block) thermal properties source: IES-VE software, 2019
Figure 4.13: Combo roof thermal properties source: IES-VE software, 2019
Figure 4.14: Double glazed properties source: IES-VE software, 2019
73
gains implemented in the simulation model of the villa, which was collected from several resources.
Table 4.4: Example of energy consumption of residential households’ electrical appliances sources: ASHRAE handbook, 2017, Ruellan, Park and Bennacer, 2016 & Setlhaolo and Xia, 2015.
Electrical appliance Power consumption (watts) Duration (average)
Microwave 1200 30 mints daily
Dishwasher 1800 3 hours daily
Freezer 320 24 hours daily
Fridge 180 24 hours daily
Coffee maker 1000 30 mints daily
Stove 2000 4 hours daily
Vacuum cleaner 1200 3 hours daily
Washing machine 2000 3 hours daily
Laptop 50 4 hours daily
Computer + monitor 113 2 hours daily
TV 110 10 hours daily
Satellite + Set-top box 104 10 hours daily
Wi-Fi router 7 24 hours daily
Play station 200 5 hours on weekends
Clothes dryer 2000 3 hours daily
Water cooler 100 24 hours daily
Developing thermal and lighting profiles for the villa will enhance the result of the base case's efficiency and reliability. These profiles can be set daily, weekly and annually. For this villa, weekdays, weekend and annual profiles had been created in the IES-VE software for thermal and lighting systems as the followings:
A. Cooling system profile
In the morning hours, the villa will be occupied by housemaids from 8:00 am to 2:00 pm, while the rest of the day will be occupied by the whole household, as shown in Fig (4.15). On the weekend, the villa will be empty from the family from 1:00 pm to 7:00 pm, as displayed in Fig (4.16).
74
During winter months most of the of households in UAE rely on the natural ventilation for cooling, therefore the cooling system of the villa will be switched off from 15 of November to 15 of March as presented in Fig (4.17).
Figure 4.15: HVAC weekdays profile source: IES-VE software, 2019
Figure 4.16: HVAC weekends profile source: IES-VE software, 2019
Figure 4.17: HVAC annual profile source: IES-VE software, 2019
75 B. Natural ventilation profile
On winter season the simulation model assume that the occupants of the villa will depend only on natural ventilation. Therefore, a window profile was created applied in the living rooms, bedrooms and kitchen. The window will be opened the whole day, but during afternoon the window will be closed. The rest of the year as mentioned before the villa will rely on the mechanical cooling system.
In this simulation model, the author assumed that the villa not air tight and there are a few leakedges in thre villa enevelope, so an infiltration rate was set in the software. Aaording to Abu-Tair, Fırat and Kinuthia (2018), the inflitration flow rate value equivalent to 0.25 ACH (air change per hour).
The cooling system temperature setpoints that used in the simulation model is 24°C for all the villa rooms, which is the recommended temperature for the body from DEWA. Moreover, the energy efficieny rate of the system was set as the mentioned before to be 13.
According to their AC drawings, all toilets and kitchen was provided with wall/mounted extract fan. A daily profile was set for all of them as shown in below table.
Table 4.5: Wall/mounted extract fan power consumption and daily work hours source: Clipsal, 2010
Function Power consumption (Watts) Duration (average)
Kitchen fan 40 5 hours daily
Toilets fan 30 3 hours daily
Figure 4.18: window daily profile source: IES-VE software, 2019
76 C. Internal lighting profile
During weekdays the villa required the artificial lighting mostly at night hours from 17:30 pm to 23:00 pm, the rest of the night hours the artificial lights will be turned off from 23:00 pm until 5:00 am when the household member prepare themselves for their works and schools and it will be turned off again at 7:00 am. On the weekends the lighting system has another profile, where the lamps will be turned on from 19:00 pm to 1:00 am, then it turned on again from 5:00 am to 6:00 am to do their religious duties. All the lighting lamps types were addressed in the simulation model as presented in lighting drawings.
D. External lighting profile
The external lighting of the villa was also considered in the analysis of the base case. During the weekdays the external lighting switched on from 18:00 pm to 24:00 am, while during weekends the turned on from 19:00 pm to 2:00 am.
Figure 4.19: Lighting weekdays profile source: IES-VE software, 2019
Figure 4.20: Lighting weekend profile source: IES-VE software, 2019
77
Although the main system of generating domestic hot water is the solar system, but it only generates 75% of the occupants’ demands. Therefore, the system provided with 2.5 kw pack up electrical heater, which require around 1282 kw of electricity annually. Also, this amount of consumption considered in the simulation of the case study.